Lecture 6 - The Heart as a Pump

Question 1

How to increase force of cardiac contraction? (2)

Answer 1

1. Increase cytosolic Ca levels
2. Therefore increase the number of cross bridges (the extent of x bridges formed at rest is not maximised)

REMEMBER: each cardiomyocyte is activated during heart beat

Question 2

Cellular mechanism of relaxation (5 things - three things happen)

Answer 2

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Question 3

Heart failure with the Ca story

Answer 3

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Question 4

What pattern does the heart beat in?

Answer 4

Twists and contorts

Cardiac fibres are in a helical pattern

Question 5

Blood flow can be calculated by dividing changes in blood pressure by what value?

Answer 5

Vascular resistance

Question 6

Cardiac Cycle and it’s main phases (5)

And….go!

Answer 6

1. AV valves open = blood flowing in ventricles so want as much pressure and volume (atrial systole).
2. (AV close) Isovolumetric ventricular contraction = ventricles contracting but ALL valves closed so blood volume in ventricles is same so pressure is going up. When pressure of ventricles higher than aorta then SL open and blood goes out
3. Ejection = SL open and blood flows into aorta + pulmonary artery (only about 60% ejected)
4. Isovolumetric ventricular relaxation = ventricles relax and still some blood so pressure falling (all valves closed). Atria are refilling with blood from vena cava
5. Passive ventricular filling = yeah, blood comes on. Pressure builds up to certain point and AV valves open and ventricles are filled

Systole = 2 and 3
Disatole = 4, 5 and 1

Question 7

Cyclical changes in arterial pressure network

1. Does the heart spend more time in systole or diastole

Answer 7

1. Dias

Check out that slide though

Question 8

Check out the pulsatile blood flow in art to continuous flow in cap

Answer 8

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Question 9

What’s different between right and left ventricle?

Answer 9

One has more power (left one) to get higher pressure but same blood flow i.e the resistance of left is higher