|
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 pacemaker cells |
|
Visceral Reflexes |
| |
|
(receptor, afferent neurons, interneurons, efferent neurons, effectors), |
|
Visceral reflex arc |
| |
|
Mainly adapts body for activity, (“fight or flight”) |
|
Sympathetic |
| |
|
Mainly a calming effect, reduced energy expenditure, normal body maintenance (“rest & digest”) |
|
Parasympathetic |
| |
|
Background rate of activity from both divisions |
|
Autonomic Tone |
| |
|
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 |
|
Neural Pathways |
| |
|
Soma in brainstem or SC, ends in ganglion |
|
Preganglionic |
| |
|
Begins in ganglion and extends to target cells |
|
Post ganglionic |
| |
|
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 |
|
Sympathetic Division; also called thoracolumbar, |
| |
|
Small myelinated, enter ganglia via white communicating rami |
|
Preganglionic |
| |
|
Unmyelinated, exit ganglia by gray communicating rami or other route |
|
Postganglionic |
| |
|
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 |
|
Preganglionic |
| |
|
secretes steroid hormones |
|
Adrenal Cortex |
| |
|
modified postganglionic sympathetic neurons, secretes hormones epinephrine (85%) and norepinephrine (15%) into blood stream |
|
Adrenal Medulla |
| |
|
Also called craniosacral division, long preganglionic and short postganglionic fibers, cell bodies in brain stem and segments S2 to S4 |
|
Parasympathetic Division |
| |
|
preganglionic fibers end in terminal ganglia in or near target, little divergence more selective |
|
SC |
| |
|
exit via 4 cranial nerves, III Oculomotor, VII Facial, IX Glossopharyngeal, X Vagus |
|
Preganglionic (brainstem) |
| |
|
(lens and pupil of eye) |
|
III Oculomotor |
| |
|
(tear, salivary, nasal glands) |
|
VII Facial |
| |
|
(parotid salivary glands |
|
IX Glossopharyngeal |
| |
|
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) |
|
X Vagus |
| |
|
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 ANS |
|
Enteric Nervous System |
| |
|
Secrete ACh, released by all Sym & Parasym PG fibers & Parasym POG fibers, a few Sym POG fibers |
|
Cholinergic Fibers |
| |
|
all cardiac muscle, smooth muscle, and glands, two types, work via 2nd messenger systems |
|
Muscarinic Receptors |
| |
|
all synapses in autonomic ganglia, cells in adrenal medulla, at neuromuscular junction, always excitatory, work via ligand-gated ion channels |
|
Nicotinic Receptors |
| |
|
Secrete NE, released by almost all POG Sym fibers |
|
Adrenergic Fibers |
| |
|
usually excitatory, two subclasses cause different effects, α1 (suppress synthesis of cAMP), α2 (use Ca+2 as 2nd messenger) |
|
α-Adrenergic Receptors |
| |
|
usually inhibitory, two subclasses cause different effects, β1 & β2 (use cAMP as 2nd messenger), many drugs are designed to be receptor selective |
|
β-Adrenergic Receptors |
| |
|
tend to last longer due to lingering effects of NE. |
|
Sympathetic Effects |
| |
|
Most viscera receive dual innervation |
|
Dual Innervation |
| |
|
. |
|
. |
| |
|
cardiac, digestive, pupils, |
|
Antagonistic Effects |
| |
|
salivary glands |
|
Cooperative Effects |
| |
|
partial constriction of vessels due to baseline sympathetic innervation |
|
Vasomotor Tone |
| |
|
Limbic system provides a pathway connecting sensory and mental experiences with the ANS |
|
Cerebral Cortex |
| |
|
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 spinal cord. |
|
Hypothalamus |
| |
|
House numerous ANS nuclei many in the reticular formation, for cardiac, vasomotor, salivation, swallowing, sweating, GI secretion, bladder control, pupil control, and others, output is via spinal cord and cranial nerves III, VII, IX, X |
|
Midbrain, Pons and Medulla Oblongata: |
| |
|
Autonomic reflexes like micturation, defecation, erection, and ejaculation are integrated in the spinal cord |
|
Spinal Cord |
| |
