User:Benlee/Notes/ANP/14

The Autonomic Nervous System

 * maintains homeostasis by controlling organs, glands, and heart
 * controls blood flow, pressure, body temp, and stomach secretions

Introduction

 * Definition: motor neurons that supply nerves to glands, smooth muscles, and cardiac muscles
 * The somatic nervous system has different effectors, pathways, and neurotransmitters
 * motor unit of ANS is two-neuron chain
 * preganglionic neuron is in CNS
 * preganglionic axon synapses with ganglionic neuron (an autonomic ganglion) outside CNS
 * axon is lightly myelinated, thin
 * postganglionic axon extends from the ganglionic neuron to the effector organ
 * axon is unmyelinated, thinner
 * somatic motor division has no ganglia
 * norepinephrine is released at effector organs in sympathetic division
 * acetylcholine is released at effector organs in parasympathetic division

ANS Divisions

 * Parasympathetic and Sympathetic
 * usually have opposite effects on same organs/glands - called dual innervation
 * 1) Parasympathetic Division
 * 2) *conserves body energy
 * 3) *maintains base levels for homeostasis
 * 4) Parasympathetic effects:
 * 5) *pupils constrict
 * 6) *increased digestion activity
 * 7) *lowered blood pressure, heart rate, breathing
 * 8) Sympathetic division
 * 9) *fight-or-flight
 * 10) Sympathetic responses:
 * 11) *pupils dilate
 * 12) *increased blood pressure, heart rate, breathing
 * 13) *bronchioles dilate
 * 14) *increased blood glucose levels for increased muscle activity
 * 15) *sweating
 * 16) *During exercise, blood is taken from the skin and digestive viscera to the heart, brain, and skeletal muscles.

ANS Anatomy

 * divisions are distinguished by
 * origin
 * parasympathetic - brain and sacrum
 * sympathetic - thoracic and lumbar
 * length of fibers
 * parasympathetic - long preganglionic, short postganglionic
 * sympathetic - short preganglionic, long postganglionic
 * location of ganglia
 * parasympathetic - close to visceral effector organs
 * sympathetic - close to spine

Parasympathetic

 * oculomotor nerves (III) - for constricting pupils
 * facial nerves (VII) - activates nasal, lacrimal, and salivary glands
 * glossopharyngeal nerves (IX) - salivary glands
 * vagus nerves (X) - 90% of preganglionic parasympathetic fibers
 * to neck, nerve plexuses
 * cardiac plexuses
 * pulmonary plexuses
 * esophageal plexuses
 * aortic plexus
 * supplies liver, gallbladder, stomach, small intestine, kidneys, pancreas, proximal large intestine
 * sacral outflow
 * serves distal large intestine, bladder, ureters, reproductive organs
 * parasympathetic fibers never run in spinal nerves

Sympathetic

 * more complex than parasympathetic - more organs
 * sympathetic neurons produce the lateral horns, which are absent in sacral region of spinal cord
 * nerves leave cord through the ventral root
 * pass through the white ramus
 * enter chain ganglion, where it either:
 * synapses in same ganglion
 * moves to another ganglion and synapses there
 * passes through ganglion without synapsing
 * If 1 or 2, nerve goes through gray ramus and exits
 * If 3, exits through white ramus