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BDS2 BAMS Local Anesthetic > Action Potentials > Flashcards

Action Potentials Flashcards

1
Q

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

A

The resting membrane potential

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2
Q

What is the range for the resting membrane potential

A

in the range of 20-90 mV

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3
Q

Which is negative - ICF or ECF

A

ICF

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4
Q

How is the charge distributed across the membrane

A

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

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5
Q

What ions are in high concentration in the ECF

A

Na+ and Cl-

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6
Q

What ions are in high concentrations in the ICF

A

K+

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7
Q

What is the resting membrane impermeable to

A

Sodium

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8
Q

What is the resting membrane permeable to

A

Potassium

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9
Q

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

A

a negative charge

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10
Q

What does the RMP arise from

A

the separation of charges on either side of the membrane

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11
Q

What is the RMP due to

A

diffusion of potassium from cell interior through potassium channels

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12
Q

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

A

sodium potassium pump

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13
Q

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

A

Na/K pump exchanging unequal numbers of sodium and potassium

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14
Q

What is the rising phase in an AP due to

A

na influx from voltage gated channels

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15
Q

What is the falling phase in an AP due to

A

K efflux through voltage gated channels

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16
Q

What are the ion channels

A

they are membrane proteins

they are aqueous channels through the membrane

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17
Q

What are the different types of gated opening channels

A

ligand

voltage

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18
Q

What are the ion specific channels

A

sodium
potassium
calcium 2+

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19
Q

What are the 2 gates on the voltage gated sodium channel

A

m gate

h gate

20
Q

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

A

The m gate is closed

The h gate is open

21
Q

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

A

The m gate is open

The h gate is open

22
Q

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

A

The m gate is open

The h gate is closed

23
Q

Describe the stages of an AP

A
  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
Q

What does the refractory period mean

A

It is a period of inexcitability

After an AP is initiated, the neuron cannot generate another AP until the first one has ended

25
Q

What is the refractory period due to

A 
inactivation of voltage gated sodium channels
The inactivation ('h) gates are shut so sodium cannot diffuse into the neuron
26
Q

What are the consequences of the refractory period

A

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
Q

Describe AP propagation

A

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
Q

How does axon diameter effect the speed of AP propagation

A

it increases as the axon diameter increases

29
Q

What does myelin do

A

speeds up AP propagation

30
Q

Why are not all axons myelinated

A

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

31
Q

How does myelin speed up conduction

A

It forms an insulating layer, reducing leakage of current from axon

32
Q

What are nodes of ranvier

A

Where the myelin sheet is interrupted

Here the axon membrane is exposed to the ECF and ion flow can occur

33
Q

What is saltatory conduction

A

Saltatory conduction (from the Latin saltare, to hop or leap) is the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials.

34
Q

What is the endoneurium

A

a layer of connective tissue around the myelin sheath of each nerve fiber in the peripheral nervous system

35
Q

What is the perineurium

A

the sheath of connective tissue surrounding a bundle (fascicle) of nerve fibres within a nerve

36
Q

What is the epineurium

A

The epineurium is the outermost layer of dense irregular connective tissue surrounding a peripheral nerve

37
Q

What is the end, peri and epineurium made up of

A

lipid

38
Q

What respects are the axons in peripheral nerves different

A 
in their size (axon diameter and conduction velocity 
function (sensory, motor)
39
Q

What are the axon types present in cutaneous nerves

A

Abeta
Adelta
C

40
Q

What is the structure of Abeta nerves in cutaneous nerves

A

myelinated

41
Q

What is the structure of Adelta nerves in cutaneous nerves

A

myelinated

42
Q

What is the structure of C nerves in cutaneous nerves

A

unmyelianted

43
Q

What is the function of Abeta nerves

A

mechanoreceptors

44
Q

What is the function of Adelta nerves

A

mechanoreceptors
thermoreceptors (cold)
nociceptors
chemoreceptors (taste)

45
Q

What is the function of C nerves

A

mechanoreceptors
thermoreceptors (hot and hot)
nociceptors

46
Q

Is there a lot of myelinated axons in the coronal tooth pulp

A

In the pulp there will be a larger number of unmyelinated fibers

BDS2 BAMS Local Anesthetic (3 decks)

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