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TABLE 9.1 Responses to Adrenergic and Cholinergic Nerve Stimulation

Organ or Tissue Function

Predominant

Adrenoceptor Type Adrenergic Response

Cholinergic Response9

Heart4

Rate (chronotropic effect) Contractile force (inotropic effect) Conduction velocity (dromotropic effect)

Pupil size

Accommodation

Bronchial smooth muscle Blood vessels (arteries and arterioles)' Cutaneous Visceral Pulmonary Skeletal muscle Coronary Cerebral Veins

Gastrointestinal tract (tone, motility, and secretory activity) Sphincters Splenic capsule Urinary bladder Detrusor muscle Trigone-sphincter muscle Uterus

Glycogenolysis Skeletal muscle Liver Lipolysis Renin secretion Insulin secretion

Increase Increase Increase

Constriction of radial muscle causing dilation (mydriasis) No innervation

Relaxation

Constriction

Constriction

Constriction

Constriction^

Constriction, dilation

Constriction

Constriction

Decrease8

Contraction Contraction

Relaxation

Contraction

Contraction-relaxation*

Increase Increase Increase Increase Decrease

Decrease

None

Decrease

Contraction of circular muscle (miosis) Contraction of ciliary muscle producing accommodation for near vision Contraction

No innervation6 No innervation6 No innervation6 No innervation6 No innervation6

No innervation Increase

Relaxation No innervation

Contraction Relaxation

Contraction-relaxation

None None None None Increase

"Muscarinic cholinoceptors. See Chapter 12 for a discussion of subtypes.

There are some p2-receptors in the heart. The ratio of p1 to p2 varies with the region and the species. In the human heart, the ratio of p1 to p2

is about 3:2 in atria and 4:1 in ventricles.

There are some a2-receptors in some vascular smooth muscle.

"Tow doses of epinephrine of endogenous or exogenous origin plus other p2-receptor agonists dilate these blood vessels.

6Exogenously administered cholinergic drugs dilate these blood vessels. ^Dilation is the dominant in vivo response, owing to indirect effects.

^-Adrenoceptors may be involved in hypersecretory responses.

'Responses depend on hormonal state.

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