Cardiac Muscle Contraction - Blue Book Flashcards
In resting state what ions are greater outside cell? Inside cell?
Outside = Na+ and CA++ Inside = K+
Phase O?
Na+ influx = rapid depolarization (rapid upstroke on graph)
Phase 1?
Inactivation of Na+ influx
K+ efflux (notch of initial depolarization)
Paste 2?
Plateau phase
Ca++ influx via (L-type Ca++ channels)
Phase 3?
Inactivation of Ca++ influx
Continuation of K+ efflux (rest of repolarization)
Phase 4?
Removal of excess Na+ and Ca++
Restoration of resting membrane potential using Na+/K+ pump (Na+ out, K+ in)
What determines the force of the contraction in the myocardial cell?
Amount of intracellular Ca++
No action potential can be initiated: called?
Absolute refractory period (ARP)
What phase is the ARP?
Phase 1 through mid-3
Why can their be no action potential during ARP?
Because Na+ channels are closed
An action potential can be initiated but needs a greater stimulus?
Relative refractory period (RRP)
RRP extends between which phases?
Mid-3 to start of phase 4
Why is cardiac muscle incapable of tetani (sustained contraction) like in skeletal muscle?
b/c of relative long refractory period
Cardiac output is directly proportional to the venous return. Law?
Frank Starling Law
Frank Starling Law: force of contraction is _________ proportional to the length the myocardial fiber.
directly
Frank Starling Law: the ___ the amount of blood entering the heart during diastole, the _____ the stretching of the cardiac myocytes.
Greater
greater
Frank Starling Law: The greater the stretch, ?
The greater the force of contraction.
1st heart sound is due to what? LUB
Closure of AV valves
2nd heart sound is due to what? DUB
Closure of semilunar valves
3rd heart sound: sound?
DUBup
4th heart sound: sound?
deLUB
3rd heart sound is heard in what condition?
Congestive heart failure
4th heart sound is heard in what condition?
Hypertrophic ventricles
3rd heart sound occurs after what?
2nd heart sound
