Pacemaker activity

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Describe Pacemaker activity:

1. Slow depolarisation.

Presence of 'Funny' channels-voltage gated channels

High Na+ influx

Low K+ efflux

Transient cA2+ CHANNELS OPEN, ALLOWS cA2+ influx

2. TCa2+ Channel closes, but LCa+ channel opens-(long-lasting). Quick increase in Ca2+ influx.

2. L-Ca2+ channel closes, no influx of Ca2+. K+ chennel opens, allowing K+ out

Heart Rate controlled by AP:

Sympathertic NS:

Increase in Norepinephrine

Increase in Epinephrine from Adrenal medulla

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Beta receptors in Pacemaker cells activate cAMP pathway

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Increase permeability Na+ and Ca2+

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Insrease depolarisation

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Increase in heart rate

Parasympathetic NS:

ACh decreases

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Causes closing of Ca2+ and opening of K+

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increase in K+ efflux

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Decrease in rate of depolarisation

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decrease in heart rate

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