Autonomic Nervous System PDF

The Autonomic Nervous System Images from Human Anatomy 6th ed., © 2009, by Martini, Timmins and Talitsch, denoted by “Ma”. Images from Human Anatomy, 2nd ed., © 2008 by McKinley & O’Loughlin, denoted by “Mc”. 1 Fxns of the Autonomic Nervous System (ANS) Functionally maintains homeostasis • regula...

The Autonomic Nervous System Images from Human Anatomy 6th ed., © 2009, by Martini, Timmins and Talitsch, denoted by “Ma”. Images from Human Anatomy, 2nd ed., © 2008 by McKinley & O’Loughlin, denoted by “Mc”. 1 Fxns of the Autonomic Nervous System (ANS) Functionally maintains homeostasis • regulates body temperature via control of sweat glands and vascular smooth muscle • regulates the activity of body systems: – cardiovascular – respiratory – digestive – excretory – reproductive systems • monitors and adjusts body fluids, fine-tuning concentrations of – electrolytes – nutrients – dissolved gases 2 The ANS differs from the Somatic NS Anatomically: • in the somatic NS, neurons in the CNS synapse directly onto effectors: Brain stem or spinal cord (CNS) Somatic motor neuron Skeletal muscle Peripheral nerve • in the ANS, the CNS controls effectors via a two neuron chain: Brain stem or spinal cord (CNS) Preganglionic neuron Autonomic ganglion Postganglionic neuron Peripheral nerve Smooth or cardiac muscle or glands • The somatic NS and the ANS may share a given peripheral nerve • there are two subdivisions of the ANS, the sympathetic nervous system (SyNS) and the parasympathetic nervous system (PsyNS) 3 The SyNS & PsyNS Differ Functionally • the PSyNS predominates during resting conditions: “rest & digest” • the SyNS predominates during exertion or emergencies: “fight or flight” • within a given system, the two divisions usually oppose each other – e.g. SyNS  HR, PSyNS  HR – e.g. PSyNS  digestion, SyNS  digestion • occasionally they work independently – SyNS alone controls most vascular smooth muscle and all smooth muscle in the limbs & body wall (BVs, erector pili muscle, glands) 4 The SyNS & PSyNS Differ Anatomically The two divisions differ in the locations of their: A Preganglionic neuron Autonomic ganglion Postganglionic neuron B Peripheral nerve Smooth or cardiac muscle or glands A. preganglionic neuronal cell bodies in the CNS • SyNS (“thoracolumbar division”): spinal cord, T1-L2 levels • PSyNS (“craniosacral division”): brainstem cranial nerve nuclei & spinal cord, S2-S4 levels B. postganglionic neuronal cell bodies in the PNS • sympathetic ganglia located near the spinal cord in either the paired sympathetic chain ganglia or unpaired preaortic ganglia • parasympathetic ganglia located in or near effector organs 5 Organization of the Spinal Grey Matter • deep, forms a continuous column extending the length of the cord Gray matter White matter Ventral root • at all levels, grey matter forms a butterfly in XS, divided into: Spinal nerve Dorsal root ganglion Dorsal root – dorsal horns: sensory, receives input via spinal nerves and dorsal roots – ventral horns: somatic motor, conducts output via ventral roots, spinal Ns Ma14.2 • at certain levels, (T1-L2 & S2-S4) intermediolateral cell column (IML), contains autonomic preganglionic motor neurons, conducts output via ventral roots, ensuing nerves 8 The Sympathetic Division targets: A. smooth muscle of limbs & body wall B. viscera of head & thorax C. viscera of abdomen & pelvis preganglionic neurons (for ALL targets) • cell bodies located in lateral gray horns, T1-L2; • axons travel via ventral roots, spinal nerves, synapse onto: postganglionic neurons • cell bodies located in sympathetic ganglia near the vertebral column, either: – in bilaterally paired sympathetic chain ganglia (targets A&B) or – in unpaired prevertebral (preaortic) ganglia (targets C) • postganglionic axons innervate the target organ 9 Somatic Innervation of the Body Wall & Limbs • somatic motor neurons innervate skeletal muscle – cell bodies in the ventral grey horn of the spinal cord • sensory Ns monitor skin, joints, skeletal muscle – cell bodies in dorsal root ganglia (DRG), axons convey info to dorsal grey horn of spinal cord • their axons form peripheral nerves A. Dorsal horn B. Lateral horn H E G I C. Ventral horn D F A D. Dorsal root B E. DRG C F. Ventral root G. Spinal nerve H. Dorsal ramus XS through spinal cord between T1 and L2 I. Ventral ramus 10 A. Sympathetic Innervation of the Body Wall & Limbs • the body wall & limbs are innervated by postganglionic sympathetic neurons located in the paravertebral