Session 2 Flashcards
The heart as a pump and CVS development
Left atrioventricular valve?
mitral/bicuspid
Right atrioventricular valve?
tricuspid
Left Outflow valve?
aortic
Right outflow valve?
Pulmonary
Which ion enters cell during action potential?
calcium
Length of action potential/systole?
280ms
What do pacemakers do?
generate an action potential at regular intervals
What is the spread of excitation
SAN (right atrium) -> atria (atrial systole) -> AVN (120ms delay) -> septum -> ventricular myocardium from endocardium to epicardial surface (contraction from apex up)
When does the left ventricle open and close?
Intra-ventricular pressure exceeds aortic pressure (closes when aortic pressure>intra-ventricular pressure
The cardiac cycle - start?
(end of ventricular systole) Ventricles contracted ventricular pressure high, outflow valves open blood flowing into arteries A/V valve closed
The cardiac cycle - 2
Ventricles relax ventricular pressure falls brief backflow closes valves all valves closed "isovolumentric relaxation"
The cardiac cycle - 3
During systole, blood has continued to return to atria
Atrial pressure high
ventricular pressure falls below atrial pressure
AV valves open
The cardiac cycle - 4
With the A/V valves open -
ventricles fill rapidly (rapid filling phase ~ 200-300ms)
The cardiac cycle - 5
Diastole continues - ventricles fill more slowly
Ventricular pressure rises as ventricular walls stretch
When ventricular pressure equals atrial pressure, filling stops
The cardiac cycle - 6
Atrial systole
Forces a small extra amount of blood into ventricles
(heart can still function without atrial systole)
The cardiac cycle - 7
Ventricular systole ventricular pressure rises very rapidly exceeds atrial pressure after brief backflow, AV valves close all valves closed "isovolumetric contraction"
The cardiac cycle - 8
Ventricular pressure rises very rapidly
outflow valves open
The cardiac cycle – 9
Blood is ejected into the arteries (rapid ejection phase)
Arterial pressure rises rapidly
The cardiac cycle - 10
As arterial pressure rises
Rate of ejection of blood falls
outflow ceases with blood still in ventricle
The cardiac cycle - 11
systole ends
Heart sounds? (2)
‘lup’ closure of A/V valves
‘dup’ closure of outflow valves
interval between sounds -280ms
interval to next - 700ms
Cardiac Output?
Stroke volume x heart rate = cardiac output /l.min-1
