This Journal Belongs to: _________________
The NERVOUS SYSTEM & SENSES
ANATOMY & PHYSIOLOGY JOURNAL
Types of Neurons
The Synapse
Structure of Neurons
Nerve Impulses
“All Or Nothing” Law
Resting Neuron
Movement of the Impulse
Neural Impulse Terms
The Brain
Structure of the Brain
The Spinal Cord
The Eye and Vision
Functions of the Brain
The Reflex Action
The Ear: Hearing and Balance
Chemical Senses (Nose & Tongue): Smell and Taste
1
THE NERVOUS SYSTEM
The nervous system is the master coordinating system of the body. Every thought, action, and sensation
reflects its activity. The structures of the nervous system are described in terms of two principle divisionsthe central nervous system (CNS) and the peripheral nervous system (PNS). The CNS (brain & spinal cord)
interprets incoming sensory information and issues instructions based on past experience. The PNS (cranial
and spinal nerves & ganglia) provides the communication lines between the CNS and the body’s muscles, glands,
and sensory receptors. The nervous system is also divided functionally in terms of motor activities into the
somatic and autonomic divisions. These divisions are important, however, one must recognize that these
classifications are made for the sake of convenience and that the nervous system acts in an integrated manner
both structurally and functionally. Overall, it is imperative that one understands that every body system is
controlled, at least in part, by the nervous system.
1.
List the three major functions of the nervous system.
a. ______________________________________________________________________
______________________________________________________________________
b. ______________________________________________________________________
______________________________________________________________________
c. ______________________________________________________________________
______________________________________________________________________
2.
Choose the key responses that best correspond to the descriptions provided in the following statements.
Insert the appropriate letter in the blank.
Key Choices:
3.
A. Autonomic Nervous System
C. Peripheral Nervous System
______ 1. NS subdivision that is composed of the brain and spinal cord.
______ 2. Subdivision of the PNS that controls voluntary activities such as activation of
the skeletal muscles.
______ 3. NS subdivision that is composed of cranial nerves and spinal nerves and ganglia.
______ 4. Subdivision of the PNS that regulates the activity of the heart and smooth
muscle, and of glands; it is also called the involuntary nervous system
______ 5. A major subdivision of the NS that interprets incoming information and issues
orders.
______ 6. A major subdivision of the NS that serves as communication lines, linking all parts
of the body to the CNS.
Nervous Tissue is made up of neurons and neuroglia both specialized cells. Indicate which type of cell is
identified by the following descriptions. Insert the appropriate letter in the answer blank.
Key Choices:
4.
B. Central Nervous System
D. Somatic Nervous System
A. Neurons
B. Neuroglia
______ 1. Support, insulate, and protect cells.
______ 2. Demonstrate irritability and conductivity, and thus transmit electrical messages
from one area of the body to another area.
______ 3. Release neurotransmitters.
______ 4. Are able to divide; therefore responsible for most brain neoplasms (an abnormal
new growth of tissue)
Relative to neuron anatomy, match the anatomical terms given in Column B with the appropriate
descriptions of functions provided in Column A. Place the correct term on the line.
Column A
Column B
______ 1. Releases neurotransmitters
A. Axon
______2. Conducts electrical currents towards cell body
B. Axon terminal
______3. Increases the speed of impulse transmission
C. Dendrite
______4. Location of the nucleus
D. Myelin sheath
______5. Generally conducts impulses away from the cell body
E. Cell Body
2
5.
Label the motor neuron and trace the impulse.
6.
Classify the neurons below:
_____________________
7.
__________________
____________________
Read the passage and fill-in the blanks. Hint: All answers can be found in the reading
Human beings respond to their environment in pretty similar way as other animals. Human _______________controls these responses with the outer world. Human nervous system is a complex
system comprising of millions of neurons. The function of these neurons can be classified into two major types, firstly bringing the stimuli from the peripheral organ to the central nervous
system and second carrying the responses from the central nervous system to the peripheral organs. Afferent and efferent neurons are the two types of nerve fibers which perform these
functions. Let us understand in detail the comparison between afferent vs. efferent neurons.
Difference Between Afferent and Efferent Neurons
Before we proceed to the comparison between afferent vs. efferent neurons it is imperative that we gain some insight upon the processing of impulses by the nervous system. Nervous system
comprises of a closed loop of neurons which deal which sensation, decision and reaction. Whenever an impulse or stimuli is received by a receptor organ, it is carried to the brain for processing.
A decision is made regarding the impulse which is again carried back to the receptor organ. Depending upon this decision a reaction to the impulse is produced by the receptor organ. Three
types of neurons take part in this entire cycle, namely afferent, interneurons and efferent neurons. Afferent neurons are concerned with carrying the impulse from the receptor organ towards
the ________________ whereas efferent neurons carry the response of the brain back to the _________________. Both these neurons communicate with each other through the medium
of ______________________________.
