School Science Lessons
2024-07-30a
Please send comments to: j.elfick@uq.edu.au
(UNBiology2)
Human Physiology and Health
Websites, Health and nutrition, the human body
Contents
9.1.0 Nervous system, senses
9.2.0 Respiration, Aerobic respiration
9.2.11.0 Resuscitation
9.3.0 Ear and hearing, balance
9.4.0 Eyes and sight
9.5.0 Nose and smelling, taste, flavour, odour
9.6.0 Touch and feeling
9.8.0 Voice and speaking
9.1.0 Nervous system, senses
9.1.1 Absolute threshold
9.1.2 Deep tendon reflexes
9.1.3 Nervous system, CNS, PNS, ANS, SNS, PSNS
9.1.4 Reflex arc
9.1.5 Senses, "the five senses"
Experiments
9.1.6 Circular movement of foot
9.1.7 Hands in hot and cold water
9.1.8 Hands of sleeper in warm water
9.1.9 Human reaction time
9.2.0 Respiration, Aerobic respiration
5.8 Aspiration hazard
3.37 Carbon dioxide and respiration equations
Cooling by evaporation, sweat glands
20.0.9 Henry's law and decompression sickness, "the bends"
9.2.1 Mountain sickness and hyperventilation
9.244 Scuba diving and Boyle's law
Respirators, Safety respirators
5.3 Respiratory sensitization or skin sensitization
Experiments
9.2.2 Breath, simulated diaphragm breathing
9.2.3 Breath volume
9.2.4 Elimination of wastes when we breathe
9.2.5 Feel your pulse, electrocardiogram
24.6.0 Heat loss by human body
9.2.6 Hiccups
9.2.7 Human pulse rate, recording and averaging
9.2.8 Lung simulator
9.2.9 Oxygen absorbed in the lungs
9.2.10 Oxygen content of inhaled and exhaled air
9.2.11.0 Resuscitation
9.2.12 Respiration, humans
9.2.13 Respiration rate of humans, respiratory rate and heart rate, stethoscope
26.4.2 Sound waves travel through an air column, stethoscope
6.6.12 Tests for gases collected in a respirometer
9.2.14 Volume of air breathed out, spirometer
9.2.11.0 Resuscitation
9.11.1 Cardiopulmonary resuscitation (CPR), Adult
9.11.2 Cardiopulmonary resuscitation (CPR), Child (aged 1-8)
9.11.3 Cardiopulmonary resuscitation (CPR), Infant (under 1 year)
9.11.4 Expired air resuscitation (EAR), Adult
9.11.5 Expired air resuscitation (EAR), Infant (under 1 year), and Child (aged 1 to 8)
9.3.0 Ear and hearing, balance
Ear protection, Safety ear muffs, ear plugs
9.3.1 Ear and hearing
12.6.0 Sound
Experiments
9.3.2 Human ear, how the ear works, model of the ear
9.4.0 Eyes and sight
3.6.3 Eye washing, safety showers
9.4.1.0 Eye, structure and physiology
9.1.0 Optical illusions
Experiments
9.4.1 Astigmatism
9.4.2 Blind spot
9.4.3 Chromatic aberration of the eye
9.4.4 Colour blindness
9.4.5 Distance of object seen
9.4.6 Eyeglasses
9.4.7 Examine your eyes
9.4.8 Eyesight test
9.4.9 Fluorescence of retina
9.4.10 Inversion of image on the retina
9.4.11 Jarring the eye
9.4.12 Mach disc
9.4.13 Resolving power of the eye
9.4.14 Retinal fatigue colour
9.4.15 Subjectivity of colours
9.4.16 Water flask model of the eye
9.4.17 Afterimage
9.5.0 Nose and smelling, taste, flavour, odour
Taste
19.2.2 Aspartame sweetener
9.1.11 Cork taint of wine, "corky" wine (2,4,6-TCA)
19.2.6 Phenylalanine sweetener
9.9.5 PTC tasters and non-tasters
19.1.26 Relative sweetness of some artificial sweeteners
9.5.2 Sense of taste, the gustatory system
19.1.25 Sweeteners, food additives
12.3.17 Taste of acids, solid acids in the home
3.4.13 Tasting chemicals
9.5.3 The five different taste qualities
Smell
35.1,11 Odour and taste, (Geology)
9.5.1 Sense of smell, the olfactory system
16.6.1 Tests for trimethylamine fish smell
9.6.0 Touch and feeling
35.18 Feel and conductivity, (Geology)
Five senses (Primary): 1.15
9.6.1 Sense of feeling temperature
9.6.2 Sense of touch, somatic sensory system
Experiments
12.7.1 Feel of alkalis
9.2.5 Feel your pulse, electrocardiogram
9.6.4 Feel two noses, tactile illusion
32.2.6 Test electricity with the tongue
9.6.5 Women feel colder then men
9.8.0 Voice and speaking
9.102 Voice and speaking
Experiment
26.2.0 Pitch, frequency
9.1.1 Absolute threshold
The absolute threshold is the smallest detectable level of a stimulus, (50 % of the time.)
1. Hearing
The smallest level of a tone that can be detected by normal hearing when there are no other interfering sounds present, e.g. ticking.
The quietest sound that children with normal hearing can detect is about 1, 000 Hz.
2. Vision
The smallest level of light that a participant can detect, e.g. the distance a participant can detect a candle flame in the dark.
A human can detects a stimulus as little as 90 photons, after controlling for dark adaptation, wavelength, location and stimulus size.
3. Smell
The smallest concentration that a participant can to smell, e.g. the smallest amount of perfume in a large room.
Two very low odour threshold values:
16.1.3.3.2: Allyl mercaptan: 6 X 107 molecules / mL of air
Vanilla, odour threshold value: 2 X 109 molecules / mL of air.
9.1.2 Deep tendon reflexes
Hammers, medical, 3 point, (Commercial).
To examine deep tendon reflexes, use a reflex hammer (3 point medical hammer) or the side of the hand.
Note the extent or power of the reflex, visually and by palpation of the tendon or muscle.
Clonus muscular spasms involving repeated contractions that may be rhythmic.
A reflex may be rated by 1. Sustained clonus, 2. Very brisk with clonus, 3. More reflexive than normal, 4. Normal, 5. Diminished, 6. Only elicited with reinforcement, 7. No response
The student sits up on the edge of the table with one hand on top of the other, arms and legs relaxed.
For reinforcement of the reflex ask the student to clench the teeth.
Experiments
1. Biceps reflex
Place your thumb on the student's biceps tendon and strike your thumb with the reflex hammer or the side of the hand.
Observe the arm movement.
Repeat and compare with the other arm.
The biceps reflex is mediated by the C5 and C6 nerve roots.
2. Brachioradialis reflex
Strike the student's brachioradialis tendon directly with the hammer or the side of the hand when the student's arm is resting.
Strike the tendon roughly 8 cm above the wrist.
Note the reflex supination (in the supine position).
Repeat and compare to the other arm.
The brachioradialis reflex is mediated by the C5 and C6 nerve roots.
3. Triceps reflex
Strike the student's the triceps tendon directly with the hammer or the side of the hand while holding the student's arm with your other hand.
Repeat and compare to the other arm.
The triceps reflex is mediated by the C6 and C7 nerve roots, predominantly by C7 or reinforcement of the lower extremity reflexes.
Ask the student to hook together their flexed fingers and pull apart.
This is called the Jendrassik manoeuvre.
4. Knee jerk reflex
With the student's lower leg hanging freely off the edge of the table, strike the student's quadriceps tendon directly with the reflex hammer or side of the hand.
Repeat and compare to the other leg.
A normal or brisk knee jerk would have little more than one swing forward and one back.
The knee jerk reflex is mediated by the L3 and L4 nerve roots, mainly L4.
5. Ankle reflex
Hold the relaxed foot with one hand and strike the Achilles tendon with the hammer or the side of the hand and note the plantar flexion.
Compare to the other foot.
The ankle jerk reflex is mediated by the S1 nerve root.
6. Plantar reflex
Coarsely run a key or the end of the reflex hammer up the lateral aspect of the foot from heel to big toe.
The normal reflex is toe flexion.
If the toes extend and separate, called Babinski's sign, an upper motor neurone lesion affects the lower extremity.
7. Hoffman response
Hold the student's middle finger between the thumb and index finger.
Ask the student to relax their fingers completely.
Once the student is relaxed, using your thumbnail to press down on the student's fingernail and move downward until your nail "clicks" over the end of the student's nail.
Normally, nothing occurs.
A positive Hoffman response is when the other fingers flex transiently after the "click".
