Difference between revisions of "CARDIAC ELECTRICAL ACTIVITY-CONTROL"
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===== [[Summary Article|'''SUMMARY''']] ===== | ===== [[Summary Article|'''SUMMARY''']] ===== | ||
1. Control mediated by constant balance between sympathetic & parasympathetic activity. | 1. Control mediated by constant balance between sympathetic & parasympathetic activity. | ||
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<br/><i>MECHANISMS</i> | <br/><i>MECHANISMS</i> | ||
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<br/>2. Parasympathetic stmulation via vagus nerve ⟹ release Ach at SA & AV nodes ⟹ in SA node Ach binds to M<sub>2</sub> muscarinic receptors ⟹ increased intracellular G protein ⟹ opens up special K<sup>+</sup> channels ⟹ hyperpolarisation of membrane ⟹ it takes longer for cell to reach threshold ⟹ therefore reduce HR & AV nodal conduction. | <br/>2. Parasympathetic stmulation via vagus nerve ⟹ release Ach at SA & AV nodes ⟹ in SA node Ach binds to M<sub>2</sub> muscarinic receptors ⟹ increased intracellular G protein ⟹ opens up special K<sup>+</sup> channels ⟹ hyperpolarisation of membrane ⟹ it takes longer for cell to reach threshold ⟹ therefore reduce HR & AV nodal conduction. | ||
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==Reference(s)== | ==Reference(s)== | ||
Barrett, K.E., Barman, S.M | Barrett, K.E., Barman, S.M., Brooks, H.L., X, J. and Ganong, W.F. (2019). Ganong’s review of medical physiology. 26th ed. New York: Mcgraw-Hill Education | ||
[[Category:Cardiac Electrical Activity]] | [[Category:Cardiac Electrical Activity]] | ||
[[Category:Physiology]] | [[Category:Physiology]] | ||
Latest revision as of 02:30, 21 March 2023
SUMMARY
1. Control mediated by constant balance between sympathetic & parasympathetic activity.
MECHANISMS
2. Parasympathetic stmulation via vagus nerve ⟹ release Ach at SA & AV nodes ⟹ in SA node Ach binds to M2 muscarinic receptors ⟹ increased intracellular G protein ⟹ opens up special K+ channels ⟹ hyperpolarisation of membrane ⟹ it takes longer for cell to reach threshold ⟹ therefore reduce HR & AV nodal conduction.
3. Sympathetic stimulation via the thoracic splanchnics ⟹ release NA at the SA & AV nodes ⟹ binds B1 receptors ⟹ increased intracellular cAMP ⟹ increases permeability of sarcolemma to Na & Ca ions ⟹ cells reach threshold quicker ⟹ therefore increases HR & AV nodal conduction.
Reference(s)
Barrett, K.E., Barman, S.M., Brooks, H.L., X, J. and Ganong, W.F. (2019). Ganong’s review of medical physiology. 26th ed. New York: Mcgraw-Hill Education