Afferent neurons are also called as _________________________ neurons as they mostly carry impulses from sensory organs. Afferent neurons are classified as pseudounipolar neurons
with a single long dendrite and a short axon. The axon extends in both directions, with peripheral axon directing towards the receptor organ, whereas central axon passing into the spinal cord.
Although, dendrites are structurally and functionally identically to axons, they are myelinated. The cell body in afferent neurons is perfectly rounded and smooth. The aggregation of afferent
neurons can be found in a swelling called dorsal root ganglion, which is located just outside the spinal cord.
Efferent neurons are also called as _______________________________as they mostly carry responses to the muscles or glands and bring about movement. Efferent neurons are bipolar
with dendrite on one end and axon on the other. The cell body is connected at one end to a single long axon while several dendrites form the other end of the cell body. The cell body in
efferent neurons is satellite shaped. The impulse enters the cell body via several dendrites and then leaves it through the single axon at the other end. The efferent neurons are present in the
gray matter of spinal cord as well as medulla oblongata. The efferent neuron forms an electrochemical pathway towards the effector organ.
Afferent neurons are connected to efferent neurons via multipolar neurons called ___________________. Interneurons are also called as relay neuron, association neuron or local circuit
neuron. Similar to efferent neurons, the cell bodies of interneurons are located inside the central nervous system. Interneurons vary greatly in structure and function. Hence, it is impossible to
predict the types of interneurons present in the central nervous system. It is estimated that human brain contains about 100 billion interneurons with an average of 1000 synapses, on each
interneuron.
The most important point of comparison between afferent vs efferent neurons is that they perform an exactly opposite function and follow an opposite electrochemical pathway in the
central nervous system loop.
Flow Chart that Depicts Afferent Vs. Efferent Responses
3
Introduction to the Nervous System Lab:
Reaction Time of An Impulse
PROBLEM: What can change reaction time?
Introduction: The human nervous system is composed of the brain and spinal cord (Central Nervous System,
CNS) and the nerves which branch out from the CNS, the Peripheral Nervous System (PNS). Sensory neurons
of the PNS carry information to the CNS. Signals from the brain are carried to motor neurons (PNS), which
carry out responses by muscles. In this lab, you will be comparing the rate at which sensory neurons, working
through the brain, can elicit responses via motor neurons. Basically, you will test reaction time. Reaction time
is how long it takes for a message to travel along your nerve pathways.
Materials: Metric ruler
Calculator
Procedure:
1) Have a partner hold a metric ruler at the end with the highest number. Note: Both partners should do the
test.
2) Place the thumb and first finger of your left hand close to, but not touching, the end with the lowest
number.
3) When your partner drops the ruler, try to catch it between your thumb and finger.
5) Record where the top of your thumb is when you catch the ruler. Make your measurements to the nearest
0.5cm. Put this number in your data table as trial 1. At any time if you do not catch the ruler in time,
record this as 35 cm.
6) Repeat steps 2 to 5 three more times.
7) State if you think the ruler will fall farther if you catch it with your right hand.
8) Repeat steps 2 to 5 four times using your right hand to catch the ruler.
9) Switch roles and drop the ruler for your partner.
10) Calculate: To complete your data table, calculate the time in seconds needed for the ruler to fall. Do the
following for each trial:
Steps for Calculation:
1) Multiply the distance in cm by 2. 2) Divide the result in step 1 by 1000. 3) Calculate the square
root of the result in step 2. Round all answers to 2 decimal places.
11) Find the average for each column.
12) Answer all discussion questions
Trial
Left Hand
Distance Ruler Falls
Time in Seconds
(cm)
Right Hand
Distance Ruler Falls
Time in Seconds
(cm)
1
2
3
4
Total
Average
4
Discussion Questions:
1) Which hand is your writing hand?
_______________________________________________________________________
2) Did you catch the ruler faster with your left hand or right hand? Why might this be so?
__________________________________________________________________________
__________________________________________________________________________
3) Why did you run several trials for each hand?
__________________________________________________________________________
__________________________________________________________________________
4) Explain why a message moving along nerve pathways takes time.
__________________________________________________________________________
__________________________________________________________________________
5) How might the results change if you did this experiment with a person of 70 years old? Why might this be
so?
__________________________________________________________________________
__________________________________________________________________________
6) How might the results change if you did this experiment with a professional athlete? Why might this be so?
__________________________________________________________________________
__________________________________________________________________________
7) What is the definition of reaction time?
__________________________________________________________________________
__________________________________________________________________________
5
“Lights, Camera, Action Potential”
Directions: Go to the following website http://faculty.washington.edu/chudler/ap.html.Read “Lights,
Camera, Action Potential and then answer the questions below.
