Lecture 4 - Cardiac Cycle and Haemodynamics

Question 1

What happens when the ECG peaks in the QRS complex ?

Answer 1

Action potential spreads upwards through the ventricular muscle

Question 2

What does T on the ECG signify?

Answer 2

The heart returning to a resting state, remaining there until another action potential is generated at the SA node

Question 3

What happens at P

Answer 3

An action potential is generated at the SA node

Question 4

What happens at after the P wave before Q

Answer 4

Action potentials are conducted from the SA node to the atrial muscle

Question 5

What at the start of the slope before Q

Answer 5

Action potentials spread through atria to to the AV node where conduction flows.

Question 6

What happens at Q

Answer 6

Action potentials travel rapidly through the conduction system to the apex of the heart

Question 7

What is ventricular systole?

Answer 7

Contraction and ejection of blood by the ventricles

Question 8

What is a ventricular diastole?

Answer 8

Ventricular relaxation and filling

Question 9

What does the cardiac cycle consist of?

Answer 9

Alternate periods of ventricular systole and diastole

Question 10

How do atrial activities alternate with ventricular activities?

Answer 10

Atrial filling during ventricular systole and Atrial contraction during ventricular filling

Question 11

When is ventricular filling active and when is it passive

Answer 11

Passive during early diastole and active during late diastole

Question 12

What happens in phase 1 of the cardiac cycle

Answer 12

Atrial contraction and ventricular filling

Question 13

What happens in phase 2 of the cardiac cycle

Answer 13

Isovolumetric contraction (systole) and pressure build up in ventricles

Question 14

What happens in phase 3 of the cardiac cycle?

Answer 14

Systolic ejection. When the ventricle contracts and blood is pumped into the aorta and the pulmonary artery.. There is a peak in aortic pressure and LV pressure drops. Ventricular ejection

Question 15

What happens in stage 4 of the cardiac cycle?

Answer 15

Isovolumetric relaxation. Aortic pressure starts to drop slightly.

Question 16

What kind of energy is required to maintain circulation?

Answer 16

Hydraulic energy. It is supplied by the work done by the heart

Question 17

What is cardiac power

Answer 17

Rate of work done by the heart

Question 18

What is the power calculated?

Answer 18

Pressure x flow rate

Question 19

What is stroke volume?

Answer 19

Stroke volume is the amount of blood ejected by the left ventricle in one contraction. 70-90ML

Question 20

What is end diastolic volume?

Answer 20

Volume of blood left in each ventricle when it relaxes and fills. Usually around 130 ml.

Question 21

What is end systolic volume

Answer 21

Is amount of blood left at the end of contraction. about 50 ml of blood is left in each ventricle at the end of systole.

Question 22

Stroke volume equation

Answer 22

EDV - ESV

Question 23

What is the ejection fraction

Answer 23

Percentage of end diastolic ventricular volume that is ejected with each stroke - SV/EDV

Question 24

Cardiac output = ?

Answer 24

Mean flow output of heart L/min

= Heart rate per minute x stroke volume ml

Question 25

What is cardiac output in a resting supine man and when exercising ?

Answer 25

5 L per minute and 20 L/min

Question 26

What is cardiac reserve?

Answer 26

During maximal exercise, the cardiac output can be as high as thirty-five liters per minute. This tremendous capacity of the heart to increase its pumping ability is accomplished by increasing the heart rate and stroke volume and is termed the reserve capacity of the heart.

Question 27

cardiac reserve during diastolic ventricular filling

Answer 27

during exercise 16 L/min | cardiac reserve - 13 L/min

Question 28

How is cardiac reserve flow diminished b ventricular fibrillation

Answer 28

there is no flow as there is no ventricular ejection.

Question 29

What is the primary function of the heart?

Answer 29

to convert chemical into hydraulic energy (FFA's to ATP) in order to maintain a physiological circulation

Question 30

What is blood pressure

Answer 30

Force exerted on per unit area of blood mm/Hg

Question 31

Pulmonary artery pressure

Answer 31

25/10

Question 32

Left ventricular Systolic and diastolic pressure

Answer 32

120mm/hg and 10 mm/hg | pulse pressure 110 mmhg

Question 33

Aortic systolic and diastolic pressure and pulse pressure

Answer 33

120 mm/hg, 80 mm/hg and 60 mm/hg

Question 34

During aortic stenosis, what happens to left ventricular and aortic pressures

Answer 34

when valve is stenosed, the back flow of blood causes an increase in pressure on the LV which causes and increase in systolic pressure - 170 mm/hg

Question 35

What happens to pressure in severe aortic stenosis?

Answer 35

Can exert around 50 mm/hg of extra LV pressure

Question 36

What can aortic stenosis cause

Answer 36

Left ventricular hypertrophy - there is a structural response due to high LV pressure