Repeat this manoeuvre multiple times on both hands.
A positive Hoffman response indicates an upper motor neurone lesion affecting the upper extremity.
8. Test for clonus
If any of the reflexes appeared hyperactive, hold the student's relaxed lower leg in your hand, and sharply dorsiflex the foot and hold it dorsiflexed.
Feel for oscillations between flexion and extension of the foot indicate clonus.
Normally, nothing is felt.
9.1.3 Nervous system, CNS, PNS, ANS, SNS, PSVS
1. Central nervous system, CNS
* Brain and spinal cord
* Grey matter
* White matter
2. Peripheral nervous system, PNS
2.1 Autonomic nervous system, ANS, visceral nervous system, involuntary nervous system
2.1.1 Sympathetic nervous system, SNS, emergency action (fight or flight), parallel action to adrenaline, but more immediate:
* increases heart rate, blood pressure, breathing rate,
* dilates the pupil, trachea (lump in throat),
* contracts hair erector pili muscles, e.g. hair "stands on end", tingling spine feeling, ruffling of cat's fur and chicken's feathers,
* constricts blood vessels to skin (turned white in fright), salivary glands (dry mouth) constricted,
* contracts bladder wall. (urination due to fright),
* inhibits digestion
2.1.2 Parasympathetic nervous system, PSNS, return to normal after emergency
9.1.4 Reflex arc
A reflex arc is a simple nerve pathway for reflex actions, e.g. patellar reflex (knee jerk).
The pathway has a minimum of three neurones:
1. A sensory neuron exists from a receptor through a spinal nerve and into the spinal cord or brain.
2. A connector interneuron within the spinal cord.
2. A motor neurone from the spinal cord and through a motor spinal nerve to a muscle or gland.
The three neurones are connected by synapses.
It is a theoretical idea, because nobody has ever dissected out a simple reflex arc!
A conditioned reflex involves a new response behaviour, e.g. a dog associated the sound a bell with feeding, so when a bell rings, the response is to salivate.
A reflex reaction is an involuntary response to an internal or external stimulus.
During sleep, the atonia associated with rapid eye movement (REM) stops messages moving from the brain to the muscles, causing a partial paralysis to stop sleepers moving about.
For example, sneezing is not possible during sleep in a normal healthy person.
9.1.5 Senses (1 to 5 = "the five senses")
1. Sight, vision
2. Hearing, audition
3. Taste, gustation
3.1 Sweet, 3.2 Salty, 3.3 Sour, 3.4 Bitter, 3.5 Umami ("The fifth basic taste"), savoury taste of glutamates, e.g. monosodium glutamate.
4. Smell, olfaction (Flavour is taste + the smell of food)
5. Touch (perceiving physical contact)
6. Balance and acceleration sense, equilibrioception detected by the inner ear (this sense may be called "the sixth sense".
However "the sixth sense may refer to extrasensory perception, ESP, the title of a famous movie, songs, etc.)
7. Temperature sense, heat sense on the skin, thermoception
7.1 Heat receptors, 7.2 Cold receptors
8. Kinesthetic sense, proprioception, body awareness
8.1 Skin sensors, 8.2 Joint and bone receptors, 8.3 Body organ receptors
9. Pain sense, nociception, pain from skin, joints and body organs
10. Internal senses
* Brain, vasodilatation causing headache
* Colon, stretch during colic (excess gas pressure, "wind")
* Lungs - stretch
* Oesophagus, swallowing, vomiting, reflux oesophagitis (heartburn)
* Pharynx, gagging reflex, cannot swallow
* Skin, touch, pressure
11. Direction (magnetoreception in some birds and cattle)
12. Detection of electric fields, electriception, sharks
13. Detection of magnetic fields, magnetoception, bird and insect navigation
14. Detection of pressure, echolocation, lateral line canal of fishes
15 Detection of infrared radiation, owls and deer to allow night feeding
9.1.6 Circular movement of foot
Sit on a chair.
Lift your right foot off the floor then move it in a clockwise circle.
While keeping the foot moving in a circle, use the pointing finger of your right hand to draw the number 6 in the air.
Your right foot changes the direction of circular movement.
9.1.7 Hands in hot and cold water
Use a bowl of warm water, iced water and water with middle temperature.
1. Hold one hand for one minute in the warm water and hold the other hand for one minute in the iced water.
2. Place both hands in the middle temperature water.
The previously in the warm water feels cold and the hand previously in the iced water feels warm.
The experiment shows that temperature sense is relative to the temperature of the skin.
The skin of the hand placed in the warm water had become warmer and the skin of the hand placed in the iced water had become colder.
9.1.8 Hands of sleeper in warm water
This experiment is in the category of "sleep over pranks".
The hand of a sleeping child is place in warm water.
The child urinates while still asleep.
9.1.9 Human reaction time
Reaction Timer (recording timer, ticker timer), (Commercial).
See diagram 9.249: Reaction time
If a body falls from a height s, the distance it falls after t seconds = gt2 /
2. So if you measure s, you can obtain t, t = 2S / g.
Experiments
1. Hold metre ruler vertically with the zero on the scale down and the 100 on the zero on the scale up.
With your arm stretched horizontally, hold the ruler vertically between the thumb and first finger with the lower edge of the first finger at the zero on the scale.
Open your fingers then close them again as quickly as possible to catch the ruler again.
Record the distance to the downward edge of your first finger.
Repeat the experiment and calculate the average distance down the metre stick.
Use t = 2S / g to calculate the time of the falling ruler, i.e. your reaction time.
2. Repeat the experiment under the following pairs of conditions:
1. Hold the ruler first with your left hand
2. Hold the ruler first with your left hand
3. Talk to others while doing the experiment
4. Do not talk to others while doing the experiment
5. Allow loud background music
6. Do not allow loud background music.
Try other contrasting conditions to see whether your reaction time is affected.
Compare results with the results of other students.
9.2.1 Mountain sickness and hyperventilation
Persons climbing above 2500 m may experience headaches, nausea and rapid breathing caused by hyperventilation to compensate
for the low concentration of oxygen above that height.
The condition can be treated by breathing pure oxygen, rest and return to lower altitudes.
After about 7 days the symptoms may disappear.
In most passenger aircraft, the cabin air pressure at 10, 000 metres is about two thirds of normal sea-level pressure.
This lower pressure may cause sealed bags of potato chips to inflate and cause discomfort to passengers with blocked sinuses caused by a heavy cold.
9.2.2 Breath, simulated diaphragm breathing
See diagram 9.242: Simulated diaphragm.
See diagram 9.240: VS Lungs and a bronchiole.
Breathing movements cause the change of air in the lungs necessary for breathing, because the lungs have no muscles and cannot inhale or exhale air by themselves.
Experiments
1. Breathe deeply in an out.
Note that the volume of the chest cavity changes in two ways.
1.1 When you inhale, the thorax expands to produce decreased pressure in the airtight chest cavity that causes air to flow into the lungs.
When you exhale, the thorax contracts to decrease the size of the chest cavity, compress the elastic lung tissue and force air out of the lungs.
The thorax rises and falls, because of the action of the muscles between the ribs.
In this way you can increase breathing to allow stronger bodily activity.
1.2 In diaphragm breathing, abdominal breathing, the diaphragm rises and falls, because of the action of the diaphragm muscle controlled by the respiratory centre.
At rest, or during with low bodily activity, breathing acts mainly in this
manner.
2. Show the mechanism of diaphragm breathing.
Pull a rubber balloon over each of the two ends of the glass Y-tube.
Smear the ends of the glass tube with glycerine.
Pass the long limb of the Y-tube from below through the neck of a 5 litre polystyrene large jar and through a hole in a rubber stopper lubricated with glycerine.
Use a rubber cloth with a loop on one side to close the opening at the base of the large jar so that the loop remains outside.
Secure the rubber cloth to the large jar with a clamping ring.
Press the rubber stopper firmly into the neck of the large jar.
Grab the model by the neck in one hand, and pass the other hand through the loop.
Move the rubber cloth up and down to simulate the breathing rhythm.
Draw down the rubber cloth to inflate the balloons.
Push the rubber cloth upwards to collapse the balloons.
If the rubber cloth is drawn downwards, the volume in the large jar outside the rubber balloons increases.
A decrease in pressure occurs that is immediately equalized by the flow of air into the elastic balloons, so they expand.
When you press the rubber cloth upwards, the volume in the large jar outside the rubber balloons decreases to produce excess
pressure that forces air out of the elastic balloons that then collapse.
9.2.3 Breath volume
See diagram 9.241: Volume of air in a breath.