1.
Describe the characteristics of a resting membrane. 2 points
_______________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
2. Define the terms threshold potential, action potential, nerve impulse, and re-polarization. 3
points
_______________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
3. Analyze the illustration below. For each step, describe the events involved in the propagation of
an action potential in a neuron. 5 points
A.______________________________
________________________________
________________________________
B.______________________________
________________________________
________________________________
C.______________________________
________________________________
________________________________
D.______________________________
________________________________
________________________________
E.______________________________
________________________________
________________________________
4. Define the terms synapse and neurotransmitter (NT), and discuss the steps involved in the
synaptic transmission of a nerve impulse from one neuron to another. 5 points
6
Steps:
5. Color and label the picture below. Make sure you identify the neurotransmitter, pre-synaptic
terminal, post-synaptic terminal
The Synapse
6.
Circle the term that does not belong in each of the following groupings.
a. Neurotransmitter Synapse Axon
b. K+ enters cell K+ leaves cell
Repolarization
c. Nodes of Raniver Myelin sheath Unmyelinated
d. Inside cell
High Na+
Low Na+
7
Message Transmission
Messages can travel in neurons at speeds up to 268 miles/hr! These signals are transmitted from neuron (nerve
cell) to neuron across "synapses."
Let's make a chain of neurons...have everyone stand up and form a line. Each person in the line is a neuron. As
shown in the figure on the right, your left hands are the dendrites of a neuron; your body is the cell body; your
right arm is an axon and your right hand is the synaptic terminal. Your right hand should have a small vial of
liquid or some other item, such as a button or pebble, to represent neurotransmitters.
Each person should be about arms length away from the next person. When the leader says "GO," have the
person at the beginning of the line start the signal transmission by placing his or her "neurotransmitter" into
the hand of the adjacent person. Once this message is received, this second neuron places its
neurotransmitter into the dendrite of the next neuron. The third neuron then places its neurotransmitter into
the dendrites of the next neuron and the "signal" travels to the end of the line. The transmission is complete
when the "signal" goes all the way to the end of the line.
Remember that each "neuron" will pass its own transmitter to the next neuron in line. Each neuron HAS ITS
OWN neurotransmitter.
Let's review


What are the parts of a neuron? The hand that receives the neurotransmitter is the
"dendrite." The middle part of your body is the "soma" or "cell body." The arm that passes
the neurotransmitter to the next person is the "axon" and the hand that gives the slap is
the "synaptic terminal". In between the hands of two people is the "synaptic gap". For more
about the parts of a neuron, see cells of the nervous system and the synapse.
Measure how long it takes the message to get from the first neuron to the last. Also,
measure the distance from the first to the last neuron. Now calculate the speed (speed =
distance/time). How fast did the message travel from first to last neuron? Why do you think
the speed of transmission of the model is so slow? Record your answers on the line below.
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
8
Action Potential Game
Objective: Race to raise the resting potential above threshold to fire an action potential.
Background: When neurotransmitters cross a synapse, they can bind with receptors on dendrites. This binding
can result in a change in the electrical potential of a neuron. An excitatory postsynaptic potential occurs with
the neuron becomes depolarized, raising the electrical potential from its baseline of about -70 mV and bringing
it closer to threshold and increasing the chance that an action potential will fire. An inhibitory postsynaptic
potential occurs when the electrical potential is lowered, making it less likely an action potential will be
generated. If the electrical potential is raised so that it reaches the threshold, an action potential will fire
down the axon of a neuron.
How to Play: Players should be divided into two teams: the Excitatory Postsynaptic Potential (EPSP) Team and
the Inhibitory Postsynaptic Potential (IPSP) Team. The teams will race to see who can get the greatest signal
to their team's cell body in 30 seconds. Each team lines up to act like a dendrite. A signal, (a small ball), is
passed from person to person much like how an electrical signal travels down a dendrite toward the cell body.
Each EPSP team signal successfully transferred to the cell body is worth +5 or +10 mV (millivolts); each IPSP
Team signal is worth -5 or -10 mV. The signals are passed down the dendrites until they reach the end and are
tossed into the cell body container. Only one signal ball can be passed at a time meaning that a dendrite must
drop the ball (signal) into the cell body container before the first person in the dendrite can pass the next ball
(signal).
To Win: The typical resting potential of a neuron is -70 mV. To cause an action potential the membrane
potential must reach -55 mV. Therefore at the end of 30 seconds the signals are summed from the cell body
container. The total amount of millivolts is added to -70 mV to see if an action potential is fired. If an action
potential is fired the EPSP team wins! If not then the IPSP team wins!
