Biol 216 9 Circulatory System 65-96.pdf

Biol 216 9 Circulatory System 65-96.pdf - What else can...

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5/24/17 1 What else can effect the force of contraction? 5/24/17 65 What else can effect the forceof contraction? Sympathetic Activity Parasympathetic Activity 5/24/17 66
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5/24/17 2 ParasympatheticandSympathetic Parasympathetic and Sympathetic nerve fibers innervate the heart Influence the pumping action of the heart by affecting both the heart rate and strokevolume This keepsthe blood pressure,blood O 2 and CO 2 levels, and blood pH in the appropriate range. http://highered.mheducation.com/sites/0072943696/student_view0/chapter13/ani mation__baroreceptor_reflex_control_of_blood_pressure.html 5/24/17 67 Parasympathetic Vagus nerve carries parasympathetic nerve fibers to the heart (primarily) Vagus nerve innervates the SA node (cluster of cells in the right atria that generate electrical impulses that initiate the heart beat. Is the heart’s pacemaker ) Parasympathetic nerve stimulation has an inhibitory effect à decreases heart rate 5/24/17 68
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5/24/17 3 Parasympathetic-Acetylcholine Parasympathetic neuronsproduce the neurotransmitter, Acetylcholine (ACh) ACh binds to ligand gated channels on cardiac cell membrane which causes K+ to go out à Hyperpolarizes the cell Alsodecreases permeabilityof Na+ and Ca++ The hyperpolarized membrane takes longer to depolarize (and thereby cause an action potential) à heart rate decreases. 5/24/17 69 FYI: Receptors Neurotransmitter receptors can be classifiedintotwobroad categories: metabotropic and ionotropic (basedon their structural and functional characteristics). Ionotropic receptors form an ion channel pore Metabotropic receptors are indirectly linked withion-channels on the plasma membrane of the cell through signal transduction mechanisms (eg, G proteins). Metabotropic receptors haveneurotransmitters as ligands, which, when bound to thereceptors, initiatecascades that can lead to channel-opening or other cellular effects. Ex. Muscarinic acetylcholine receptors 5/24/17 70
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5/24/17 4 Acetylcholine receptorin the heart: M2 The M2 muscarinic receptors are located in the heart, where they act to slow the heart rate down to normal sinus rhythmafter stimulatory actions of the sympathetic nervoussystem, by slowing the speed of depolarization.
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