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Regulation of a heartbeat

For discussing the functions of different structures of all organisms.

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Regulation of a heartbeat

Postby Fatty » Wed Apr 22, 2009 10:09 am

Hi,

So I have this question about the regulation of the heartbeat. After having dome some research, I've gotten myself confused.

Basically, I know that the impulse starts in the SA node --> AV node --> Bundle of His --> Purkinje fibres.
However, I've also read that the ANS plays a role in the regulation, along with its sympathetic and para sympathetic nervous system, but I don't quite understand how it fits in with regulating the heartbeat, other than that it is an involuntary activity.

If any of you have time to help me out of my confusion.. it'd be greatly appreciated =D
Fatty
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Postby MohammedAmer » Wed Apr 22, 2009 4:45 pm

ANS connects to SA node via dual innervation:

First from sympathetic nervous system (Spinal nerve T1-4)
Second from parasympathetic nervous system(Cranial nerve CN-X)

Sympathetic stimulation lead to increase rate of SA impulses so increase heart rate
Parasympathetic stimulation lead decrease rate of SA impulses so decrease heart rate

Conditions which lead to sympathetic stimulation like (anger,stress.....etc.) lead to increase heart rate and force of contraction
Conditions that lead to parasympathetic stimulation like (rest state) lead to decrease heart rate but have nothing to do with contractility as no innervation to muscles of atria and ventricles

there are other factors which contribute to heart rate regulation like direct action of Epinephrine and NorEpinephrine (Adrenaline&NorAdrenaline),also there are physical factors like local warming of SA which lead to increased heart rate,cooling which lead to decreased heart rate,there are chemical factors as hypoxia and hypercarbia.

Also increasing blood pressure will affect baroreceptors and will lead to decreased heart rate(Marey's law).
But the main regulation mechanism is mediated by ANS

You have to read some Cardiovascular Physiology.
:)
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Re: Regulation of a heartbeat

Postby sanjidcapa » Tue May 05, 2009 9:18 am

Hello guyz
Conditions which lead to sympathetic stimulation like lead to increase heart rate and force of contraction
Conditions that lead to parasympathetic stimulation like lead to decrease heart rate but have nothing to do with contractility as no innervation to muscles of atria and ventricles
There are other factors which contribute to heart rate regulation like direct action of Epinephrine and NorEpinephrine also there are physical factors like local warming of SA which lead to increased heart rate,cooling which lead to decreased heart rate,there are chemical factors as hypoxia and hypercarbia.
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