Regulation of SV and HR

Question 1

How does TPR fall in the control of cardiac output?

Answer 1

Arteriolar dilation in muscle, skin and heart

Question 2

How does venous return increase in the control of cardiac output?

Answer 2

Venoconstriction

Skeletal/respiratory pumps

Question 3

How does the sympathetic nervous system increase heart rate?

Answer 3

Releases NA/ adrenaline
These act on beta-1 receptors at SA node
Increases slope of pacemaker potential

Question 4

How does the parasympathetic nervous system decrease heart rate?

Answer 4

Vagus nerve releases Ach
This acts on muscarinic receptors at the SA node
Hyperpolarises cell and decreases slope of pacemaker potential

Question 5

How is stroke volume increased by venous return?

Answer 5

Increased venous return increases end diastolic volume which increases stroke volume

Question 6

What is afterload?

Answer 6

Load against which the muscle tries to contract

Question 7

How does TPR decrease stroke volume?

Answer 7

An increase in TPR increases aortic pressure which decreases stroke volume

Question 8

Why is stroke volume decreased by an increase in TPR?

Answer 8

Due to less energy being able to push through blood into the aorta

Question 9

How does the sympathetic nervous system’s effect the SV?

Answer 9

Release NA/ adrenaline
Acts on beta-1 receptors on the myocytes
Increases contractility - shorter but stronger contraction

Question 10

What kind of effect does the parasympathetic system have on the stroke volume?

Answer 10

Little effect

Vagus nerve does not innervate the ventricular muscle