1. Fix a glass tube bent at right angles through a one-hole stopper.
Push the stopper into the neck of a large jar.
Immerse the large jar in the water of a fish tank.
Connect one end of rubber tubing to the glass tube.
Suck out the residual air in the large jar with a rubber bulb.
Close the stopcock and raise the large jar by 10 cm.
Connect the other end of the rubber tubing to a glass mouthpiece.
Take a few normal breaths, in through the nose and out through the mouth.
Blow breaths of air into the large jar.
If two litres of air are blown into the large jar with 6 breaths, the volume
of air expelled per breath is 330 mL.
2. Normal breathing exchanges 200 to 500 mL of air at each breath.
Vigorous inhaling and exhaling exchange 2.5 to 5 litres of air at each breath.
This value is called the vital capacity, measured with a spirometer.
After the most powerful exhalation, about 1 000 mL of air is left in the lungs, the residual air.
The vital capacity + the residual capacity = the total volumetric capacity of the lungs.
Measure the vital capacity with a method similar to that used for measuring the volume of air in one breath.
Breathe in as much air as possible.
Place the glass mouthpiece in the mouth and attempt to blow all the air out of the lungs with one breath into the large jar.
3. Use the rubber bulb to pass air through limewater.
The limewater does not turn milky.
Immerse the large jar in the water and dip the mouthpiece into limewater so that the air bubbles through the limewater.
The limewater has turned milky, showing the presence of carbon dioxide in exhaled air.
4. Measure the volume of air breathed out.
Take a deep breath.
Blow air out slowly into one jar until all the water has been pushed out.
Transfer to the next jar and blow more air out until the lungs are empty.
For example, the volume of the air in a student's lungs may be 1 000 cm + 1 000 cm + 200 cm = 2 200 cm.
Make air replace water by blowing air into inverted jars filled with water.
Estimate the volume of the lungs by measuring the volume of air pushed out.
Be careful! Do not let students blow so hard that they feel sick.
5. Measure chest expansion.
Use a tape measure to measure the perimeter of the chest where it is widest.
Note the chest measurement after breathing out.
Note the chest measurement after breathing in.
Calculate the chest expansion.
Measure again after breathing really hard out and in.
Observe the movement of the ribs when breathing in.
Stand up and push one finger into the stomach, up and under the lower rib.
Then breathe in.
The diaphragm muscle pushes the finger down.
The volume of the chest increases when the ribs move up like the handle of a bucket, just when the diaphragm muscle drops down.
6. Record the breathing rate per minute and chest expansion,
6.1 when sitting quietly,
6.2 after running.
Breathing rate and chest expansion is greater after running.
9.2.4 Elimination of wastes when we breathe
See diagram 9.154: Limewater test for carbon dioxide in the breath.
1. Use a rubber bulb to pump air into a beaker containing limewater.
Note the slow change in the limewater.
The air contains about 0.4% carbon dioxide.
2. Fit a short glass tube into the bore of a stopper that can fit into the neck of a bottle of aerated water, soda water.
Attach rubber tubing to the glass tube.
Fit the stopper into the neck of an opened bottle of aerated water.
Put the other end of the rubber tubing into a beaker of limewater.
Warm the bottle of aerated water with the hands.
Note the change in the limewater.
The aerated water contains carbon dioxide that forms bubbles, effervesces, and escapes when the bottle is opened.
3. Blow exhaled air into the limewater.
Note the change in the limewater.
A cloudy precipitate soon forms, because exhaled breath contains about 4% carbon dioxide.
9.2.5 Feel your pulse, electrocardiogram
See diagram 9.239: Feel your pulse.
See diagram: 9.239.1: Electrocardiogram (Ecg) of heart at rest.
Feel your pulse and note how it changes with different body activity.
Practice feeling your own pulse.
It beats about 70 times per minute?
1. Children must be seated quietly and not move about.
Put the forearm on the desk, palm up with the wrist on the edge of the desk and hand in the air.
Press the four fingers of the other hand down on the side of the wrist.
Wait a little while, keep still, and you will feel your pulse.
Start counting the pulse.
2. Repeat after running.
The pulse tells us how fast the blood is pumped around the body.
If you are sick or after a big meal it is faster, when you are asleep it is slower.
3. Push a thumbtack (drawing pin) into the base of a large matchstick.
Balance it on the wrist is the same place where you feel your pulse, with the hand resting on the table.
The match head will vibrate slightly with the pulse.
4. Roll up some paper to make a tight tube.
Hold it against the chest of another child.
Press your ear against the other end.
Can you hear the heart pump the blood?
Extra Activity: Use a watch to tell the children when a minute starts and stops.
Write down your pulse rates on the chalkboard in beats per minute.
What is the average pulse rate?
An electrocardiograph records the electric currents generated by the heartbeat and records them on an electrocardiogram.
9.2.6 Hiccups
If the diaphragm is irritated by eating too quickly, drinking too much alcoholic drinks or carbonated drinks, or swallowing too much air, it may go into spasms, sudden involuntary contraction of muscles, that bounce air off the vocal cords.
We call the movement and the sound "hiccups".
In a healthy person, hiccups will gradually lessen and stop.
Immediate remedies include hold the breath while pinching the nose, taking 10 sips of water, blowing into a paper bag and holding the breath to increase the concentration of carbon dioxide in the blood, inhale for count of five and exhale for count of eight, give patient a reward if patient can cause a hiccup, inhale increasing levels of caron dioxide by breathing into paper bag under medical supervision, give patient a teaspoonful of sugar.
If hiccups are severe, doctors may administer antispasmotic drugs, which relieves or prevents spasms of smooth muscle, involuntary muscle spasms.
9.2.7 Human pulse rate, recording and averaging
Pules rate is the artery beat due to the blood rush when the heart contracts.
The number of the times every minute that heart contracts is expressed by the pulse rate, the beat of blood vessel felt when your fingers press on your wrist.
The pulse rate of a healthy adult resting quietly is about 60 to 80 times per minute.
Pules rate may accelerate after taking part in sport or having a fever.
Measure your pules rate by counting for a minute, take it three times and calculate the average.
Use a table to record the data.
A table for a group of students should either record the numbers of each student in each measuring or record the numbers of all students.
Should you calculate the average of each student's pules rate or calculate average those of all students?
9.2.8 Lung simulator
See diagram 9.240: V.S. Lungs and alveoli.
See diagram 9.242: Lungs, VS.
See diagram 9.242.1: Simulated diaphragm.
1. Cut the bottom off a large plastic or glass bottle.
Fit a cork to the neck with a Y-tube in it.
On each of the lower limbs of the Y-tube tie a rubber balloon or some small bladder.
Tie a sheet of brown paper or sheet rubber round the bottom of the container, with a piece of string knotted through a hole and sealed with wax.
Pulling this string lowers the diaphragm and air enters the neck of the Y-tube causing the balloons to dilate.
Pressing the diaphragm upwards has the opposite effect.
9.2.9 Oxygen absorbed in the lungs
See diagram 9.240: Lungs and alveoli.
Air breathed in: O2 21%, CO2 0.04%, Moisture 2% (varies)
Air breathed out: O2 16%, CO2 4.0%, Moisture 5% (varies)
Experiments
1. Immerse a large jar so that the water level coincides with the 5 litre mark.
The large jar then contains 5 litres of air, inhalation air.
Insert a burning candle into the large jar.
Be careful! Melting wax from a burning candle can cause severe skin burns.
Use safety glasses and insulated, heat-proof gloves.
Close the neck of the large jar immediately.
Record the burning time of the candle.
For example, the candle was extinguished after 90 seconds.
2. Insert the mouthpiece in the mouth and fill the large jar to the 5 litre mark with exhalation air.
With normal breathing this air has only been in the lungs for a few seconds.
Adjust the large jar so that the water level in it is 3 mm lower than in the tank.
Remove the stopper and put the candle holder with the lighted candle in the large jar.
Close the neck of the large jar immediately.
Record the burning time of the candle.
The candle burns for a much shorter period than in experiment 1.
3. Repeat experiment 2 with air retained in the lungs for a longer period than normal, e.g. 30 seconds, before breathing it out.
The candle in the large jar is extinguished immediately.
The longer air remains in the lungs, the more oxygen is absorbed into the bloodstream.
9.2.13 Respiration rate of humans, respiratory rate and heart rate, stethoscope
Sound, Stethoscope, (Commercial).
See diagram 9.239: Feel your pulse.
See 3.4.6: Gas or vapour inhalation, EAR, CPR
Heartburn (pyrosis) has nothing to do with the heart.
