Lecture 2 - The Heart as a Pump Flashcards
what are the properties of cardiac muscle?
striations
branching
central nuclei (1 or 2)
intercalated discs (electrical and mechanical coupling with adjacent cells)
adherens-type junctions (anchor cells)
gap junctions (electrical coupling)
t tubules in line with z bands, not a-i band junction
how long is the cardiac ap?
280ms
how long does diastole last?
700ms
describe the spread of excitation in systole
- sa node fires an ap which spreads over the atria causing atrial contraction
- ap reaches the av node where it is delayed by 120ms
- excitation spreads down the septum
- excitation spreads from inner (endocardial) to outer (epicardial) surface
- ventricle contracts from apex up
how is ventricular muscle organised?
figure of eight bands
allow effective ejection
what are the differences between right and left side of the heart?
left side has thicker myocardium
right side has sa node
when do the pulmonary and aortic valves open and close?
open: systole when ventricular pressure is higher than in the arteries
close: end of systole
when do the tricuspid and mitral valves open and close?
open: early diastole when ventricular pressure is lower than atrial
close: systole when ventricular pressure is higher than atrial
what causes the first heart sound?
av valves closing
what causes the second heart sound?
semi lunar valves closing
what causes the third heart sound?
diastole
what causes the fourth heart sound?
atrial contraction
what causes murmurs during exercise?
turbulent flow
What produces the contraction of each cell?
Rise in intracellular calcium triggered by an action potential
What is required for pumping action?
Regular, coordinated pattern of contraction
