Summer Lecture Circulation 1 final

Change membrane potenal of autorhythmic myocardial

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Unformatted text preview: ons innervate the S- A node (pacemaker) – Normal heart rate 60- 72 beats per minute – Block both the sym and parasym inputs, spontaneous polariza(on- depolariza(on rate of SA node is 90- 100/min • This suggest that at rest the parasympathe(c is slowing heart down • how is heart rate increased? - - parasympathe(c influence removal, up to 90- 100 - - sympathe(c influence via norepinephrine (also, later, by epinephrine) Friday, July 20, 12 How do Norepinephrine and Acetylcholine Affect Heart Rate? • Change membrane poten(al of autorhythmic myocardial cells (pace maker cells) Friday, July 20, 12 How do Norepinephrine and Acetylcholine Affect Heart Rate? • Change membrane poten(al of autorhythmic myocardial cells (pace maker cells) • Sympathe(c s(mula(on increases Na+ permeability - Think about ENa • Parasympathe(c s(mula(on increases K+ permeability - Think about EK ACer a heart aEack, give beta- blockers (antagonists to β1 norepinephrine/epinephrine receptors) this slows the heart rate, reducing O2 demand of heart muscle Friday, July 20, 12 How do Norepinephrine and Acetylcholine Affect Heart Rate? • Change membrane poten(al of autorhy...
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