The autonomic nervous system maintains homeostasis by adapting your body to the external environment. Composed of two distinct units: 1. Sympathetic Nervous System 2. Parasympathetic Nervous System Homeostasis and the Autonomic Nervous System

All autonomic nerves are motor nerves that regulate organs without conscious control. Motor nerves lead to muscles that are controlled by conscious control.

The ANS and Visceral Sensory Neurons

Autonomic Nervous System A.K.A. Involuntary N.S. Visceral motor system Automatic N.S.

Autonomic and Motor Nervous System

Anatomy of ANS DivisionOrigin of FibersLength of Fibers Location of Ganglia SympatheticThoracolumbar region of the spinal cord Short preganglionic and long postganglionic Close to the spinal cord ParasympatheticBrain and sacral spinal cord Long preganglionic and short postganglionic In the visceral effector organs

Issue from different regions of the CNS Sympathetic (thoracolumbar division) Parasympathetic (craniosacral division) Anatomical Differences

Comparison of Somatic and Autonomic Systems Effectors (Targets) Somatic = skeletal muscle Autonomic = smooth/cardiac muscles, glands and internal organs Efferent pathways Somatic = no ganglia; myelinated axon from ventral horn of spinal cord all the way to effector Autonomic = 2 neuron pathway; first is preganglionic and body resides in brain/S.C.; 2 nd is postganglionic and body resides in autonomic ganglion Pre’s are lightly myelinated; post’s are unmyelinated SNS = short pre/long post ganglionic axon PsNS = long pre/short post ganglionic axon

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Autonomic and Motor Nervous System Pre-ganglionic Ganglion Post-ganglionic

Comparison of Autonomic and Somatic Motor Systems

Somatic Motor Division One motor neuron extends from the CNS to the skeletal muscle (direct connection). The axons are well myelinated, and conduct impulses rapidly. Autonomic Nervous System (Visceral Motor Division) Chain of two motor neurons  PREGANGLIONIC (PRESYNAPTIC) MOTOR NEURON - before the synapse or before the ganglion  POSTGANGLIONIC (POSTSYNAPTIC) MOTOR NEURON - after the synapse or after the ganglion Conduction is slower due to thinly or unmyelinated axons.

Anatomical Differences Between Sympathetic and Parasympathetic Divisions Length of preganglionic fibers: Sympathetic: short preganglionic fibers Parasympathetic: long preganglionic fibers Length of postganglionic fibers Sympathetic: long postganglionic fibers Parasympathetic: short postganglionic fibers Sympathetic fibers connect to the SYMPATHETIC CHAIN GANGLIA (collections of neuron cell bodies in the PNS) before they innervate the organs.

Anatomical Differences Between Sympathetic and Parasympathetic Divisions The NEUROTRANSMITTERS released by the different motor neurons: Both parasympathetic and sympathetic preganglionic motor neurons release ACETYLCHOLINE. Sympathetic postganglionic motor neurons – most release NOREPINEPHRINE. Parasympathetic postganglionic motor neurons – release ACETYLCHOLINE

Divisions of the Autonomic Nervous System Sympathetic and Parasympathetic Divisions Innervate mostly the same structures, but cause opposite effects Sympathetic – “fight, flight, or fright”  Activated during exercise, excitement, and emergencies  Increases heart rate, breathing rate, and blood supply to the skeletal muscles Parasympathetic – “rest and digest”  Concerned with conserving energy  Activated during rest and sleep  Decreases heart rate, breathing rate, and blood supply to skeletal muscles  Increases blood supply to digestive organs

Comparison of somatic and autonomic systems

Somatics: All motor neurons release ACH which is always stimulatory. Viscerals: ACH & norepinephrine All preganglionic fibers release ACH All postganglionic PsNS fibers release ACH Most postganglionic SNS fibers release norepinephrine Can be stimulatory or inhibitory based on receptor types Comparison of Somatic and Autonomic Systems

Branching of axons: Sympathetic axons are highly branched to influence many organs while parasympathetic axons have few branches so have a localized effect. Comparison of Somatic and Autonomic Systems

Terms Synapse: Junction between 2 neurons that communicates the message from the presynaptic neuron to the postsynaptic neuron. Ganglion (pl. ganglia): A cluster of neuronal cell bodies in the PNS Preganglionic neuron: Cell body lies within the CNS - Its axon, the preganglionic fiber synapses with the 2 nd motor neuron, the ganglionic neuron, in a peripheral autonomic ganglion Postganglionic fiber (axon) of the ganglionic neuron extends to the visceral organs.

