Chapter 15 - The Autonomic Nervous System and Visceral Reflexes

A motor nervous system that controls glands, cardiac and smooth muscle to maintain homeostasis, actions are involuntary

Slower than somatic reflexes, include a visceral reflex arc, Example Elevated BP; baroreceptors stretch receptors (aorta & carotid), glossopharyngeal n., medulla, vagus n., heart pacemaker cells

(receptor, afferent neurons, interneurons, efferent neurons, effectors),

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 chain ganglia, interconnected by nerve cords there are typically 3 cervical, 11 thoracic, 4 lumbar, 4 sacral, 1 coccygeal

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 in muscles and body wall), sympathetic n. (effectors in head and thoracic cavity), and splanchnic n. (effectors in abdominopelvic cavity), neural convergence and divergence are present

Secretes steroid hormones

Modified postganglionic sympathetic neurons, secretes hormones epinephrine (85%) and norepinephrine (15%) into blood stream