Neurology - The medical science that deals with the nervous system and disorders affecting it.
Central Nervous System (CNS) - The gross anatomical subdivision of the nervous system consisting of the brain and spinal cord housed in the dorsal body cavity and protected by the bones of the skull and vertebral column and the three connective tissue meninges; this system is the major rapid response control system for the entire organism.
Peripheral Nervous System (PNS) - The gross anatomical subdivision of the nervous system consisting of the nerves (with sensory = afferent and motor = efferent components) which project from the brain and spinal cord, along with the various visceral ganglia and the various sensory receptors distributed throughout the body.
Somatic Nervous System (SNS) - A functional subdivision of the nervous system; those neurons which respond to stimuli from the external environment and conduct somatic afferent sensory impulses from cutaneous and special sense receptors (exteroreceptors) to the CNS, and those somatic efferent motor neurons which conduct impulses from the CNS to skeletal muscle tissue.
Autonomic Nervous System (ANS) - A functional subdivision of the nervous system; those visceral sensory neurons (interoreceptors) which respond to stimuli from the internal environment and conduct impulses from visceral organs to the CNS, and, especially, those visceral motor neurons which convey impulses from the CNS to smooth and cardiac muscle tissue, and glands; the motor part of the ANS consists of the sympathetic division and the parasympathetic division.
Parasympathetic Division of ANS - The functional subdivision of the ANS which dominates in controlling the body for metabolic "business as usual"; its preganglionic fibers originate in brain stem and exit with certain cranial nerves or in the lateral horns of the sacral spinal cord (thus its alternative label of the "craniosacral" division), have relative long axons, and synapse with their postganglionic sympathetic neurons in the parasympathetic ganglia located in the walls of visceral effector organs (smooth muscle, cardiac muscle, endocrine glands or exocrine glands); its postganglionic axons are relatively shorter and synapse with various effector organs; all parasympathetic cells, preganglionic and postganglionic, are cholinenergic, i.e., they release the neurotransmitter acetylcholine.
Sympathetic Division of ANS - The functional subdivision of the ANS which prepares the body for muscular exertion or stressful activities ("fight or flight"); its preganglionic fibers originate in the lateral horns of the thoracic and lumbar spinal cord (thus its alternative label of the "thoracolumbar" division), have relative short axons, and synapse with their postganglionic sympathetic neurons in the sympathetic chain/trunk ganglia or the celiac or mesenteric ganglia; its postganglionic axons are relatively longer and synapse with various visceral effector organs (smooth muscle, cardiac muscle, endocrine glands or exocrine glands); most sympathetic postganglionic cells are adrenergic, i.e., they release the neurotransmitter norepinephrine; the exception being cholinergic stimulation of sweat glands.