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Homeostasis and the Autonomic Nervous System • The autonomic nervous system maintains homeostasis by adapting your body to the external environment. • 1. Composed of two distinct units: 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 Division Location of Ganglia Origin of Fibers Length of Fibers Sympathetic Thoracolumbar region of the spinal cord Short preganglionic Close to the and long spinal cord postganglionic Parasympathetic Brain and sacral spinal cord Long preganglionic and short postganglionic In the visceral effector organs Anatomical Differences • Issue from different regions • of the CNS Sympathetic (thoracolumbar division) • Parasympathetic (craniosacral division) 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.; 2nd 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 Autonomic and Motor Nervous System Pre-ganglionic Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Post-ganglionic Ganglion Comparison of Autonomic and Somatic Motor Systems 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 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 Comparison of Somatic and Autonomic Systems 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 Comparison of Somatic and Autonomic Systems Terms • Synapse: • Ganglion (pl. ganglia): • Preganglionic neuron: Cell body lies within the CNS Junction between 2 neurons that communicates the message from the presynaptic neuron to the postsynaptic neuron. A cluster of neuronal cell bodies in the PNS - Its axon, the preganglionic fiber synapses with the 2nd motor neuron, the ganglionic neuron, in a peripheral autonomic ganglion • Postganglionic fiber (axon) of the ganglionic neuron extends to the visceral organs. Ganglia Sensory Motor Spinal ganglion Sympathetic Parasympathetic Trigeminal ganglion Paravertebral ganglia (Ganglia of sympathetic trunk) Ciliary ganglion Geniculate ganglion Prevertebral ganglia (Collateral ganglia = preaortic ganglia): Pterygopalatine ganglion Spiral (cochlear) ganglion Submandibular ganglion Vestibular (Scarpa’s) ganglion Superior (jugular) and inferior (petrosal) ganglia of IX Otic ganglion Superior (rostral) and inferior (nodose) ganglia of X Terminal ganglion Sympathetic Ganglia- Paravertebral 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 - Prevertebral 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 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 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 Preganglionic Options Upon Entering Sympathetic Ganglion 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. Sympathetic nervous system • 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 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 Sympathetic Pathways to the Thorax Sympathetic Pathways to the Thorax Pathways with Synapses in Collateral Ganglia • These fibers (T5-L2) 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 Abdomen 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 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 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 Parasympathetic Division Outflow Cranial Outflow Cranial Nerve Ganglion Effector Organ(s) Occulomotor (III) Ciliary Facial (VII) Pterygopalatine Eye (constriction of pupils & bulging of lens for close vision) Submadibular & sublingual salivary glands, nasal, and lacrimal glands Parotid salivary glands Submandibular Glossopharyngeal Otic (IX) Vagus (X) Sacral Outflow Located within the walls of target organs (Intramural, terminal) S2-S4 lateral horns Located within the walls of the target organs (Intramural) Heart, lungs, bronchi, aorta, liver, gall bladder, stomach, small intestine., proximal ½ of large intestine Large intestine, urinary bladder, ureters, and reproductive organs 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 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 Facial Nerve and Submandibulare Ganglion • Chorda tympani • Joins to lingual nerve • Reach to submandibular ganglion via rami ganglionares • Submandibular ganglion • Postganglionic parasympathetics • Subligual gland • Submandibular gland Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Facial Nerve and Pterygopalatine & Submandibular Ganglions Greater petrosal nerve Pterygopalatine ganglion Vidian Lingual nerve Sumandibular ganglion Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Deeper petrosal nerve Superior salivatory nucleus Chorda tympani 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 Glossopharyngeal Nerve and Otic Ganglion Lesser petrosal nerve Auriculotemporal nerve n. petrosus profundus Tympanic plexus Tympanic nerve Otic ganglion Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Autonom Nervous System-Summary Autonom Nervous System-Summary Autonom Nervous System Autonom Nervous System Autonom Nervous System