Materials:


3 large containers or Tupperware
About 32 ping pong balls, labeled with black marker -5, +5, -10, +10 (8 of each). Each ball should also
be labeled with the team name: EPSP or IPSP.
Game Set-up
9
Reflexes
Reflexes are interesting and can be life-saving responses. The following activities will help you understand reflex action.
Partners should switch roles during each activity so each person gets to try it.
1.
Patella Reflex
Sit on a chair with one leg crosses over the other. Have your lab partner gently tap your leg
with a reflex hammer, just below the kneecap. If struck in the correct place, your leg should jerk forward.
Repeat the procedure, but this time try to keep your leg from jerking. Can you stop this reflex? ________
2.
Achilles’ Reflex Kneel on one knee on a chair while standing with your other foot on the floor. Have your lab
partner tap the Achilles tendon just above your heel with a reflex hammer. What happens?
___________________________________________________________________________________
3.
Pupil Reflex
The iris is the colored part of the eye. It controls the amount of light entering the eye through
the pupil. Have your partner close his eyes and also cover them with his hands for thirty seconds. Observe what
happens to the pupils when he opens his eyes. Do the pupils get smaller or larger? _______________
Now, have your partner close and cover his eyes again. This time, however ask him to concentrate very hard on
keeping his pupils from changing size when you signal him to open his eyes. Can he control the size of his pupils?
_______________
How is it that the eye’s response to light is considered a reflex action?
________________________________________________________________________________
4.
Eye Blink Reflex
Sit with your elbows resting on the lab table and your chin in your cupped hands. Have your
partner hold a drinking straw about two inches from one of your eyes and blow gently through the straw. Be
careful not to blow too hard or poke the eye. Did the air make you blink your eye? _________________
5.
Reflex Pathway Reflex pathways are very simple responses to stimuli. Although you are consciously aware of
some of them, they are not normally under conscious control. Spinal reflexes involve a sensory nerve which
receives the stimulus, a motor nerve which controls the muscular response, and the spinal cord, in which the
impulse is transferred from the sensory nerve to the motor. In the box below, illustrate the reflex pathway when
a finger is pricked by a pin. The pin is the stimulus. Use arrows to show the direction of the impulse in the reflex
pathway. Finally, label the sensory nerve, spinal cord, motor nerve, and muscle.
10
Brain Dissection
Sheep brains, although much smaller than human brains, have similar features and can be a valuable addition to
anatomy studies. See for yourself what the cerebrum, cerebellum, spinal cord, gray and white matter and
other parts of the brain look like! Use this as a dissection guide complete enough for a high school lab, or just
look at the labeled images to get an idea of what the brain looks like.
Observation: External Anatomy
A. You'll need a preserved sheep brain for the dissection. Set the brain down so the flatter side, with the white spinal
cord at one end, rests on the dissection pan. Notice that the brain has two halves, or hemispheres. Can you tell the
difference between the cerebrum and the cerebellum? _________Do the ridges (called gyri) and grooves (sulci) in the
tissue look different? ___________
How does the surface feel?
_______________________________________________________________________________
B. Turn the brain over. You'll probably be able to identify the medulla, pons, midbrain, optic chiasm, and olfactory bulbs. Find
the olfactory bulb on each hemisphere. These will be slightly smoother and a different shade than the tissue around them.
The olfactory bulbs control the sense of smell. The nerves to the nose are no longer connected, but you can see nubbly ends
where they were. The nerves to your mouth and lower body are attached to the medulla; the nerves to your eyes are
connected to the optic chiasm. Using a magnifying glass, see if you can find some of the nerve stubs? _________
Observation: Internal
A.
Use the labeled picture to identify the corpus callosum, medulla, pons, midbrain, and pituitary gland. Use your fingers
or a teasing needle to gently probe the parts and see how they are connected to each other. What does that opening
inside the corpus callosum lead to? ____________________
How many different kinds of tissue can you see and feel?
_________________________________________________________________________________________
11
B. Look closely at the inside of the cerebellum. You should see a branching "tree" of lighter tissue surrounded by darker
tissue. The branches are white matter, which is made up of nerve axons. The darker tissue is gray matter, which is a
collection of nerve cell bodies. You can see gray and white matter in the cerebrum, too, if you cut into a portion of it.
C. You can also use the letter labels on the internal anatomy picture to try to find the following:
Ventricles contain cerebrospinal fluid
The occipital lobe receives and interprets visual sensory messages
The temporal lobe is involved in hearing and smell. You can find this by looking on the outside of one of the
hemispheres. You will see a horizontal groove called the lateral fissure. The temporal lobe is the section of the
cerebrum below this line.
The frontal lobe also plays a part in smell, plus dealing with motor function
The parietal lobe handles all the sensory info except for vision, hearing, and smell.
