Green- Cardiac Muscle Flashcards
Phases 0-3 when cardiac muscle cells cannot be restimulated; also called absolute refractory period
Effective refractory period
Fast response action potential occurs in
Atrial and ventricular cells
Increasing the length of the cardiac sarcomere increases the force of contraction
Frank-starling law
Na current that initiates the action potential in a pacemaker cell
Funny current
Regulation of contraction either positively or negatively
Inotropy
Mechanical connection of fascia adherens and desmosomes that keeps cardiac cells from pulling apart
Intercalated disc
Protein in the SR that regulates calcium uptake by the SR
Phospholamban
Increased stretching of cardiac muscles prior to contraction
Preload
Phases 3-4 when action potential can be generated with a strong stimulus
Relative refractory period
Slow response action potentials occur in
Pacemaker cells
Resting potential. Sodium and calcium channels closed Potassium channels (inward rectifying) open. Higher exctracellular [Na} Higher Intracellular [K]
Phase 4
Partial repolarization due to effflux of potassium through transient outward channels and
Inactivation of sodium channels
Phase 1
L-type Ca channels open and remain open.
Potassium channels close
Plateau phase.
Calcium ions trigger internal Ca release from SR
Phase 2
K exits thru delayed rectifier channels
K efflux exceed Ca influx
Ca channels close.
Soon becomes all potassium efflux
Repolarizes back to resting potential
Phase 3
Ion concentrations returned to normal
Na removed by Na/K ATPase
Ca removed by Na-Ca exchanger and Ca pump
Phase 4
In pacemaker cells, the resting potential is _______ compared to atrial ventricular cells
Less negative
The refractory period in cardiac cells is due to ?
The inactivation of fast sodium channels.
Fast sodium channels open during which phase?
Phase 0
During phase ____ of action potential, calcium enters cell through L-Type channels in t-tubules and sarcolemma
2
When does calcium influx end in cardiac muscle cells?
Starting at the end of phase 2 and going into phase 3
When phospholamban is phosphorylated, SERCA is _____-
More active at uptakee
Ventricular cells are ______ than atrial cells to cholinergic stimulation (parasympathetic nervous system, decrease heart rate)
Less sensitive
Stimulation of beta-adrenergic receptors increases contractility by?
Increasing the activity of L-type calcium channels
Stretching the heart ______ sensitivity to calcium, allowing for stronger contraction
Increases
