Cardiac cycle

Question 1

What is the volume output of the heart

Answer 1

5L per min

70ml per beat

Question 2

What is isovulemtric ventricular contraction

Answer 2

The filling of the ventricles due to atrial contraction

Increase in ventricular pressure closes AV valves

Ventricular pressure is still less than aortic pressure so aortic valve shit

No blood ejected yet (ventricular contraction hasn’t occurred yet)

Question 3

What occurs during isovolumic ventricular relaxation ?

Answer 3

Ventricular pressure < aortic pressure , aortic valve closes

Ventricular pressure is still > atrial pressure so AV valve still shut

Pressure falls but no filling

Question 4

Label on this graph ; 
Atrial systole 
Isovolumetric ventricular contraction
Ventricular ejection
Isovolumic ventricular relaxation
Ventricular filling (diastole)

Answer 4

Question 5

What condition is this?

Answer 5

Aortic stenosis

Question 6

Clinical importance of the jugular venous pulse

Answer 6

Pulsation in the internal jugular vein reflect right atrial presssure

Right sided heart failure have an exaggerated pulse

Question 7

What condition is this? https://youtu.be/_k5u933BIbo

Answer 7

Leaky valve (aortic regurgitation)
Diastolic murmur

Question 8

How do we calculate cardiac output

Answer 8

Cardiac output (L/min) = stroke volume (L/beat) x heart rate (beat/min)

Question 9

What is a normal cardiac output at rest and during exercise

Answer 9

At rest approx 5 L/min (70ml x 70beat/min)

During exercise approx 22L/min (110ml x 200beat/min)

Question 10

Control of cardiac output

Factors affecting heart rate and stroke volume

Answer 10

Factors affecting heart rate -
sympathetic nervous system (via beta-adrenoceptors) ;
parasympathetic nervous system (via muscarinic receptors) ;
hormones such as adrenaline (also acts on beta-adrenoreceptors) ; extra/intracellular ions (alterations in membrane potential)

Factors affecting stroke volume :
Pre-load 
Cardiac contractility 
After-load
The more blood entering the heart the more blood pumped out

Question 11

What influences cardiac contractility :

Answer 11

increased by:
increased Sympathetic NS activity
calcium
Positive inotropic drugs (increase Ca2+) such as digoxin

decreased by :
reduced SNS activity
hypoxia
Acidosis
Heart failure

Question 12

What is preload?

What influences preload?

Answer 12

Pre-load (how much blood is returned to the heart per heart beat) and this is influenced by posture/intrathoracic pressure/venous pressure/filling time/atrial contractility

Higher pre-load = increased stroke volume

Question 13

What is afterload?

What influences afterload?

Answer 13

Afterload- the extent of the aortic pressure the heart has to work against

The higher the aortic pressure (due to increased peripheral resistance or aortic stenosis) wil increase afterload and reduce stroke volume (as less time available for ejection as time needed for LV to contract more forcefully so the pressure inside is greater than aortic pressure)

This results in LV hypertrophy

Question 14

where is aortic stenosis best heard?

Answer 14

right sternal border of the 2nd intercostal space

Question 15

describe the normal heart sounds

Answer 15

1st heart sound - av valve closing

2nd heart sound - aortic/pulmonary valve closure

Question 16

what is the S3 sound? when is it found in healthy people? when is it a worrying sign and what does it indicate?

Answer 16

the s3 sound is caused by the blood hitting the ventricles ; the 3 heart sounds together will have the cadence of Kentucky

normal in young adults, children, pregnancy and athletes ;

if heard in middle aged adult and the elderly its a sign of heart failure, cardiomyopathy, severe mitral or tricuspid regurgitation

Question 17

what does the Frank-Starling curve tell us ?

Answer 17

the more the cardiac muscle is stretched, the higher the force of contraction