or sympathetic chain ganglia • target organs are smooth muscle of erector pili, BVs, glands in ALL dermatomes of body Rami communicantes Paravertebral ganglion XS through spinal cord between T1 and L2 11 Preganglionic sympathetic fibres can ascend or descend within the sympathetic chain before synapsing. In this way, sympathetics are distributed to dermatomes* ABOVE T1 and BELOW L2 *dermatome: the area of skin innervated by a specific spinal segment and nerve 12 Summary: The Sympathetic Nervous System PONS Dermatomes C2–C3 NV C2–C3 Cervical Superior sympathetic Middle ganglia Inferior C2 C3 Gray rami to spinal nerves T2 C6 L1 L2 C8 Postganglionic fibers to spinal Ns (innervating BVs, sweat glands, erector pili muscles, adipose tissue) C7 T1 L3 L4 L5 Sympathetic chain ganglia C3 C4 C5 T2 3 T1 T T4 T2 T T3 T5 T4 T67 T5 T8 T6 T9 T7 T10 T8 T11 T9 T L12 T10 L21 T11 L4L3 T12 L5 S2 C4 C5 T2 C6 C7 T1 SS 4 3 L1 S5 S1L5 C8 L2S2 L3 S1 Ma17.4 Preganglionic Ns Ganglionic Ns Coccygeal ganglia (Co1) fused together (ganglion impar) L4 ANTERIOR POSTERIOR 13 B. Sympathetic Innervation of Thoracic Viscera & Face Thoracic viscera & targets in the face are innervated by postganglionic sympathetic Ns located in the paravertebral or sympathetic chain ganglia. For targets in the thorax: Axons of postganglionic Ns form splanchnic Ns (cardiac, pulmonary, esophageal splanchnic Ns) which contribute to autonomic plexuses (cardiac, pulmonary, esophageal plexuses) that innervate targets in the thorax. For targets in the face: Axons of postganglionic Ns form autonomic plexuses, which “hitch a ride” with arteries to reach their targets. Named for artery, eg. carotid plexus. 14 Summary: The Sympathetic Nervous System Eye PONS Salivary glands Cervical Superior sympathetic Middle ganglia Inferior Gray rami to spinal nerves Heart Cardiac and pulmonary plexuses Lung Postganglionic fibers to spinal Ns (innervating BVs, sweat glands, erector pili muscles, adipose tissue) Sympathetic chain ganglia Ma17.4 Preganglionic Ns Ganglionic Ns 15 C. Sympathetic Innervation of Abdominopelvic Viscera Abdominopelvic viscera are innervated by postganglionic sympathetic neurons located in the prevertebral ganglia, eg. the celiac, superior mesenteric and inferior mesenteric ganglia. Axons of postganglionic neurons contribute to autonomic plexuses, which “hitch a ride” with arteries to reach their target organs. The plexuses are named by the BV, ie. celiac, superior and inferior mesenteric plexuses. 16 The Adrenal Medulla • is a modified sympathetic ganglion • is innervated by preganglionic sympathetic neurons of the lateral gray horns • postganglionic “neurons” of the adrenal medulla release epinephrine & norepinephrine which is picked up by blood vessels for systemic distribution • consequences? 17 Summary: The Sympathetic Nervous System Eye PONS Salivary glands Cervical Superior sympathetic Middle ganglia Inferior Gray rami to spinal nerves Heart Celiac ganglion Cardiac and pulmonary plexuses Lung Superior mesenteric ganglion Liver and gallbladder Stomach Spleen Pancreas Large intestine Small intestine Inferior mesenteric ganglion Postganglionic fibers to spinal Ns (innervating BVs, sweat glands, erector pili muscles, adipose tissue) Adrenal medulla Kidney Sympathetic chain ganglia Ma17.4 Preganglionic Ns Ganglionic Ns Coccygeal ganglia (Co1) fused together (ganglion impar) Urinary bladder Ovary Uterus Testicle 18 Mc18.7 19 The Parasympathetic Division preganglionic neuronal cell bodies located either in: 1. brainstem cranial nerve nuclei; axons travel via cranial nerves (III, VII, IX, and X (the vagus nerve)), OR 2. IML cell column, S2-S4 • preganglionic fibres synapse onto postganglionic PS neurons within: S2 – S4 parasympathetic ganglia • located in or near the effector organ (intramural or terminal ganglia) • short postganglionic fibres innervate the cells of the effector organ CN III, VII & IX innervate viscera of the face CN X (the vagus nerve) innervates viscera of the thorax & most of abdomen pelvic splanchnic nerves innervate the viscera of the distal abdomen & pelvis note: no parasympathetic innervation of smooth muscle targets in limbs or body wall, nor most vascular smooth muscle elsewhere 20 Lacrimal gland Eye PONS Salivary glands N X (Vagus) Heart Lungs Liver and gallbladder Autonomic plexuses Stomach Spleen Pancreas Pelvic splanchnic nerves Large intestine Small intestine Rectum Spinal cord Kidney Urinary bladder Ma17.8 Preganglionic neurons Ganglionic neurons Uterus Ovary Penis Testicle 