KINS 2295 Lecture Notes - Myelin, Motor System, Efferent Nerve Fiber

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10 May 2013

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It provides support, regulates the extracellular concentration of neurotransmitters and provides immune protection. The action potential moves along the axon by propagation. When na gates are open and na flows into the cell it becomes depolarize then it spreads to the other sections. However, the message can only be sent in 1 direction because of refractory period (inactivated loop). K inside the cell na outside the cell. It maintains a concentration gradient for na and k transporting 3 na out and 2 k in. K have more open channels than na. So fewer na diffuse into the cell and more k diffuse outwards. By increasing the cell membrane to be more permeable to k making the cell more negative. By increasing the cell membrane to be more permeable to na making the cell more positive. Resting state, depolarization, rising phase of action potential, falling phase of action potential, and undershoot.

Related Questions

6. Consider the presence of hemoglobin in the catheter bag. Whatsymptom would this loss of

hemoglobin most strongly and immediately be linked to in thepatient?

A. Loss of blood volume

B. Loss of heartbeat

C. Drop in blood oxygen saturation

D. Liver failure

When a neuron is stimulated, the area of the membrane at thepoint of stimulation becomes

more permeable to Na+. If a cell starts at resting potential(-70mv), and is then stimulated:

A. The membrane voltage will become < -70mV, because Na+will move OUT of the cell.

B. The membrane voltage will become > -70mV, because Na+will move OUT of the cell.

C. The membrane voltage will become < -70mV because Na+will move INTO the cell.

D. The membrane voltage will become > -70mV because Na+will move INTO the cell.

. At the peak of the action potential, the Na+ voltage-gatedchannels close, and K+ voltage-gated

channels open in response to the positive membrane potential.In order to return the cell to its

negative resting potential quickly:

A. K+ will diffuse along its concentration gradient INTO thecell.

B. K+ will diffuse along its concentration gradient OUT of thecell.

C. Na+ will reverse its direction of diffusion OUT of thecell.

D. The sodium-potassium pump will move Na+ OUT of the cell andK+ INTO the cell.

E. None of the above would return the cell to its negativeresting potential quickly.

You experiment with higher concentrations of toxin and findcases when the cell could not

repolarize at all or, if it began to repolarize, itimmediately depolarized again. This tells you that

the toxin:

A. Prevents voltage-gated K+ channels from opening.

B. Increases the speed that the Na+ ion channels open.

C. Prevents the Na+ ion channels from closing.

D. Makes the Na+ ion channels close too soon.

E. Doesn

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When the na-channels of an axon open, what would happen?

a. Saltatory conduction

b. repolarization

c. hyperpolarization

d. Na+ ions flow into the neuron

e. Na+ ions flow out of the neuron

When the K-channels in the axon open, what would happen?

a. depolarize the neuron

b. block action potential

c. maintain the membrane potential

d. repolarize the neuron

e. release neurotransmitters.

When a neuron is depolarized closer to the threshold, the neuron is

a. more excitable

b. less excitable

c. more inhibitory

d. inactivated

e. blocked from finding action potentials

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

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KINS 2295 Lecture Notes - Myelin, Motor System, Efferent Nerve Fiber

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