Cardiac output - mechanical events and stroke volume

Question 1

What is the average heart rate?

Answer 1

6-72bpm.

Question 2

What effect does a bigger heart have on stroke volume and heart beat?

Answer 2

Bigger stroke volume so slower heart beat.

Question 3

Why do both ventricles have to have the same volume?

Answer 3

Otherwise blood would collect at a point in the body.

Question 4

What are the two phases that the cardiac cycle can be divided into?

Answer 4

Systole and diastole. Systole is ventricular contraction and blood ejection whereas diastole is ventricular relaxation and blood filling.

Question 5

What is the average blood pressure?

Answer 5

120mm/80mm.

Question 6

What is the cardiac cycle mostly driven by?

Answer 6

Changes in pressure within the ventricles. There is a minor part played by atrial contraction.

Question 7

What is isovolumetric contraction?

Answer 7

When the ventricles contract but there is no change in volume - the pressure is increasing but is not high enough yet.

Question 8

What happens when the pressure in the ventricles continues to increase?

Answer 8

The aortic and pulmonary valves will open when the pressure is above 80mm on both sides.

Question 9

What happens when the blood has left the heart and the pressure in the arteries starts to increase?

Answer 9

The valves will shut.

Question 10

What draws blood into the heart?

Answer 10

There is a vacuum that is created as the heart relaxes which draws blood into the ventricles.

Question 11

What happens when the vacuum has been created and the blood is drawn in?

Answer 11

The atria will contract to push the extra 10% of blood into ventricles.

Question 12

What is the end diastolic volume?

Answer 12

The volume left in the heart when the heart as contracted - usually 65ml.

Question 13

What is the maximal volume of blood the heart can hold?

Answer 13

130-140ml of blood.

Question 14

What are the 4 stages of diastole and systole?

Answer 14

Ventricular filling, isovolumetric ventricular contraction, ventricular ejection, isovolumetric ventricular relaxation.

Question 15

What is the first sound created when you listen with a stethoscope? (lub)

Answer 15

The closure of the atrioventricular valves.

Question 16

What is the second sound created by the heart when you listen with a stethoscope? (dub)

Answer 16

The closure of the pulmonary and aortic valves.

Question 17

What causes heart murmurs?

Answer 17

The change from laminar to turbulent flow.

Question 18

What is the condition called with narrowed vessels?

Answer 18

Stenosis.

Question 19

What is it called when blood flows backwards through leaky valves?

Answer 19

Insufficiency.

Question 20

What is a septal defect?

Answer 20

A hole in the heart.

Question 21

What is pre-load (end diastolic ventricular volume) determined by?

Answer 21

Central venous pressure.

Question 22

What can affect the central venous pressure?

Answer 22

Breathing (respiratory pump) - the pressure difference between the abdomen and chest, changes in blood volume - reduced blood volume leads to reduced CVP, skeletal muscle pump - blood can be squeezed back towards the heart, and contraction of central and peripheral veins can increase CVP, gravity.

Question 23

What is the Frank-Starling mechanism?

Answer 23

The idea that the ventricles contract with more force if it contains more blood. It is determined by the length-tension relationship in the muscle - the greater the strength the more tensioned developed in the cardiac muscle.

Question 24

What is the purpose of the Frank-Starling mechanism?

Answer 24

It maintains the balance between right and left sides of the heart to stop accumulation of blood in the lungs.

Question 25

What factors affect/regulate stroke volume?

Answer 25

The filling pressure (preload), the contractility and arterial pressure.

Question 26

What is the equation for cardiac output?

Answer 26

Heart rate x stroke volume

Question 27

What is congestive heart failure?

Answer 27

Reduced cardiac output.

Question 28

What are some of the symptoms of congestive heart failure?

Answer 28

Tiredness and shortness of breath, fluid retention.

Question 29

What is the most common type of congestive heart failure?

Answer 29

Chronic left ventricular failure - coronary artery disease leading to ischaemic heart disease and myocardial infarction (systolic dysfunction), hypertension (diastolic dysfunction) and cardiomyopathy (viral infection, heavy drinking).

Question 30

What is systolic dysfunction?

Answer 30

Problems with ventricular ejection.

Question 31

What is diastolic dysfunction?

Answer 31

Ventricular filling.