June 23rd
Transcript of June 23rd
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Autonomics of the Abdomen and Pelvis
M.Pizzimenti
Required Reading: Moore and Agur p.37-43; 180-184 (Table 3.9); organ specific readings
Objectives:
• Outline the basic structure of the autonomic nervous system. Define the concept of
ganglion, preganglionic neuron, postganglionic neuron.
• Discriminate between sympathetic and parasympathetic pathways based on organ location
and blood supply.
• Present a working definition of referred pain and outline how this may be indicative of
problems with internal organs.
Autonomic Nervous System
Composed of the sympathetic and parasympathetic
divisions that activate the involuntary (smooth) and
cardiac muscles, glands, eyes, and skin.
Uses a two-neuron system:
• preganglionic neurons have cell bodies in the central
nervous system (CNS) with its axon being
myelinated
• postganglionic neurons have cell bodies within a
ganglion outside the CNS with its unmyelinated
axon reaching a target organ.
Ganglion is a collection of cell bodies outside of the
CNS
Sympathetic (Thoracolumbar) Nervous System
This division is concerned with fight or flight responses.
Examples of structures supplied by this system include
sweat glands, dilator pupillae m, arrector pili mm.
(causes "goose bumps"), blood vessels (constriction),
heart (increase rate). Preganglionic neurons have their
cell bodies in the intermediolateral column of the spinal
cord at levels T1-L2(3)
Sympathetic chain ganglia (containing post ganglionic
nueron cell bodies) are located paravertebrally and
extend from the based of the skull to the coccyx
(ganglion impar)
Prevertebral ganglia (containing post ganglionic neuron
cell bodies) are located primarily in abdominal cavity.
Associated with the major aa. studied (i.e., celiac,
superior mesenteric, inferior mesenteric).
CNS
Target organ
MA43
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Travel with spinal nerves (ventral rami) a short distance
then leave the spinal nerves and join the sympathetic
chain via white rami communicantes
They may:
• Synapse in a ganglion (same level or different level)
Postsynaptic nerves return to the spinal nerves via
gray rami communicantes
• Leave the sympathetic chain without synapsing and
travel via splanchnic nerves to the prevertebral
ganglia. Synapse. Postsynaptic fibers travel to
organs.
• Leave the sympathetic chain without synapsing and
go to the medulla of the adrenal gland. Cells release
neurotransmitter
Neurotransmitter at most the target organs:
• Norepinephrine
• acetylcholine for sweat glands and blood vessels of
skeletal muscle
Where are white rami communicantes found?
Where are gray rami communicantes found?
Check points
• Outline the pathway to have sweat production just lateral to the nipple.
• Outline the pathway to allow vasoconstriction of the R. gastric a. and inhibition of peristalsis
of the stomach
• Review arterial supply to the foregut, midgut, hindgut
Sympathetic Supply to Pelvis. As an overview, sympathetic supply (from inferior mesenteric
ganglia, lumbar and sacral splanchnics) makes its way to pelvic viscera via the hypogastric nn.
The (R/L) superior hypogastric plexus is located near the bifurcation of aorta. The hypogastric
nn. travel through endopelvic fascia and merge in the inferior hypogastric plexus. (see
diagram)
Sympathetics and Visceral Sensation. Although technically not part of the autonomics,
afferent information dealing with pain (i.e., ischemia, chemical injury, over-distention) from
viscera travels with the sympathetic nn. As such these neurons will have their cell bodies in
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the DRG at the appropriate spinal level (typically at the level associated with the preganglionic
neuron)
Parasympathetic (Craniosacral) Nervous System
This division is concerned with motor functions that allow the body to feed and assimilate.
Cranial portion - CN III, VII, IX, X responsible for decrease heart rate, digestion
(increased peristalsis), tearing, gland secretion, constricting pupils of eye, accommodating eye
lens for near vision (more later)
Sacral portion - derived from sacral segments S2-S4, responsible for urination
defecation, sexual response.
Preganglionic cell bodies located in the brain stem or
sacral level of spinal cord. Postganglionic cell bodies
are located near or within the walls of the target organ.
Neurotransmitter is acetylcholine.
CN X carries preganglionic axons to viscera of the neck,
thorax, and abdomen. Its course to the abdominal
viscera includes the foregut and midgut up to the splenic
flexure.
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Pelvic viscera receives its preganglionic parasympathetics from the S2-S4
sacral segments > pelvic splanchnic nn. The pelvic splanchnics contribute to
the inferior hypogastric plexus. These preganglionic fibers run through the
plexus without synapsing until they meet their target organ. Pre ganglionic
parasympathetics to the hindgut and portions of ureter make their way "up"
the hypogastric nn. to reach their target organ. Post ganglionic
parasympathetic cell bodies are located within the walls (intramural) of the
organ.
Check points
• Outline the pathway for parasympathetic supply to the stomach.
• Outline the pathway for parasympathetic supply to the descending colon
• Outline the pathway for parasympathetic supply to the bladder
Parasympathetics and Visceral Sensation. Although technically not part of the autonomics,
afferent information dealing with distention from viscera travels with the parasympathetic nn.
Referred Pain is a phenomenon where 'pain/distress' from an organ is interpreted by the brain
as though the 'pain/distress' originates from a part of the body surface. Pain from an organ
varies in 'sensation' from dull to severe but is not well localized (person cannot point to an
exact location). The pain from an organ radiates to a part of the body supplied by sensory
fibers that share the same spinal level. That is, the sensory cell bodies for both the organ and
the body part are at the same spinal level.
Check points
• A person with pancreatitis presents with pain in the epigastric region. Outline the anatomic
pathway that links the irritation of the pancreas with the pain superior to the umbilicus.
• Given the autonomic innervation of the midgut, hypothesize where pain associated with
appendicitis might be referred
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modified
modifi
T10
T11
L1
• Given the autonomics of distal ureter, how might a 40 y.o. male with a ureteric calculus
(kidney stone) lodged at the junction of the ureter and bladder present?
MA = Moore, KL and Agur, AMR. 2007. Essential Clinical Anatomy (3rd Ed), Lippincott Williams & Wilkins
MD = Moore, KL and Dalley, A. 1999. Clinically Oriented Anatomy (4th Ed), Lippincott Williams & Wilkins
GD = Tank, PW, 2005. Grant’s Dissector (13th Ed), Lippincott Williams & Wilkins
GA = Agur AMR and Dalley, A 2005. Grant’s Atlas of Anatomy (11th Ed), Lippincott Williams & Wilkins
N = Netter’s Atlas of Human Anatomy, 2003, ICON Learning Systems.
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N 311
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N 318
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MA184