Chapter 14Chapter 14

Autonomic Nervous SystemAutonomic Nervous System

System of motor neurons innervating System of motor neurons innervating smooth and cardiac muscle and smooth and cardiac muscle and glands glands

Autonomic nerves make adjustments Autonomic nerves make adjustments to many changes identified by the to many changes identified by the sensory division of the PNS sensory division of the PNS

ANS differs from the SNS in: ANS differs from the SNS in: Their effectors Their effectors

SNS innervates skeletal muscle and ANS SNS innervates skeletal muscle and ANS innervates smooth and cardiac muscle innervates smooth and cardiac muscle and glands and glands

Efferent pathways Efferent pathways SNS - cell bodies of the motor neuron SNS - cell bodies of the motor neuron

are in the CNS, and their axons are in the CNS, and their axons extend in spinal nerves all the way to extend in spinal nerves all the way to skeletal muscles skeletal muscles

ANS - two neuron chain ANS - two neuron chain The cell body of the first neuron The cell body of the first neuron

((preganglionic neuronpreganglionic neuron) resides in the ) resides in the brain or spinal cord brain or spinal cord

Its axon (Its axon (preganglionic axonpreganglionic axon) synapses ) synapses with the second motor neuron (with the second motor neuron (ganglionic ganglionic neuronneuron) in an autonomic ganglion outside ) in an autonomic ganglion outside the CNS the CNS

The axon of the ganglionic neuron The axon of the ganglionic neuron ((postganglionic axonpostganglionic axon) extends to the ) extends to the effector organ. effector organ.

Synapse in a gangliaSynapse in a gangliaParasympathetic: intramural ganglia: close to Parasympathetic: intramural ganglia: close to

the effector organthe effector organSympathetic: chain (paraverterbral) gangliaSympathetic: chain (paraverterbral) ganglia

Target organ responses - Target organ responses - neurotransmitter effects neurotransmitter effects

SNS - acetylcholine released at their SNS - acetylcholine released at their synapse synapse

ANS - norepinephrine, epinephrine ANS - norepinephrine, epinephrine (adrenergic)(adrenergic)

and acetylcholine (cholinergic)and acetylcholine (cholinergic)

Divisions of the ANSDivisions of the ANS Parasympathetic and sympathetic Parasympathetic and sympathetic Action via ANS is by dual innervation Action via ANS is by dual innervation

(divisions counterbalance each other's (divisions counterbalance each other's activities) activities)

Parasympathetic division in general is Parasympathetic division in general is most active in nonstressful situations most active in nonstressful situations - - rest and digestrest and digest

SSympathetic (ympathetic (sstress) division in tress) division in general is most active in emergency general is most active in emergency or threatening situations - "or threatening situations - "fight-or-fight-or-flightflight" "

Parasympathetic:Parasympathetic:- pupils constrict- pupils constrict- stimulates salivary, lacrimal and - stimulates salivary, lacrimal and pancreas glandspancreas glands- decrease heart rate- decrease heart rate- causes contraction and emptying of - causes contraction and emptying of hollow organs: bladder, gallbladder, hollow organs: bladder, gallbladder, stomach, intestines (peristalsis)stomach, intestines (peristalsis)- vasodilation of penis (erection) and - vasodilation of penis (erection) and

clitorisclitoris- no effect on blood vessels- no effect on blood vessels

Sympathetic:Sympathetic:- dilates pupils- dilates pupils- inhibits secretion of glands- inhibits secretion of glands- stimulates sweating- stimulates sweating- stimulates arrector pili- stimulates arrector pili- stimulates medulla of adrenal gland to - stimulates medulla of adrenal gland to secrete secrete epi/norepinephrineepi/norepinephrine- increases heart rate- increases heart rate- decreases digestive processes- decreases digestive processes- decreases urine output- decreases urine output- causes ejaculation- causes ejaculation- stimulates glycogenolysis in liver - stimulates glycogenolysis in liver (glucose (glucose release)release)- blood vessel constriction/dilation and - blood vessel constriction/dilation and blood blood coagulationcoagulation- bronchiole dilation- bronchiole dilation