It is a burning feeling behind the breastbone and sometimes acid or bitter taste in the mouth caused by regurgitation of stomach contents after a heavy meal.
Experiments
1. The respiratory rate is the number of breaths per minute.
Measure it by observing the chest rising and falling with every breath.
Rest for ten minutes and measure the respiratory rate again.
Normal values for resting persons, per minute: 3 months 30-50, 10 years 18-30, adult 8-18.
2. After ten minutes rest, measure the heart rate by feeling the pulse.
The heart rate is the number of beats per minute, bpm.
Put the forearm on the desk, palm up with the wrist on the edge of the desk and hand in the air.
Press the four fingers of the other hand down on the side of the wrist.
Keep still and feel your pulse.
Feel the pulse in the radial artery on the palm side of the wrist in the same direction as the thumb.
Start counting the pulse.
Note the number of beats per minute.
It is from 60 to 100, usually about 70.
Do ten knee bends and measure the activity pulse.
The pulse rate tells us how fast the blood is pumped around the body.
After ten minutes rest, measure the recovery pulse.
Note whether the pulse has returned to the original resting pulse.
If a student is sick or just had a big meal, the pulse increases.
During sleep the respiratory rate is slower.
The best resting pulse is taken when awakening in the morning.
Normal values for resting persons, per minute: 3 months 70-170, 10 years 70-110, adult 50-95.
3. Roll up some paper to make a tight tube.
Hold it against the chest of another student.
Press the ear against the other end.
Hear the heart pumping the blood.
The doctor uses a stethoscope instead of a paper tube for listening to the different sounds in the body, auscultation.
Sold as: Stethoscope, nurses' type, flat.
9.2.10 Oxygen content of inhaled and exhaled air
Compare the oxygen content of inhaled and exhaled air with a burning candle.
Candles can only burn in the presence of oxygen.
The more oxygen present, the longer they burn.
Fix a candle into a candle holder.
Light the candle and put it quickly into a glass container and at the same time cover the glass container with a glass disk.
Insert a glass tube in the glass container and again cover it with a glass disk.
Exhale through the glass tube 20 times so that only exhaled air remains in the vessel.
Take out the glass tube, introduce the candle holder with the burning candle and immediately cover the glass container.
Note how long the candle burns.
Use the data to compare the oxygen content of inhaled and exhaled air.
9.2.11.1 Cardiopulmonary resuscitation (CPR), Adult
1.0 Position hands for CPR.
1.1 Place patient on back.
1.2 Find groove at neck between collarbones.
1.3 Find lower end of breastbone by running finger along last rib to centre of body.
1.4 Extend thumbs equal distances to meet in the middle of the breastbone.
1.5 Keep thumb of one hand in position and place heel of other hand below it.
1.6 Place heel of other hand on top of first and interlock fingers of both hands.
2.0 Commence chest compression.
2.1 Position yourself vertically above patient's chest.
2.2 With your arms straight, press down on breastbone to depress it about 4 to 5 cm.
2.3 Release pressure.
3.0 Continue CPR.
3.1 Complete 15 compression.
3.2 Give two effective breaths (EAR).
3.3 Continue compression and breaths in ratio of 15 : 2 at a rate of 4 cycles per minute.
3.4 Check for signs of circulation every minute.
9.11.4 Cardiopulmonary resuscitation (CPR), Child (aged 1-8)
9.2.11.2 Cardiopulmonary resuscitation (CPR), Child (aged 1-8)
1. Use the heel of one hand over lower half of breastbone.
2. Compress the chest approximately 1 / 3 depth of chest.
3. Give one effective breath (EAR).
4. Continue compression and breaths in ratio of 5: 1 at a rate of 12 cycles per minute.
9.2.11.3 Cardiopulmonary resuscitation (CPR), Infant (under 1 year)
1. Place the tips of 2 fingers (index and middle) on lower half of breastbone.
2. Compress chest approximately 1 / 3 depth of chest.
3. Give 5 chest compression in 3 seconds.
4. Give one effective breath.
5. Continue compression and breaths in ratio of 5 : 1 at a rate of 12 cycles per minute.
6. Check for signs of circulation every minute.
9.2.11.4 Expired air resuscitation (EAR), Adult
9.2.11.4 Expired air resuscitation (EAR), Adult
If breathing:
1.0 Clear airway,
1.1 Place patient in recovery position: Patient on back, straighten both legs, lift one leg at knee to make right angle, one arm across chest, other arm at right angle to body, roll patient onto side, knee of leg at right angles touches ground so patient does not roll on face.
1.2 Lift chin and open mouth.
1.3 Use finger to remove any obvious obstruction.
1.4 Tilt head back gently.
1.5 Check breathing for up to 10 seconds.
If not breathing:
2.0 Open airway.
2.1 Turn patient onto back.
2.2 Gently tilt head back.
2.3 Pinch nose closed, using thumb and index finger.
2.4 Open mouth and maintain chin lift.
3.0 Give EAR (mouth-to-mouth resuscitation).
3.1 Take a full breath and place lips on patient's mouth to ensure good seal.
3.2 Blow steadily into mouth for 1.5 to 2 seconds.
3.3 Watch for chest to rise.
3.4 Take mouth away and watch for chest to fall.
3.5 Take another breath and repeat sequence, to give two effective breaths.
4.0 Check for signs of circulation.
4.1 Look for any movement, including swallowing or breathing.
4.2 Observe colour of skin on face.
4.3 Check pulse at neck or wrist.
4.4 If circulation absent, commence CPR.
4.5 If circulation present, continue EAR at 15 breaths per minute.
4.6 Look for signs of circulation about every minute.
5.0 Place in recovery position when breathing 5 returns.
9.2.11.5 Expired air resuscitation (EAR), Infant (under 1 year), and Child (aged 1 to 8)
If breathing:
1.0 Clear the airway.
1.1 Place the infant / child in recovery position: Patient on back, straighten both legs, lift one leg at knee to make right angle, one arm across chest, other arm at right angle to body, roll patient onto side, knee of leg at right angle touches ground so patient does not roll on face.
1.2 Lift the chin and open the mouth.
1.3 Use a finger to remove any obvious obstruction.
1.4 Tilt the head back very gently.
1.5 Check breathing for up to 10 seconds.
If NOT breathing:
2.0 Open the airway
2.1 Turn the patient onto the back
2.2 Tilt the head back slightly
2.3 Open the mouth and lift the chin.
3.0 Give EAR (mouth-to-mouth resuscitation)
3.1 Cover the patient's mouth and nose with your mouth
3.2 Give two gentle breaths/puffs into child's /infant's mouth and nose
3.3 Check for signs of circulation: swallowing, breathing, colour of skin on face and pulse (infant on inside upper arm, child at neck or wrist)
3.4 If circulation absent, commence CPR
3.5 If circulation present, continue EAR at 20 breaths per minute
3.6 Look for signs of circulation about every minute.
4.0 Place in recovery position if breathing returns.
9.11.3 Cardiopulmonary resuscitation (CPR), Adult
9.2.12 Respiration, humans
H2O (l) <--> H+ (aq) + OH- (aq)
2H+ (aq) + CO32- (aq) <--> H2CO3 (aq) carbonic acid
CO2 + H2O <--> H3O+ + HCO3-
HCO3- + H2O <--> H3O+ + CO32-
Add one drop of sodium carbonate solution, Na2CO3.10H2O, to a test-tube full of water.
Shake the test-tube then pour out the contents leaving 2 cm depth.
Add one drop of phenolphthalein solution.
The solution in the test-tube turns red.
Blow through a straw or glass tube into the solution in the test-tube.
The red colour disappears, because the carbon dioxide gas in the breath has formed carbonic acid in water and neutralized the sodium carbonate solution.
9.2.14 Volume of air breathed out, spirometer
Spirometer, (Commercial).
A spirometer is an instrument for measuring the volume of inhaled or exhaled air, also called a pulmometer.
See diagram 6.16: Volume of air breathed out.
1. Measure how much air breathed out by displacement of water.
Use marked jars, each group should have at least three jars, buckets, basins or any pool of water, lengths of rubber hose or hollow pawpaw (papaya) sticks.
Each child will probably need three jars to measure how much air in the lung.
The children take turns using the jars.
Do the activity outside, because water will be spilt.
Take a deep breath.
Blow air out slowly into one jar until all the water has been pushed out.
Transfer to the next jar and blow more air out until your lungs are empty.
You may need a third jar.
The volume of the air in this person's lung is 1 000 cm3 + 10003 cm + 2003 cm = 2 2003cm.
