Neurophysiology 2

Question 1

Axon hillock

Answer 1

takes all of the information from the dendrites that will SEND OUT information through the axons

Question 2

Is the threshold for an action potential more negative or less negative?

Answer 2

LESS negative

Question 3

What are the steps of the action potential?

Answer 3

1) resting
2) reaches threshold
3) depolarization
- sometimes overshoot
4) repolarization
5) hyperpolarization
6) resting

Question 4

At (1) resting state (what channels/pumps open?)

Answer 4

only leaky K+ channels are open

Question 5

At (2) first part of depolarization? (what channels/pumps open up?)

Answer 5

K+ leaky channels, Voltage-gated Na+ channels open up

Question 6

At (3) second part of depolarization? (what channels/pumps open up?)

Answer 6

K+ leaky channels, Voltage-gated Na+ channels, and Voltage-gated K+ channels open up

Question 7

At (4) repolarization? (what channels/pumps open up?)

Answer 7

K+ leaky channels, Voltage-gated K+ channels (Voltage-gated Na+ channels start to close)

Question 8

At (5) hyperpolarization? (what channels/pumps open up?)

Answer 8

K+ leaky channels (both Voltage-gated K+ channels and Voltage-gated Na+ channels close)

Question 9

All-or none action potential concept

Answer 9

An action potential will only fire if it reaches the threshold

Question 10

T/F If you have a Suprathreshold stiumulus, you will get more than one firing of the neuron.

Answer 10

FALSE; no matter how much you stimulate the cell you’re only going to get ONE firing of the neuron

Question 11

Absolute Refractory Period

Answer 11

the interval during which a second action potential absolutely cannot be initiated, no matter how large a stimulus is applied.

Question 12

Why can’t you receive a second action potential in the absolute refractory period?

Answer 12

because the Na+ channels are being utilized already and therefore no extra stimulus can be applied.

Question 13

Relative Refractory Period

Answer 13

the interval immediately following absolute, during which initiation of a second action potential can be perhaps initiated but it is not impossible; needs a larger stimulus

Question 14

What are the 3 reasons why the Relative Refractory Period can establish a second action potential?

Answer 14

1) Na+ channels are inactivated
2) K+ channel activity states are in transition and are responsive to voltage changes
3) Membrane voltage is somewhere between threshold voltage and hyperpolarized voltage