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BIOL 201 Lecture Notes - Lecture 35: Synaptic Vesicle, Axon Hillock, Axon Terminal

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27 Nov 2015

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McGill University

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Document Summary

Mice sense the deflection of their whiskers against walls. Influx of ions causes a small and local change in the membrane potential. Initial increase in membrane potential - becomes more positive. The initial spike causes a local flood of na into the neuron: voltage-sensing helix will move as the voltage changes and the membrane becomes depolarized. Na ions diffuse outward, triggering neighbouring na channels to open: spread of na ions causes a wave of depolarization which triggers voltage-sensing helices to move. Inactivation of v-gated na channels stops flow of na. April 1, 2015: pore gets plugged up by channel-inactivating segment to close the channel, length of linker determines how long the channel remains open. If channel-inactivating segment was longer, channels would stay open for longer. Inactivation of v-gated na channels makes action potentials unidirectional: channels stay open for a long time, the action potential does not move backward due to inactivated na channels.

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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

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.

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