2. We can make air replace water by blowing air into the upside down jars filled with water.
Now measure the volume of the lungs by measuring the volume of water the air pushed out.
3. Use one group to show the rest of the class how to fill the bottles of water, blow into the jar and refill with water.
How much air breathed out is about equal to how much air is in the lungs.
4. Let each child to try to find out how much air in the lungs.
5. Draw a table of results on the chalkboard.
Which child has the largest volume of air in the lungs?
Do not let children blow hard and do not make them blow if they feel sick!
9.3.1 Ear and hearing
See diagram 9.235: Vertical section of human ear
1. A sound wave is a longitudinal wave, so it consists of alternating compression and rarefaction, i.e. particles move closer together and farther apart.
A sound wave can pass through the ear canal of the outer ear to reach the sensitive eardrum, tympanic membrane, and causing it to vibrate at the same frequency.
The eardrum is attached to the bones of the middle ear, the ossicles.
The hammer (malleus) connects the eardrum to the anvil (incus) that connects to the stirrup (stapes) that connects to the oval window of the middle ear.
These bones transmit vibration from the eardrum to fluid in the cochlea, the portion of the inner ear responsible for hearing.
It looks like a snail's shell.
These vibrations in the inner ear cause nerve impulses to be transmitted to the brain by the auditory nerve.
The bones of the skull can also transmit vibrations.
You hear a sound if the waves reach the cochlea by either route.
When a sound reaches your two ears, you can distinguish the direction from which it comes.
If it comes from straight ahead, the vibrations reach both ears simultaneously and with the same strength.
If source of sound is on one side, one ear is farther away from it and receives the sound waves less strongly and with a slight delay.
The eardrum must be protected.
A perforated eardrum can lead to serious infection.
Never use a bobby pin or cotton buds to clean the ear.
When the ear canal gets blocked with wax, treat it with medical ear drops.
Do not hit anyone on the ear!
The eardrum can become perforated if the outer ear is hit with the open palm of the hand.
The Eustachian tube extends from the middle ear to the nasopharynx.
Usually it is closed.
It can open to let air pass and equalize the pressure between the middle ear and the atmosphere, causing a small "pop" sound.
This happens during change of height in an aircraft or during mountain travel.
People, and especially babies, with eustachian tubes blocked with mucus experience pain when an aircraft changes height.
2. Besides the cochlea, the inner ear also contains three small semicircular canals to maintain balance.
Movement of fluid in the semicircular canals sends messages to the brain about the speed of rotation of the head and the direction of movement of the head, e.g. nodding or looking behind.
Spinning the whole body causes giddiness, vertigo.
Experiments
3. Extreme vertigo: Mark a cross on the floor, bend the body at right angles, rotate the body with one eye looking down at the cross.
Be careful! This rotating movement may cause nausea!
4. To balance the pressure in the middle ear with the outside pressure, hold the nose shut and blow softly or blow the nose or chew chewing gum.
During flight, the air pressure in a passenger aircraft is usually regulated to the pressure at 2000 metres above ground.
5. In the ear, the three circular canals filled with fluid are set at angles to each other, so any movement of the head sets off nervous impulses to allow the brain to interpret the signals and maintain balance.
This action is similar to the way a gyroscope can keeps a forward motion in a constant direction.
6. Earwax that lubricates the ear canal is a mixture of cerumen, skin cells, bits of hairs and substances caught in the wax.
Cerumen is a secretion produced by the sebaceous glands in the outer ear canal.
Cerumen may be "dry" or "wet", with Asians having dry cerumen and Europeans having wet cerumen.
The colour of cerumen may vary from grey (dry) to light brown (wet).
With age, wet cerumen darkens and becomes less liquid.
9.102 Voice and speaking
See diagram 9.237: Vocal cords. 1. vocal cords, 2. epiglottis, 3. larynx.
Mouth, teeth, tongue, throat and lungs are all used in the production of the voice.
Sound is produced by vibrations of two thin sheets of membrane called the vocal folds (formerly vocal cords), stretched across the sound chamber, the larynx.
The larynx is the upper end of the windpipe, at the base of the tongue.
The front of the larynx, the "Adam's apple" is usually prominent in males.
A trap door of cartilage, the epiglottis, automatically drops down over the larynx when swallowing, so no food can pass down the windpipe.
When the vocal folds, are stretched by the contraction of muscles in the throat, a narrow slit forms between them.
When air is forced through this narrow slit that the vocal folds are forced to vibrate, causing air to vibrate in the windpipe, lungs, mouth and nasal cavities.
The vocal folds in the throat act as a double reed and are set in motion by air exhaled from the lungs.
The quality and tone of the sound depends on the size and shape of the resonating cavities, e.g. the windpipe, the back of the throat, the mouth and other air filled parts of the head.
For the human voice, the vocal folds in the throat act as a double reed and are set in motion by air exhaled from the lungs.
The quality and tone of the human sound depends on the size and shape of the resonating cavities such as the windpipe, the back of the throat, the mouth and other air filled parts of the head.
Ventriloquists speak in the normal manner, but with some modification of their speech.
They allow their breath to escape slowly, narrow the glottis at the back of the throat, open their mouth as little as possible and retract the tongue while moving only its tip.
The resultant pressure on the vocal folds diffuses the sound so that it appears to come from another source.
The greater the pressure on the vocal folds, the greater the deception.
Ventriloquists use a dummy with moving lips to aid in their deception that the sound they are making is not coming from themselves.
Other animals, including lions, can "throw their voices".
Experiments
1. Feel vibration of the vocal folds (not vocal "cords"), which allow puffs of air to pass and produce sound waves.
Sing or speak loudly while pressing your fingers on your neck near the your larynx or the male "Adam's apple", (laryngeal prominence).
Press your thumb and forefinger against your larynx and make a low pitched sound with your voice.
Feel your own sound vibration.
Place your finger on your throat then speak.
Feel and experience that the throat oscillates when it speaks.
Try to stop pronouncing suddenly during speaking.
The oscillation of the throat will stop suddenly.
2. Make a nasal sound ("ng"), and a non-nasal sound ("ah"), with your mouth open / closed, with your nose sealed with the fingers / not sealed.
The soft palate, velum, is usually in a high position when all of the air and sound goes through the mouth.
However, it can be lowered to connect the nasal pathway to the mouth and lower vocal tract and lowered further to seal the mouth off from the nasal pathway from nose to larynx.
Repeat the experiment while whispering to produce a windy sound.
You cannot feel any vibrations, because the vocal folds have closed and do not vibrate.
Try to sing in a whisper.
3. Sing and whistle octaves into a two metres long pipe and use the resonance to show your whistling range is much higher than your singing range.
4. Sit in a comfortable space, breathe deeply, sing a low note and listen to it.
While holding the low note, slowly change the shape of your mouth.
Hear different vowel sounds.
Keep listening and hear other notes, overtones.
You are now an oscillator.
Your vocal cords producing the main note and the mouth shape filter emphasizes particular overtones.
9.5.8 Respiration, small animals
and plants
See diagram 9.155: Respiration of soaked peas.
See diagram 9.3.61: Respiration of grasshopper.
1. Attach a 50 cm3 syringe to a 1 cm3 pipette, as
in the diagram.
The sodium hydroxide solution absorbs carbon dioxide released during respiration.
Change in air pressure inside the syringe is caused by the consumption
of oxygen by the organism and is shown by change of the
water level in the pipette.
The rise in the water level per unit time indicates the rate of respiration
of the organism.
A steady drop of the liquid level in the pipette indicates a leak in the
apparatus.
When testing green plants, cover the syringe with aluminium foil to exclude
light.
When the meniscus reaches the upper part of the pipette, move it down again
by adjusting the position of the plunger.
To correct for changes in air volume inside the syringe, because of change
in room temperature during the experiment, use a control
identical to the experiment, but without the organism.
Then any difference between the readings of the two sets of apparatus
is because of respiration of the organism.
2. Put a grasshopper in a closed jar containing
absorbent paper soaked in 0.5% potassium hydroxide solution.
Use a two-holes stopper with a fine bore glass tube and graph paper or
ruler behind it to measure the movement of a drop of
coloured water through the tube.
Keep the organism off the absorbent paper by adding crumpled paper or tying
the moist paper on a string attached to a drawing
pin stuck in the underside of the stopper.
The grasshopper breathes in oxygen and breathes out carbon dioxide absorbed
by the potassium hydroxide solution causing
the coloured drop to move.
Record the movement of the coloured drop at regular intervals.
Observe the distribution and movement of spiracles on the grasshopper.
