Currents Flashcards

1
Q

Explain how the pacemaker potential works?

A

At full hyperpolarisation the funny channel is activated - Decreases K+ Permeability and increases Na+

The Membrane potential slowly rises (aided by opening of some T-type Ca2+ channels) till it hits threshold (~-40mV)

At threshold L-type Ca2+ channels open and the cells rapidly depolarises firing an AP.

At full depolarisation Ca2+ channels close and K+ channels open, an efflux of K+ causes repolarisation.

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

Explain how the non-pacemaker potential works?

A

Steady resting membrane potential is maintained by a high resting permeability to K+

Voltage gated Na+ channels open and Na+ floods the cell causes massive depolarisation.

Triggers opening of Ca2+ channels and closing of K+ channels which maintians plateu phase of depolarisation.

Ca2+ channels close and K+ open leading to repolarisation.

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

How does Temp affect HR?

A

a rise of 1C = a rise of 10BPM

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

How does Ivabradine work?

A

It inhibits the funny channel, slowing the pacemaker potential and so reducing HR

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

How do CCBs work?

A

They reduce the amount of Ca2+ allowed into the cell thus reducing force of contraction

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

How does hyperkalemia affect the heart?

A

Hyperkalemia
-> Loss of conc. gradient
-> K+ doesnt flow out of cell
-> Cell depolarises on its own
-> Random Contraction
-> Afib and AV block

(Hypokalemia does the same)

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

How does hypercalcaemia affect the heart?

A

It increases Contraction strength by increasing calcium available to cell.
Also causes Ca2+ to flood the cell faster leading to a raised HR

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