the autonomic nervous system keith sequeira md, frcpc assistant professor uwo
TRANSCRIPT
Objectives
1. Anatomy of ANS
2. Physiology of ANS
3. Elicit a Hx. From a SCI individual
4. Identify Autonomic Dysreflexia (A.D)
5. Treat A.D.
Autonomic Nervous System
Innervation of INVOLUNTARY structures such as the heart, smooth muscle and glands
Distributed throughout the central and peripheral nervous system
Differences
SomaticCell bodies inside CNSAxons extend to skeletal muscleAll excitatory
AutonomicSynapse outside CNSFirst and second order axons
Autonomic Nervous Systems
Sympathetic
ParasympatheticBoth have afferent and efferent fibersLength of pre and postganglionic fibers
differs
Afferent
Peripheral receptors in wall of viscera and blood vessels
Cell bodies in dorsal root ganglia or Cranial Nerve Ganglia
Central processes end in dorsal grey column or spinal cord or brainstem
General layout
Efferent pathway – 2 neurons:Preganglionic neuron (myelinated) in spinal
cord or brainstem, synapsing with;Postganglionic neuron (unmyelinated) in
autonomic ganglion
General Layout
Sympathetic ganglia are further from the target organs
Parasympathetic are located near or in the walls of target organs
Chemical transmission in the ANS
Pre-gang
fibers
Post-gang
fibers
Effector
organs
Parasymp Acetylchol Acetylchol Heart, Sm. Muscle, lac/sal
glands
Chemical transmission in the ANS
Pre-gang
Fibers
Post-gang
Fibers
Effector organs
Sympath Acetylchol Acetylchol Sweat glands
Norepi Heart, Sm muscle, Vessels, Glands
Parasympathetic
Supplies heart, glands and smooth muscles of the viscera
NOT sweat glands, blood vessels or erector pilorum muscles
Sympathetic Nervous System
Redistributes blood from skin and intestine to the brain, heart and skeletal muscle
Closes sphincters, inhibits peristalsis
Sympathetic Nervous System
Chief transmitter at the end organ is norepinephrineHormone which circulates along with
epinephrine, especially in states of alarm or defense
Released by the adrenal medulla
Adrenal Medulla
Cells of the adrenal medulla behave as neurons in sympathetic ganglia without axons
Mostly epinephrine
Parasympathetic
Aim at conserving and restoring energy
Slows the heart rate, increases peristalsis of the intestines and glandular activity and opens the sphincters
Heart
ParasympatheticCardiac inhibitionVasoconstriction of the coronary arteries
SympatheticCardiac accelerationDilation of the coronary arteries
Sexual Function
ParasympatheticsS2-S4 originate in the intermediolateral
column In males, fibers end in erectile tissue,
prostate, vas deferens, seminal vesicles, ejaculatory ducts
In females, fibers go to vagina and erectile tissue
Sexual Function
Sympathetic In females, nerves originate from
splanchnic nerves of the ovarian plexus, T10-L2
In males, nerves originate in the hypogastric nerves, T10-L2
Sympathetic
Increases HR and ventricular contraction, dilates blood vessels in skeletal muscles, constricts blood vessels in skin and gut, increases blood sugar level, stimulates sweating, dilates pupils, inhibits gut and gastric secretion
Parasympathetic
More active at rest
Slows down heart rate, constricts pupils, increases gastric secretion and intestinal motility
Autonomic Dysreflexia
Syndrome of massive imbalanced reflex sympathetic discharge with SCI above the splanchnic outflow (T5-T6)48-85% of all T6 and above8
Autonomic Dysreflexia
SCI subjects with a lesion level above T6
Also been reported in other conditionsCVA, MS
Autonomic Dysreflexia
Noxious stimulus below the level of the lesion
Reflex release of the SNS below the level of the lesion
Descending input to SNS is interrupted cannot provide interruption of SNS firing
Autonomic Dysreflexia
Parasympathetic above lesionFlushing of facePounding headacheStuffy noseBlurred visionSlow heart rate
Autonomic Dysreflexia
Sympathetic below lesionElevated blood pressure JitterinessGoosebumpsPallor of the skinSweating (above lesion)
Autonomic Dysreflexia
Triggering factors Bladder distention Bowel distention/impaction Ulcer Ingrown toenail Sex/Orgasm Pregnancy/Delivery Cystoscopy Electrostimulation, vibratory stimulation
Autonomic Dysreflexia
Complications include:Retinal hemorrhageSubarachnoid hemorrhage Intracerebral hemorrhageMISeizureDeath
Autonomic Dysreflexia
Very important
Life threatening
Most serious complication of spinal cord injuries
Treatment
AcutelySit the patient upright
Prevents further increase in blood pressureRapid survey of triggering factors If pressure doesn’t begin to improve after 1
minute, consideration for pharmacological treatment
“Boosting”
The intentional induction of autonomic dysreflexia to try and enhance athletic performance