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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

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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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