Ganglia SensoryMotor Spinal ganglion SympatheticParasympathetic Trigeminal ganglionParavertebral ganglia (Ganglia of sympathetic trunk) Ciliary ganglion Geniculate ganglionPrevertebral ganglia (Collateral ganglia = preaortic ganglia): Pterygopalatine ganglion Spiral (cochlear) ganglion Vestibular (Scarpa’s) ganglion Submandibular ganglion Superior (jugular) and inferior (petrosal) ganglia of IX Otic ganglion Superior (rostral) and inferior (nodose) ganglia of X Terminal ganglion

Along the length of the sympathetic trunk are ganglia known as ganglia of sympathetic trunk or paravertebral ganglia. The ganglia are distinguished as cervical, thoracic, lumbar, and sacral and, except in the neck, they closely correspond in number to the vertebrae. Arrangement Only the cervical ganglia have specific names. They are arranged thus: Cervical ganglia - 3 ganglia Thoracic ganglia - 12 ganglia Lumbar ganglia - 4 ganglia Sacral ganglia - 4 ganglia Sympathetic Ganglia- Paravertebral Ganglion

Prevertebral ganglia (or collateral ganglia, or preaortic ganglia) are sympathetic ganglia which lie between the sympathetic chain and the organ of supply. Examples Include 1. Celiac ganglia 2. Aorticorenal ganglion 3. Superior mesenteric ganglia 4. Inferior mesenteric ganglia Sympathetic Ganglia - Prevertebral Ganglion

Parasympathetic Ganglia Parasympathetic ganglia are the autonomic ganglia of the parasympathetic nervous system. Most are small terminal ganglia or intramural ganglia, so named because they lie near or within (respectively) the organs they innervate. The exceptions are the four paired parasympathetic ganglia of the head and neck.  Ciliary ganglion (sphincter pupillae, ciliary muscle)  Pterygopalatine ganglion (lacrimal gland, glands of nasal cavity)  Submandibular ganglion (submandibular and sublingual glands)  Otic ganglion (parotid gland)

Sympathetic Trunk (Chain) The paravertebral ganglia form the sympathetic trunk or chain from neck to pelvis. Typically 23 ganglia C: 3, T: 11, L: 4, S: 4, Co: 1 Fibers enter chain from ventral root via white ramus communicantes (myelinated fibers) Found only in T1-L2 cord segments. Postganglionics exit ganglia via gray ramus communicantes (unmyelinated) Found along entire length of chain allowing sympathetic output to reach all areas of the body.

Preganglionic Options Upon Entering Sympathetic Ganglion 1. Synapse w/ a ganglionic neuron w/in the sympathetic chain (same level, ascend, or descend). 2. Pass thru the chain to synapse w/collateral ganglia These form splanchnic nerves to supply the abdomen & pelvis 3. Synapse directly with adrenal medulla

Sympathetic Trunk The sympathetic trunks (sympathetic chain, gangliated cord) are a paired bundle of nerve fibers that run from the base of the skull to the coccyx.

Sympathetic Trunk

Preganglionic Options Upon Entering Sympathetic Ganglion 1. Synapse w/ a ganglionic neuron w/in the sympathetic chain (same level, ascend, or descend). 2. Pass thru the chain to synapse w/collateral ganglia. These form splanchnic nerves to supply the abdomen & pelvis. 3. Synapse directly with adrenal medulla

Preganglionic Options Upon Entering Sympathetic Ganglion

Sympathetic nervous system The sympathetic division is the “fight-or-flight” system. Involves E activities – exercise, excitement, emergency, and embarrassment. Non-essential activities are dampened (GI/urinary). Promotes adjustments during exercise – blood flow to organs is reduced, flow to muscles is increased. Its activity is illustrated by a person who is threatened Heart rate increases, and breathing is rapid and deep. The skin is cold and sweaty, and the pupils dilate. Bronchioles dilate…increasing ventilation, delivering more oxygen to cells. Constriction of visceral & cutaneous bv’s (blood is shunted to skeletal mm) Liver releases more glucose into blood to provide more readily avail energy. Targets adipocytes for lipolysis.

The ANS consists of all visceral motor neurons innervating smooth muscle, cardiac muscle and glands.

Its activity is illustrated by a person who is threatened Heart rate increases, and breathing is rapid and deep. The skin is cold and sweaty, and the pupils dilate. Bronchioles dilate…increasing ventilation, delivering more oxygen to cells. Constriction of visceral & cutaneous bv’s (blood is shunted to skeletal mm) Liver releases more glucose into blood to provide more readily avail energy. Targets adipocytes for lipolysis. Sympathetic nervous system

Sympathetic Pathways to the Head Preganglionic fibers from T1-T4 ascend sympathetic chain to synapse w/ superior cervical ganglion Fibers run w/ several CN’s & first 4 cervical nerves Serve skin & blood vessels of head Dilate iris of eyes Inhibits nasal & salivary glands (dry mouth w/ nervousness) Innervates smooth mm to lift upper eyelid sup. cervical ganglion also has direct branches to heart

Sympathetic Pathways to the Body

Sympathetic Pathways to the Periphery

Sympathetic Pathways to the Head

Sympathetic Pathways to the Thorax Fibers from T1-T6 Synapse in middle & inferior cervical ganglia Enter cervical nerves C4-C8 (heart, thyroid, skin) Some fibers synapse at their respective level & the postganglionic fibers pass directly to the organ served Heart, aorta, lungs, eating tube, thyroid, & skin

Sympathetic Pathways to the Thorax

Pathways with Synapses in Collateral Ganglia These fibers (T 5 -L 2 ) have been left the sympathetic chain without synapsing. They form thoracic, lumbar, and sacral splanchnic nerves. Their ganglia include the celiac, the superior and inferior mesenterics, and the hypogastric.