The thalamus is a "relay station" for sensory information. It receives messages from the nerve axons and then
transmits them to the appropriate parts of the brain.
The pineal gland produces important hormones.
D. It has been said that the human brain is the most complex 3lb bit of organized matter known in the universe. It is a fact
that while you are reading this sentence, your brain is also maintaining all the systems of your body, including breathing,
heart rate, body temperature, and thousands of other body functions. At this moment you are using the most marvelous
living computer ever conceived. Below are pictures of various animal brains including man’s. Using a color pencil, color in the
cerebrum (marked) on each brain below.
a.
b.
Does the relative size of the cerebrum compared to the rest of the brain, seem to be related to the
organism’s “intelligence” or level of nervous response? Explain.
__________________________________________________________________________________
__________________________________________________________________________________
What relationship do you see, if any, between relative cerebrum size and learning ability? (For example, birds
can be trained to talk, while fish cannot generally be taught to do much more than come to a food source.)
__________________________________________________________________________________
__________________________________________________________________________________
E. Make a color key for the external human brain drawing on the left and then color the picture accordingly. Label the
following parts on the cross section of the human brain on the right: Cerebrum, Corpus Callosum, Thalamus, Hypothalamus,
and Hippocampus.
Cerebrum
Cerebellum
Medulla
Spinal Cord
12
Which Side is Dominant?
Many things that you do with the right side of your body are controlled by your brain’s left side and vice versa. The
following activities will help you determine which side of your brain is dominant. Record your data to each step in the table
below.
1. Which hand, left or right, you use to write your name and to wave “hello.”
2. Draw a simple outline drawing of a side view of a horse in the box and mark in the table below what direction
the horse faces.
3. Which way you swing a baseball bat. If you swing the bat left-handed (to the right), check the left column. If
you swing the bat right-handed (to the left), check the right column.
4. Which foot, left or right, you start down stairs, and which foot you begin skipping on.
5. Which thumb is on top when you fold your hands.
6. Look at the clock while holding your finger about 6 inches in front of your face. Line your finger up with the
clock while keeping both eyes open. Close your left eye. Open it and then close your right eye. Which eye is lined
up with your finger and the clock.
7. Which leg your weight is on when you are at rest.
8. Draw a circle with your right hand in the space below. Note which direction you drew it. Draw a circle with left
hand in the other space. Which way did you draw it? If you drew both circles clockwise, mark the right column. If
you drew both circles counterclockwise, mark the left column. If you drew once circle in each direction, check
both columns.
Data Table:
Questions:
Procedure
Step
1
2
3
4
5
6
7
8
Test
Left
Right
Writing
Waving
Drawing a horse
Starting down stairs
Skipping
Folding hands
Looking a distance
object
Drawing Circles
Which column has more marks? _______
Which side of your brain is dominant? _______
Which side of the body seems to be dominant? _______
13
Mr. Egghead - The Cerebrospinal Fluid
The cerebrospinal fluid (CSF) has several functions. One of these functions is to protect the brain
from sudden impacts. To demonstrate how this works, we need to bring in "Mr. Egghead." Mr. Egghead
is a raw egg withdrawn-on face. The inside of the egg represents the brain and the egg shell represents
the pia mater (the inner most layer of the meninges or coverings of the brain).
Put Mr. Egghead in a container (Tupperware works fine) that is a bit larger than the egg. The container
represents the skull. Now put a tight top on the container and shake it. You should observe that shaking
the "brain" (the egg) in this situation results in "damage" (a broken egg).
Now repeat this experiment with a new Mr. Egghead, except this time, fill the container with water. The water represents
the cerebrospinal fluid. Note that shaking the container does not cause the "brain damage" as before because the fluid has
cushioned the brain from injury.
You could make this into a science fair project: test the hypothesis that "The cerebrospinal fluid and skull protect the brain
from impact injury." Drop Mr. Egghead from a standard height (or heights) in different conditions: 1) with fluid in the
container, 2) without fluid in the container, 3) with different fluids or materials (sand, rocks) or 4) in different shaped
containers, etc. Make sure you keep notes to record your observations!
Materials:




Eggs (at least 2)
Markers to draw on a face (waterproof)
Plastic container with top.
Water (to fill the container)
14
Spinal Cord
Refer to the diagram showing the relationship between spinal nerve roots and vertebrae to answer the
question below.
Diagram Showing the Relationship between Spinal Nerve Roots and Vertebrae
Case Study of the Spinal Cord:
Jim was driving to work when he was in a severe car accident. Somebody hit him from the behind
while he was stopped at a red light. Instantly, he knew something was wrong with his body. He was
taken to Lutheran General Hospital. It was at the hospital that the neurologist discovered he had
damaged the posterior side of his spinal cord. Which would be more likely a result of his injury—
paralysis or parethesia (loss of sensory input)? Explain your answer.
