Functional Human Anatomy & Autonomic Nervous System PDF

Functional Human Anatomy Autonomic Nervous System D R. D O N AL M U R R AY PH D C O N T R IBU T IO N S BY: D R. E LLE N C O S T E LLO, PT, P H D By the end of the session you should be able to…. Describe the overall responsibilities of the Autonomic Nervous System Describe the structure and functio...

Functional Human Anatomy Autonomic Nervous System D R. D O N AL M U R R AY PH D C O N T R IBU T IO N S BY: D R. E LLE N C O S T E LLO, PT, P H D By the end of the session you should be able to…. Describe the overall responsibilities of the Autonomic Nervous System Describe the structure and function of the sympathetic nervous system Describe the structure and function of the parasympathetic nervous system Compare and contrast the anatomical and functional differences between the SNS and PNS Nervous System Central Nervous System (CNS)- brain & spinal cord Peripheral Nervous System-cranial nerves & spinal nerves ANS-anatomically part of CNS & PNS  function is generally involuntary & unconscious for control of homeostatic function of the body  can be excitatory or inhibitory in nature  controls activities of cardiac ms, lungs, smooth ms, glands, viscera (involuntary structures) ANS Overview Sensory responsibility: returns sensory information to brain: visceral (gut) sensation, baroreceptor/chemoreceptor information Varied motor responsibilities Motor system: requires 2 neurons (preganglionic nerve & postganglionic nerve) to transmit a nerve impulse from the CNS to an end organ (versus a single neuron in the peripheral voluntary system to skeletal muscle) Preganglionic cell bodies arise in the CNS Postganglionic cell bodies arise in ganglia outside CNS ANS Overview Consists of sympathetic & parasympathetic systems Both are a two neuron system  Preganglionic (myelinated) fiber synapses with postganglionic (unmyelinated) fibers near the end organ The anatomical distinction between the sympathetic and parasympathetic divisions of the ANS is based primarily on  the location of the presynaptic cell bodies  which nerves conduct the presynaptic fibers from the CNS ANS-Parasympathetic Parasympathetic NS innervates:  glands in head & neck (secrete saliva/tears)  sphincter pupillae,  blood vessels (vasodilation/erection; decrease Bp)  Heart (decrease HR, decrease force of contraction)  lungs (bronchoconstriction),  digestive tract,  bladder,  bowel Parasympathetic system-responsible for maintenance of resting function  “rest & digest” Usually a long preganglionic fiber and a short postganglionic fiber ANS-Sympathetic Nervous System Responsible for fast reactions to emergency situations-”fight or flight” Mediates response to stress; mobilizes the body's resources for action in emergency ↑HR, ↑bp, ↑contractility of heart, vasoconstriction, bronchodilation, sweating, ejaculation, dilates pupil Sympathetic Nervous System Anatomy Each sympathetic pathway from the cord to the stimulated tissue is composed of two neurons, a preganglionic neuron and a postganglionic neuron Axons of presynaptic neurons leave the spinal cord through ventral roots and enter the ventral rami of spinal nerves T1–L2 or L3 Almost immediately after entering, all the presynaptic sympathetic fibers leave the ventral rami of these spinal nerves and pass to the sympathetic trunks (chain) through white rami communicantes (communicating branches) Pathway-IMLG >ventral root>spinal nerve>ventral rami of spinal nerve>white rami communicante >sympathetic chain Within the sympathetic trunks, presynaptic fibers follow one 3 choices  1. synapse at that level in a sympathetic chain ganglion & leave via gray rami  2. synapse in a nearby level in a sympathetic chain ganglion & leave via gray rami  3. pass through sympathetic chain (without synapsing) as splanchnic n. & synapse near the target organ dorsal rami – muscle of deep back at corresponding level White ramus communicate is anatomically lateral; Grey ramus is medial Intercostal nerve – ventral rami Ganglion of sympathetic trunk (chain) Sympathetic Chain (Trunk) Stellate ganglion A series of paired ganglia (paravertebral) Runs from C1-S4; paired ganglia unite to form ganglion impar at sacral level Lies lateral to vertebral column, on heads of ribs 22-23 pairs of sympathetic ganglia T1 ganglion blends with lower C ganglion=“stellate ganglion” Ganglion Impar  How to differentiate btw symp chain and vagus n. Superior Cervical Ganglion Middle Cervical Ganglion Inferior Cervical Ganglion (Stellate) Note: symph chain bilaterally; easily misidentified as CN X Splanchnic Nerves Convey visceral efferent (autonomic) and afferent fibers to and from the viscera of the body cavities Postsynaptic sympathetic fibers destined for the viscera of the thoracic cavity (e.g., the heart, lungs, and esophagus) pass through cardiopulmonary splanchnic nerves to enter the cardiac, pulmonary, and esophageal plexuses The presynaptic sympathetic fibers innervate viscera of abdominopelvic cavity (e.g., the stomach and intestines) pass to the prevertebral ganglia through abdominopelvic splanchnic nerves  Greater Splanchnic Ns.-T5-9 or 10  Lesser Splanchnic Ns.-T10, T11  Least Splanchnic Ns.