9.6.2 Sense of touch, somatic sensory system
Meissner corpuscles are just below the epidermis of the skin and are sensitive to any light touch.
They occur mainly in the face, fingertips, genitals, lips, palms of hands, soles of feet, and tongue.
Merkel nerve endings are in superficial skin layers and fingertip ridges and are sensitive to pressure.
Pacinian corpuscles are deep in the skin, in mesenteries (membranes connecting the small intestine to the posterior wall of the abdomen),
and around joints and detect vibration and big pressure changes.
These mechanoreceptors are not uniformly distributed in the skin, so some parts of the body are more sensitive to touch than others.
When the skin is touched in two separate points within a single receptive field, the student cannot feel the two separate points.
If the two points touched span more than a single receptive field then both will be felt.
The closer the receptive fields, the greater the resolution of touch.
So mechanoreceptors are more dense in the fingertips and less dense in the palms of the hands.
The sense of touch is used by blind people reading the Braille alphabet, people feeling coins and banknotes that have raised letters to help their identification and wool-classers that rate the fineness of wool
by feel.
Experiments
See diagram 9.243: Touch with dividers
1. Investigate the sensitivity to touch of different parts of the body.
Tie a blindfold over the eyes and touch objects with the fingers, e.g. table top, coins, cup, pins, clothing.
Describe the feelings.
Repeat the experiment by touching the same objects with the back of the hand.
Describe the feelings and whether they are the same as before.
2. Tie a blindfold over the eyes and ask another student to touch gently different parts of the back of the hand with a touching bristle.
Note when and where you feel the touching bristle.
Repeat the experiment on the end of a finger and on the bare forearm.
Do not test on other parts of the body.
3. Use a paper clip opened to be V-shaped or a hairpin or two thick hairs.
Start with the points 40 mm apart.
Tie a blindfold over the eyes and ask another student to touch gently different parts of the back of the hand with only one point or with both points.
Point to where the body was touched and say whether it was one point or two points.
Repeat the experiment by reducing the distance between the points.
Note the distance between the points when a touch with both points feels like a touch with only one point.
When the points touch close together, they feel like one point.
Repeat the experiment on the end of a finger and on the bare forearm.
Different parts of the body have different sensitivity, but do not test on other parts of the body.
This experiment was originally done with the points of geometrical dividers or even two pins, but these objects may be too dangerous for school children to use in this experiment.
4. Make a sensitivity test stick by attaching one toothpick to a flat stick, e.g. craft stick, ice cream stick, popsicle stick, "Paddle Pop" stick.
Make five more sensitivity test sticks by attaching two toothpicks to a flat stick, 1 cm apart, 2 cm apart, 3 cm apart, 5 cm apart.
Press the toothpick points of the sensitivity sticks against the upper arm of a blindfolded student.
Ask the students to report on how many points are felt.
Test other parts of the body, e.g. fingertips, side of the face, legs, back, to find the most sensitive part of the body.
9.6.4 Feel two noses, tactile illusion
Cross the middle finger over the index finger.
Close your eyes.
Move the tips of these fingers along your nose with one finger each side of the nose.
When your fingers reach the tip of your nose your fingers feel further apart and you get the illusion (Aristotle's illusion) that you have two noses, because your brain assumes that your finger tips are in the usual position.
You can get the same illusion by holding a marble, pencil, or another person's finger, (dead man's finger). between the crossed fingertips.
9.6.1 Sense of feeling temperature
See diagram 9.244: Feeling temperature
1. Fill three containers with water at 10oC,
20oC and 30oC.
Test the temperatures with the end of the elbow to check that the hot water is not too hot.
Put the containers in one line on the table.
Dip a finger of the left hand in the water at 10oC.
Dip a finger of the right hand in the water at 30oC.
After two minutes, take both fingers out of water and dip them simultaneously in the middle container at 20oC.
The water feels arm to the finger that has been in the cold water, but cool to the finger that has been in the hot water.
You do not have an absolute sense of temperature.
2. Use three containers of water, ice water, room temperature water and hot water.
Test the temperatures with the end of the elbow to check that the hot water is not too hot.
Hold one hand in the ice water and the other hand in the hot water for 20 seconds then quickly put both hands in the water at room temperature.
The hand from the ice water feels warmer and the hand from the hot water feels cooler.
9.5.1 Sense of smell, the olfactory system
The olfactory neuroepithelium is at the upper area of each nasal chamber.
As humans age, the number of olfactory neurones steadily decreases.
The sense of smell is caused by stimulation of the olfactory receptor cells by volatile chemicals carried as airborne molecules.
An odour's stimulating effectiveness depends on the duration, volume, and velocity of a sniff.
Each olfactory receptor cell is a sensory neurone.
The average nasal cavity contains more than 100 million sensory neurones generated throughout life by the underlying base cells.
So new receptor cells are generated every 30-60 days.
Humans have many hundreds of different olfactory receptors, but each neurone expresses only one receptor type, part of an olfactory "map".
An odour activates a set of odour receptors depending on its chemical composition.
The vomeronasal organ (VNO) (Jacobson organ) is a membranous structure within pits of the anterior nasal septum.
Its opening 2 cm from the nostril is visible in nearly all adult humans.
It detects the external chemical signals called pheromones, but these signals are not detected as perceptible smells by the olfactory system.
Pheromones send messages to all individuals in the species to mediate behaviour, e.g. alarm, food trail for ants, sex responses and possibly synchronization of menstrual cycles among women living together.
Experiments
See diagram 1.13: Smelling a gas.
Do not inhale gases directly from a test-tube!
Fan the gas towards the nose with the hand and sniff cautiously.
If you detect no odour, move closer and try again.
1. Pour 1 cm of methylated spirit into a small beaker.
Hold the beaker under the nose and note the smell while breathing:
* without inhaling,
* inhaling steadily,
* inhaling with jerky sniffs.
Repeat the experiments with different foodstuffs.
2. Repeat the experiment with one nostril closed.
Note whether both nostrils give the same smell sensation.
3. Test the ability to detect the smell of baby powder, chocolate, cinnamon, coffee, mothballs, peanut butter, soap, banana, petrol (gasoline) lemon, onion, paint thinner, pineapple, rose, and turpentine.
4. Collect different substances that have different kinds of smell.
Be careful! Do not let students smell volatile liquids, e.g. petrol, methylated spirit, alcohol, pesticides, correcting fluid and dry cleaning fluid.
A description of smells may include the following: "fruity" from ripe fruit, "fragrant" from flowers and perfume, "onion" from onion or garlic, sulfur from sulfur or volcanic gases, "burning" from burning meat or coffee or tobacco, "burning feathers' from feathers or silk or wool or rubber or hair, "sweaty", from sweat, old cheese, and goats, "foul" from rotten meat, rotten vegetables and faeces.
Repeat the experiment with the students blindfolded.
5. Check some folklore about smell and taste
* If you take too much mustard, you must smell fresh bread.
* If you hold your breath while eating mint, you cannot taste it.
9.5.2 Sense of taste, the gustatory system
Flavour is a mixture of taste, smell and feel of the food in the mouth.
Taste perception occurs in individual taste buds with multiple receptor cells in each bud.
Taste buds are modified epithelial cells, with a life span of about 10 days and arise continuously from the underlying base cell layer.
If you burn your tongue, new taste buds can later replace any damaged taste buds.
Taste buds occupy projections embedded in the tongue epithelium called lingual papillae.
A single nerve fibre innervates multiple taste papillae.
A single nerve fibre can respond to different types of tastes, called
"broad tuning".
Lingual papillae have 4 forms, each in different areas of the tongue.
Taste buds also occur in the soft palate, epiglottis and larynx, and the pharynx.
9.5.3 The five different taste qualities
1. salty, 2. sweet, 3. sour, 4. bitter, and 5. umami (savoury taste of monosodium glutamate).
Another proposed taste quality is chalky (calcium salts).
There are no "taste areas" on the tongue.
The five taste qualities can be detected in all regions of the tongue, but certain areas of the tongue have lower thresholds for each quality.
Sweetness is most readily detected at the tip of the tongue.
Salty taste receptors focus on the front and side borders of the tongue.
Sour tastes are best perceived along the lateral border, and bitter sensations are tasted most in the posterior one third.
Salt taste is caused by sodium ions and sour taste is cause by hydrogen ions in solution.
Sweet taste, bitter taste and umami taste is caused by reactions with proteins on the surface of the taste buds.
You can experience all the qualities of taste in all regions of the tongue where taste buds occur.
Some people experience differences in sensitivity and people may vary in the number of taste buds in different regions of the tongue.
Some people in Africa who an eat very hot chillies are supposed to have a low density of taste buds on the tongue.