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
15
Special Senses
Introduction
Our bodies, via the nervous system, are sensitive to dozens of different stimuli both internal and external. The senses we
are most familiar with are sometimes called the “special senses” and they include sight, hearing, smell, taste, and touch.
Odoriferous
(Olfaction)
1.
Find the scent samples and see if you can identify some common “mystery” odors.
A._________
B.__________
C.___________ D.__________ E.___________
2.
Look at the diagram of the nasal cavity at the right. A human olfactory tract is pictured. On the diagram, circle an
olfactory receptor neuron. When we smell something, odor molecules come in contact with about 100 million olfactory
neurons in the uppermost part of the nasal cavity. Each odor is chemically different in shape and is thought to uniquely
“fit” into the olfactory membrane area. Why is cilia present in this membranous area?
______________________________________________________________________________________
3.
Olfactory Fatigue
a. Close one nostril and smell oil on clove leaves until you can’t smell it anymore.
b. Now, see if you can smell peppermint extract with your “fatigued” nose.
c. Can you smell a different odor, if your nose is tired out from smelling another odor? Explain.
__________________________________________________________________________________
d.
Using the information in #2 above, why do you suppose your nose can get tired out on one odor, you can still
smell another.
__________________________________________________________________________________
16
MMM….. GOOD
(Gustation)
The mouth contains a special sensory organ. What is it? ________________ Label the picture below of this organ. Then,
identify the part that actually contains the sensory receptor. Label the diagram of it. Then, complete the lab.
Organ
Contains sensory receptor: _______________
Materials:
Each student: 4 cotton-tipped applicators, 1 plastic taste solution dish, 1 taste map.
Class sharing: bottles of bitter solution, sour solution, salty solution, and sweet solution
Procedure: Part I
1.
Rinse mouth out with water.
2. Pour a small amount of one of the taste solutions into the taste dish so there is enough to cover the bottom of the
dish.
3. Dip a clean cotton-tipped applicator into the liquid. Drain the excess solution from the applicator by pressing it
against the side of the dish.
4. Touch the applicator to the tongue of your partner in the regions outlined on the taste map. Tell your partner to
place a plus (+) sign on the corresponding area of his/her taste map if he/she can sense the taste. If he/she cannot
sense the taste, have him/her place a minus (-) sign in the appropriate place on the map.
5. After the four areas of the tongue have been tested with one solution, snap the applicator and discard it.
6. Exchange roles with your partner and repeat the test with the same solution.
7. Rinse your mouth with water. Also, rinse out the taste dish.
8. Repeat the procedure with each of the other three taste solutions.
Back of Tongue
Sweet
Sweet
Bitter
Salty
Sour
Front of Tongue
17
Part II:
Materials Per Group: 4 Dixie cups, each with one of the four mixtures of the unknowns, and eight straw sections.
Procedure:
1.
Label the four cups unknown #1, unknown #2, unknown #3, and unknown #4. DON”T SMELL YET!
2. The person who is going to taste the mixtures will close their eyes.
3. Have the taster hold their nose, take a straw section and a bit of the mixture and have the taster eat the mixture.
Keep the nose closed the whole time.
4. The taster will try to identify the substance before releasing their nose and swallowing. Record the results in the
following table. Use a “+” if the guess was correct and an “O” if incorrect.
5. The taster should rinse their mouth out between tastes.
6. Repeat for each of the remaining three mixtures in random order. And then switch roles. Record the results.
7.
Next, have one partner close their eyes and have them try to identify the mixtures by smell. Do this in a random
order. Switch roles and record all results.
Mixture
Unknown #1
Unknown #2
Unknown #3
Unknown #4
Taste no smell
Smell
Questions:
1.
What are the unknowns?
2.
What do the results indicate about the senses of smell and taste? Explain
3.
While there are only four basic tastes, many flavors are experienced. How is this possible?
18
An Eye for an Eye….. (leaves the entire world blind)
Label the special sensory organ below. What is it? ____________
Give the function of each of the following parts.
 Layers and coats
o
Sclera—

Cornea—
o
Choroid—

Ciliary body—

Iris—
o
Retina—

Rods (black & white)

Cones (color)

Fovea centralis
Optic disc (no photoreceptor cells) AKA Blind Spot
 Cavities of the Eye
o
Anterior cavity—

Filled with aqueous humor—clear, watery fluid
o
Posterior cavity—

Filled with vitreous humor—soft, gelatin-like substance

Helps with intraocular pressure to prevent collapse

Glaucoma—too much intraocular pressure due to too much aqueous humor
 Muscles of the Eye
1.
