Lynn Schuster
Chiles High School
Name________________________
Period _______________________
TITLE:
PURPOSE:
MATERIALS:
PROCEDURE:
Nervous Reflex Lab
to understand that the entire nervous system can be considered a
system of innumerable reflex arcs
mallet, cotton swab, feather, 3x5 index card, textbook, ruler,
light, cotton ball
Complete the following activities and answer the corresponding
questions in each section. Possible abnormal spinal reflex results
include: hyperflexia (exaggerated response), which results from
damaged or diseased motor areas in the CNS; and hypoflexia
(inhibited response), which results from degeneration of nerve
pathways, voluntary motor control, and other factors.
DATA:
Patellar Relfex (aka. knee-jerk reflex)
This reflex is mediated by a two-neuron arc centered in the spinal cord.
1.
Subject should sit on the edge of a table or chair so that his leg hangs freely.
The observer should locate the patella and the tendon below it. Then tendon
should then be struck sharply with the flat end of the mallet. If done properly,
this should produce the patellar reflex. The tap stretches a quadriceps muscle
in the anterior thigh, stimulating stretch receptors located in the muscle. In
response to the increased stretch, which normally would only occur when the
muscle load has suddenly increased, the muscle contracts and extends the
lower leg. Describe your results:
_______________________________________________________________
2.
Repeat the above procedure but have the subject interlock his fingers and
attempt to pull them apart as vigorously as possible just as the blow is struck.
What effect does this muscular tension have on the reflex action?
_______________________________________________________________
Explain how clenching your fists during a fight or athletic contest may affect
your reflex responses: _____________________________________________
_______________________________________________________________
Biceps Reflex
This is a spinal reflex that involves nerves C5 and C6.
Have the subject sit with the elbow flexed at about 90 degrees and palm facing
downward. Put your thumb on the biceps brachii tendon at the inside angle of the elbow
and press gently. Tap your thumb with a reflex mallet. Describe your response:
_______________________________________________________________________
_______________________________________________________________________
Lynn Schuster
Chiles High School
Achilles Reflex
This is a spinal reflex that results in plantar flexion of the foot.
Have the subject kneel on a chair, facing away from you, with the toes pointing toward
the floor. Tap the middle of the Achilles (calcaneal) tendon with a reflex mallet.
Describe your response: __________________________________________________
______________________________________________________________________
Triceps Reflex
This is a stretch reflex.
Have the subject sit in a chair, with an arm across the abdomen. Supporting the subject’s
arm with the elbow flexed at a 90 degree angle, sharply tap the posterior surface of the
upper arm just proximal to the olecranon fossa (see page 155 in your text). Describe your
response: _______________________________________________________________
How might you explain this response? ________________________________________
_______________________________________________________________________
Uvular Reflex
1.
Ask your subject to open his mouth widely.
2.
Touch the uvula lightly with the cotton swab. What is the reaction?
_______________________________________________________________
How does this reflex aid in swallowing? ______________________________
_______________________________________________________________
Cilio-spinal Reflex
Gently pinch the skin at the nape of the subject's neck. Note the reaction of the pupils
of his eyes: ___________________________________________________________
Sneezing Reflex
1.
Stimulate the lining of the nose with a few strands of thread or a feather. Be
careful that these items are not inhaled. Describe the results:
_____________________________________________________________
2.
Try to inhibit this reflex by having the subject press on the upper lip just below
the nose. Describe the results you obtain: ______________________________
________________________________________________________________
Pupillary Reflex
This is a reflex which is mediated by the brainstem, involving cranial nerves and
autonomic reflex centers.
Lynn Schuster
Chiles High School
1.
Have the subject close both of his eyes for ninety seconds. Hold a 3x5 index
card along the bridge of his nose so that the right eye is shielded from the left.
2.
Shine a bright light into his left eye as soon as he opens their eyes. Normally,
the light receptors in the eye receive the bright light and trigger a reflexive
response by the muscles in the iris. Note the effect it has on the pupil of the left
eye: _____________________________________________________________
What is the advantage of such a response? ______________________________
_________________________________________________________________
3.
The right pupil may also exhibit a reflexive response, even though the light is not
shown on it. This is an example of a consensual reflex in which one side of the
body responds to a stimulus applied to a corresponding organ on the other side.
Describe your results: _______________________________________________
_________________________________________________________________
Corneal Reflex
This is a reflex mediated by the brain which involves the fifth cranial nerve.
Have the subject stand facing at a 90 degree angle to you. While the subject stares
straight ahead, quickly move a clean, sterile cotton ball toward the surface of one eye.
Do NOT actually touch the eye! What is the reaction? ___________________________
_______________________________________________________________________
What survival advantage does this reflex have? _________________________________
_______________________________________________________________________
Accomodation Reflex
1.
Examine the pupils of the subjects eyes.
2.
Have the subject read a page in a textbook.
3.
Ask the subject to glance up to look at a distant object. Describe what happens to
the subject's pupils: _________________________________________________
Reaction Time
1.
Reaction time is defined as the interval between the application of a stimulus and
the beginning of a response. Have the subject rest his forearm on the edge of a
table with his arm with his hand projecting over the edge. His thumb and index
finger should be separated by about 1 ½ inches.
2.
The observer should suspend a ruler above the hand of the subject, with the lower
edge of the ruler even with the upper margin of the thumb and finger. Make
certain that the ruler is suspended with the one inch measurement at the bottom.
3.
The observer should drop the ruler without warning and measure the distance at
Lynn Schuster
Chiles High School
4.
5.
which the subject caught the ruler. Record your results: ____________________
Why is it so difficult to catch the card? __________________________________
_________________________________________________________________
Repeat the above step 10 times. Record your results each time:
1.
__________________
6.
______________________
2.
__________________
7.
______________________
3.
__________________
8.
______________________
4.
__________________
9.
______________________
5.
__________________
10.
______________________
Do you feel that repeated trials decreased your reaction time? ______________
Why do you feel that this occurred? __________________________________
_______________________________________________________________
CONCLUSION: