Cardiac output

Question 1

What is is cardiac output?

Answer 1

Rate at which a ventricle pumps blood (L/min)

Question 2

What is heart rate?

Answer 2

Number of contractions per minute

Question 3

What is the calculation for cardiac output?

Answer 3

Heart rate x stroke volume

Question 4

What is extrinsic control?

Answer 4

Regulation of the heart by neural input, circulating hormones or any other factor from outside the heart

Question 5

What is intrinsic control?

Answer 5

Regulating factors originating in the heart

Question 6

What does the CNS do?

Answer 6

Controls muscles and other organs by way of signals sent through the efferent branch of the peripheral nervous system

Question 7

What are the two divisions of the autonomic nervous system?

Answer 7

Sympathetic and parasympathetic

Question 8

Where are the parasympathetic nerves?

Answer 8

Craniosacral, ganglia in/near viscera

Question 9

Where are the sympathetic nerves?

Answer 9

Thoracolumbar, paraspinal ganglia

Question 10

What cranial nerve is commonly associated with the autonomic input to the heart?

Answer 10

Vagus

Question 11

What is the parasympathetic neurotransmitter?

Answer 11

Acetylcholine

Question 12

What is the sympathetic neurotransmitter?

Answer 12

Noradrenaline

Question 13

What is the chain of events that occurs when there is increased sympathetic activity in the heart?

Answer 13

Acts on pacemaker cells of the SA node, more action potentials, increased heart rate so more cardiac output.
- Acts on AV node and conduction system, faster speed of conduction, ventricular contraction sooner after atrial contraction and less duration of systole

Question 14

What is the chain of events that occurs when there is increased parasympathetic activity in the heart?

Answer 14

Acts on pacemaker cells of the SA node, less action potentials, decreased heart rate so less cardiac output
AV node and conduction system, slower speed of conduction, ventricular contraction longer than atrial contraction, longer duration of systole

Question 15

What does adrenaline do?

Answer 15

Faster and more action potentials at SA node so increased heart rate.

Question 16

What does thyroid hormones (glucagon and insulin) do?

Answer 16

Increased force of myocardial contraction, glucagon promotes increased heart rate

Question 17

What are the three main things that affect stroke volume?

Answer 17

1) Ventricular contractility
2) End diastolic volume
3) Afterload

Question 18

What is ventricular contractility?

Answer 18

Force of the ventricular contraction, sympathetic neurons project to the ventricular myocardium, influence on myocardial contractility.
Increased sympathetic activity, ventricular contractility and increased cardiac output

Question 19

How does ventricular contractility work?

Answer 19

Increase of Ca concentration and permeability which increased contractility, adrenaline also increases myocardial contractility

Question 20

What is Starling’s law of the heart?

Answer 20

When the rate at which blood flows into the heart from the veins (venous return) changes, the heart automatically adjusts its output to match the inflow

Question 21

What does an increase in end diastolic volume result in?

Answer 21

Increased force of ventricular contraction, increased stroke volume and cardiac output

Question 22

What does an increased stretch of cardiac muscle result in brought on by an increase in EDV?

Answer 22

Increased affinity of troponin in muscle fibres for calcium, more cross bridges activated with contraction.
Cardiac muscles optimum length is more than the resting length so increased EDV brings muscle fibres closer to optimum length for contraction, contract with greater force

Question 23

What are the axis of Starlings curve?

Answer 23

Stroke volume (Y)
End diastolic volume (x)

Question 24

What does an increase in sympathetic activity show on Starlings curve?

Answer 24

Shifts curve upwards, due to an increase in ventricular contractility SV increases

Question 25

How does Starlings law regulate heart size?

Answer 25

Adjusting SV so that CO matches venous return

Question 26

What is preload?

Answer 26

End diastolic pressure - determined by pressure of blood inside heart before contraction-tension on the myocardium

Question 27

What is preload determined by?

Answer 27

Filling time
Heart rate
Atrial pressure (dependent on venous return and force of atrial contraction)

Question 28

What does an increase in arterial pressure result in?

Answer 28

Decreased stroke volume

Question 29

What is after load?

Answer 29

Arterial pressure placing a load on the myocardium after contraction starts

Question 30

What is after load determined by?

Answer 30

Pressure in the aorta

Question 31

True or false - an increase in sympathetic innervation on pacemaker cells decreases heart rate?

Answer 31

False

Question 32

True or false - the speed of conduction of an action potential is increased by noradrenaline released from the sympathetic nervous system?

Answer 32

True

Question 33

True or false - an increase in venous return causes an increase in stroke volume and cardiac output?

Answer 33

True

Question 34

True or false - after load is the pressure placed on the myocardium by the arteries after contraction starts?

Answer 34

True