The Autonomic Nervous System Flashcards
Peripheral nervous system (PNS)
Somatic nervous system
Motor and sensory pathways regulating voluntary motor control of skeletal muscle
Autonomic nervous system
Motor & sensory pathways regulating the body’s internal environment through involuntary control of organ systems (smooth muscle, cardiac muscle, and glands)
- Sympathetic– FFF
- Parasympathetic– Rest and digest
Describe the Neurons of the ANS
Preganglionic:
cell body in CNS (myelinated B fibers)
Postganglionic:
cell body in autonomic ganglia (unmyelinated C fibers)
Two divisions classified anatomically
(often but NOT ALWAYS physiologic antagonists)
Sympathetic
Parasympathetic
+/- Enteric
Activation of the ANS via autonomic centers in:
Hypothalamus (influenced by connections to limbic system) Brain stem --Medulla- Vasomotor vasodilation --Pons- micturition Spinal Cord
Controls Visceral Functions
ANS partial Control
Partial control Systemic blood pressure GI motility and secretion Urinary bladder emptying Sweating and body temperature
Sympathetic innervation
Thoracolumbar:
-Preganglionic
-Post ganglionic
Preganglionic neurons cell bodies located in (T1-L2/3) of spinal cord
Intermediolateral horn of grey matter
Post ganglionic neuron cell bodies are located in ganglia
Paravertebral chains (either side spinal column)
Prevertebral ganglia (i.e. celiac, superior, inferior mesenteric ganglia in abdomen)
Short preganglionic neurons, long post ganglionic
The Sympathetic Nervous System (Thoracolumbar division)
How do nerve fibers leave the spinal cord?
Nerve fibers leave the spinal cord ventrally via white rami and travel to 22 paravertebral ganglia (the sympathetic chain ganglia)
From the 22 paravertebral ganglia (the sympathetic chain ganglia) nerve fibers synapse with?
Synapse with post-ganglionic neuron at same level OR
Move caudad or cephalad to synapse at another level
Pass ganglia without synapsing to collateral ganglia surrounding the abdominal aorta (celiac, superior mesenteric, inferior mesenteric)
Some ganglia have inhibitory interneurons as well
From the 22 paravertebral ganglia (the sympathetic chain ganglia) nerve fibers synapse with?
Synapse with post-ganglionic neuron at same level OR
Move caudad or cephalad to synapse at another level
Pass ganglia without synapsing to collateral ganglia surrounding the abdominal aorta (celiac, superior mesenteric, inferior mesenteric)
Some ganglia have inhibitory interneurons as well
Post-ganglionic nerve cell bodies found in ganglia of paravertebral chain exit to travel to various peripheral organs. How do they return to spinal nerves via
via gray rami travel with these nerves to blood vessels, piloerector muscles and sweat glands
Note: Distribution of SNS fibers is based on embryonic development and NOT spinal segments T1 T2 T3-6 T7-11 T12-L2
Distribution T1 SNS fibers usually ascend into the paravertebral sympathetic chain to head T2 neck T3-6 chest T7-11 abdomen T12-L2 legs
Parasympathetic innervation
Pre-ganglionic neurons
arise in
“Cranial” (medullary CN 3,7, 9, 10)
“Sacral” (spinal cord S2-4) regions
Post-ganglionic neurons cell bodies located in:
Target organs
Discrete ganglia in the head and neck (i.e. ciliary ganglia)
Long preganglionic neurons, short post
Parasympathetic Nervous System “Craniosacral division”
Functions to conserve and restore energy
“Rest or repose response”
