Side ASide B
A motor nervous system that controls glands, cardiac and smooth muscle to maintain homeostasis, actions are involuntary
ANS - Autonomic
Slower than somatic reflexes, include a visceral reflex arc, Example Elevated BP; baroreceptors stretch receptors (aorta & carotid), glossopharyngeal n., medulla, vagus n., heart...
(receptor, afferent neurons, interneurons, efferent neurons, effectors),
Visceral reflex arc
Mainly adapts body for activity, (“fight or flight”)
Mainly a calming effect, reduced energy expenditure, normal body maintenance (“rest & digest”)
Background rate of activity from both divisions
Control nuclei in hypothalamus and other brain stem regions, motor neurons in SC, peripheral ganglia and fibers in cranial and spinal nerves, pathway involves 2 neurons
Soma in brainstem or SC, ends in ganglion
Begins in ganglion and extends to target cells
Short preganglionic and long postganglionic fibers, cell bodies in lateral horns and nearby gray matter of SC, fibers exit via spinal nerves T1 to L2 and go to nearby sympathetic...
Sympathetic Division; also called thoracolumbar,
Small myelinated, enter ganglia via white communicating rami
Unmyelinated, exit ganglia by gray communicating rami or other route
Enter ganglia, take one of 3 paths (end and synapse, go up or down the chain, pass through chain to another ganglia nearer target), fibers leave chain by: spinal n. (effectors...
secretes steroid hormones
modified postganglionic sympathetic neurons, secretes hormones epinephrine (85%) and norepinephrine (15%) into blood stream
Also called craniosacral division, long preganglionic and short postganglionic fibers, cell bodies in brain stem and segments S2 to S4
preganglionic fibers end in terminal ganglia in or near target, little divergence more selective
exit via 4 cranial nerves, III Oculomotor, VII Facial, IX Glossopharyngeal, X Vagus
(lens and pupil of eye)
(tear, salivary, nasal glands)
(parotid salivary glands
contains 90% of all PS preganglionic fibers, (heart, bronchi, blood vessels to lungs, esophagus, liver, pancreas, stomach, small intestine, kidney & ureter, proximal half of colon)
form Pelvic Splanchnic ns.: (distal half colon, rectum, bladder, reproductive organs)
Preganglionic (sacral cord)
Within walls of digestive tract, innervates smooth muscle and glands, regulates motility of esophagus, stomach, intestines and secretion of digestive enzymes and acid, interacts with...
Enteric Nervous System
Secrete ACh, released by all Sym & Parasym PG fibers & Parasym POG fibers, a few Sym POG fibers
all cardiac muscle, smooth muscle, and glands, two types, work via 2nd messenger systems
all synapses in autonomic ganglia, cells in adrenal medulla, at neuromuscular junction, always excitatory, work via ligand-gated ion channels
Secrete NE, released by almost all POG Sym fibers
usually excitatory, two subclasses cause different effects, α1 (suppress synthesis of cAMP), α2 (use Ca+2 as 2nd messenger)
usually inhibitory, two subclasses cause different effects, β1 & β2 (use cAMP as 2nd messenger), many drugs are designed to be receptor selective
tend to last longer due to lingering effects of NE.
Most viscera receive dual innervation
cardiac, digestive, pupils,
partial constriction of vessels due to baseline sympathetic innervation
Limbic system provides a pathway connecting sensory and mental experiences with the ANS
Major control center of the ANS, includes hunger, thirst, thermoregulation, emotions, and sexuality, output is mainly to more caudal areas of brainstem and then to cranial nerves and...
House numerous ANS nuclei many in the reticular formation, for cardiac, vasomotor, salivation, swallowing, sweating, GI secretion, bladder control, pupil control, and others,...
Midbrain, Pons and Medulla Oblongata:
Autonomic reflexes like micturation, defecation, erection, and ejaculation are integrated in the spinal cord