ParasympatheticParasympatheticCraniosacral divisionCraniosacral division

Cranial:Cranial:CN nerves III, VII, IX and XCN nerves III, VII, IX and X

CN III (Oculomotor):CN III (Oculomotor): Preganglionic fibers: from oculomotor Preganglionic fibers: from oculomotor

nuclei in the midbrain synapses in the nuclei in the midbrain synapses in the ciliary ganglion (in eye)ciliary ganglion (in eye) Postganglionic fiber: innervates smooth Postganglionic fiber: innervates smooth muscle of eye muscle of eye

  Pupil constriction and lens movement to Pupil constriction and lens movement to cause focusing cause focusing

Facial nerve (VII) Facial nerve (VII) Preganglionic fibers: from lacrimal nuclei in Preganglionic fibers: from lacrimal nuclei in

the pons synapses in the pterygopalatine the pons synapses in the pterygopalatine gangliaganglia

Postganglionic fiber: innervates lacrimal Postganglionic fiber: innervates lacrimal glands of eye glands of eye Lubrication of eye and tear formation Lubrication of eye and tear formation

Preganglionic fibers: from superior salivatory Preganglionic fibers: from superior salivatory nuclei in the pons synapses in the nuclei in the pons synapses in the submandibular gangliasubmandibular ganglia

Postganglionic fibers: innervate Postganglionic fibers: innervate submandibular and sublingual salivary glands submandibular and sublingual salivary glands Production of saliva and secretion of salivary Production of saliva and secretion of salivary

enzymesenzymes

Glossopharyngeal nerve (IX) Glossopharyngeal nerve (IX) Preganglionic fibers: from the inferior Preganglionic fibers: from the inferior

salivary nuclei in the medulla synapses in salivary nuclei in the medulla synapses in the otic gangliathe otic ganglia

Postganglionic fibers: innervate the Postganglionic fibers: innervate the parotid salivary gland parotid salivary gland

Vagus nerve (X) “wanderer” Vagus nerve (X) “wanderer” Preganglionic fibers from the dorsal motor Preganglionic fibers from the dorsal motor

nuclei (nucleus ambiguus) of the medulla nuclei (nucleus ambiguus) of the medulla synapses in terminal ganglia located synapses in terminal ganglia located within the walls of the target organ within the walls of the target organ (intramural)(intramural)

Intramural ganglia ....effects: Intramural ganglia ....effects: Heart -decreases/steadies heart rate Heart -decreases/steadies heart rate

and constricts coronary veins and constricts coronary veins Lung - constricts bronchioles Lung - constricts bronchioles Gall bladder - expel bile Gall bladder - expel bile Stomach - stimulates secretion of Stomach - stimulates secretion of

enzymes enzymes Intestines - increase motility Intestines - increase motility

(peristalsis) and relaxes sphincters (peristalsis) and relaxes sphincters

Sacral Outflow Sacral Outflow Preganglionic fibers from lateral gray Preganglionic fibers from lateral gray

matter of spinal cord in segments S2-matter of spinal cord in segments S2-S4 synapse in terminal ganglia within S4 synapse in terminal ganglia within walls of the target organ walls of the target organ Intramural ganglia....effects: Intramural ganglia....effects:

Distal large intestines - relaxes Distal large intestines - relaxes sphincters sphincters

Bladder - contraction of smooth Bladder - contraction of smooth muscle of bladder wall; relaxes muscle of bladder wall; relaxes urethral sphincter - promotes voiding urethral sphincter - promotes voiding

Genitalia - causes penile and clitoral Genitalia - causes penile and clitoral erectionerection

Sympathetic Nervous SystemSympathetic Nervous SystemThoracolumbar divisionThoracolumbar division

All preganglionic fibers of sympathetic All preganglionic fibers of sympathetic division arise from cell bodies of division arise from cell bodies of preganglionic neurons located in lateral preganglionic neurons located in lateral horn of the spinal cord segments T1-L2 horn of the spinal cord segments T1-L2

These fibers exit the ventral roots of spinal These fibers exit the ventral roots of spinal nerves and continue through branches nerves and continue through branches called white rami communicantes before called white rami communicantes before entering the paravertebral sympathetic entering the paravertebral sympathetic ganglia located in chains along side the ganglia located in chains along side the spine. These ganglia make up the spine. These ganglia make up the sympathetic trunksympathetic trunk

