3. Physiology
        3.2. Cardiovascular
            3.2.4. Regulatory mechanisms
                3.2.4.2. Regulation of peripheral blood flow
                    3.2.4.2.2. Systemic control by hormone
3.2.4.2.2.1. Effects of catecholamines on BP

Effects of catecholamines on BP

Keynotes

Both NE and E increase contractility via beta-1

E

Vasodilation in skeletal muscle and liver (beta-2 receptor)
-->
Overall vasodilation

Reflex bradycardia insufficient

NE

Overall vasocontriction (alpha-1)

Reflex bradycardia sufficent to dominate

 

[Ref: WG21:p362-363]

Norepinephrine = NE

Epinephrine = E

 

Effects on heart

NE and E both increase HR and contractility in isolated heart, via beta-1 receptors.

Also see ANS innervation of the heart

 

Epinephrine on vasomotor tone

Epinephrine causes vasodilation in skeletal muscles and liver via beta-2 receptors

--> This vasodilation overwhelms vasoconstriction caused by E elsewhere

--> PVR decrease (not increase)

Thus,

NB:

[BL8:p245] Low doses of epinephrine cause muscle vasodilation, but high doses cause muscle constriction

Norepinephrine on vasomotor tone

Norepipherine causes vasoconstriction in almost all organs via alpha-1 receptors.

Thus,

 

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