Cardiac Conduction Flashcards
what are the 2 atrioventricular valves?
mitral valve and tricuspid valve
what does the mitral valve divide? another name for it is?
the left atrium and left ventricle
left atrioventricular valve
what does the tricuspid valve divide? another name for it is?
the right atrium and right ventricle
right atrioventricular valve
what are the 2 outflow valves?
aortic valve and pulmonary valve
what does the aortic valve separate? another name for it is?
the left ventricle from the aorta
left semilunar valve
what does the pulmonary valve separate? another name for it is?
right ventricle from the pulmonary artery
right semilunar valve
what is the purpose of the outflow valves?
separate the heart from the two main arteries
explain the process of the contraction and relaxation of the heart
depolarizing current passes through gap junctions to the contractile cell. action potential travels and opens Ca channels in plasma membrane and sarcoplasmic reticulum. Ca induces Ca release from SR which binds to troponin, exposing myosin-binding sites. crossbridge cycle begins and muscle fiber contracts. Ca is actively transported back into the SR and extracellular fluid. tropomyosin blocks myosin-binding sites and muscle fiber relaxes
describe leakage channels and give an example
gates randomly open and close, K+ channels
describe ligand gated channels and give an example
open and close in response to specific chemical stimulus- nicotinic cholinergic receptor opens when acetylcholine binds to it
describe mechanically gated channels
channels which open in response to mechanical receptors
a. an action potential in the heart is initiated by?
the SA node
b. action potentials are conducted from the SA node to the?
arterial muscle
c. action potentials spread through the atria to the?
AV node
d. action potentials travel rapidly through the conduction system to the ___ of the heart
apex
e. action potentials spread upward through the?
ventricular muscle
f. what is the last step of an action potential?
the entire heart returns to the resting state until another action potential is generated in the SA node
what is phase 0 of a ventricular and atrial action potential?
depolarization: voltage gated Na channels open
what is phase 1 of a ventricular and atrial action potential?
initial repolarization: Na channels close and cell begins to repolarize as K leaves
what is phase 2 of a ventricular and atrial action potential?
plateau: voltage gated Ca channels open and enter cell, fast K channels close
what is phase 3 of a ventricular and atrial action potential?
repolarization: Ca channels close and slow K channels open
what is phase 4 of a ventricular and atrial action potential?
resting potential: Na leaves and K reenters cells via the Na-K-ATPase pump
describe the process of a nodal action potential:
Phase 4: spontaneous depolarization with Na currents
then phase 0: depolarization phase with increased Ca conductance
then phase 3: repolarization with K channels opening, Ca channels decrease
then back to phase 4
how fast is phase 0 of an action potential?
how fast is the inactivation of phase 0?
very fast, fast
how fast is phase 1 of an action potential?
how fast is the inactivation of phase 1?
fast, fast
how fast is phase 2 of an action potential?
how fast is the inactivation of phase 2?
slow, slow
how fast is phase 3 of an action potential?
how fast is the inactivation of phase 3?
very slow, no inactivation
how fast is phase 4 of an action potential? (ventricular/atrial)
how fast is the inactivation of phase 4?
fast, no inactivation
how fast is phase 4 of an action potential? (nodal)
how fast is the inactivation of phase 4?
slow, no inactivation
how are contractile cell APs started versus autorhythmic?
contractile: depolarization via gap junction
auto: Na entry reinforced by Ca entry
rising phase of AP is caused by what ion for contractile cells versus autorhythmic?
con: Na entry
auto: Ca entry
refractory period of contractile cells vs autorhythmic?
con: long, resetting Na channels delayed
auto: no refractory period
what does the P wave represent?
SA depolarization, action potential begins in atria
the QRS complex represents?
ventricular depolarization
what does the P-R interval represent?
time taken from first atrial depolarization to the first ventricular depolarization
what does the ST segment represent?
period during ventricular depolarization (plateau)
what does the T wave represent?
ventricular repolarization
describe what a delayed afterdepolarization is
spontaneous release of Ca from SR under Ca overload, or extra cytosolic Ca is removed, or production of Na influx causes depolarization
describe what a early afterdepolarization is
interruption of phase 3 repolarization or reactivation of Ca channels when AP is prolonged
describe wolff-parkinson-white syndrome
A syndrome in which an extra electrical pathway in the heart causes a rapid heartbeat.
List the layers of the heart from most outer to inner
Pericardium -> Epicardium -> Myocardium -> Endocardium
