Drug effects on the heart

Created by: sophieridge
Created on: 15-05-18 13:25

What are the actions of the PNS?

Ach from vagus nerve to heart cells decease HR (-ve chronotropic effect) acts on M2 muscarinic receptors in the SA node-open receptor=operator k channel. Decay of current is slowed down so HR slows

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Drugs that mimic PNS action

Muscarinic agonists. Muscarinic antagonists-atropine used in emergency to increase HR if too slow. Ivabradine-new inhibits funny current. slows HR

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What are the actions of the SNS?

NA from nerve terminals and A from adrenal medulla. increase HR. +ve chronotropic effects. increases contractile force (+ve inotropic effect) increase Co as =^HR and ^SV mainly via B1-adrenoceptors on heart muscle. leads to phosphorylation by pKA

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How does NA work

NA speeds up funny current due to release of Ca from SR.

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Drugs that mimic SNS action

Isoprenaline - non selective. adrenaline - ^HR when heart has stopped beating. dobutamine-increases force of contraction for acute heart failure

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Actions of drugs that inhibit SNS actions.

B-adrenoceptor antagonists (B-clockers)- decrease HR and force. propranolo and bisoprolol (only b1 selective)

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What are cardiac glycosides?

only for heart failure. makes people feel better increases force of contraction. doesn't make them live longer.

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How do cardiac glycosides work?

Block NA/J ATPase. increase Na in cell, less Ca pumped out more Ca in cell more into Sr so greater CA release. promotes contraction.

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CA2+ channel blockers CCBS

Verapamile nifedipine. reduce Ca2+ entry decrease contractile force (high HP and angina)

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What are arrhthmias.

when another pacemaker controls rhythm not SA, mainly due to out of place sites of action potential generation. . most decrease HR by decreasing excitability of tissue or prolonging action potential, so less high frequency potentials

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Other cards in this set

Card 2

Front

Drugs that mimic PNS action

Back

Muscarinic agonists. Muscarinic antagonists-atropine used in emergency to increase HR if too slow. Ivabradine-new inhibits funny current. slows HR

Card 3

Front

What are the actions of the SNS?

Back

Card 4

Front

How does NA work

Back

Card 5

Front

Drugs that mimic SNS action

Back

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Drug effects on the heart