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Cardiac Physiology test 3

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Cardiovascular system is composed of:
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Terms in this set (54)
Cardiovascular system is composed of:
The heart and blood vessels
Functions in transportation of blood
delivers oxygen and nutrients to tissues
removes carbon dioxide and waste products from tissues
Cardiac muscle
is striated, short, fat, branched, and interconnected
Intercalated discs
anchor cardiac cells together and allow free passage of ions through gap junction
contractile cardiac muscle cells
99% of the heart is made of contractile cardiac muscle cells,
Generates the force of contraction produced by the heart
autorhythmic cells
Generate action potentials spontaneously without neural stimuli
1% self-excitable
Intrinsic conduction system of the heart
Autorhythmic cells coordinates the rhythmic excitation and contraction of the cardiac muscle to ensure efficient pumping
Image: Intrinsic conduction system of the heart
Intrinsic conduction system of the heart
The action potential generated by autorhythmic cells travel through the conduction system and to surrounding myocardial tissue by gap junction
Sinoatrial (SA) node
-pacemaker, generates impulse (70 times/minute)
Atrioventricular (AV) node
(40-60 times/minute), delays the impulse about 0.1 second. Impulse passes from atria to ventricles via the atrioventricular bundle (bundle of His)
Bundle branches
carry the impulse toward the apex of the heart (35 times/minute)
Purkinje fibers
carry the impulse from the heart apex to the ventricular walls (30 times/minute)
Ectopic focus -
Abnormal overly excitable area begins to depolarizes faster than the SA node
Can lead to a premature heartbeat (extrasystole) and/or accelerated heart rate
Can be caused by heart disease, anxiety, lack of sleep, to much caffeine, nicotine
Image: Ectopic focus -
What gives autorhythmic cells the unique ability to spontaneously generate action potentials?
They have an unstable membrane potentials called pacemaker potentials
Their membrane gradually depolarizes and drifts towards threshold due to slow Na+ entry
What gives autorhythmic cells the unique ability to spontaneously generate action potentials? #2
When threshold is reached they fire an action potential
Calcium influx (rather than sodium) causes the depolarization phase of the action potential
Repolarization is cause by K+ efflux
Image: What gives autorhythmic cells the unique ability to spontaneously generate action potentials? #2