Anatomy Exam 3 - Autonomic Nervous System

Front 1

Autonomic Nervous System

Back 1

-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

Front 2

Sympathetic Nervous System

Back 2

-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

Front 3

Parasympathetic Nervous System

Back 3

-Active under ordinary, restful conditions
-Rest & Digest
-Much simpler & less extensive than Sympathetic NS

Front 4

Autonomics

Back 4

-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)

Front 5

2 Divisions of ANS Use Different Transmitters

Back 5

-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

Front 6

Sympathetic Outflow

Back 6

-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

Front 7

Displaced Paravertebral/Preaortic Sympathetic Ganglia

Back 7

-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

Front 8

Sympathetic Targets

Back 8

-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

Front 9

All preganglionic sympathetic fibers enter the sympathetic chain using...

Back 9

-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

Front 10

Courses Taken By Preganlionic Sympathetic Fibers

Back 10

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

Front 11

Vasculature Throughout the Body is Innervated

Back 11

-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

Front 12

To reach sympathetic targets in head...

Back 12

-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

Front 13

Sympathetic Pathway to Thoracic Organs

Back 13

-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

Front 14

The cardiac autonomic nervous system also has...

Back 14

-parasympathetic fibers that join in the form of vagus nerves
-visceral afferent fibers are also part of this plexus

Front 15

Sympathetic Pathways to Body Walls & Extremities

Back 15

-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

Front 16

Sympathetic Pathway to Abdominal Organs

Back 16

-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

Front 17

Greater Splanchnic Nerve

Back 17

-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)

Front 18

Lesser Splanchnic Nerve

Back 18

-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)

Front 19

Lumbar Splanchnics

Back 19

-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)

Front 20

Sympathetic Pathways to Pelvic Organs

Back 20

-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)

Front 21

Adrenal Medulla

Back 21

-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
-

Front 22

Kidney (innervation)

Back 22

-gets innervation via postganglionic fibers from the aorticorenal ganglia
-these small displaced sympathetic ganglia receive preganglionic input via the least splanchnic nerve (T12)

Front 23

Summary of Various Sympathetic Pathways

Back 23

Review Pg. 28 - Lecture 25

Front 24

Preganglionic Outflow

Back 24

1) Cranial Division
-Occulomotor N. (III)
-Facial N. (VII)
-Glossopharyngeal N. (IX)
-Vagus N. (X) --> 75% of innervation

2) Spinal Division
-S2-S4

Front 25

Targets of Parasympathetic Nervous System

Back 25

-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

Front 26

Parasympathtic Postganglionic Neurons in Head are found in:

Back 26

-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

Front 27

Parasympathetic Nervous System: Sacral Outflow

Back 27

-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)

Front 28

Visceral Sensory Neurons

Back 28

-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***)

Front 29

Sensory Innervation of Viscera

Back 29

-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

Front 30

Reference of Pain

Back 30

-Reference of pain to body wall is the result of "confusion" at higher CNS levels that conciously perceive pain

Front 31

Autonomic Dysreflexia

Back 31

-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

Front 32

Autonomic Dysfunction in Raynaud's Disease

Back 32

-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

Front 33

Autonomic Dysfunction in Achalasia Cardia

Back 33

-Defect in autonomic innervation of the esophagus
-Hyperactive lower esophageal sphincter which fails to relax upon swallowing

Front 34

Other Disorders linked to ANS Dysregulation

Back 34

-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

Front 35

Visceral Reflexes

Back 35

-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