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35 Cards in this Set
- Front
- Back
Autonomic Nervous System
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-General Visceral Motor division of PNS
-Innervates smooth muscle, cardiac muscle, & glands -Functions independently -Functions continuously -Functions without concious control -Regulates visceral function; maintains homeostasis (heart ratem blood pressure, digestion, urination) -Regulated by visceral reflexes |
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Sympathetic Nervous System
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-Prepares for energy expending, stressful, or emergency situations
-Fight or Flight response -Continual over-activation of sympathetic nervous system is not compatible with good health |
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Parasympathetic Nervous System
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-Active under ordinary, restful conditions
-Rest & Digest -Much simpler & less extensive than Sympathetic NS |
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Autonomics
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-ALWAYAS a 2 neuron relay
-Cell body of first neuron is in CNS (its axon is the preganglionic fiber) -Synapses with 2nd neuron -Cell body of second neuron is located in autonommic ganglion (its axon is the post ganglionic fiber) |
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2 Divisions of ANS Use Different Transmitters
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-Both sympathetic & parasympathetic preganglionic neurons release the neurotransmitter Acetylcholine at their endings
-Postganglionic axons of symapthetic are called adrenergic because they release noradrenaline at synapse with target -Postganglionic axons of Parasympatheic called cholinergic because they release acetylcholine at synapse with target |
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Sympathetic Outflow
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-Sympathetic Division --> aka Thoracolumbar Division
-Preganglionic fibers from intermediolateral cell column of spinal cord -Arise from T1-L2/3 level only -Preganglionic fibers exit via ventral roots and enter sympathetic chain |
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Displaced Paravertebral/Preaortic Sympathetic Ganglia
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-Unpaired, not segmentally arranged
-Occur only in abdomen & pelvis -Lie anterior to the vertebral column -Main Ganglia: Celiac, Superior Mesenteric, Inferior Mesenteric, Inferior Hypogastric -Serve gut & excretory structures -These ganglia are functionally identical to those in the sympathetic chain, but are in an unusual location |
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Sympathetic Targets
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-while preganglionic sympathetic fibers only originate from thoraco-lumbar region (T1-L3), postganglionic sympathetic fibers are found in all regions of the body including the head
-thus, sympathetic fibers must reach their targets through several different routes |
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All preganglionic sympathetic fibers enter the sympathetic chain using...
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-a white communicating ramus which branches from spinal nerves (T1-L3)
-only T1-L3 spinal nerves have white communicating rami -ALL spinal nerves have grey communicating rami |
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Courses Taken By Preganlionic Sympathetic Fibers
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1) Ascend & then synapse
2) Synpase at level of entry 3) Descend then synapse 4) Pass through sympathetic trunk without synapsing and go to a prevertebral synpase via a splanchnic nerve |
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Vasculature Throughout the Body is Innervated
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-Postganglionic fibers leave the sympathetic chain at all levels and “catch a ride” or follow vasculature through the body, innervating the smooth muscle in its walls as needed
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To reach sympathetic targets in head...
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-post ganglionic fibers follow vasculature
-the pre ganglionic sympathetic fibers enter the sympathetic chain and ascend without synapsing immediately -when they get to appropriate level, they synapse with a neuron in the cervical part of the sympathetic chain and then post ganglionic sympathetic fibers leave the chain ganglia & follow vasculature in the head |
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Sympathetic Pathway to Thoracic Organs
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-for the heart, cervical sympathetic ganglia (and 1st 4 thoracic ganglia) are ussed
-postganglionic sympathetic fibers leave the sympathetic chain directly and form a cascade of axons in the cardiac plexus |
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The cardiac autonomic nervous system also has...
