The autonomic system
Terms
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- Somatic efferent
- Produces voluntary skeletal muscle contractions
- Autonomic (visceral efferent)
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System consists of:
gen. visceral sensory (afferent)neurons
gen. visceral motor (efferent) neurons
visual effectors
involuntarily regulates visceral activities
Sympathetic nervous system
Parasympathetic nervous system
efferent fibers: preganglionic and postganglionic
many visceral organs have dual innervation - not all - Visceral effectors
-
smooth and cardiac muscle
glands - Autonomic nervous system
-
Sympathetic nervous system
Parasympathetic nervous system - Sympathetic nervous system
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Preganglionic neurons (thoracolumbar outflow)
Autonomic ganglia
Sympathetic trunk ganglia
Prevertebral ganglia
Autonomic plexuses
Postganglionic neurons
White rami communicants
Gray rami communicants - Parasympathetic nervous system
- producing a "rest relaxation" response
- Visceral efferent fibers
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Preganglionic fibers
Postganglionic fibers - Preganglionic fibers
- Run from the c.n.s. to autonomic ganglia
- Postganglionic fibers
- Run from autonomic ganglia to visceral effectors
- "autonomic ganglia"
- A ganglion occurs btwn. preganglionic and postganglionic fibers
- Why is the sympathetic response (stress reaction) so widespread in the body?
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"1" preganglionic fiber can stimulate up to "20" plus postganglionic neurons that supply different organs - thus stress reaction widespread
neurotransmitters get into blood and remain a while before being broken down. - Visceral efferent pathways
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consists of two neurons:
Preganglionic neurons
Postganglionic neurons - Preganglionic neurons
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thoracolumbar division
Cell bodies originate in lateral gray horns of T1 - T2
Axons terminate in autonomic ganglia of the s.n.s. - Postganglionic neurons
- The 2nd autonomic neuron in an autonomic pathway having its cell body an dendrites located in an autonomic ganglion and it's a myelinated axon ending at cardiac muscle, smooth muscle, or a gland.
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Prevertebral ganglia (collateral)
EXAMPLES -
Celiac
Sup. mesenteric ganglion
Inf. mesenteric ganglion - Splanchnic nerves
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Are preganglionic neurons
belong to s.n.s.
bypass or pass through sympathetic trunk and terminate in collateral ganglia - Autonomic plexuses
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In thorax
abdomen and pelvic region of body
are network of axons of both sympathetic and parasympathetic neurons - Preganglionic neurons (craniosacral outflow)
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Cell bodies of parasympathetic in nuclei of cranial nerves III, VII, IX, and X and lateral gray horns of S2 - S4 (sacral parasympathetic outflow)
Axons terminate in autonomic ganglia of the P.N.S. - White rami communicants
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Branches - connect ventral root of sp. nerve with sympathetic trunk
are myelinated preganglionic fibers - Gray rami communicants
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Run from ganglia back to ventral ramus of sp. nerve
are gray postganglionic neurons - Autonomic ganglia of P.N.S.
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Terminal ganglia (intramural)
May be divided into 3 gen. groups
sympathetic division
parasympathetic division - Terminal (intramural) ganglia
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Preganglionic axons of the parasympathetic division synapse with postganglionic neurons
located close to or actually within the wall of a visceral organ.
longer the most axons of sympathetic preganglionic EXAMPLES
neurons
ciliary
pterygopalatine
submandibular
otic - Neurotransmitters
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Ap. 50 + known
one neuron may contain several types
Released at:
endbulbs
Synapse
Neuroeffector junction
Cholinergic fibers
Adrenergic fibers - synapse
- space btwn. axonal ending and dendrite or effector
- Neuroeffector junctions
- Specifically btwn. postganglionic axonal ending and effector
- Cholinergic fibers
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release acetylcholine (Ach)
is released at:
Sympathetic and parasympathetic preganglionic axons
All parasympathetic postganglionic axons
Few sympathetic postganglionic axons
Ach inactivated by acetycholinesterase (AchE) - Acetylcholine
- esp. excites - as in the contraction of skeletal muscle - but - it can also inhibit cardiac muscle - thus receptors determine effect of neurotransmitters
- Adrenergic fibers
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released norepinephrine
released at most sympathetic postganglionic axons - norepinephrine
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inactivated slowly by:
Catechol-o-methyltransferase (COMT)
Monoamine oxidase (MAO)
may enter the bloodstream
secreted from adrenal medulla - Sympathetic reaction
- prepares body for stress - "fight or flight" response
- Parasympathetic reaction
- restores and/or conserves energy - "rest and repair" response
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Sweat glands
(visceral effector) -
s.n.s stimulation: secretion gen. up
p.n.s stimulation: no known innervation -
Gastric secretion
(visceral effector) -
s.n.s stimulation: secretion inhibited
p.n.s stimulation: increased secretion -
Muscles of bronchi
(visceral effector) -
s.n.s stimulation: relation leads airway dialation
p.n.s stimulation: contraction leads to airway contriction -
Heart rate
Force of contraction
(visceral effector) -
s.n.s stimulation: Increased heart rate and force of atrial and ventrile contractions
p.n.s stimulation: Decrease heart rate and Decreased force of atrial contraction -
Blood vessels to:
Skin (periphery)
Skeletal muscles
(visceral effector) -
s.n.s stimulation: Contraction leads to vasocontriction; relaxation leads to vasodialation
p.n.s stimulation: Vasodialation, which may not be physilogically significant
S.M. No known effect -
Intestines
(visceral effector) -
s.n.s stimulation: decreases
motility and tone; contraction of sphincters
p.n.s stimulation: Increased motility and tone; relaxation of sphincters - Visceral autonomic reflexes
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responses that occur when nerve impulses pass over an autonomic reflex arc
regulating controlled condition of body - blood pressure - digestion - Receptor
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distal end of sensory neuron
responds to a stimulus and produces a change that will ultimately trigger nerve impulses. - Sensory (afferent) neurons
- Conducts nerve impulses from receptors to the CNS.
- Association neuron
- A nerve cell found entirely within the central nervous system that acts as a link between sensory neurons and motor neurons.
- Visceral efferent
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smooth muscle
cardiac muscle
glands - Hypothalamus
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receives input from or is linked to:
Higher brain centers
Emotions
Visceral functions
senses
others - SNS
- appears to be controlled by post. and lat. portions of the hypothalamus.
- PNS
- appears to be controlled by ant. and med. portions of the hypothalamus.
- Meditation
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mind and body
trance like state
clearing your mind for relaxation - Biofeedback
- A technique in which an individual is provided w/ info regarding an autonomic response such as heart rate, blood pressure, or skin temp. using electronic devices
- Progressive relaxation
- tense and relax different parts of body and then learning how to relax those muscles.