Extrinsic eye muscle—
2. Intrinsic eye muscle—
Iris
Ciliary body
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Sheep Eye Dissection
This lab should not take you more than 25 minutes. Follow all directions precisely! Remember to follow all lab safety rules.
Materials: One sheep eye, dissecting kit, dissecting tray, paper towels, latex gloves, goggles, partner
Part 1—External Observations
1.
Note the eye’s shape. ________________________________
2. Examine the pupil, iris, sclera, and cornea.
3. What does the texture of the eye feel like? _______________
Part 2—Internal Structures
1.
Using the scalpel, very carefully remove the cornea from the eye.
2. Approximately how thick is the cornea? _________________
3. What happens to the rest of the eye when you remove the cornea from it?
__________________________________________
4. Make a small incision in the ciliary body.
5. What happens when you do this? _________________________
6. Remove the lens from the eye using scissors. Cut as close as possible to the muscles holding it in place.
7. Using the scalpel, very carefully shave the lens. What does this remind you of? What other “object” peels just
like the lens does? ____________________________________________________
Part 3—Deep in the Eye
1.
After removing the lens, what is exposed? ____________________
2. Turn the eye upside down. What does the fluid coming out remind you of? ______________________
3. What is it really? __________________________________
4. Once all the fluid is removed, take a probe and lightly scrap the back of the retina.
5. What do you see? Look closely.
Part 4—Clean-up
1.
Clean all utensils. Wash with soap and water. Dry and return to kit.
2. Throw away all sheep parts. These go in the TRASH CAN!
3. Wash and dry the dissecting trays. Remove the mat and make sure all the fluids are washed out.
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Vision: Image Formation
As with any image being formed, it takes two or more rays from the same spot on an object to cross or appear to cross. In
this case, looking at two rays from the candle flame, we find that the rays cross right at the location of the retina. This
image would be in focus. It is important to notice that the real image of the candle is actually upside down on the retina.
Your brain actually takes care of flipping it so it seems to be right side up. Some experiments that have been done involve
people wearing some glasses that make everything seem upside down. After a few days, their brain flips the image. If they
take the glasses off, their brain, after a delay, will flip it right side up again.
Nearsightedness
If the lens in the eye is too strong, or the cornea is too thick, or the eye is too long, it will cause the real image to get
formed in front of the retina. This will cause a blurred image. We would call it nearsightedness (myopia). Uncorrected,
nearsightedness basically means you can't see things from a distance.
Since the problem is that the rays are converging too soon, we want to undo some of the convergence. Divergence undoes
convergence. As a result, nearsightedness is usually corrected by placing a diverging lens in the front eye.
Farsightedness - Draw the disorder in the box below. Refer to nearsightedness to help you.
If the lens in the eye is too weak, or the cornea is too thin, or the eye is too short, it will cause the real image to get formed
in beyond the retina. This will cause a blurred image. We would call it farsightedness (hyperopia). Uncorrected,
farsightedness basically means you can't see things close up.
Now, draw how to correct it in the box below.
Since the problem is that the rays aren't converging soon enough, we need to increase the convergence. Farsightedness is
usually corrected by placing a converging lens in the front eye.
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Next, Use the mnemonic ‘racc’ to help you list the steps for the formation of vision. Briefly describe each step.
R
A
C
C
Lastly, match the eye disorder with the proper explanation
Myopia ____
Hyperopia ____
Presbyopia ____
Astigmatism ____
Cataract ____
Retinal detachment ____
Glaucoma ____
Analyze the special sensory organ below.
A. Nearsightedness
B. Farsightedness
C. degeneration of accommodation
D. clouding of lens
E. Cornea or lens not uniformly curved
F. pressure by aqueous humor
G. could cause blindness
What is it?_____________
What do the numbers represent?_________________ Explain this sensory
process._______________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
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Hearing Lab
1. You will be performing four hearing tests on your laboratory partner today. These tests are:
1) auditory acuity test
2) sound localization test
3) Rinne’s test
4) Weber’s test
2. It will probably be necessary to have quiet surroundings to perform these tests with some degree of accuracy.
3. For the auditory acuity test, ask your laboratory partner to place a cotton ball in one ear, and ask to sit with eyes closed.
a. Take two coins and tap them together lightly close to the open ear and slowly move it straight away from that ear.
b. Ask your laboratory partner to indicate when the sound of the ticking can no longer be heard. Use a meter stick to
measure the distance the clock/coins is away from that ear. Record your results in the following table.
c. Repeat this procedure with the other ear.
Ear Tested
Audible Distance (in cm)
Right
Left
d. What is the significance of the results of this test?
4. For the sound localization test, ask your laboratory partner to sit with eyes closed.
a. Use the same coins tapped together, hold the coins somewhere within the audible range of your laboratory partner
and at one of the locations listed below.
b. Ask your lab partner to point to the location of the coins.
c. Record your observations below.
