Transcript Chapter 17

Autonomic Nervous
System
A look at sympathetic and
parasympathetic divisions,
Portions of Chapter 17
Compare Somatic & Autonomic
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Somatic nervous system- voluntary, consists of
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sensory convey info from somatic & special sensory
receptors, primarily head, body wall, & limbs to CNS
motor neurons to conduct impulses to skeletal muscles
only
Autonomic nervous system-involuntary,consists of
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sensory neurons convey info from autonomic sensory
receptors, located primarily in viserca, to the CNS
motor neurons conduct nerve impulses to smooth muscle,
cardiac muscle, glands and adipose tissue. Motor portion
consists of 2 branches:
sympathetic division & parasympathetic division
Autonomic Nervous system
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ANS sensory neurons- usually interoreceptors,
monitor: blood CO2, degree of stretch in walls of
organs or b.v.
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Can produce conscious sensations if intense
 Damaged viscera or angina pectoris
Somatic pain can produce changes in ANS
ANS motor neurons regulate viscera by or activity
of effectors (smooth & cardiac muscle, glands)
ANS effector tissues generally function even if their
nerve supply is interrupted
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ex- heart being removed for transplant is still beating
Somatic
vs. Autonomic
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Special & somatic senses
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Voluntary from c.c, some
basal ganglia, cerebellum,
brain stem, s.c.
1 neuron: motor neuron
from CNS to effector
NT= Ach
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Effector= skeletal muscle
Contraction of skeletal
muscle
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Interoreceptors, some
special and somatic
Involuntary; from limbic sys,
hypothalamus, brain stem
and s.c., some c.c
2 neuron: pregang
postgang effector
NT=Ach in pre, Ach or NE in
post
Smooth & cardiac muscle,
glands
Contract or relax smooth
muscle, orforce of
cardiac,or gland secrete
Dual innervation
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Motor output of ANS has 2 branches:
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Sympathetic and parasympathetic
Most organs have dual innervation- receive
impulses from both sympathetic & para
Generally, one will be excitatory and the other
inhibitory
Sympathetic & Para- fig 15.2,3
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Sympathetic =
 fight or flight response:
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“E situations:” exercise, emergency, excitement, and
embarrassment
Parasympathetic= resting & digesting activities
 SLUDD- salivation, lacrimation, urination, digestion, defecation
 3 decreases: heart rate, airway diameter, pupil diameter
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Pupils dilate
 heart rate, force of contraction, b.p
airways dilate
bv to kidneys and GI constrict  blood flow there &  urine output
bv to skeletal, cardiac muscle dilate
glycogenolysis & lipolysis by liver;  blood glucose
Processes not essential to stress response slow or stop
Sympathetic ganglia
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Sympathetic- at synapses between pre & postganglionic
neurons, 2 groups of ganglia:
 sympathetic trunk- vertical row on either side of the vertebral
column
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prevertebral ganglia- anterior to vertebral column & close to the
large abdominal arteries
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extending from the base of the skull to the coccyx
since near the spine, most axons are short
generally innervate organs above the diaphragm.
generally post ganglionic innervate organs below diaphragm
3 main: celiac, superior mesenteric, inferior mesenteric
Preganglionic may synapse w/ 20+ postganglionic sympathetic
affect almost entire body simultaneously
Parasympathetic ganglia
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Parasympathetic- at synapses between pre &
postganglionic neurons in:
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terminal ganglia -close to or within wall of viscera
axons extend CNS to terminal ganglion in an innervated
organ  longer than most sympathetic preganglionic axons
In ganglion, presynaptic usually synapes with 4-5
postsynaptic neurons
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all supply single visceral effector
parasympathetic response localized to one effector
Symp vs. Para-- effects
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Balance between 2 regulated by hypothalamus
Generally, effects are regulating controlled
conditions in the body such as:
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blood pressure, by adjusting heart rate
force of ventricular contraction, & b.v. diameter
regulating diameter of bronchial tubes
adjust motility & muscle movement in digestion
defecation & urination by regulating sphincters
Few have only sympathetic innervation:
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Sweat glands, arrector pili, kidneys, spleen, bv, adrenal
medulla
Comparison of NT, table 17.2
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Cholinergic neurons- release Ach, brief effect due
AchE
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Ach excitatory at NMJ, inhibitory at some others
ALL symp & parasymp preganglionic neurons
Symp postganglionic innervate (most sweat glands)
ALL parasymp postganglionic neurons
Adrenergic neurons- release norepinephrine (NE),
AKA noradrenalin
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Produce actions similar to Ach (excite or inhibit)
most sympathetic postganglionic neurons