From Power To Pump

Question 1

What is the primary function of calcium in cardiac muscle contraction

Answer 1

To bind to troponin to expose the actin binding sites so myosin can then bind

Question 2

Where is calcium stored in cardiomyocytes and what role does it have in contraction?

Answer 2

In the sarcoplasmic reticulum, the calcium is released to initiate contraction

Question 3

How is ATP used in muscle contraction

Answer 3

ATP is required to bind calcium to troponin

Question 4

What is the purpose of the plateau phase in the cardiac action potential

Answer 4

To allow for increased permeability of calcium ions, which will then be released into the cytosol

Question 5

What is cardiac functional reserve

Answer 5

The blood left in the heart during diastole

Question 6

What would cause a rightward shift in the frank starling curve?

Answer 6

Heart failure - right shift is when the heart is less effective at increasing stroke volume even though the preload may increase

Question 7

What would cause leftward shift of the frank staling curve

Answer 7

Exercise -

A leftward shift means there is an increase in the hearts ability to produce higher stroke volume with the same preload

Beneficial as exercise causes high cardiac demand

Question 8

How does SNS stimulation affect myocardial contractility?

Answer 8

• enhancement of calcium channel opening and contractility
• increases calcium influx into cells, allowing for stronger greater force of contraction

Question 9

How h=does the heart try and compensate for a failing ventricle in heart failure?

Answer 9

SNS and RAAS overactivate

• body detects lower cardiac output/pressure = baroreceptors signal to SNS
• this leads to increased preload and increased blood volume
• this can eventually worsen someone’s condition as they are overloaded

Question 10

What is the ejection fraction

Answer 10

The percentage of blood pumped our in each beat

Stroke volume / end diastolic volume

Question 11

Explain how the trpopmyosin, actin,, troponin complex works to shorten the sarcomere (for muscles to contract)

Answer 11

1. calcium ions bind to troponin
2. Causes conformational protein change
3. Actin binding sites are exposed
4. Myosin fibrils can now interact with actin
5. Binds, and myosin pulls on actin ATP needed

Question 12

What is cardiac functional reserve (plus equation)

Answer 12

The capacity to augment cardiac performance on demand

Maximal cardiac output - cardiac output at rest