Cardiac function

Question 1

What is the normal resting cardiac output?

Answer 1

75ml x70 beats/min = 5250 ml / min

Question 2

What is the normal ventricular volume?

Answer 2

150ml but we eject less than that

Question 3

What determines how much blood leaves the heart?

Answer 3

Aortic pressure

Contractility (how hard are muscles in heart contracting)

Question 4

What is cardiac work?

Answer 4

Pressure work is done moving blood from a region of low pressure to regions of high pressure

Question 5

What happens to cardiac output after a meal?

Answer 5

increases 20 - 30%

Question 6

What happens to CO when sleeping?

Answer 6

Drops by 10%

Question 7

What factors affect CO?

Answer 7

Central venous pressure

Blood volume

Gravity

Peripheral venous tone

The muscle pump

Respiration

Systemic Vascular Resistance

Myocardial contractility

Heart rate

Question 8

How can EDV be changed?

Answer 8

Increasing preloading pressure (Venous filling pressure)

Force of atrial contraction (25% in humans)

Time available for filling the ventricle

Distensibility of ventricular wall

Question 9

How can ESV be changed?

Answer 9

Force of ventricular contraction

Resistance or backpressure in outflow artery (Afterload)

Question 10

What is the Frank-Starling Law?

Answer 10

increased heart volume stretches muscles and causes a stronger contraction

Question 11

What happens in cardiac muscles to increase power

Answer 11

Elastic recoil can be used for more power in contraction. This is due to the closer packing of sarcomeres together resulting in more tension when stretched out

Question 12

How do we get more blood back to the heart?

Answer 12

Increasing Venous return

Question 13

What factors influence venous return?

Answer 13

Peripheral venous tone

Gravity

Blood volume

Skeletal muscle pump

Respiratory pump

Question 14

What does the sympathetic NS do to venous tone?

Answer 14

It increases tone and increases venous return

Question 15

Why does the muscle pump work?

Answer 15

Due to presence of valves

Question 16

What is the main factor that influences contractility?

Answer 16

Calcium

Question 17

What is inotropy?

Answer 17

Increase in strength of contraction from delivery of calcium to our heart muscles

Question 18

What does digitalis do?

Answer 18

A cardiac glycoside drug that lowers the activity of Na+/K+ ATPase and therefore NCX transporter activity resulting in elevated ICF Ca2+ which creates a stronger graded contraction

Question 19

How can aCh affect on the heart?

Answer 19

Through the blood directly not through the parasympathetic NS

Question 20

Can the heart be affected by the parasympathetic NS?

Answer 20

No

Question 21

How does contractility get affected by sympathetic inotropy?

Answer 21

It increases length of time voltage gated Ca channels are open

Increases amount of Calcium in sarcoplasmic reticulum

Question 22

What receptors do the heart have for sympathetic NS?

Answer 22

Beta 1 receptors

Question 23

What does increasing afterload result in?

Answer 23

lower ejection volume and in turn a lower ESV this can be caused by elevated blood pressure or a loss of compliance in the aorta due to loss of elasticity

Question 24

What happens to preload when heart rate goes up?

Answer 24

It drops