4. the heart

Question 1

why is left ventricle thicker (more muscular) than right ventricle

Answer 1

needs to contract powerfully to pump blood all way round body

Question 2

why ventricles thicker walls that atria

Answer 2

have to push blood out of heart

atria only need to push blood into ventricles

Question 3

atrioventricular AV vales

Answer 3

link atria to ventricles

stop blood flowing back when ventricles contrct

Question 4

semi lunar SL valve

Answer 4

link ventricles to pulmonary artery and aorta

stop blood flowing back after ventricles contract

Question 5

cords

Answer 5

attach AV valves to ventricles. stop them being forced up into atria when ventricles contract

Question 6

cardiac cycle step 1

Answer 6

1. ventricles relax atria contract (increased pressure) blood pushed into ventricles

Question 7

cardiac cycle step 2

Answer 7

2. atria relax ventricles contract (increased pressure)
   pressure higher in ventricles than atria = AV valves shut
   pressure higher in ventricles than aorta/pulmonary artery = SL valves open

Question 8

cardiac cycle step 3

Answer 8

3. ventricles and atria relax.
   atria fill again due to high pressure in vena cava and pulmonary vein.
   increased pressure in atria = more pressure than relaxed ventricles = AV valves open and blood flows passively into ventricles.
   -> ATRIA CONTRACT process begins again

Question 9

cardiac output =

amount of blood pumped by heart per min

Answer 9

stroke volume x heart rate
(volume of blood pumped from left ventricle per beat)
(bets per min)