Cardiovascular Physiology Flashcards

1
Q

What is the resting potential of cardiac pacemaker cells?

A

-55 to -60

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2
Q

What is the stimulus for the cardiac pacemaker action potential generated by, at what level does depolarisation occur?

A

Na funny channels which slowly leak into the cell. When they reach a threshold the n L-type calcium channels open and cause the action potential. depolarisation is at -40mV.

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3
Q

How does the site of innervation of the PNS and SNS differ in the heart?

A

The PNS tends to impact nodal function whereas the SNS affects all areas.

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4
Q

Mechanism of PNS slowing heart rate

A

Act increases the permeability to potassium ions. These will leak out of the cell and cause the membrane potential to become more negative.

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5
Q

What effects does sympathetic stimulation have on the heart?

A

Increases nodal firing rate
Increases conductibility throughout all areas of the heart
Increases strength of contraction

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6
Q

What is the mechanism by which SNS has its cardiac effects?

A

It likely increases permeability to Na and Ca ions.

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7
Q

Which division of the circulation is not innervated by the sympathetic nervous system?

A

Capillaries (although pre-capillary sphincters and met arterioles may be innervated).

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8
Q

Where, anatomically, is the vasomotor centre located?

A

In the medulla and lower third of the pons.

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9
Q

Equation that predicts venous return.

A
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