Functional Properties of Receptors in Striated Muscle

Abstract

A mammalian striated muscle has cholinergic receptors for chemical stimulation and an action potential mechanism for electrical excitation. With chemical stimuli the receptors are activated and this causes a graded membrane depolarization through the simultaneous opening of channels for sodium and potassium ions across the membrane. With electrical stimulation on the other hand, the membrane depolarization produced by the electric current, triggers a selective, voltage-dependent and short-lasting increase in the permeability of the muscle membrane to sodium ions followed in time by an opposite potassium current. Chemical and electrical stimuli thus produce in some respects similar effects, that is, both cause the opening of membrane channels for sodium and potassium ions, but in other aspects they are markedly different.