Neuro 3

Question 1

Does voltage travel actively or passively?

Answer 1

Passive

Question 2

Which membranes have the ability to generate action potentials?

Answer 2

Excitable membranes

** the presence of Na channels make the membrane excitable

Question 3

3 phases of action potential

Answer 3

Depolarization

Repolarization

After - hyper polarization

Question 4

If a membrane potential is measured at the site of stimulus and again at the axon hillock, where will the membrane potential be greater?

Answer 4

At the site of the stimulus

Decays as it travels

Question 5

An action potential will only be triggered if the membrane potential reaches which value

Answer 5

-50

Question 6

How are action potentials different from graded potentials?

Answer 6

Action potentials have the same size and duration for any particular Neuron and are usually conducted the entire length of an axon without decaying

Question 7

Do graded potentials depend on an all or nothing principle?

Answer 7

No. Only action potentials depend on that property

Question 8

During the rapid depolarization of an Action potential the membrane potential is closer to ENa or EK?

Answer 8

Na will rush in causing the potential of the cell to be closer to ENa

Question 9

Which potentials bring the membrane to threshold?

Answer 9

Graded

Question 10

What does threshold trigger?

Answer 10

Rapid opening of Na channels
Slow closing of Na channels
Slow opening of K channels

Question 11

Which 2 gates are associated with the sodium channel?

Answer 11

1. Activation gate

2. Inactivation gate

Question 12

3 main points about the Activation Gate

Answer 12

1. Voltage dependent
2. Opens at threshold and depolarization
3. Positive feedback

Question 13

3 important points on Inactivation Gate

Answer 13

1. Voltage and time dependent
2. Close during depolarization
3. Open during depolarization

Question 14

Define the all or nothing principle

Answer 14

Minimum depolarization necessary to induce the regenerative mechanism for the opening of the sodium channel

Question 15

What is a refractory period

Answer 15

The period of time following an action potential

Marked by decreased excitability (some or all Na channels are inactivated)

Question 16

What are the two types of refractory period

Answer 16

1. Absolute - none of the Na channels are reconfigured

2. Relative - some Na channels are reconfigured

Question 17

When and why does the absolute refractory period occur ?

Answer 17

When - soon after opening of the Na channels

Why - so that second AP cannot be generated

Question 18

When and why does the relative refractory period occur?

Answer 18

When - last part of the Repolarization phase

Why - able to generate another AP (small one)

Question 19

True/false

A stimulus a little stronger than normal is necessary to generate an action potential late in the refractory period

Answer 19

True

Question 20

True/false

A stimulus a little stronger than normal is necessary to generate an action potential early in the refractory period

Answer 20

False

-much stronger than normal

Question 21

Propagation of action potentials depend on the presence or absence of:

Answer 21

Myelin

Question 22

What is the mechanism by which action potentials are prolog aged in unmyelinated axons

Answer 22

ELECTROTONIC conduction

Question 23

How does an action potential travel down an unmyelinated axon

Answer 23

The region of depolarization continues to move down the axon. A refractory period then occurs behind the region of depolarization

Question 24

The region of depolarization in an unmyelinated axon is more positive where

Answer 24

On the inside

Question 25

The diameter of an axon determines

Answer 25

How quickly current spreads (conduction velocity)

Larger diameter = less resistance

Question 26

The node of Ranvier contains

Answer 26

High density of voltage gated Na channels. There are no K channels therefore no hyper polarization

Question 27

Saltatory conduction

Answer 27

AP jumps between nodes

No signal is lost

Create a new AP at every node