Cardiac physiology

Question 1

How many mechanical pumps does the heart have?

Answer 1

• The heart has 2 mechanical pumps, left and right side.
• The right side deal with the deoxygenated blood coming from the body and pumping the blood back to the lungs.
• The left side deals with oxygenated blood, receiving blood from the lungs and then pumping it to the rest of the body.

Question 2

How many chambers does the heart have?

Answer 2

4 chambers:

1. At the top of the heart:

• Left and Right atrium where blood is received from the veins.
• In the right side of the heart, the blood is being received from the superior vena cava
• In the left side the blood is coming from the pulmonary vein.

2. At the bottom of the heart

• The left and right ventricles
• Thee right ventricle deals with deoxygenated blood and pumps it to the lungs
• The left ventricle deals with oxygenated blood and pumps it via the aorta to the rest of the body.

Question 3

Why does the left side of the heart have a thicker wall?

Answer 3

Because it generates more forces than the right side.

Question 4

What is the left and right sides of the heart separated by?

Answer 4

By a septum

Question 5

Where do the top chambers receive blood from?

Answer 5

The veins

Question 6

Where does the bottom ventricles push blood into?

Answer 6

Into the arteries

• The right side pushes blood into the pulmonary artery
• The left side pushes blood into the aorta to go the rest of the body.

Question 7

How many one-way valves are in the heart?

Answer 7

4

• The valves work by a passive process so when the weight of the blood pushes on them, they will open.

Question 8

What are the 2 AV (atrial ventricular) valves called?

Answer 8

1. Bicuspid (Mitral) - Left (It has two leaflets on the valve)
2. Tricuspid - right (It has three leaflets on the valve)

Question 9

What are the valves supported by?

Answer 9

Chordae tendineae

• Which are activated by papillary muscles.
• The papillary muscles contract with ventricles to prevent back-flow, hence they seal the valve shut, separating the atria from the ventricles.

Question 10

What are 2 valves in the arteries called?

Answer 10

Pulmonary and Aortic valves
- Its only the arteries not the veins
- These contain 3 cusps
- They’re semi-lunar (so forms half-moon shapes)
- They’re prevented from upturning because of evertion which prevents them from flipping the wrong way.
- They close under back pressure - so as soon as theres any back pressure, these valves close

Question 11

What is the heart doing during diastole?

Answer 11

During diastole the heart is relaxing and filling.

So at the beginning of diastole, the AV valves are closed and the aortic pulmonary valves are closed, and this is when the heart heart begins to fill with blood, the atria fill with blood from the veins. The ventricles are relatively empty and the atria start to fill with blood.

As diastole proceeds (middle process), the weight of the blood will eventually open the AV valves but the aortic and pulmonary valves remain closed. The blood will pass from the atria into the ventricles, and the ventricles will start to fill with blood.

At the final stage of diastole, the AV valves are open and this is when the atria begin to contract to push the remaining blood into the ventricles but the aortic and pulmonary valves remain closed. This is where the blood is now being transferred to the ventricles ready for pumping into the arteries, but it’s still filling with blood.

Question 12

What is the heart doing during systole?

Answer 12

This is the active phase. This is where we now have contracting and emptying of the heart.

At the start of systole, the AV valves will close and this will prevent backward flow of the blood from the ventricles to the atria but the aortic and pulmonary valves remain closed. At this point the ventricles begin to contract. The blood now is remaining inside the ventricles but it starts to build pressure. There is no change in volume at this point because the blood can’t go anywhere, it can’t go back to the atria because the AV valves are closed, and it can’t be pushed into the arteries because the aortic and pulmonary valves are closed. Therefore there’s no change in volume and the heart begins to contract.

Then we proceed to the end stage of systole where the AV valves remain closed so the blood now can’t get back into the atria but now the aortic and pulmonary valves open. At this point the blood is pushed from the ventricles into the aortic and pulmonary arteries.

Question 13

What does the ‘end systolic volume’ tell us?

Answer 13

Amount of blood in ventricle at end of systole.

Question 14

What does the ‘end diastolic volume’ tell us?

Answer 14

Amount of blood at end of diastole

Question 15

How do you work out the stroke volume mass?

Answer 15

Stroke volume= End diastolic volume - End systolic volume

Question 16

What is the stroke volume mass?

Answer 16

The amount of blood ejected by the heart in a single beat.

Question 17

What does the desmosome provide?

Answer 17

Mechanical support, so the cells are attached and can’t pull away from each other.

Question 18

What does the gap junction provide?

Answer 18

They provide the transmission of the action potentials.

Question 19

Why does the heart need to be a lubricated system?

Answer 19

If not then the heart will rub against the surrounding tissues.

Question 20

How is the heart prevented from rubbing against surrounding tissues? (lubrication)

Answer 20

The heart is surrounded by a pericardial sac.

• This is a double walled sac
• Its a tough covering
• It has 2 functions; Firstly it anchors the heart and secondly its a secretory lining - it has pericardial fluid which serves to lubricate the heart and stops it from rubbing against the surrounding ribcage and other tissues.
• This can become infected, known as Pericarditis (painful rubbing). It is often because of viral or bacterium infection. This is where the fluid becomes inflamed and you start to feel the rubbing which is quite painful.