Sympathetic Pathways to the Abdomen Fibers from T5-L2 traveling in the thoracic splanchnic nerves Synapse in mainly the celiac & superior mesenteric ganglia Serve stomach, intestines (up to distal ½ of large intestine), liver, spleen, & kidneys

Sympathetic Pathways to the Abdomen

Sympathetic Pathways to the Pelvis Fibers from T10 – L2 descend to the lumbar & sacral chain ganglia. Some synapse there & most go out lumbar & sacral splanchnic nerves to the inferior mesenteric & hypogastric ganglia. Serves distal ½ of lg intestine, urinary bladder, & pelvic reproductive organs.

Sympathetic Pathways to the Pelvis

Adrenal Medulla Embryologically arises from the same tissue as sympathetic ganglia. Some fibers in the thoracic splanchnic nerves pass thru the celiac ganglion w/o synapsing & terminate in the hormone producing medullary cells of the adrenal gland. Secrete epi & norepi into the blood.

Sympathetic Pathways to the Adrenal Medulla

Parasympathetic Nervous System SLUDD – Salivation, Lacrimation, Urination, Digestion, Defecation Most active in non-stressful situations Concerned with keeping body energy use low Lenses of eyes accommodated for close vision Its activity is illustrated in a person who relaxes after a meal Blood pressure, heart rate, and respiratory rates are low Gastrointestinal tract activity is high The skin is warm and the pupils are constricted

Cranial OutflowCranial NerveGanglionEffector Organ(s) Occulomotor (III)CiliaryEye (constriction of pupils & bulging of lens for close vision) Facial (VII)Pterygopalatine Submandibular Submadibular & sublingual salivary glands, nasal, and lacrimal glands Glossopharyngeal (IX) OticParotid salivary glands Vagus (X)Located within the walls of target organs (Intramural, terminal) Heart, lungs, bronchi, aorta, liver, gall bladder, stomach, small intestine., proximal ½ of large intestine Sacral OutflowS 2 -S 4 lateral hornsLocated within the walls of the target organs (Intramural) Large intestine, urinary bladder, ureters, and reproductive organs Parasympathetic Division Outflow

Parasympathetic nervous system Fibers emergency from C.N.’s III,VII,IX, & X (>75% of all preganglionic PsNS fibers) as well as S2-S4 AKA craniosacral division Long preganglionic fibers synapse in terminal or intramural ganglia (w/in wall of effector)

Parasympathetic Nervous System “cranio-sacral” Parasympathetic nerves orjinal from cranial nerves III, VII, IX, and X and the sacral spinal cord. Occulomotor nerve: fibers to the pupillary sphincters and ciliary muscle Facial nerve: fibers to lacrimal and submandibular gland Glossopharyngeal nerve: fibers to parotid gland Vagus nerve: motor inputs to visceral organs sacral segments - fibers to descending colon, rectum, bladder and genitalia

Parasympathetic Division Outflow

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Oculomotor Nerve and Ciliary Ganglion

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Facial Nerve and Pterygopalatine Ganglion Greater petrosal nerve + Deep petrosal nerve Nerve (Vidian) of pterygoid canal Pterygopalatine ganglion Postganglionic parasempathetics Lacrimal glands Nasalivary glands Salivary glands

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Chorda tympani Joins to lingual nerve Reach to submandibular ganglion via rami ganglionares Submandibular ganglion Postganglionic parasympathetics Subligual gland Submandibular gland Facial Nerve and Submandibulare Ganglion

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Facial Nerve and Pterygopalatine & Submandibular Ganglions Greater petrosal nerve Deeper petrosal nerve Chorda tympani Lingual nerve Sumandibular ganglion Pterygopalatine ganglion Vidian Superior salivatory nucleus

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Facial Nerve and Pterygopalatine & Submandibular Ganglions

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Glossopharyngeal Nerve and Otic Ganglion Parasympathetics of CN IX Lesser petrosal nerve Otic ganglion Postsinaptic parasempatetics join to auriculotemporal nerve Parotid gland

Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings n. petrosus profundus Tympanic nerve Auriculotemporal nerve Otic ganglion Tympanic plexus Lesser petrosal nerve Glossopharyngeal Nerve and Otic Ganglion

Autonom Nervous System-Summary

Autonom Nervous System