01:146:295 Lecture Notes - Lecture 6: Resting Potential, Action Potential, Tetrodotoxin

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violetseal1

17 Jun 2020

School

Rutgers University

Department

Cell Biology and Neuroscience

Course

01:146:295

Professor

J.Schjott

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Document Summary

Action potential continue 9/21/2018: voltage gated sodium channels open first and are responsible for the rising phase, sodium channels inactivate, and the delayed potassium channels open around the peak of the action potential. However, there is no net flow of potassium, approximately the same amount is moving in and out. The conductance of sodium now exceeds that of potassium. At this point the sodium voltage channels have closed and the voltage gated potassium channels are closing: absolute refractory period during the falling phase another action potential cannot occur on top of the current one. It must return to rest before another one can occur. The sodium spreads causing the threshold to be met in other parts of the cell causing the opening of other sodium channel, propagating action potential down the neuron. The axon is exposed to the extra cellular environment. Not all axons are myelinated for vertebrates most are.

Related Questions

What would be most strongly affected by a drug that inhibited the opening of voltage-gated potassium channels (also known as delayed rectifiers)?

A. Falling phase of an action potential

B. Rising phase of an action potential

C. Resting membrane potential

D. Threshold for an action potential

Why does the voltage during the undershoot phase of the action potential become more negative than the resting membrane potential?

A. During the undershoot potassium ions are flowing into the cell due to the reversal of the potassium concentration gradient occurring during the action potential

B. The undershoot phase results from a delay in the activation of sodium channels, resulting in some sodium channels being open after the voltage-gated potassium channels have closed. C. The potassium conductance is higher during the undershoot than during the resting membrane potential.

D. The concentration gradient for potassium has been reversed as a result of the action potential, and the undershoot phase lasts until this the concentration gradient is restored.

silverdinosaur935

This is the peak depolarization in an action potential. At this point in an action potential two events start to happen.

1. Na+ channels begin to inactivate, which is equivalent to closing.

2. A majority of the K+ channels are beginning to open.

Determine what happens to the membrane potential when voltage-gated K+ channels are open simultaneously with voltage-gated Na+ channels (and the leak K+ channels which are still open). Increase the membrane permeability to K+ by increasing it to 115.

i. What happens to the membrane potential Em? __________________________

j. Why does the membrane potential change in this direction? __________________________ Now inactivate the voltage-gated Na+ channels by reducing the membrane permeability for Na+ back to 1. k. What is the new membrane potential? _____________

l. Is the new membrane potential less negative or more negative than the resting membrane potential listed in line âbâ of this section? _____________

m. Why? (hint: what 2 types of K+ channels are open now?) n. Under the current ionic concentrations given, what is the most negative value that the membrane potential could reach? _____________ (Increase the permeability of the membrane to K+ to confirm your answer.)

o. What equilibrium potential has the same value? _____________

p. At this point in the action potential, when the membrane potential is more negative than the resting potential, the membrane potential is said to be hyperpolarized. What happens to voltage-gated K+ channels (membrane permeability to K+) to bring the membrane potential back to its resting potential near -70mV?_____________

When the membrane potential became more negative than the Threshold potential, the inactivated voltage-gated Na+ channels became reactivated. After the voltage-gated K+ channels closed to enable the membrane potential to return to resting membrane potential they became ready to open again. Both channels are ready to open again in order to fire another action potentia

sapphirepanda54

1.A stronger stimulus to a neuron results in ________.

A. larger voltage changes in graded potentials and greater frequency of action potentials produced in response

B. greater frequency of graded potentials and larger voltage changes in the action potentials produced in response

C. larger voltage changes in the graded potentials, but no changes in action potentials

D. larger voltage changes in both graded and action potentials

E. larger voltage changes in graded potentials but smaller action potentials

2. Why is it more difficult to fire an action potential when the interval between stimuli decreases?

A. because sodium is flowing out of the cell

B. because potassium is flowing into the cell

C. because some sodium channels may still be in an inactivated state

D. because chloride is flowing into the cell

E. because chloride is flowing out of the cell

3. As an action potential zips down an axon,

A. voltage gated potassium channels open first followed by voltage-dependent sodium channels

B. voltage- gated sodium channels ahead of the wave and not yet activated are influenced by the depolarizing electrical field of other nearby sodium channels

C. voltage-gated potassium channels ahead of the wave and not yet activated are influenced by the depolarizing electrical field of nearby sodium channels

D. leak channels are opened by the wave of electricity passing along the axon

E. B and C

01:146:295 Lecture Notes - Lecture 6: Resting Potential, Action Potential, Tetrodotoxin

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