Autonomic Nervous System
The motor (efferent) nervous system has two components: the somatic and the autonomic. These two systems differ in a number of ways but are chiefly distinguished by the types of effector organs they innervate and the types of functions they control.
The somatic nervous system is a voluntary motor system under conscious control. Each of its pathways consists of a single motoneuron and the skeletal muscle fibers it innervates. The cell body of the motoneuron is located in the central nervous system (CNS), in either the brain stem or spinal cord, and its axon synapses directly on skeletal muscle, the effector organ. The neurotransmitter acetylcholine (ACh) is released from presynaptic terminals of the motoneurons and activates nicotinic receptors located on the motor end plates of the skeletal muscle. An action potential in the motoneuron causes an action potential in the muscle fiber, which causes the muscle to contract.
autonomic nervous system definition :
The autonomic nervous system is an involuntary system that controls and modulates the functions primarily of visceral organs. Each pathway in the autonomic nervous system consists of two neurons: a preganglionic neuron and a postganglionic neuron. The cell body of each preganglionic neuron resides in the CNS. The axons of these preganglionic neurons synapse on the cell bodies of postganglionic neurons in one of several autonomic ganglia located outside the CNS. The axons of the postganglionic neurons then travel to the periphery, where they synapse on visceral effector organs such as the heart, bronchioles, vascular smooth muscle, gastrointestinal tract, bladder, and genitalia. All preganglionic neurons of the autonomic nervous system release ACh. Postganglionic neurons release either ACh or norepinephrine, or, in some cases, neuropeptides.
0 comments:
Post a Comment