Lab 5: Reflexes
Part One: Autonomic Reflexes
Part 1: Skeletal Muscle Structure
Objective: To observe the microscopic structure of a skeletal muscle.
Materials:
Skeletal muscle long. section (HD 2-21)
Skeletal muscle cross section (HD 2-22)
Histology guide
Procedure:
1. Examine the skeletal muscle at high power. Draw what you see. Label as many parts of the sarcomere as possible.
Part 3: Autonomic Reflexes
In this part of the lab, we will examine 3 different autonomic reflexes.
Materials:
Small flashlight
Small plastic metric ruler
Procedure:
Pupillary Reflexes (pg 367-368)
1. Conduct the reflex test in an area where the lighting is dim. Measure the size of the subject’s pupils at rest using a small plastic
metric ruler.
Right pupil = _____________ mm
Left pupil = _____________ mm
2. Have the subject shield his/her right eye by holding a hand vertically between the right eye and the right side of the nose.
3. Stand to the left of the subject, and shine a flashlight into the subject’s left eye (from below the eye, not directly into it!).
Observe the change and measure the size of the subject’s left pupil (direct pupillary light reflex).
Left pupil = _____________ mm
4. Repeat step 3, but this time, observe the change and measure the approximate size of the subject’s right pupil (consensual
pupillary light reflex).
Right pupil = _____________ mm
Ciliospinal Reflex
1. While observing the subject’s eyes, gently stroke the skin (or just the hairs) on the left side of the back of the subject’s neck,
close to the hairline. Note: If you see no reaction, repeat using a gentle pinch in the same area.
2. Record the reaction of the left pupil:
3. Record the reaction of the right pupil:
QUESTIONS Related to Autonomic Reflexes
1. Create a labeled diagram showing the reflex arc involved in the direct pupillary light reflex and consensual pupillary light reflex.
It may be helpful to draw more than one diagram.
2. Compare and contrast an ispilateral response with a contralateral response. Use these terms to label the autonomic reflexes we
investigated today.
Bio 7: Human Physiology
95
Spring 2014: Riggs
Lab 5: Reflexes
Part Two: Somatic Reflexes
For this part of the lab, consistency is critical. Make sure you can easily and consistently initiate the patellar reflex in the subject.
Devise a method to quantify the magnitude of the elicited reflex.
Materials:
Reflex hammer
Math problem
Procedure:
1. Work in pairs. Have the subject close her eyes (why?) and sit on the edge of the examining table with her legs dangling free.
2. Locate the patellar ligament and palpate the soft tissue depression on either side of the ligament.
3. Deliver a smart tap to the patellar ligament with the reflex hammer.
A. Which muscle will be stretched if this ligament is tapped? _____________________
B. What nerve innervates this muscle? ________________________,
4. Elicit the reflex by tapping the ligament with a reflex hammer at the level of the knee joint, using a short, smart wrist action.
Describe the response.
5. Test the effect of mental distraction on the patellar reflex by having the subject mentally add a column of three-digit numbers
while you test the reflex again. Is the response greater or less than the first time? How do you explain this?
6. Now test the effect of muscular activity occurring simultaneously in other areas of the body. Tap the patellar ligament while the
subject performs the Jendrassik’s maneuver (claping her hands in front of her and, with fingers locked, trying vigorously to pull
her hands apart). Is the response greater or less than the first time? How do you explain this?
7. Vigorously exercise (tuck jumps? Lunges? High knees? Squats?) until your heart rate is elevated and your quads are burning.
Test the patellar reflex again, and record your results.
Questions Related to Patellar Reflex
1. Which muscles contracted?
2. What muscles were being inhibited?
3. What nerve is carrying the sensory & motor impulses?
4. Was the patellar reflex greater or lesser when the subject was distracted?
5. What are your conclusions about the effect of mental distraction on reflex activity?
6. How does the effect of the patellar reflex change if the subject is undergoing some other muscular activity?
Bio 7: Human Physiology
96
Spring 2014: Riggs