Intro to ANS Flashcards
Function of Autonomic Nervous System
regulation of involuntary physiologic process
Give examples of involuntary physiologic processes
heart rate, blood pressure, respiration, digestion, sexual arousal
Anatomically distinct divisions of ANS
sympathetic, parasympathetic, enteric
Type of nerves/action of ANS
Visceral motor; motor fibers (multipolar) carry info toward targets in PNS
sensory ANS “associated”
pseudo unipolar fibers that provide a mechanism to monitor activities of ANS
Is the ANS primarily sensory or motor
Simply - viceromotor
Somatic
structures associated with outer body wall, derived from ectoderm, paratial mesoderm, and somatic LP of mesoderm). Conscious motor and sensation
Visceral
structures associated with inner organs; derived from splanchnic layer of lateral plate mesoderm, intermediate mesoderm, endoderm. Includes glands, cardiac muscle, and smooth muscle. Unconscious and involuntary movement of your viscera
How many neurons make up the ANS unit?
2 neuron-system in periphery
Visceral afferents
pseudo-unipolar fibers that transmit info that we cannot perceive (osmolality, pain of viscera) to the CNS. Located in dorsal root ganglia
Visceral efferents
multipolar motor fibers from ANS relay info toward targets in 2 neuron peripheral connection; functions: organ movement, vasoconstriction, airway diameter. Control of cardiac and smooth muscle, glandular tissue
preganglionic axons
originate from neurons in CNS and travel to peripheral ganglion
postganglionic axons
axons originating from the cell bodies making up ganglia, travel to target tissue
List the similarities between the parasympathetic and sympathetic nervous system
- both efferent systems
-both involve regulation of the internal environment
-both involve 2 neurons that synapse at peripheral ganglia
-Innervate glands, smooth muscle, cardiac muscle
Target tissues of the sympathetics
-Organs of head, neck, trunk, external genitalia
-adrenal medulla
-sweat glands
-arrector pili
-all vascular smooth muscles
»>ALL TISSUES
Target tissues of parasympathetics
-organs of head, neck, trunk, external genitalia
»» “INTERNAL ONLY”
Function/anatomical characteristics of the sympathetics
“fight of flight”
preganglionic neurons in thoracic and lumbar spinal cord. Chain ganglia alongside vertebral colum
Sympathetic tone is “always on”
Function/anatomical characteristics of the parasympathetics
“feed and breed” & “rest and digest”
preganglionic from cranium through cranial nerves, some in sacral spinal cord
Effectors receiving sympathetic innervation only
adrenal medulla, arrector pili muscles, sweat glands, many blood vessels
Sympathetic vasomotor tone
baseline action potential
increase in firing frequency = vasoconstriction
decrease in firing frequency= vasodilation
can shift blood supply to organs as needed
Sympathetic stimulation ______ blood to skeletal/cardiac muscles while ____ blood flow to skin
Increases; Decreases
Where are sympathetic postganglionic cell bodies located?
In paravertebral ganglia (sympathetic chain) OR preaortic (prevertebral) ganglia
Where are parasympathetic postganglionic cell bodies located?
in, on, or near the walls of their target organs
Where are sympathetic preganglionic cell bodies?
Located in lateral horn of T1 to L2 spinal cord. Axons go to sympathetic chain
Where to sympathetic postganglionic fibers travel from the chain ganglia?
supply everything from top of head to bottom of feet, axons travel with all spinal nerves going to muscles/skins
Where do the axons of sympathetic postganglionic fibers travel from preaorrtic ganglia?
amdominopelvic organs
Where do parasympathetic preganglionic neurons originate?
Cranial Nerves III, VII, IX, X
Lateral horns of S2-S4
Where do are sympathetic postganglionic neurons located?
In or near the wall of the organ being supplied (except head)
Rami Communicans
connections from segmental nerves to sympathetic chain
White Rami Communicans
Myelinated preganglionic axons from Ventral primary ramus to sympathetic ganglia
Found only wehere preganglionic cells exist in spinal cord. (T1 to L2)
Grey Rami Communicans
unmyelinated postganglionic axons travel from sympathetic chain ganglia to segmental nerves
associated with. ALL segmental nerves
Carries sympathetic supply for different levels of the body
Options for travel of sympathetic preganglionic neurons
- Synapse in chain at same level
- Travel up chain to synapse at higher level
- Travel down chain to synapse at lower level
- Pass through chain to. synapse at pre-aortic ganglia
Functions of sympathetic nervous system on body wall/limbs
Erector pili muscles of skin (smooth m. )
Sweat glands
Vascular smooth muscle
Splanchnic nerves
Provide sympathetic innervation to visceral organs and DO NOT synapse at chain ganglia
Where are the postganglionic cell bodies of splanchnic nerves located
pre-aortic ganglia, travel with blood vessels
How do thoracic splanchnic nerves reach the pre-aortic ganglia?
by leaving the sympathetic trunk ventrally
What are preganglionic axons destined to innervate?
foregut, midgut, hindgut
How do the postganglionic fibers of sympathetic splanchnic nerves travel?
With arterial supply
3 Major types of sympathetic splanchnic nerves
Thoracic, lumbar, sacral
Thoracic splanchnic nerves
arise from T5 to T12 spinal cord levels
Lumbar splanchnic
arise from L1-L2
Sacral splanchnic nerves
arise from lumbar spinal cord levels descend the chain to make their way to pelvic organs (mostly preganglionic)
Do parasympathetic neurons synapse in the chain ganglia?
NO
at a ganglion located in, at, or on target organ
How do parasympathetic postganglionic neurons travel?
within organ walls
What is the path of parasympathetic preganglionic neurons
Travel from brainstem (CIII, VII, IX, X) or spinal cord to ganglion in target organ for synapse
Vagus nerve
CN X; parasympathetic innervation to visceral organs from nexk, thorax, abdomen through the foregut to transverse colon of midgut
-ends at transverse colon wherre. pelvic. splanchnic nerves take. over parasympathetic innervation
Give an example of a parasympathetic target of the vagus nerve
Cardiac ganglia
esophageal plexus
spleen
splenic flexture of colon
acetylcholine
chemical transmitter at most junctions of ANS and skeletal m.
Released by all preganglionic neurons of PSNS and SNS
Released by all postganglionic PSNS
Sweat gland postganglionic of SNS
Norepinephrine
NT released only by Postganglionic of SNS (except sweat glands)
Epinephrine
NT release by adrenal medulla
How do visceral afferents run?
with sympathetic/parasympathetic nerves
cell bodies located in DRG
Nerves end in the viscera
Referred pain
pain. originating in visceral structure, perceived as being from an area of skin innervated by same segmental level as visceral afferent. Result of “cross talk” in dorsal horn between somatic and visceral afferents
what surgery to control peptic ulcers can result in gastroparesis?
surgical vagotomy
Raynaud’s disease
characterized by constriction of blood vessels, provoked by cold exposure of emotional stress
=> Sympathetic hyperactivity
Referred pain site of stomach
upper back, between scapulae
Referred pain site of gallbladder, liver, duodenum
Right trapezius fold extending posteriorly to approximately cover scapulae (diaphragm irritation)
Referred pain site of kidney and ureter
extending from inguinal region posteriorly to lumbar region