However, there are NO "taste areas" on the tongue.
Salt taste is caused by sodium ions and sour taste is cause by hydrogen ions in solution.
Sweet taste, bitter taste and umami taste is caused by reactions with proteins on the surface of the taste buds.
Experiments
Never taste a chemical or any substance in the laboratory!
1. Crush different fruits and vegetables into a pulp using a food chopping mill.
Tie a blindfold over the eyes, taste the different foods and record the tastes in order of tasting.
Repeat the experiment while holding your nose and breathing only through the mouth.
Taste the different foods and record the tastes in the same order of tasting.
If the nose is held tight, no air can move through the nasal space and you cannot smell anything.
You may notice that foods tastes the same when you have a cold.
2. Crush different fruits and vegetables into a pulp using a food chopping mill.
Tie a blindfold over the eyes, taste the different foods and record the tastes in order of tasting.
Repeat the experiment while holding your nose and breathing only through the mouth.
Taste the different foods and record the tastes in the same order of tasting.
If the nose is held tight, no air can move through the nasal space and you cannot smell anything.
You may notice that different foods taste the same when you have a cold.
Flavour is a mixture of taste, smell and feel of the food in the mouth.
3. Report on the taste sensations of your tongue.
Dry the surface of the tongue with a clean handkerchief, stretch it out as far as possible and look at the tongue with a mirror to note the many taste buds.
Describe the taste sensation after you place on different parts of the tongue a drop of the following:
* Dilute solution of sucrose, saccharin or aspartame for sweet taste.
* Dilute vinegar solution for sour taste.
* Dilute table salt solution for salt taste.
* Dilute quinine solution (tonic water) or raw almond for bitter taste.
* Dilute solution of the amino acid monosodium glutamate, MSG, for "umami" taste.
* Experience all the qualities of taste in all regions of the tongue where taste buds occur.
Some people experience differences in sensitivity and people may vary in the number of taste buds in different regions of the tongue.
4. Put a drop of boiled starch solution on your tongue and let it mix with the saliva.
Leave it there until you can notice a slight change in taste.
The saliva contains an enzyme ptyalin that changes starch to maltose sugar.
It causes the sweet taste.
Repeat the experiment with a piece of raw meat and a piece of pure fat.
You do not notice any change of taste, because ptyalin does not act on protein or fat.
9.247 Direction of sound heard
All students form a large circle.
One student stands in the middle of the circle with a blindfold tied overthe eyes.
Each student in the circle claps once, one at a time, in any order.
After each clap, the blindfolded student turns in that direction with one arm extended.
Record the number of successful turns and their direction relative to the direction at the time of the clap.
Repeat the experiment with the right ear of the blindfolded student blocked with cotton wool and with the right index finger pressed into that ear.
Repeat the experiment with the student's left ear blocked with cotton wool and the left index finger pressed into that ear.
Record the number of successful turns and their direction relative to the direction at the time of the clap.
Examine the records and describe the necessary conditions to tell the direction of sound correctly.
9.3.2 Human ear, how the ear works, model of the ear
See diagram 9.235: Human ear, VS
The ear drum is a very thin membrane is moved by sound energy of the sound.
If the ear drum does not vibrate, you do not hear sound.
If the longitudinal wave has the right frequency and enough energy, your ear drum antennas will pick it up and your brain will turn the energy into what we call sound.
Air vibrations enter the ear by the auditory passage formed at the base of the ear by the eardrum membrane.
They set the eardrum in motion and, in doing so, set in motion the system of three little bones attached to it.
By this means they reach a cavity in the bone called the inner ear.
One part of the ear is shaped like a snail shell.
Here is found the organ that receives the sound vibrations and is connected with the brain by the auditory nerve.
Another part of the inner ear includes three small semicircular canals and serves to maintain equilibrium.
It plays no part in hearing.
Sound vibrations are normally transmitted to the snail shell shaped cochlea by the eardrum and the small bones.
This causes a nerve message carried to the brain.
They can also be transmitted by the bones of the skull, and you hear a sound if the waves reach the cochlea by either route.
When a sound reaches your two ears, you can distinguish the direction from which it comes.
If it comes from straight ahead, the vibrations reach both ears simultaneously and with the same strength.
However, if the source of the sound is on one side of us, one of your ears is further away from it and receives the waves less strongly and with a slight delay.
The pinnae collect the sound and contributes to your sense of direction.
Sound is transmitted from the auditory canal via the eardrum into the middle ear.
In the middle ear small bones act as an impedance matching mechanism.
This maximizes the amount of signal that is passed on to the brain.
The bones also magnify the vibrations of the eardrum.
The message is then passed into the cochlea and on to the nerve that takes the message to the brain.
The auditory canal is a tube of air that can vibrate and is closed at one end by the eardrum.
Experiments
1. Binaural hearing
Hold the ends of a long tube to each ear and have someone tap in the centre and then a few centimetres to each side.
2. Direction of sound, direction judgment of the ear
To identify the direction and position of sound cover your eyes with a piece of black cloth.
Other students emit sounds at different positions at a classroom, e.g. shake a string of keys, rub a piece of paper.
Describe each sound source and its direction and position.
Repeat the experiment with various sound sources emitting the sounds at the same time.
Human hearing can not only identify the directions and positions of a sound sources, but also tell their characters.
High frequency location depends on difference in intensity produced by the shadow of the head.
Location of low pitched sounds depends on phase difference.
Use a model stethoscope with one tube longer than the other.
3. Range of hearing
The range of human hearing is from about 20 vibrations per second to about 20, 000 vibrations per second, nearly 10 octaves.
Use an oscillator driving an audio system to show the range of hearing.
Use a set of good speakers.
Use whistles, tuning forks to establish upper range of hearing.
The Galton whistle can be adjusted to produce an intense sound into the ultrasonic range.
9.4.1.0 Eye, structure and physiology
See diagram 9.245: Human eye.
Blind spot, binocular vision, defects, spectacles and contact lenses, persistence of vision
9.4.1 Astigmatism
Astigmatism is cased by irregular curvature of the cornea resulting in bluured vision.
It can be cured by glasses or eye surgery.
Observe the radial black lines in the chart below.
If the lines appear blurred, then astigmatism is a likely diagnosis.
See Astigmatism chart
9.4.2 Blind spot
The blind spot, scotoma, is an area about the side of a pin head where the optic nerve passes through the retina.
In this small are of the retina, there are no photoreceptors so it is called a blind spot.
In the left eye, the blind spot is about 15 to the left of looking straight ahead, i.e. about two hand widths at the ends of extended arms.
In the right eye, the blind spot is about 15 to the right of looking straight ahead, i.e, about two hand widths at the ends of extended arms.
Experiment
1. Find the blind spot.
On a piece of paper, make a small dot with a black marker.
About 15 cm to the right of the dot, make a small plus sign (+)
.
With your right eye closed, hold the paper about 50 cm away from you.
Focus on the plus sign with your left eye, and slowly bring the paper closer while still looking at the plus sign.
Notice when the dot vanishes from your sight.
This is the blind spot of your retina.
If you close your left eye and look at the dot with your right eye, and repeat the process, the plus sign should disappear in the blind spot of your other eye.
2. Some people think they do not see cars approaching from behind in the parallel lane because the image of the car falls in the blind spot.
If this is true, the side-view mirrors give a different angle to view the approaching car, so you an see it because there is no blind spot.
9.4.3 Chromatic aberration of the eye
Chromatic aberration occurs when different wave lengths of light have different focal lengths.
So different wavelengths of light are refracted at a different angle.
The duochrome chart has black letters on a red background and a green background.
The red and green wavelengths in the chart are equally distant from the yellow wavelength (570 nm).
The longer wavelength (red) is refracted less than the shorter (green).
The eye focuses at about the midpoint of the spectrum, at yellow wavelength, between the red and green wavelengths.
During a test, the patient must not prefer red because red is a favourite colour!
An optician can use spherical correction glasses so that the red and green letters appear equally sharp to the patient.
See Duochrome chart
9.4.4 Colour blindness
Colour blindness, eye test book, (Commercial).
Use standard colour blindness slides or charts to test for colour blindness.
9.4.5 Distance of object seen
The eye can distinguish separate lights if they subtend an angle of at least one minute of arc.
So two lamps one metre apart can be seen as separate light sources at a distance of about two kilometres.
Experiments
1. Hold a pencil in each hand horizontally in front of the face with the points of the pencils 50 cm apart.
Move the pencils towards each other so that the points touch.
Repeat the experiment with the right eye closed.
