2 CVS

Question 1

The contraction of each myocyte is produced by a intracellular rise in which ion?

Answer 1

calcium

Question 2

How long is a cardiac action potential?

Answer 2

200-300ms, this is very long!

Question 3

The normal heart pacemaker is the … ?

Answer 3

Sinoatrial node

Question 4

The period when the myocardium is contracting is called …

Answer 4

Systole

Question 5

The period the myocardium is relaxing and filling between contractions is called

Answer 5

Diastole

Question 6

What is the rapid filling phase of diastole? What is it due to?

Answer 6

Rapid filling phase is the initial filling of the ventricle with blood from the atria. This is a PASSIVE mechanism, and it occurs because of differential pressure between the atria (full of blood) and the ventricle (relaxed).
This rapid filling phase is responsible for 90% of the EDV.

Question 7

What does atrial contraction do?

Answer 7

It force a small extra amount of blood into the ventricles. This ACTIVE filling phase is only responsible for 10% of EDV.

Question 8

What is the first heart sound (cause, sound)?

Answer 8

S1 is caused by mitral and tricuspide valves closing.

• it is the LUP
• sound is crescendo-decrescendo

Question 9

What is the second heart sound (cause, sound)?

Answer 9

S2 is caused by the aortic and pulmonary valves closing.

• is is the DUB
• shorter duration, higher frequency, lower intensity

Question 10

how is cardiac output defined?

Answer 10

• volume pumped per minute by the left heart

- stroke volume x heart rate

Question 11

What is stroke volume?

Answer 11

It is the volume of blood ejected per cardiac cycle (i.e. per contraction)
Is it the difference between the EDV and the ESV.

Question 12

What is afterload?

Answer 12

It is the force necessary to expel blood into the arteries.

Question 13

Can preload and afterload vary independently?

Answer 13

Yes

Question 14

If the myocardium is stretched before contraction (ie. preload is increased) then, within limits it will … harder during the following systole.

Answer 14

… contract…

increased V stretch = increased force of contraction

Question 15

increase in venous pressure induces an increase in… (2)

Answer 15

• EDV

- stroke volume

Question 16

A decrease in total peripheral resistance TPR induces … in stroke volume

Answer 16

Increase in stroke volume!

=> decrease in TPR = increase in stroke volume

Question 17

A decrease in total peripheral resistance can be called reduced …

Answer 17

afterload

Question 18

What leads to an increase in stroke volume? Name 2

Answer 18

• decrease in total peripheral resistance

- increase in venous pressure

Question 19

if stroke volume increases, what else will increase?

Answer 19

• cardiac output

Question 20

What happens if TPR falls, how does the body respond?

Answer 20

arterial pressure will fall, venous pressure will rise.

- heart will respond by pumping more, which increase arterial pressure and reduce venous pressure = restoring status quo