During the flight or fight response, sympathetic pathways cause arterioles to co

colleen

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12 years ago

During the flight or fight response, sympathetic pathways cause arterioles to co

During the flight or fight response, sympathetic pathways cause arterioles to contract. If this is true, how is it possible to increase blood flow to areas that require additional oxygen, such as skeletal muscle?

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Saoris

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12 years ago

If generalized sympathetic activation occurs, arterioles in skeletal muscle will tend to dilate and those in nonvital tissues will tend to constrict. The vital tissues (brain, kidney, heart) will have their arterioles held constant through control by intrinsic mechanism. The net effect of this will be a small increase in TPR but a diversion of blood from skin and gut to skeletal muscle. Vital tissue blood flow will change very little. (I'm not sure if this completely answers the question, but I hope this helps.)

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aphelp

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12 years ago

While vasoconstriction is useful for areas that don't require additional oxygen, such as the gut and kidneys, skeletal muscles need extra oxygen. While the sympathetic pathways dictate that arterioles contract, local paracrine factors released by muscles and the heart, such as nitric oxide and adenosine, signal the vessels to dilate, and the local factors override the sympathetic signal.

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