Human Anatomy & Physiology Laboratory Manual

Marieb Mitchell SmithTenth Edition

Human Anatom

y & Physiology Lab Manual Marieb et al. 10e

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ISBN 10: 1-292-02637-5ISBN 13: 978-1-292-02637-4

ISBN 10: 1-292-02637-5ISBN 13: 978-1-292-02637-4

Neurophysiology of Nerve Impulses: Frog Subjects

9. Flush the nerve preparation with room temperature Ringer’s solution again and then gently lift the nerve by its attached threads. Then turn the nerve around so that the end formerly resting on the stimulating electrodes now rests on the record-ing electrodes and vice versa. Stimulate the nerve. Is the impulse conducted in the opposite direction?

_________________________________________________

10. Dispose of the frog remains and gloves in the appropriate containers, clean the lab bench and equipment, and return your equipment to the proper supply area. ■

8. Flush the nerve with room temperature Ringer’s solution once again, and allow the nerve to sit for a few minutes while you obtain a bottle of Ringer’s solution from the ice bath. Repeat steps 5 and 6 while your partner continues to flush the nerve preparation with the cold saline. Record the thresh-old and maximal stimuli, and watch the oscilloscope pattern carefully to detect any differences in the velocity or speed of conduction from what was seen previously.

Threshold stimulus: _______________ V

Maximal stimulus: _______________ V

Figure 4 Setup for oscilloscope visualization of action potentials in a nerve.

START

TIMING

OUTPUTRANGE

PERIOD

DURATION

BURST WIDTH

DELAY

MULTIPLIERMULTIPLIER

MULTIPLIERMULTIPLIER

Oscilloscope

Input terminalsRecording electrodes

Nervechamber

Nerve to be positioned across all four electrodes

Stimulating electrodes

Outputterminals

Stimulator

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286

Neurophysiology of Nerve Impulses: Frog Subjects

The Action Potential 1. Match the terms in column B to the appropriate definition in column A.

Name ____________________________________

Lab Time/Date ________________________

RE

VI

EW

S

HE

ET

Column A Column B

1. period of depolarization of the neuron membrane during which it cannot respond to a second stimulus

2. reversal of the resting potential due to an influx of sodium ions

3. period during which potassium ions diffuse out of the neuron because of a change in membrane permeability

4. period of repolarization when only a strong stimulus will elicit an action potential

5. mechanism in which ATP is used to move sodium out of the cell and potassium into the cell; restores the resting membrane voltage and intracellular ionic concentrations

a. absolute refractory period

b. action potential

c. depolarization

d. relative refractory period

e. repolarization

f. sodium-potassium pump

2. Define the term depolarization . ______________________________________________________________________________________

____________________________________________________________________________________________________________________

How does an action potential differ from simple depolarization? ________________________________________________________

____________________________________________________________________________________________________________________

3. Would a substance that decreases membrane permeability to sodium increase or decrease the probability of generating an action potential? Why?

___________________________________________________________________________________________________________________

___________________________________________________________________________________________________________________

4. The diagram here represents a section of an axon. Complete the figure by illustrating an area of resting membrane potential, an area of depolarization, and local current flow. Indicate the direction of the depolarization wave.

[Na+]

[K+][Na+]

[K+]

287

Neurophysiology of Nerve Impulses: Frog Subjects

Physiology of Nerves Stimulating and Inhibiting the Nerve 5. Respond appropriately to each question posed below. Insert your responses in the corresponding numbered blanks to the

right.

1–3. Name three types of stimuli that resulted in action potential genera-tion in the sciatic nerve of the frog.

4. Which of the stimuli resulted in the most effective nerve stimulation?

5. Which of the stimuli employed in that experiment might represent types of stimuli to which nerves in the human body are subjected?

6. What is the usual mode of stimulus transfer in neuron-to-neuron in-teractions?

7. Since the action potentials themselves were not visualized with an oscilloscope during this initial set of experiments, how did you recognize that impulses were being transmitted?

1. ______________________________

2. ______________________________

3. ______________________________

4. ______________________________

5. ______________________________

6. ______________________________

7. ______________________________

6. How did the site of action of ether and tubocurarine differ? ___________________________________________________

___________________________________________________________________________________________________

In the curare experiment, why was one of the frog’s legs ligated? _______________________________________________

___________________________________________________________________________________________________

Visualizing the Compound Action Potential with an Oscilloscope 7. Explain why the amplitude of the compound action potential recorded from the frog sciatic nerve increased when the voltage

of the stimulus was increased above the threshold value. _____________________________________________________

___________________________________________________________________________________________________

8. What was the effect of cold temperature (flooding the nerve with iced Ringer’s solution) on the functioning of the sciatic

nerve tested? ________________________________________________________________________________________

___________________________________________________________________________________________________

9. When the nerve was reversed in position, was the impulse conducted in the opposite direction? ______________________

How can this result be reconciled with the concept of one-way conduction in neurons? ______________________________

___________________________________________________________________________________________________

___________________________________________________________________________________________________

___________________________________________________________________________________________________

288

Neurophysiology of Nerve Impulses: Frog Subjects

Illustration Credits

All illustrations are by Imagineering STA Media Services, except for Review Sheet art and as noted below.

2–4: Precision Graphics.

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