L3 - the cardiac cycle

Question 1

define the terms systole and diastole

Answer 1

systole - contraction and ejection of blood from the ventricle
diastole - relaxation and filling of the ventricles

Question 2

Define the term - stroke volume

Answer 2

The volume of blood ejected per beat

Question 3

cardiac muscle has a much longer/shorter AP than skeletal muscle?

Answer 3

longer

Question 4

Describe the spread of electrical activity throughout the heart in a typical cardiac cycle

Answer 4

AP generated by pacemaker cells at SAN->deoplarisation spreads over both atria -> depolarisation reaches AV node where itis delayed->spread from endocardial to epicardial surface -> spread up the ventricles from apex up ensuring blood is forced up and out

Question 5

What is the point of the delay of electrical activity at the AV node?

Answer 5

This ensures that the ventrices don’t start contracting until the atria have finished contracting

Question 6

When HR increases which gets shorter, systole or diastole?

Answer 6

diastole, systole remains the same length

Question 7

Briefly describe the 7 phases of the cardiac cycle starting with atrial contraction

Answer 7

AIRRIRR

1) atrial contraction - atria contract filling up the remainder of the ventricles (atrial kick - 10%)
2) Isovolumetric contraction - ventricles contract and increase the ventricular pressure, volume remains the same
3) Rapid ejection - Pressure in the ventricles exceeds that in the aorta, the aortic valve opens and blood fills the aorta
4) Reduced ejection - ventricles repolarise and ejection falls. Atria pressure begins to rise as they start to fill again
5) isovolumetric relaxation - when aortic pressure exceeds interventricular pressure the aortic valve shuts
6) Rapid filling - When atrial pressure exceeds interventricular pressure the mitral and tricuspid valves open
7) - reduced filling - Rate of filling begins to slow down

Question 8

Explain the origin of the 1-3rd heart sounds

Answer 8

S1 - closure of the AV valves (mitral and triccuspid)
S2 - closure of the aortic and pulmonary valves
S3 - Filling of the ventricles - this is normal in young children but in adults needs investigating
NOTE S1 and S2 mark the beginning and end of systole respectively

Question 9

What stages are systole?

Answer 9

2-4 inclusive

Question 10

changes in the pressure of the internal jugular vein can be seen as reflecting changes in atrial pressure. Describe the major areas seen in each phase and what it represents

Answer 10

phase 1 - A wave = atrial kick
phase 2 - C wave = closure of the mitral valve
phase 3 - X descent = atrial pressure initially decreases as its pulled down in the ejection
phase 4 - V wave = atrial pressure slowly increases as atrial fill a little
phase 5 - V wave continues
phase 6 - Y descent as atrial pressure drops as ventricles fill
DONT NEED TO BE ABLE TO NAME JUST GET THE GIST

Question 11

distinguish between valve stenosis and regurgitation

Answer 11

Stenosis - obstruction to blood flow through valve

Regurgiation - back leakage of blood through valve when it should be closed

Question 12

Pathology occurs more in the left heary because it is under higher pressures, give some causes of aortic valve stenosis

Answer 12

Age (calcification)/congenital (bicuspid aorta)/rheumatic fever

Question 13

what does aortic valve stenosis lead to?

Answer 13

Blood can’t leave the ventricle efficiently-> increased LV pressure and then hypertrophy->microangiopathic haemolytic anaemia due to shearing of the RBC’s as they pass through the valve

Question 14

Describe some causes of aortic valve regurgitation

Answer 14

aortic root dilation/rheumatic fever

Question 15

What does aortic valve regurgitation result in?

Answer 15

Blood flows back into LV during systole -> increased stroke volume to compensate -> LV hypertrophy