HUMAN ANATOMY AND PHYSIOLOGY

 NERVE ENDING OF SMOOTH AND CARDIAC MUSCLE::

Smooth muscle and cardiac muscles are innervated by the sympathetic or parasympathetic nervous system or both when both types of autonomic nerves are present the impulses of one type of nerve produces excitation or contraction of the smooth muscle while those of the other type causes inhibitions or relaxation of the muscle the specific effects vary from organ to organ eg parasympathetic impulses may produce contractions in some organs and relaxation in others while sympathetic impules produce the opposite effects the chemical transmitters involved in the neuromuscular transmission also differ the vesicles in the endings of parasympathetic nerves contain accetylcholine whereas the neurotransmitter substance of the sympathetic nerves is norepinephrine just as in skeletal muscles these chemical transmitters induce local depolarization of the muscle cell membrane and when the threshold is passed an action potential is generated