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29 Cards in this Set
- Front
- Back
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What is the only direct innervation in the SNS?
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To the adrenal medulla.
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How many divisions in the ANS are there?
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3 - PNS (cranial), SNS (thoracolumbar), PNS (sacral)
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what is the baroreceptor pathway?
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receptors in the carotid body and the aortic arch project to the NST which inturn projects to the CVLM. The CVLM has inhibitory efferents to the RVLM which affects the firing rate of the SNS. This is further enhanced by projections onto the PNS via the Nucleus ambiguus.
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If the BP decreases does the vagal afferents firing increase or decrease? What about the peripheral Sym nerves?
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Decreases, increases.
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The carotid body sends its signals via which nerve?
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CN IX
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the aortic arch receptors send their signals via which nerve?
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CN X
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Which receptors are responsible for decreasing HR at the SAN?
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Muscarinic 1 receptors.
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what is the effect of Sym innervation of the B1 receptors in teh heart?
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Increased contractility, Increased HR.
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What is the effect of baroreceptor activation on muscle vasoconstriction, skin vasoconstriction and cardiac sympathetic activity?
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MV - very decreased.
SVC - decreased CSym - decreased |
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What is the effect of Chemoreceptor activation on muscle vasoconstriction, skin vasoconstriction and cardiac sympathetic activity?
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MV - increased.
SVC - decreased CSym - decreased |
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What is the effect of Thermoreceptor activation on muscle vasoconstriction, skin vasoconstriction and cardiac sympathetic activity?
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MV - none
SVC - very decreased CSym - Increased |
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what is the effect of NPY?
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It potentiates NA postsynaptically, but inhibits NA release presynaptically.
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What is the delay in HR to BP response in exercise?
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a few seconds.
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T/F the instantaneous HR increases during inspiration?
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True
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Mean arterial pressure increases or decreases during inspiration?
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Increases, but it is slightly delayed.
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What are the 2 pathways that inspiration influences CO?
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i) increased pulmonary stretch receptor activity causes a reflex via the vagal nerves and brainstem to increase HR.
ii) decreased intrathoracic pressure, decreases CVP, which increases pressure gradient for venous return, increasing venous return. BOTH INCREASE CO & therefore Art. pressure. |
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Describe a ventricular cell.
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Small cells (100um x 15um), striated, numerous mitochondria, joined to other myocytes by gap junctions.
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Whats the purpose of teh small diameter in myocytes?
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Allows fastdifussion of O2.
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What is the protein in the gap junctions? What is the purpose of the gap junctions?
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Connexin 43. A gap junction allows a conduction of the AP from cell to cell.
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What is the duration of the AP across a cardiac cell?
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300ms, contraction peaks at end of AP duration
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What are the 3 currents involved in the AP generation in cardiac muscle?
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INa, ICa, IK
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What role does the INa play in the AP generation?
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fast inward current, rapidly depolarises AP, crucial for fast conduction across the myocardium.
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What role does the ICa play in the AP generation?
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slow inward current, maintains long plateau of AP, contributes to ECC.
(target of calcium channel blocking drugs) |
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What role does the IK play in the AP generation?
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repolarizing current, voltage sensitive, sensitive to intracellular constituents, Common sideeffect of many drugs.
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Describe the process of excitation contraction coupling in relation to Cardiac muscle.
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AP down the tubule activates Ica through the Ryr channel. This activates Ca induced Ca release (CICR) from the sarcoplasmic reticulum. Large Ca release, which binds to troponin exposing the myosin sites.
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How is Ca removed from the cytosol?
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i) reuptake of Ca into SR by the SR Ca pump.
ii) Na/Ca exchanger |
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How does Adrenaline increase contractility?
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Adrenaline binds to the ADR on the cell surface, which Activates a G-protein that inccreases the cAMP in the cell. This causes activation of pkA which phosphorylates the SR Ca channel (increasing SR stores) and SM Ca channel (increasing Ica).
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Describe the mechanism of cardiac glycosides.
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they inhibit the Na/K channel, increasing the [Na] which in turn decreases Ca exiting via the Na/Ca channel, increasing the SR Ca channel
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What is the energy supply in the Cardiac muscle?
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Entirely aerobic, oxidative phosphorylation.
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