Lecture 1 - Neuronal Action Potential Flashcards Preview

FHB Exam 1 - Cardiovascular Physiology > Lecture 1 - Neuronal Action Potential > Flashcards

Flashcards in Lecture 1 - Neuronal Action Potential Deck (54)
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1

Which vertebrate cell has the longest duration?
1. Motor
2. Skeletal
3. Cardiac Ventricle

Cardiac ventricle

- duration is fast, about 200 milliseconds

- heart has long AP to protect it from additional AP'
- thus cannot be activated as quickly

2

What is the term for the response that does NOT generate an AP because the voltage is not large enough?

Sub threshold response

- decreases in amplitude with distance
- change in membrane potential not sufficient for action potential

3

What is the length constant?

Distance over which a sub threshold depolarization (local response) will spread & influence the next membrane

- larger length constant = MORE RAPID CONDUCTION
(fires an AP)

4

When you decrease Rm, what happens to the space constant? What about decreasing Ri?

1. decrease Rm = decrease length constant

2. decrease Ri = INCREASE length constant

5

What is Rm and Ri?

Rm = membrane resistance
Ri = internal resistance (or Ra)

6

With a large axonal diameter, is the length constant large or small?

length constant is LARGE since Ri is LOW(internal resistance)

-

7

As distance increases from the current source, what happens to the sub threshold voltage?What manner does this decay (graph wise)

DECREASES (decays) with increasing distance from source

- decays EXPONENTIALLY

8

Larger diameter axons have lower or higher membrane and internal resistance? (rm and Ri)

Large diamter = LOWER resistance than smaller axon

- but since Ri is squared, it decreases more than rm

9

Large diameter results in _____ conduction

Faster conduction velocity

10

What determines how easily an axon can conduct an AP?

Space constant

11

What determines the space constant?

membrane Resistance
internal Resistance

12

What occurs once an area of membrane is activated by an action potential?

REVERSAL OF MEMMBRANE POLARITY

(inside becomes more positive than outside)
- originally NEG inside

13

Local current flow occurs between activated (depolarized) and inactive regions, activating ______ channels to depolarize the next segment of membrane and initiating an AP/

NA channels!!!

14

A stimulus is a ____ or ____ response.

All or none

15

Upstroke of the action potential graph is caused by what? Repolarization is caused by what?

1. Na activation (opening of M channels)

2. delayed increase in K+ conductance and inactivation of Na channels (closing of h gates)

16

Where is the only place AP's occur?

Nodes of Ranvier

17

An action potential occurs between the E of what two ions?

Ena and Ek

18

Repolarization turns off what channel conductance completely?

K+ (deactivated)

19

Describe the gating properties of Na channel at the following stages:

1. Resting
2. Activated
3. Inactivated

1. resting: M closed, h open
2. Activated: both open, NA INFLUX (h slowly closing)
3. Inactivated: M open, h closed

20

What is the time required to reset the channel from inactivated state back to resting state?

Recovery from Inactivation

21

Recovery from inactivation requires what?

Repolarization

22

Gating kinetics for Na and K both depend on what?

Time and Voltage

23

What gates due NOT have inactivation gates?

K+

24

What channels respond RAPIDLY to depolarization?

Na+ channels

25

What occurs during regenerative depolarization?

1. Na+ moves into the cell down its electrical & conc gradient
2. DEPOLARIZE membrane to Ena
3. increase Na permeability
4. causing FURTHER DEPOLARIZATION

26

What channels close rapidly at depolarized (positive) voltages?

Na+

- inactivation is time and voltage dependent

27

What is the basis for refractory periods?

Voltage-dependent inactivation of Na+ channels

28

Recovery from inactivation requires what?(to reach resting state)

1. time
2. Negative voltages (repolarization)

29

What channels remain open with maintained depolarization of the membrane? When do these channels completely deactivate?

K+!!!

- no inactivation
- completely deactivate with DEPOLARIZATION

30

What flows into the cell, what flows out?

NA in, K+ out (down its conc gradient)

Na moves down its electric and chemical gradient