Neurophysiology - L2

Question 1

Properties of the Action Potential (3)

Answer 1

1) All or Nothing - reach threshold and it goes
2) Regenerative - once started goes to completion
3) Time Limited - Always Same time no matter stimulus

Question 2

The Overshoot

Answer 2

Brief Period of Positive Vm caused by the sodium rushing in to the cell, before the Potassium channels can combat

Question 3

The Undershoot

Answer 3

The Vm gets very close to the Ek due to K+ conductance remaining high after closure of sodium channels

Question 4

absolute refractory period

Answer 4

Cannot generate another action potential. This is due to the Inactivation Gate being closed in Sodium.

Question 5

Relative Refractory Period

Answer 5

Can start an action potential given strong stimulus. This is due to the voltage gated K channels and permeability is high so you have to overcome this
If number of sodium channel decreases then the hill is sloped less steep and absolute refractory increases in duration

Question 6

Repolarization is Caused by

Answer 6

The voltage gated K channels and not the Na K pump

Question 7

Tetroetylammonia TEA

Answer 7

Blocks the VGKC. when using you see that the depolarization fine, but the repolarization is slower

Question 8

Tetrodotoxin TTX

Answer 8

Blocks VGNaC

We see a slow depolarization

Question 9

One Depolarization Causes (3)

Answer 9

1) opening of the sodium channels
2) closing of the sodium channels (inactivation gate, delayed)
3) Open the VGKC (also delayed)

Question 10

VGNaC Two Gates Description

Answer 10

Activation Gate- Open when depolarization, closes when cross back over threshold
- it is quick
Inactivation Gate - Open at rest. Slow to close. signal received at depolarization

When we repolarize the activation gate closes and then the inactivation gate will reopen

Question 11

VGKC One Gate Description

Answer 11

Called the N gate- at negative Vm it is closed. receives signal at depolarization,
and slowly opens

Question 12

Conduction Velocity

Answer 12

Function of the diameter and resistance

creates a problem because our fibers are so small

Question 13

Myelinated Axons, Nodes of Ranvier, Saltatory Conduction

Answer 13

Axons are coated in fat spaed out. The conduction jumps in a saltatory way between the empty spaces which are called nodes of Ranvier.
This allows for less energy to restore gradient, and increases speed