Heart As A Pump (2)

Question 0

Which valves control outflow?

Answer 0

• Aortic and pulmonary

Question 1

Which valves are the atrioventricular valves?

Answer 1

• Tricuspid (RA/RV)

- Mitral (LA/LV)

Question 2

How is the contraction of heart muscles controlled?

Answer 2

• When action potential is present in membrane
• AP causes an increase in Intracellular calcium
• AP in heart is a long, single contraction that lasts 280ms
• AP is triggered by spread of excitation from cell to cell.

Question 3

How is the initial AP generated in the heart?

Answer 3

• AP generated in a small group of cells
• Spreads over whole heart
• Producing a coordinate contraction

Question 4

How does excitation spread across the heart muscle?

Answer 4

• SAN is pacemaker
• Spreads over atria-atrial systole to reach AVN delays for 120ms
• AVN spreads signal down septum (bundle of His) between ventricles
• Then through ventricular myocardium from endocardial to epicardial surface
• Ventricle contracts from apex increasing pressure and forcing blood though outflow valves

Question 5

What are the amounts of time associated with systole then diastole?

Answer 5

• Systole: short atrial systole then longer ventricular systole: ~280ms
• Diastole: ~700ms

Question 6

How do the ventricles fill with blood?

Answer 6

• Via veins during diastole

- Small proportion is from atrium

Question 7

What is the role of the mitral valve and how does it work?

Answer 7

• Inflow valve
• Allows atrium to ventricle flow not vice-versa
• Opens when ventricular>atrial pressure

Question 8

What is the aortic valve’s role and when does it open/close?

Answer 8

• Outflow valve
• Opens when intraventricular > aortic pressure
• Closes when aortic > intraventricular pressure

Question 9

The ‘lup’ and ‘dup’ noises are related to what part of the cardiac cycle?

Answer 9

• Lup: closure of a/v valves - onset of ventricular systole

- Dup: closure of outflow valves - end of ventricular systole

Question 10

What are heart murmurs?

Answer 10

• Turbulent blood flow

Question 11

Why may heart murmurs occur?

Answer 11

• Narrowing of valves - stenosis
• Valve not closing properly - incompetence
• Only occurs when blood flow is at its highest

Question 12

What is the cardiac output equation

Answer 12

• Cardiac output = stroke volume x heart rate

Question 13

What would be the at rest and exercising cardiac output values?

Answer 13

• At rest: 5L/min

- Exercise: 25L/min