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cardiac system

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cardiac system

Postby BioJunior » Sat Apr 23, 2011 9:18 am

I'm learning about the CardicOtput and how its effected by different factors. My book has a very confusing paragraph so I'm hoping someone could better explain how each of these effects the heart rate.

Already googled these so I kind of have an idea on what CO does like the basic definitions but but would like some more explanations from some members to really have a good basis ^_^

1) How does contracitlity increase/decrease SV? Why would afterload effect it?

2) How exactly does the flight or fight system effect CO? In the book it mentioned nodes but I didn't quite understand that paragraph.

3) Does rest and digest (PNS) affect only HR? In the book that's all I read but then somewhere online I read it can be both PNS and SNS.

4) The SA node of the heart is enervated by both sympathetic and parasympathetic nerve fibers. Under conditions of rest the parasympathetic fibers release acetylcholine, which acts to slow the pacemaker potential of the SA node and thus reduce heart rate. Under conditions of physical or emotional activity sympathetic nerve fibers release norepinephrine, which acts to speed up the pacemaker potential of the SA node thus increasing heart rate. Sympathetic nervous system activity also causes the release of epinephrine from the adrenal medulla. Epinephrine enters the blood stream, and is delivered to the heart where it binds with SA node receptors. Binding of epinephrine leads to further increase in heart rate.

I bolded parts I didn't understand. Could someone expand on them?
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