Cardiac cycle

Question 1

What is the CO of a general person at rest?

Answer 1

5L/min

Question 2

How much of the cycle is spent in diastole?

Answer 2

2/3

Question 3

Why is MAP closer to diastolic pressure than systolic pressure?

Answer 3

More time spent in diastole

Question 4

What is MAP?

Answer 4

Diastolic pressure + 1/3 pulse pressure

Question 5

What is pulse pressure?

Answer 5

Systolic pressure - diastolic pressure

Question 6

Describe the cardiac cycle

Answer 6

Atrial systole - allowing a small amount of blood into the relaxed ventricles. This is the EDV.
Atria diastole/ventricular systole (isovolumetric contraction) - AV valves close. Ventricular pressure pressure increases until it exceeds that in the arteries. Aortic (semi lunar) valves open and blood is ejected. The volume of blood ejected is the ESV.
Iso-volumetric relaxation/ ventricular diastole - semilunar valves close as ventricular pressure drops below arterial.
As it drops below atrial pressure AV valves open and blood flows into the atria.
Ventricles then fill passively.

Question 7

What is heart rate?

Answer 7

Number of beast per minute

Question 8

What is stroke volume?

Answer 8

Volume of blood pushed out per beat

Question 9

How is cardiac output calculated?

Answer 9

CO = HR x SV

Question 10

What is venous return?

Answer 10

The rate of blood flow back to the heart

Question 11

How is VR calculated?

Answer 11

VR = CO

Question 12

What is EDV?

Answer 12

End diastolic volume - the volume in the ventricles at the end of diastole - the maximum volume - the sarcomeres are at maximal stretch

Question 13

When are the sarcomeres at their maximal stretch?

Answer 13

EDV

Question 14

What is ESV?

Answer 14

The volume at the end of systole

Minimal volume in the ventricles

Question 15

When is the point of highest pressure?

Answer 15

ESV

Question 16

How is SV calculated?

Answer 16

EDV - ESV

Question 17

What is the ejection fraction?

Answer 17

The fraction of blood ejected from he ventricles per heart beat

Question 18

How is EF calculated?

Answer 18

SV/EDV

Question 19

What does Frank-Starlings law state?

Answer 19

Strength of systole is directly proportional to diastolic expansion

Question 20

What is the effect of Frank-Starlings law?

Answer 20

Under normal physiological conditions the heart pumps out all of the blood in the right atria without letting any back into the veins

Question 21

How does an increase in VR affect SV?

Answer 21

Increases myocardial contraction and increases SV

Question 22

What provides parasympathetic innervation to the heart?

Answer 22

Vagus nerve

Question 23

What is the effect of parasympathetic stimulation on the heart?

Answer 23

Decrease heart rate and decrease the strength of the contraction

Question 24

What neurotransmitter is used by parasympathetic fibres to the heart?

Answer 24

Acetylcholine

Question 25

What is the effect of sympathetic stimulation on the heart?

Answer 25

Increase heart rate and strength of contraction

Question 26

What neurotransmitter is used by sympathetic fibres?

Answer 26

Noradrenaline

Question 27

How does acetylcholine decrease HR?

Answer 27

Increases permeability of K+ ions which decreases the rate of depolarisation and increases rate of repolarisation

Question 28

How does noradrenaline increase HR?

Answer 28

Increases permeability of Na+ and Cl- ions which increases rate of depolarisation and decreases rate of repolarisation

Question 29

What happens to strength of contraction if length of cardiac muscle is increased?

Answer 29

It increases