Actual Location of Clock/coins
Reported Location
Front of head
Behind head
Above head
Right side of head
Left side of head
d. Repeat the procedure by moving the coins to another location and record your results below.
e. Did your laboratory partner miss-identify any of the locations? Why?
_______
5. The Rinne’s test is used to assess for conduction deafness by comparing bone and air conduction. To conduct this test, do
the following:
a. Obtain a tuning fork from the front lab bench. Ask your laboratory partner to sit.
b. Strike the tuning fork with a rubber hammer or with the heel of your hand to cause it to vibrate.
c.
Pace the handle of the fork against the mastoid process with the prongs of the fork pointed downward and away
from the ear. The sensation of sound heard by your laboratory partner is actually due to conduction of vibrations
through the bone rather than through the air as is normally done.
d. If your laboratory partner cannot hear the sound, nerve deafness exists.
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e. Ask your laboratory partner to tell you when he can no longer hear the sound.
f. Quickly remove the tuning fork from the mastoid process and hold it close to the ear. Ask your laboratory partner if
he can now hear the sound. If his hearing is normal, he will be able to hear the sound again. If not, then he has
conductive impairment. Conductive impairment is usually the result of outer and middle ear defects. Hearing aids
are frequently used to improve hearing in people with conductive impairment.
g. Perform this test with the other ear and record your results below.
Ear Tested
Rinne’s test results
(normal or impaired)
Left
Right
6. Weber’s test is used to distinguish conduction deafness or sensory deafness. To conduct this test, you will use your
tuning fork and rubber hammer.
a. Strike the tuning fork with the rubber hammer or the heel of your hand.
b. Place the handle of the tuning fork against your laboratory partner’s forehead in the middle.
c.
d.
Ask your laboratory partner if the sound appears louder in one ear or the other or if it is equally loud in both ears.
If his hearing is normal, the sound will be heard equally in both ears. If some sensory deafness exists, the sound
will be louder in the normal ear. This type of impairment involves the hearing organ (organ of Corte) or the
cochlear nerve, and cannot be corrected by hearing aids.
Record your results in the table below.
Ear
Weber’s test results
(normal or impaired)
Left
Right
e. Repeat the Weber’s test after placing a cotton ball in one of your laboratory partner’s ears. Usually the sound
appears louder in the impaired ear because of filtering out of extraneous sounds. Record your results below.
Ear
Weber’s test results
(normal or impaired)
Left
Right
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What else does the
regulate? _____________________ Let’s test it. Complete the lab below.
The purpose of this exercise is to demonstrate the importance of vision in maintaining equilibrium. To perform this test, do
the following:
1. Have your laboratory partner stand erect on one foot for one minute with his eyes open. Determine how steady or
unsteady the subject is.
2. Now ask your laboratory partner to close his eyes and observe his ability to maintain equilibrium for one minute.
What sensory organs allow for the maintenance of equilibrium when your laboratory partner’s eyes are open?
(Hint: there are three.)
What sensory organs provide this information when his eyes are closed?
Römberg test
The Romberg test is used to evaluate a person’s ability to integrate information from proprioceptors in muscles and
receptors within the saccule and utricle to maintain static equilibrium. This information is relayed to the muscles used in
maintaining posture to help maintain steadiness.
A person who demonstrates unsteadiness with the eyes closed is considered to have a positive Römberg test.
1. Have your laboratory partner stand with his back to a chalkboard.
2. Turn on a bright light placed directly in front of your laboratory partner; his shadow should be cast on the chalkboard.
3. Ask your laboratory partner to look straight ahead for three minutes. Meanwhile, you will mark his degree of
unsteadiness (side-to-side movement) with a piece of chalk.
4. Using a millimeter ruler, measure in cm the amount of side-to-side motion of your laboratory partner. Record your
results in the table below.
5. Repeat this procedure, but have your laboratory partner close his eyes. Record your results in the table below
6. Now ask your laboratory partner to turn with one side to the chalkboard and stare straight ahead. Repeat the above
procedure, and record your results below.
7. Ask your laboratory partner to close his eyes, and repeat the above procedure. Record your results below.
Romberg test results:
Test Conditions
Maximal movement (in cm)
Back toward board; eyes open
Back toward board; eyes closed
Side toward board; eyes open
Side toward board; eyes closed
Based upon your results, would you expect a person with his eyes closed to have a greater maximal movement than
with his eyes open? Why?
If a person had damage to the saccule and/or utricle, what would you predict would be the results of the Römberg
test? Why?
If a person had damage to the saccule and/or utricle, what would you predict would be the results of the Römberg
test? Why?
What is the difference between static and dynamic equilibrium?
25