Repeat the experiment with the left eye closed.
Describe the necessary conditions to tell correctly the distance of objects.
2. Look outside the classroom at something far away.
Hold up one finger 20 cm in front of the eyes, but keep looking at the distant object.
Note whether you can see the distant object clearly.
Note whether you can, at the same time, see the finger clearly.
Note whether you feel any movement in your eyes.
Keep looking at the finger and note whether the distant object is clear.
3. Hold a printed page at arms length.
Bring the book closer and closer until it is too close to read the letters.
Measure the distance from the book to the eyes.
Move the book away from the eyes until it is too far to read the letters.
Again, measure the distance from the book to the eyes.
4. Work in pairs.
One student in a pair puts a hand over one eye.
The other student holds up one finger about 40 cm in front of the partner's eyes.
The student with one eye covered has to place the tip of one finger on top of the finger that the partner is holding up.
Repeat the experiment with both eyes open.
9.4.6 Eyeglasses
Project an image of concentric circles crossed by radial lines.
Place a lens and then a correcting lens over the projection lens.
9.4.7 Examine your eyes
See diagram 9.245: Human eye.
If sheep eyes are used for dissection, soak them lens down in 1.0% sodium chloride solution before freezing, to avoid lens clouding.
Experiments
1. Work in pairs.
Look at the partner's eyes and identify each part seen.
Wrinkles at the outer corners called crow's feet.
2. Clap your hands in front of the partner's face.
The partner blinks.
3. Tell your partner to watch your finger as you move it towards the nose.
The partner blinks.
Repeat the experiment by staring into your partner's eyes and trying not to blink.
The first student to blink loses the game.
4. Tell your partner to walk slowly around you in a big circle.
Follow the partner with your eyes, but do not move your head or body.
See how long you can keep your partner in sight.
Put your hand up when you can no longer see your partner.
5. By moving your eyes only and not your head, note how far you can move your hand up and down in front of your face and keep it in sight.
6. Face your partner with both kneeling on the floor.
Put a stone between you on the floor.
Cover your right eye with one hand.
Test who can pick up the stone first.
9.4.8 Eyesight test
See diagram: 9.245: Eye test.
The standard term for normal vision is "20/20 vision", meaning able to see at 20 feet what a person with "normal" vision sees.
So it is may be called "6/6" vison, substituting 6 metres for 20 feet.
A person with vision rated as "20/10" has very good vision.
To check for 20/20 vision, a standard eye chart, the Snellen chart, is used, which has letters with each row getting smaller down the chart.
This lesson is designed to give children experience in measuring eyesight and comparing the eyesight of different children.
It is different from the Snellen chart.
Use the "E" chart in the diagram.
Cut out a big "E" from a piece of cardboard or tell the children to cut out the big "E" during the lesson or the children can make an "E" shape with their fingers.
1. Draw a line on the floor five metres from the teacher's chair and parallel to the front of the teacher's desk.
Stand on the line facing you.
Show the chart.
Point to the top E.
The child has to hold the E in the same position or make the same E shape with the hand.
2. What is the lowest line in the chart where the child can see the positions of the E?
If you can see the bottom line, move one metre away and start again.
If you cannot see the bottom line, move one metre closer.
3. Test all the children again.
Which child has the best eyesight?
4. Do the test again with one eye closed, then
test the other eye.
Is one eye stronger than the other?
5. Draw a chart of white E's on a black background.
Are they easier to see or harder to see than the black E's?
9.4.9 Fluorescence of retina
Shine an UV source with a visible filter towards the class and notice the luminous haze that covers the field of view.
9.4.10 Inversion of image on the retina
A small tube has three holes in a triangular pattern drilled in one end and a single hole in the other.
Hold the triangular end near the eye and the pattern appears inverted.
9.4.11 Jarring the eye
Oscilloscope (Commercial).
Stamp your foot while watching a free running oscilloscope.
9.4.12 Mach disc
A spinning disc appears to have light and dark rings where it should be uniform.
9.4.13 Resolving power of the eye
1. The diagram below shows vertical lines and grey colour chart.
From this distance L, you can calculate the angular resolution of your eyes:
angular resolution = (2 mm)/L (in radians).
Using the above equation, L = 4 m corresponds to an angular resolution of 0.03 degrees.
The diffraction limit of the eye can be calculated using Rayleigh's criterion:
angular resolution = (1.22)(lambda)/D,
where lambda is the wavelength of light (on the average, about 550 nm) and D is the diameter of the eye's pupil, which is about 5 mm indoors.
This calculation results in an angular resolution of 0.008 degrees.
If your eyes could resolve images at the diffraction limit, you could resolve the lines in the printed pattern.
The latter is the value used in the international definition of visual acuity = 1/gap size [arc min]
The limit of resolving two filaments of an auto headlamp is about 10 m.
See Vertical lines and grey colour chart
.
9.4.14 Retinal fatigue colour
A red light placed behind a rotating with a slot at the border of half black and half white appears different colours depending on the direction of rotation.
A disc with a notch half black half white is spun in front of a red lamp.
The lamp appears green or red depending on the direction that the disc spins.
A black and white patterned disc appears coloured when rotated.
9.4.15 Subjectivity of colours
A red spot projected on the wall looks orange or brown if it is surrounded by white or black.
9.4.16 Water flask model of the eye
1. A large flask filled with water, fluorescein and with external lenses make a model of the eye in near-sighted and far-sighted conditions.
A spherical lens filled with milky water represents the eyeball.
Use a large lens in front of the sphere to show inverted image, near sighted and far sighted.
2. Direct a parallel beam of light from a slide projector onto a large flask containing fluorescence.
The fluorescence makes the beam visible.
Use a 20 cm focal length lens attached to the flask to show normal sight.
Use other lenses to show long and short sighted conditions and their correction.
9.4.17 After imagezzz
See: Afterimage diagram
The retina at the back of the eye contains millions of photoreceptor cells that detect light and colour, and pass on signals to the brain through the optic nerver fibres..
Cconical-shaped cone photoreceptors, are for bright light vision and have three types for red, green and blue light.
All three cones together give trhe appearance of white light.
Rod photoreceptors are for night vision.
Starring at a pure colour for a long time causes cone cell fatigue, - those cone cells need a rest.
If you look at a white area after staring at a red image, you will see a different coloured after image.
Experiment
Cover one eye.
Look at the round red colour to the left in the diagram for 30 seconds.
Cover the red colour with white paper and stare at the white area to the right.
Can you see the blue-green afterimage?
Test the other eye.
Can you see the blue-green afterimage?
Were the after images the same?
9.6.5 Women feel colder then men.
Women feel the cold more than men, but their bodies are better at conserving heat when the weather turns colder.
Women are usually smaller so they have a higher surface area to volume ratio than men and thus shed heat faster.
Heat generation is proportional to volume (radius3), but heat dissipation is proportional to skin surface area (radius2).
The smaller your size, the lower your heat generation to heat dissipation ratio, and the colder you are.
So a woman with a higher surface area to volume ratio than a man, will lose heat more quickly and feel colder.
Women usually have a slightly lower metabolic rate, because of their typically smaller size, so they generate less heat.
Men have more heat-generating muscle mass.
The more muscle, the more blood flow and warmth.
Women have a higher percentage of body fat, but that does not insulate them.
Women usually have less insulating fat on the upper body and around the waist, but more padding on hips and thighs.
Men may have extra fat around the waist and upper torso, where it may help insulate vital organs and prevent the core temperature from decreasing.
Women have less vigorous blood circulation to arms and legs, so their hands and feet are often the first to feel the cold.
Cellulite
Deposits of fat that push against the connective tissue mainly in the thighs and nearby regions to form a dimpled surface, commonly called cellulite.
It occurs mainly in older women and is difficult to remove without persistent dieting.
Cellulite is indicated by pinched skin of the upper thigh that appears lumpy.
Women can shut off the blood flow to the skin and extremities to maintain their core temperature at 37oC.
Most of the temperature sensors are in the skin so we feel cold if the extremities are cold no matter the temperature of the internal organs.
The average woman has 20 to 25% body fat, but the average man has about 15% body fat.
A woman has a more even distribution of body fat, so a man will tend not experience such a change in temperature.
So women feel cold before men do.
The hands and feet of women are colder.
For example one report states that the hand temperature of women are about 2.9oC lower, but their core body temperature is about 0.4oC higher.
Women have less muscle mass than men so they need a more efficient technique to protect their core body temperature.
Also, the core body temperature of women changes during the menstrual cycle.
People who feel cold all the time could be suffering from hypothyroidism, or diabetes, or anaemia.