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