Once in the paravertebral ganglia the Once in the paravertebral ganglia the preganglionic fiber can:preganglionic fiber can:1- Synapse with a postganglionic 1- Synapse with a postganglionic neuron within the same ganglion .neuron within the same ganglion .2- Ascend/descend within 2- Ascend/descend within sympathetic trunk to synapse with sympathetic trunk to synapse with another paravertebral ganglion.another paravertebral ganglion.3- Pass through the ganglion 3- Pass through the ganglion (splanchnic nerve) and emerge from (splanchnic nerve) and emerge from the sympathetic chain without the sympathetic chain without synapsing until they reach a synapsing until they reach a collateral ganglia (prevertebral) collateral ganglia (prevertebral)

Preganglionic fibers innervating the head Preganglionic fibers innervating the head and neck arise from spinal cord levels T1-and neck arise from spinal cord levels T1-T6. These fibers ascend through the T6. These fibers ascend through the sympathetic trunk and synpase with sympathetic trunk and synpase with postganglionic fibers in the cervical gangliapostganglionic fibers in the cervical ganglia

- superior- superior- middle- middle- inferior- inferior

Superior cervical ganglion: Superior cervical ganglion: - Stimulates dilator muscles of irises - Stimulates dilator muscles of irises - Inhibits nasal and salivary glands - Inhibits nasal and salivary glands - Stimulates copious sweating - Stimulates copious sweating - Stimulates arrector pili muscle to contract - Stimulates arrector pili muscle to contract - Causes blood vessel vasodilation - Causes blood vessel vasodilation

Middle cervical ganglia - innervates Middle cervical ganglia - innervates heart and skin heart and skin

Inferior cervical ganglia (stellate Inferior cervical ganglia (stellate ganglion) innervates heart, aorta, ganglion) innervates heart, aorta, dilates bronchioles, constrict dilates bronchioles, constrict esophageal sphincter. esophageal sphincter.

Synapses in Collateral Sympathetic Synapses in Collateral Sympathetic Ganglion: Ganglion:

Preganglionic fibers of T5-L2 synapse Preganglionic fibers of T5-L2 synapse in prevertebral ganglia. Fibers enter in prevertebral ganglia. Fibers enter and leave without synapsing and and leave without synapsing and form several nerves collectively form several nerves collectively called splanchnic nerves (greater, called splanchnic nerves (greater, lesser, and lumbar) lesser, and lumbar)

Splanchnic nerves synapse at Splanchnic nerves synapse at abdominal aortic plexus that clings to abdominal aortic plexus that clings to surface of abdominal aorta surface of abdominal aorta

Synapses occur at ganglia of plexus: Synapses occur at ganglia of plexus: Greater Greater splanchnicsplanchnic nerve nerve

Celiac ganglion - innervates stomach Celiac ganglion - innervates stomach (decrease muscle activity/constricts (decrease muscle activity/constricts pyloric sphincter), adrenal medulla pyloric sphincter), adrenal medulla (secretes epinephrine/norepinephrine), (secretes epinephrine/norepinephrine), liver (epinephrine stimulates liver to liver (epinephrine stimulates liver to release glucose), kidney release glucose), kidney (vasoconstriction, decrease urine (vasoconstriction, decrease urine output), intestine (decrease smooth output), intestine (decrease smooth muscle activity) muscle activity)

Lesser splanchnic nerve Lesser splanchnic nerve Superior mesenteric (via celiac) ganglion Superior mesenteric (via celiac) ganglion

- innervates small intestine - innervates small intestine Lumbar splanchnic nerve Lumbar splanchnic nerve

Inferior mesenteric ganglion - innervates Inferior mesenteric ganglion - innervates large intestine large intestine

Lumbar Lumbar splanchnicsplanchnic nerve nerve HypogastricHypogastric ganglion - innervates bladder ganglion - innervates bladder

and urethra (causes relaxation of smooth and urethra (causes relaxation of smooth muscle of bladder wall and constricts muscle of bladder wall and constricts urethral sphincter/inhibits voiding), urethral sphincter/inhibits voiding), genitalia (causes ejaculation in males and genitalia (causes ejaculation in males and vaginal contractions in females) vaginal contractions in females)