Action potentials Flashcards

1
Q

what is the advantage of passive conduction

A

direct coding

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is direct coding

A

coded strength directly indicates the signal strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are the two disadvantages of passive conduction

A

attenuation

noise

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is attentuation

A

coded signal decreases with distance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what are three advantages of active conduction

A

high amplitude
noise resistant
quite fast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is the basis of an action potential

A

changing the relative na and k conductances the membrane potential can change from -75 to +55

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are 4 points about leakage channels

A

always open
relatively low conductance
channels not affected by voltage or ligand

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are the two examples of voltage dependent channels for an action potential

A

na and k

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what activates voltage dependent channels for an action potential?

A

depolarisation
at resting potential (low conductance) channels tend to be closed
open (high conductance) when membrane depolarises- gets more positive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

describe opening and closing of na and k channels during action potential

A
na open (active) rapdily but then shut automatically (inactive) even if membrane stays depolarised - self limiting
k channels open (active) more slowly and do not shut while membrane stays depolarised
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is it that determines the action potential slope on a graph

A

feedback loops

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are the two feedback loops of an action potential

A

positive and negative

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

describe the positive feedback loop of an action potentual

A

depolarisation
increased sodium conductance
increase inflow of sodium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

describe the negative feedback loop of an action potential

A

depolarisation
increased potassium conductance
k outflow
leads to hyperpolarisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what does hyperpolarisation do

A

counteracts the depolarisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is an action potential threshold

A

all or none factor

if stimulus is not big enough, increased sodium conductance cant overcome leakage of potassium

17
Q

what is a refractory period

A

second stimulus elicited shortly after a first spike fails to initatiate a response

18
Q

what does refractory period set

A

an upper limit to spike frequency

19
Q

what does the refractory period ensure

A

uni directional propagation

20
Q

what are the two types of refractory periods

A

absolute

relative

21
Q

what is the absolute refractory period

A

cannot get another spike with second stimulus
after na active, takes them a while to deactive
until fully deactiveted, they cannot open the channel

22
Q

what is the relative refractory period

A

needs bigger than normal stimulus to get another spike
after membrane repolarises, k channels close slowly
residual excess k conductance after spike
makes membrane more difficult to depolarise

23
Q

how do spikes propagate

A

through passive conduction

24
Q

what reduces the space constant for propagation

A

excess potassium conductance

25
what is important for travelling far distances (AP)
conduction velocity
26
how can we increase conduction velocity
increase axon diameter
27
what are two disadvantages of fat axons
expensive | cant fit too many into small nerve bundles
28
what is myelination
myelin wrap around neurons
29
what does myelination do
blocks membrane leaks increasing the time constant and reduces capacitance meaning membranes charge faster
30
what is saltatory conduction
action potential jumps from node to node (nodes of ranvier)
31
what is mutiple sclerosis
immune system destroys central myelin | reduces space constant
32
when will current flow
if there is a driving force and a conducting path
33
what was the main aim of hodgkin and huxleys work
to explain the ionic basis of action potentials
34
what are two useful drugs for HH experiments
``` tetrodotoxin (TTX) tetraethyl ammonium (TEA) ```
35
what does TTX do
blocks na channels
36
what does TEA do
blocks k channels