-T12  Lumbar splanchnic Ns – L1, L2 (L3) Splanchnic nerves Parasympathetic System Function-homeostasis; ↓HR, ↓bp, ↓ contractility of heart, vasodilatation, bronchoconstriction, promotes digestion, empty bladder & bowel, constricts pupil Acts to conserve resources Cranio-sacral outflow  Cell bodies originate in cranial nerves and sacral portion of spinal cord  CN III, VII, IX, X  Sacral segments of the spinal cord S2, 3, 4  usually long pregangs & short postgangs CN III: pupil constriction CN VII: tears/saliva CN IX: saliva CN X: heart, lungs, viscera/bowel/bladder S2,3,4: bowel/ bladder, erection (vasodilation) Parasympathetic cont. CN 3-controls smooth ms that constricts pupil & accommodation of lens of the eye CN 7-secretion of tears & saliva CN 9-secretion of saliva CN 10- cardiac, bronchi, esophagus, smooth muscle & glands of trachea, movements & glandular secretion of thoracic & proximal half of abdominal viscera  Note branches to the larynx: (may see in lab/often miss id for CN XII) S2,3,4-distal half of abdominal viscera via pelvic splanchnic ns; also promotes digestion Comparisons between Symph & Parasymph Nervous Systems Location of preganglionic cell bodies Location of peripheral ganglia Neurotransmitters  Ach (acetycholine): secreted by preganglionic neurons in both systems (cholinergic)  Noradrenaline-secreted by most all symph postganglionic fibers  Ach-secreted by most parasymph postganglionic fibers Opposing actions and properties Control of Autonomic Nervous System  Hypothalamus & solitary nucleus receive afferent input from receptors in heart, major blood vessels, lungs, viscera etc.  Local reflexes provide for regulation of most homeostatic function Carotid Sinus Reflex (Local Reflex)  Carotid sinus-dilation of proximal part of internal carotid artery; (innervated by CN IX & X); contains a baroreceptor that reacts to changes in bp or stretch  Increase in BP sensed by baroreceptors; afferent (sensory) fibers carry information to solitary nucleus through vagus n. glossopharyngeal nerve (CN IX)  RESPONSE  Causes ↑ output of parasymph fibers which act on the heart to ↓HR  AND AT SAME TIME  Causes ↓ in symph output to ↓ the action on the heart & sm ms. of blood vessels (vasodilation) Autonomic Dysreflexia Loss of supraspinal control (hypothalamus & solitary nucleus) of Symph nervous system and sacral segments (parasym) of the cord found in patients with cervical and high thoracic spinal cord lesions (usually above T5-T6) Dysregulation of the autonomic nervous system leads to an uncoordinated sympathetic response that may result in a potentially life-threatening hypertensive episode can lead to seizures, stroke or even death Syndrome that incorporates a sudden, exaggerated reflexive increase in blood pressure in response to a stimulus, usually bladder or bowel distension, originating below the level of the neurological injury  Autonomic Dysreflexia cont. AD is an uninhibited mass autonomic reflex response to a noxious stimulus Noxious afferent stimulus from below the level of the injury initiates a reflex action of the ANS (symph) of vasoconstriction of arterioles and arteries from the thoracolumbar sympathetic nerves Brain detects HTN via baroreceptors in neck (CN IX & X) The body’s normal compensatory mechanism (decrease of symph outflow which causes passive vasodilatation) cannot pass from higher centers through the level of the lesion; however the message to slow the heart can travel thru the vagus nerve and causes bradycardia (bc vagus nerve is outside of the spinal cord) Autonomic Dysreflexia cont. However……the normal symph response to continued bradycardia results in an increase in blood pressure (>200/100 & as high as 300/180) Creates a vicious cycle Signs & Symptoms  Pounding headache (b/c of ↑ bp)  Paroxysmal HTN (> 200/100)  Flushing above the level of the lesion (vasodilation)  Pallor below the level of the lesion (vasoconstriction) Signs & Symptoms Signs & Symptoms:  Goose bumps-below the level of the lesion (symph)  Cold, clammy skin below level of lesion (symph)  Sweating above the level of the lesion (symph)  Slow Pulse (< 60 bpm) (parasymp)  Nasal Congestion (parasymp) Causes of AD Bowel related Bladder related-most common  Constipation  UTI  Hemorrhoids  Urinary Retention  Anal Fissure  Blocked Catheter  Infection (appendicitis)  Overfilled Collection Bag  Tight Clothing  Non-Compliance w/ intermittent catheterization Skin Disorder  Skin lesion or pressure Sexual Activity sore  Over stimulation  Ingrown toenail  Burn Menstrual cramps Labor & Delivery Treatment Alleviate Noxious Stimuli if possible  Check for kinks in catheter (PT)  Drain Urine bag (PT)  Straight catheterization (RN)  Disimpact Stool (RN) Sit Patient up to create orthostatic hypotension on purpose (PT) Frequent bp checks (PT) Treatment High Risk Individuals Individuals w/ recurrent episodes should have atropine at bedside No longer than 3 days between BM Immediate/Emergent Care  Nitroglycerine or Nitropaste (vasodilates)  Procardia (vasodilates)  Hydralazine (vasodilates)  Clonidine (inhibits SNS) Chronic (recurrent episode prevention)  Minipress or Clonidine on daily basis (vasodilate)