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21 Cards in this Set
- Front
- Back
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What is the pace maker for the heart?
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-Sino Atrial node (SA)
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Sino Atrial (SA) Node
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-cells in this tissue produce spontaneous action potentials that set the normal heart rhythm
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The electrical activity traveling throughout the atria eventually reaches the _____ ______ _____.
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-Atrio Ventricular (AV) node
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Action potential conduction is very ____ through the AV node.
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-Slow
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Why is the delay in the ultimate arrival of the action potential important to the ventricular muscle?
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-Allows time for the ventricles to properly fill before contracting
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How do action potentials spread to the ventricles?
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-Through Purkinje fibers
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The heart has ______ ______ mechanisms to aid survival under pathological conditions.
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-safety factor
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Safety Mechanisms for the Heart's Survival (2)
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-Presence of potential (or latent) pace maker tissues (AV node pacing=weaker than SA)
-Purkinje fibers (pacemaker if SA and AV don't work) |
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SA node cells do not have a stable, dominate _______ ______ and consequently do not have a _______ ______.
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-Channel Conductance
-"Resting" Potential |
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How does an SA node form an action potential?
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-Ion channels that can open at negative potentials (Pace maker channels permeable to Na and K)-->reversal potential: -20mV
-Ions channels open that are responsible for action potential upstroke in these cells -Slow process (60 Hz) |
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What are the action potentials of SA produced by?
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-Ca2+ ions moving into the cell through voltage-dependent Ca channel proteins-predominantly L-type by with some contribution from T-type Ca channels
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Where is repolarization of the SA node?
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-By K+ ions leaving the cell through voltage-activated, delayed-rectifier K channels in a manner similar to repolarization of the nerve action potential
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How is the ventricular muscle cells' resting potential set?
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-By the same type of inward rectifier K channel expressed in skeletal muscle=keeps resting potential negative
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The upstroke of the action potential in ventricular cells is produced by voltage-gated ____ channel proteins.
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-Na
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What causes the plateau phase of the ventricular action potential?
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-The expression of L-type Ca channels in these cells
-channels inactivate slowluy and incompletely and so provide a lasting depolarizing influence on the ventricular cell membrane potential. |
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What occurrence does the long plateau phase allow?
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-Allows time for large numbers of Ca2+ ions to enter the ventricular cell and initiate Ca2+-induced-Ca2+-release from intracellular stores of Ca2+ and, ultimately, cell contraction (for blood pumping).
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Eventual repolarization of the action potential is produced by slowly-activating delayed _____ ______ _____.
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-Rectifier K channels
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________ ________ are optimized for high velocity action potential propagation. How is this accomplished?
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-Purkinje fibers
-By anatomical specialization (large cells arranged in large diameter fibers and by a high level of expression of Na channels.) |
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Purkinje fiber cells can produce spontaneous _______ ______ activity.
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-Action potential
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Why don't atrial cells have the prominent plateau phase similar to ventricular muscle cells?
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-Smaller ration of L-type Ca2+ channels to delayed rectifier K channels
=less Ca2+ influx and less Ca 2+-induced-Ca2+-release from intracellular stores of Ca2+ and smaller contractile strength than ventricular cells |
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What is the role of an atrial muscle?
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-Help load the ventricles with blood
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