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20 Cards in this Set
- Front
- Back
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cardiac muscle is ? which means that it stimulates its own contraction without a requisite electrical impulse coming from the CNS.
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Myogenic
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What will happen if a cardiac muscle cell is left without input?
What will happen if two cardiac muscle cells are placed side by side? |
Contract rhythmically at a steady state
Whichever one that contracts first will stimulate the other to contract. |
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Intercalated disks join cardiac myocytes mechanically through ? and electrically through ?
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Desmosomes
Gap Junctions |
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What generates spontaneous and periodic action potentials in the heart?
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Pacemaker -- Sinoatrial (SA) Node
Not initiated by neurons |
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How do sympathetic and parasympathetic affect the heart?
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modulate the cardiac muscle functions
they do NOT initiate cardiac muscles |
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Most heart related deaths are caused due to
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fibrillation
makes the heart beat at random |
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True or False
The ionic basis for the action potentials in the ventricles, atria, and Purkinje system is identical. |
True
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What is the resting membrane potential of cardiac cells determined primarily by?
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Potassium Ions (K+)
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When a cardiac cell is at resting membrane potential, the conductance of K+ is HIGH or LOW?
Is the resting membrane potential close to the K+ equilibrium potential? |
High
Yes |
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True or False
Na+ / K+ ATPase contribute a great deal of electrogenic contributions to the membrane potential. |
FALSE
they have a small direct electrogenic contribution to the membrane potential |
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Are action potential durations long or short in the heart?
Rank ATRIA, VENTRICLES, PURKINJE FIBER, SKELETAL MUSCLE based on shortest to longest action potential. |
Long durations
Skeletal muscle --> Atria --> ventricles --> purkinje fibers |
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Is the REFRACTORY PERIOD in cardiac cells longer or shorter?
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Longer
due to the long action potential |
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True or False
The cells of the atria, ventricles, and purkinje system exhibit a nonstable resting membrane potential? |
False
They have a STABLE resting membrane potential |
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What is characteristic of action potentials in the atria, ventricles, and purkinje system?
This is due to? |
Plateau
sustained period of DEPOLARIZATION |
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Describe the 5 phases of action potential in the heart.
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phase 0 - upstroke
rapid depolarization due to Na+ influx phase 1 - initial repolarization -inactivation of Na+ channels -K+ efflux causing repolarization phase 2 - plateau -Ca2+ influx -K+ efflux phase 3 - repolarization -Ca2+ decrease -K+ increase phase 4 - resting membrane potential / electrical diastole |
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Cardiac Contractions require Ca2+ through what?
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L-Type Ca2+ Channels
(extracellular) without Ca2+ influx contraction will not occur! |
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What is the main purpose of the extracellular Ca2+ influx?
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causes CICR from the SR through Ca2+ Release channels
(Ca2+ induced Ca2+ release) |
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How many L-Type Ca2+ channels control SR Ca2+ release channels?
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One L-type channel for One SR channel
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Where is the Na+/ Ca2+ pump found at?
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Sarcolemma
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SR Ca2+ pump is inhibited by what regulatory protein?
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Phospholamban
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