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BDS2 BAMS Local Anesthetic > Action Potentials > Flashcards

Flashcards in Action Potentials Deck (46)
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1

What is the potential difference that exists across the membrane of all cells

The resting membrane potential

2

What is the range for the resting membrane potential

in the range of 20-90 mV

3

Which is negative - ICF or ECF

ICF

4

How is the charge distributed across the membrane

There is equal numbers of positive and negative charges in the ECF and ICF but ion/charge distribution is 'polarized'

5

What ions are in high concentration in the ECF

Na+ and Cl-

6

What ions are in high concentrations in the ICF

K+

7

What is the resting membrane impermeable to

Sodium

8

What is the resting membrane permeable to

Potassium

9

What does the diffusion of potassium leave excess of inside the cell

a negative charge

10

What does the RMP arise from

the separation of charges on either side of the membrane

11

What is the RMP due to

diffusion of potassium from cell interior through potassium channels

12

What is the small amount of sodium that leaks into the cell expelled by

sodium potassium pump

13

Although the RMP is due mainly to the diffusion of potassium from cell interior what else contributes

Na/K pump exchanging unequal numbers of sodium and potassium

14

What is the rising phase in an AP due to

na influx from voltage gated channels

15

What is the falling phase in an AP due to

K efflux through voltage gated channels

16

What are the ion channels

they are membrane proteins
they are aqueous channels through the membrane

17

What are the different types of gated opening channels

ligand
voltage

18

What are the ion specific channels

sodium
potassium
calcium 2+

19

What are the 2 gates on the voltage gated sodium channel

m gate
h gate

20

When the channel is closed what gate is open and which is closed

The m gate is closed
The h gate is open

21

When the channel is open which gate is open and which is closed

The m gate is open
The h gate is open

22

When the channel is closed during the refractory period which gate is open and which is closed

The m gate is open
The h gate is closed

23

Describe the stages of an AP

1. stimulus applied results in depolarization meaning that the MP moves towards the treshold
2. threshold is reached causing sodium channels to open and a sodium influx causing more depolarization while the potassium channels remain closed
3. When MP reaches the peak the sodium channels shut with inactivation of the h gate closes. potassium channels are open and efflux begins
4.Sodium channels are inactivated resulting in the refractory period while K efflux continues

24

What does the refractory period mean

It is a period of inexcitability
After an AP is initiated, the neuron cannot generate another AP until the first one has ended

25

What is the refractory period due to

inactivation of voltage gated sodium channels
The inactivation ('h) gates are shut so sodium cannot diffuse into the neuron

26

What are the consequences of the refractory period

it limits maximum firing frequency of AP in axons
it ensures unidirectional propagation of action potentials
It prevents summation of contractions in cardiac muscle - the cardiac AP lasts as long as the ventricular contraction

27

Describe AP propagation

AP in one section of axon sets up longitudinal current flow
This depolarizes adjacent resting parts of the axon
AP is regenerated further along the axon
More current flows and the next region of the axon is activated
AP travel as a wave

28

How does axon diameter effect the speed of AP propagation

it increases as the axon diameter increases

29

What does myelin do

speeds up AP propagation

30

Why are not all axons myelinated

Shwann cells make up the myelinated axon and these cells require nutrients to survive
This means an increased number of cells meaning they require more energy so isn't efficient if speedy AP is not required