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Main input from
autonomic
sensory neurons
(most associated
with
interoceptors)
• monitor
internal
environmentnot conscious
• examplechemoreceptors
for CO2 level
Autonomic motor
neurons regulate
visceral activities
(increase or decrease)
• function somewhat
even if nerve supply
damaged
• example- heart beat
• difficult to
consciously control
(i.e. lie detector test,
yoga)
See figure 15.1
Most autonomic motor pathways consist of two motor neurons
in series through autonomic ganglion (second not myelinated)
• preganglionic (CNS) and postganglionic (PNS)
• some extend to adrenal medullae- hormones released
The
preganglionic
motor neurons
of the
sympathetic
system arise
in the spinal
cord.
They pass
into
sympathetic
ganglia which
are organized
into two
chains that
run
parallel to and
on either side
of the spinal
cord.
The main nerves
of the
parasympathetic
system is the
tenth cranial
nerve, the vagus
nerve. It
originates in the
medulla
oblongata. Other
preganglionic
parasympathetic
neurons also
extend from the
brain as well as
from the lower tip
of the spinal
cord.
Anatomy of autonomic motor pathways:
Three types of autonomic ganglia
• sympathetic trunk ganglia- vertical row on either
side of vertebral canal
• sympathetic division
• innervate organs above diaphragm
• prevertebral ganglia- anterior to vertebral canal
•sympathetic division
•innervate organs below diaphragm
•terminal ganglia- close to or actually in wall of
organ (longer)
•parasympathetic division
Postganglionic neurons- one sympathetic ganglia can
synapse with 20+ postganglionic neurons (effect
much of body simultaneously)
Autonomic plexuses
•tangled networks of axons from sympathetic and parasympathetic
neurons
•cardiac (heart), pulmonary (lungs), celiac or solar (liver, gallbladder,
stomach, pancreas, spleen, kidneys, testes, ovaries), superior
mesenteric (small and large intestines), inferior mesenteric (large
intestine), renal (kidneys and ureters)
ANS neurotransmitters and Receptors
• cholinergic- release acetylcholine (Ach)
• all preganglionic neurons, parasympathetic
postganglionic neurons, some sympathetic
postganglionic (sweat glands)
• nicotinic and muscarinic receptors- effects
brief
• adrenergic (release norepinephrine/ NE)
•most sympathetic postganglionic
•alpha and beta receptors- longer lasting
• agonists can activate receptors, antagonists
block receptors
Physiological effects of ANS- tables 15.3 and 15.4
• autonomic tone- balance between sym. and
parasym.- regulated by hypothalamus
• Sympathetic dominates during physical or
emotional stress (rapid ATP production)--- flight
or fight response--- “E situations” (exercise,
emergency, excitement, embarassment)
• Parasympathetic dominates “rest and digest”
activities- conserve and restore energy --- SLUDD
(salivation, lacrimation, urination, digestion,
defecation)
Autonomic reflexescontrolled conditions
(i.e. blood pressure)
• reflex arc: receptorsensory neuronintegrating centermotor neuroneffector
• hypothalamus
major control center