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-parasympathetic fibers that join in the form of vagus nerves
-visceral afferent fibers are also part of this plexus |
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Sympathetic Pathways to Body Walls & Extremities
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-simplest scheme occurs at T1-L3 level for sympathetics that will innervate structures in the body wall and extremities
-preganglionic axon enter the sympathetic chain via a white communicating ramus synapse with a neuron in the sympathetic chain -posganglionic axon leaves the sympathetic chain via a gray communicating ramus & re-enters spinal nerve -postganglionic sympathetic fibers then travel with the spinal nerve & leave at various places that contain targets |
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Sympathetic Pathway to Abdominal Organs
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-Splanchnic Nerve Scheme is Used
-Splanchnic Nerves which connect the sympathetic chain with the prevertebral sympathetic ganglia contain PREGANGLIONIC sympathetic fibers that have not yet synapsed with a 2nd order neuron |
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Greater Splanchnic Nerve
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-T5-T9
-Carries preganglionic fibers to the celiac ganglion where they synapse -Postganglionic fibers from neurons in the celiac ganglion serve the foregut & its derivatives (stomach, duodenum, liver, pancreas, spleen) |
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Lesser Splanchnic Nerve
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-T10-T11
-carries preganglionic fibers to the superior mesenteric ganglion where they synapse -The postganglionic fibers from this ganglion serve the midgut derivatives (part of duodenum, jejunum, ileum, cecum, ascending & transverse colon) |
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Lumbar Splanchnics
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-L1-L3
-Carry preganglionic fibers to the inferior mesenteric ganglion where they synapse -Postganglionic fibers from the inferior mesenteric ganglion innervate hindgut derivatives ( descending colon, sigmoid, rectum, & pelvic viscera) |
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Sympathetic Pathways to Pelvic Organs
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-preganglionic fibers synapse in a displaced ganglia (via a splanchnic nerve)
-postganglionic fibers follow a plexus of fibers to reach genital tissue & excretory tissue (via hypogastric plexuses) |
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Adrenal Medulla
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-directly innervated by preganglionic sympathetic fibers
-adrenal medulla contains chromaffin cells (modified sympathetic neurons) -adrenal medulla releases adrenaline when it is stimulated by preganglionic fibers - |
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Kidney (innervation)
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-gets innervation via postganglionic fibers from the aorticorenal ganglia
-these small displaced sympathetic ganglia receive preganglionic input via the least splanchnic nerve (T12) |
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Summary of Various Sympathetic Pathways
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Review Pg. 28 - Lecture 25
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Preganglionic Outflow
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1) Cranial Division
-Occulomotor N. (III) -Facial N. (VII) -Glossopharyngeal N. (IX) -Vagus N. (X) --> 75% of innervation 2) Spinal Division -S2-S4 |
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Targets of Parasympathetic Nervous System
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-some, but not all, targets of sympathetic nervous system also receive parasympathetic input that is generally opposite in effect
-Preganglionic Cell Bodies --> located in dorsal motor nucleus in medulla -Postganglionic Neurons --> confined within the walls of organs being innervated |
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Parasympathtic Postganglionic Neurons in Head are found in:
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-Ciliary Ganglia (III)
-Ptergopalatine & Submandibular Ganglia (VII) -Otic Ganglia (IX) -Vagus N. (X) --> which provides main parasympathetic preganglionic feed to much of the rest of the body, does not project to parasympathetic ganglion in head |
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Parasympathetic Nervous System: Sacral Outflow
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-preganglionic fibers arise from S2-S4 spinal cord regions in an interomediolateral cell column & exit via ventral roots
-course to small pelvic parasympathetic pelvic ganglia located in or close to walls of organs that they innervate & synapse -postganglionic axons then go on to important targets for this division (excretory sphincters of urethra & rectum; sex organs/erectile tissue of genitalia) |
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Visceral Sensory Neurons
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-General Visceral Sensory neurons monitor --> stretch, temperature, chemical changes, irritation, & PAIN
-Cell bodies are located in dorsal root ganglia -Visceral pain --> often perceived to be somatic in origin (***Referred Pain***) |
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Sensory Innervation of Viscera
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-Afferent information (sensory input) from visceral regions is conveyed by spinal ganglion neurons
-Peripheral branch axons of spinal ganglion neurons reach viscera by following autonomics or vasculature -Visceral Afferents are not considered part of ANS (which is stricly efferent), but travel along wiht autonomics to reach body cavities |
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Reference of Pain
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-Reference of pain to body wall is the result of "confusion" at higher CNS levels that conciously perceive pain
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Autonomic Dysreflexia
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-Hyperreflexia
-Affects quadriplegics & paraplegics -Over activity of the Autonomic Nervous System causing an abrupt onset of excessively high blood pressure -Persons at risk for this problem generally have spinal cord injury above level T5 -Considered a medical emergency & could be life threatening -Can lead to seizures or stroke if not treated properly |
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Autonomic Dysfunction in Raynaud's Disease
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-Disorder of ANS characterized by abnormal constriction of blood vessels in extremities
-Provoked by exposure to cold or emotional stress -Small arteries in fingers or toes go into vasospasm --> drstically, but temporarliy constricts blood supply -Can develop into gangrene upon repeated or prolonged episodes -Nose, lips, ears, & nipples can also be affected |
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Autonomic Dysfunction in Achalasia Cardia
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-Defect in autonomic innervation of the esophagus
-Hyperactive lower esophageal sphincter which fails to relax upon swallowing |
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Other Disorders linked to ANS Dysregulation
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-Hypertension --> high blood pressure
-Post Traumatic Stress Disorder (PTSD) --> high sympathetic activity coupled with low parasympathetic cardiac control -Panic Disorder -Asthma -Hypotension Issue --> vasovagal syncope -Irritable Bowel & other GI issues -Erectile Dysfunction |
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Visceral Reflexes
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-Visceral sensory & autonomic neurons participate in visceral reflex arcs
-stimulus is a visceral receptor that communicates with a preganglionic autonomic neuron to cause a response -There can be central control of this scheme by brain stem, spinal cord, and higher centers -Among areas of influence on ANS --> Reticular Formation, Hypothalamus, Amygdala (limbic region for emotion), & Cerebral Cortex |