mildus
Forum Guru
Topics: 19
Posts: 614
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Here is how I understand it:
1. immediately before muscle activity, sympathetic vasodilatator system causes vasodilatation in muscles (I won't discuss about its nature i.e. is it cholinergic which acts on cholinergic receptors or adrenergic acting on beta2 receptors, because every book says different) -
why is this vasodilatation? in order to prepare muscle for muscle work!
it is learned action!
2. when muscles start working, e.g. running, sympathetic activity is increased, so there are two possibilities: or sympath.system acts on alpha1 receptors or on beta2 receptors;
it is more logical to act on beta 2 receptors thus causing vasodilatation, but even if it is not so i.e. even if there is alpha1 stimulation, there won't be vasoconstriction! Why? Because muscles have local regulation which is dominant i.e. stronger than neural control (working muscles produce lactate, H+, CO2, K+... all of them causing vasodilatation)
(recall that each organ has control of blood flow and it can be local, humoral or neural; in some cases neural control is dominant - e.g. skin and GI system, while in some other cases, local control is more important - e.g. heart, brain, muscle)
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| mildus
Forum Guru
Topics: 19
Posts: 614
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I know that different books say different things about the same things, especially about this topic, but this is how I understand it and it seems logical to me. I can't say that is 100% correct, but it a kind of compilation from many books
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| nadiabarati
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thanks mildus.
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