Honors Anatomy & Physiology
THE AUTONOMIC NERVOUS SYSTEM
ANS
in PNS
 operates via reflex arcs
 includes:

 autonomic sensory
neurons
 integrating centers in CNS
 autonomic motor neurons
AUTONOMIC REFLEX ARC
AUTONOMIC MOTOR NEURONS

when somatic motor neurons sends impulse to
a muscle the effect always excitatory…if they
stop sending impulses that muscle atrophies

autonomic motor neurons regulate visceral
activities by either increasing (exciting) or
decreasing (inhibiting) ongoing activities in
their effector tissues (cardiac or smooth
muscle, glands)
COMPARISONS OF ANS & SOMATIC NS
AUTONOMIC SENSORY NEURONS
source of most input to ANS via sensory
receptors called interoceptors
 not consciously perceived most of time
 located in:

 blood
vessels
 visceral organs
 muscles
 in nervous system
AUTONOMIC RESPONSES

most cannot be altered to any great degree
making some responses ideally suited for lie
detector tests
AUTONOMIC MOTOR PATHWAYS
most consist of 3 motor neurons in series
 1st neuron has cell body in CNS  myelinated
axon synapses in autonomic ganglion with 2nd
motor neuron cell body: its unmyelinated axon
 effector
 except

AUTONOMIC MOTOR PATHWAY
SYMPATHETIC DIVISION


preganglionic axons from
thoracolumbar nerves
ganglia far from visceral
effector in:


sympathetic chain or collateral
ganglia
neurotransmitter used:


PARASYMPATHETIC DIVISION



preganglionic axons from
craniosacral nerves
ganglia near or w/in visceral
effector organs
neurotransmitter used:


ACh in ganglia
ACh in effector organ
ACh in ganglia
NE in effector organ
2 BRANCHES OF MOTOR PART OF ANS
MOTOR PART OF ANS
most organs have dual innervation
 nerve impulses from 1 will increase activity
(excitation) & impulses from other decrease
activity (inhibition)

SYMPATHETIC GANGLIA

1.
2 groups:
sympathetic trunk ganglia
1.
2.
lie in vertical row, either side of vertebrae
prevertebral ganglia
1.
lie anterior to vertebral column close to large
abdominal arteries
SYMPATHETIC DIVISION OF ANS
PARASYMPATHETIC GANGLIA

most close to or w/in
effector organ
EFFECTS OF SYMPATHETIC &
PARASYMPATHETIC DIVISIONS OF THE ANS
HOMEOSTATIC IMBALANCES OF THE ANS

Raynaud’s phenomenon:
 due
to excessive sympathetic stimulation of
smooth muscles in arterioles of digits
 digits become ischemic (lack of blood) after
exposure to cold or with emotional stress
MEDICAL TERMINOLOGY
autonomic nerve neuropathy: often caused by
long-standing diabetes, neuropathy affects 1 or
more autonomic nerves, can interfere with
reflexes
 hyperhydrosis: profuse sweating due to intense
stimulation of sweat glands
 vagotomy: cutting vagus nerve; often done to
decrease production of HCl in patients with
severe ulcers
