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Autonomic Nervous System
? A. Comparison of somatic and autonomic
nervous systems
? B. Anatomy of autonomic motor pathways
1. Overview
a. Preganglionic neurons
b. Autonomic ganglia
c. Postganglionic neurons
? C. Physiological effects of ANS
1. ANS neurotransmitters
2. Parasympathetic and sympathetic
responses
ANS regulates activities of cardiac muscle, smooth
muscle, and glands.
?Structurally, ANS consists of two main components:
1. visceral afferent neurons
2. visceral efferent neurons
?Functionally, the ANS operates:
1. without conscious control
2. reflex arc dependent
3. medulla and hypothalamus over ride
Somatic & Autonomic Nervous Systems
Somatic
Autonomic
cutaneous receptors chemoreceptors
proprioceptors baroreceptors
special senses mechanoreceptors
may become conscious unconscious
excitatory for skeletal excitatory or inhibitory for
muscles cardiac muscle, smooth
muscles, and glands
single motor neuron two motor neurons
Somatic and Autonomic Efferent Pathways
Overview of Autonomic Pathways
?Preganglionic neuron
?1. first of two autonomic motor neurons
?2. cell body located in gray matter of spinal
cord (lateral column) or brain
?Thoraco lumbar ? sympathetic & Craniosacral
?parasympathetic
?3. preganglionic axon passes from CNS in a
spinal or cranial nerve
?4. axon terminates in a ganglion
Overview of Autonomic Pathways
?Ganglion
?1. collection of nerve cell bodies located in
a specific site outside CNS
?2. cell bodies give rise to postganglionic
neurons
Overview of Autonomic Pathways
?Postganglionic neuron
?1. second of two autonomic motor neurons
?2. cell body located in ganglion
?3. postganglionic axon passes from ganglion
to effector Organ
?4. peripheral effector is either stimulated or
inhibited
Sympathetic Nervous System
?1. lateral gray horns (T1-L2)
?2. Thoracolumbar outflow
?3. ganglia
a. sympathetic trunk (paravertebral)
b. Prevertebral (collateral)
?4. preganglionic axons short
?5. postganglionic axons long
Sympathetic Nervous System
Parasympathetic Nervous System
?1. lateral gray horns (S2-4)
?2. cranial gray matter
(III, VII, IX, X)
?3. Craniosacral outflow
?4. terminal ganglia
?5. preganglionic axons long
?6. postganglionic axons short
Parasympathetic Nervous System
Physiological Effects of ANS
? 1. dual (duel?) innervation
? 2. different neurotransmitters
? 3. parasympathetic tone
ANS Neurotransmitters
Cholinergic
Adrenergic
acetylcholine
norepinephrine
all preganglionic neurons
most postganglionic
all postganglionic parasympathetic & sympathetic neurons
few postganglionic sympathetic neurons
acetylcholinesterase
catechol-O-methyl
transferase
monoamine oxidase
Autonomic Nervous System - Neurotransmitters &
Receptors ? Sympathetic arm
Autonomic Nervous System - Neurotransmitters &
Receptors ? Parasympathetic arm
Sympathetic System
?1. energy expenditure system
?2. fight-or-flight response
?3. dominates parasympathetic NS
?4. effects
Parasympathetic System
?1. energy conservation-restoration
system
?2. rest-and-recovery
?3. dominates sympathetic NS
This post was last modified on 05 April 2022