21 • visceral organs have dual innervation Autonomic Plexuses • two divisions generally antagonistic Trachea Left vagus nerve Right vagus nerve Aortic arch Thoracic Spinal nerves Esophagus Splanchnic nerves Diaphragm Celiac trunk Superior mesenteric artery Inferior mesenteric artery • overlap of SyNS & PSyNS Autonomic Plexuses in autonomic plexuses: and Ganglia Cardiac plexus Pulmonary plexus Thoracic sympathetic chain ganglia Esophageal plexus Celiac plexus and ganglion Superior mesenteric ganglion Inferior mesenteric plexus and ganglion Hypogastric plexus Pelvic sympathetic chain – cardiac plexus – pulmonary plexus – esophageal plexus – celiac plexus – superior mesenteric plexus – inferior mesenteric plexus – hypogastric plexus – pelvic plexus Ma17.9 22 Autonomic Afferents: Homeostatic Input • afferents from an organ retrace the path taken by the efferents to the organ  if you know the motor output pathway, you know the sensory input pathway! • afferents carrying homeostatic sensory information (eg. BP from baroreceptors, blood gas from chemoreceptors) generally travel with parasympathetic efferents • other than the distal digestive tract and pelvis, this is via the vagus nerve! 23 Autonomic Afferents: Visceral Pain • viscera are insensitive to cutting, burning, freezing • visceral pain is caused by ischemia, distension, inflammation, blood etc. • visceral pain usually travels with the sympathetic efferents eg., the Sy efferents to the heart originate from spinal cord levels T1 – T5  pain afferents from the heart travel with sympathetic efferents back to spinal cord levels T1 – T5 Sensory neuron from body wall Both project to the same dorsal horn cell • in the spinal cord, overlap with afferents from the T1 – T5 dermatomes gives rise to the referral of cardiac pain to these dermatomes, ie. chest, armpit, medial arm • this is the anatomical basis of “referred pain” Sensory neuron from viscus 24 The Ear Images from Human Anatomy 6th ed., © 2009, by Martini, Timmins and Talitsch, denoted by “Ma”. Images from Human Anatomy, 2nd ed., © 2008 by McKinley & O’Loughlin, denoted by “Mc”. Images from Neuroscience: Exploring the Brain by Bear, et al., 3rd Edition, © 2006. Sound Waves • when an object moves towards a patch of air, molecules in the air are compressed, i.e. made more dense • when an object moves away from a patch of air, molecules in the air are rarefied, i.e. made less dense • vibrating objects alternately rarefy and compress the air around it, creating alternating patches of compressed / rarefied molecules travelling through space • these sound waves and move away from the source at the speed of sound • when this mechanical energy meets the auditory apparatus, we “perceive sound” Rarefied air Air pressure Compressed air Distance One cycle Pitch of Sound • the frequency of sound waves is the number of compressed or rarefies patches of air that pass by our ears each second, expressed in cycles per second or Hz • pitch is proportional to the frequency of the changes in air pressure per unit time • our auditory system responds to sound waves over the range of 20 Hz – 20 kHz • range decreases with age and with damage to the inner ear due to loud noise • infrasound: sound waves below 20 Hz • ultrasound: sound waves above 20 kHz Lower frequency / pitch i.e. not detectable by our hearing apparatus From Neuroscience: Exploring the Brain, 3e, by Bear, et al., © 2006. Air pressure Higher frequency / pitch Distance One cycle Distance One cycle Intensity of Sound • intensity is the difference in pressure between the compressed and rarefied patches of air and determines the loudness • intensity is measured in decibels or db, a logarithmic scale that requires a ten-fold increase in intensity for a perceived doubling of “loudness” • this graphic illustrates two sounds at the same pitch, but differing in their intensity, and therefore perceived loudness From Neuroscience: Exploring the Brain, 3e, by Bear, et al., © 2006. Higher intensity / loudness Air pressure Lower intensity / loudness Distance One cycle From Neuroscence: Exploring the Brain by Bear, et al., 3e, © 2006. Distance One cycle The Ear: An Overview EXTERNAL EAR MIDDLE EAR AIR-FILLED SPACES GATHER, AMPLIFY, TRANSFER SOUND WAVES TO: Ma18.9 INNER EAR FLUID-FILLED SPACE CONTAINS SENSE ORGANS OF: 1. BALANCE 2. HEARING 5 A. pinna (auricle) gathers sound waves The External Ear EXTERNAL EAR – contributes to sound localization MIDDLE EAR Elastic cartilages – supported by elastic cartilage – the lobule (lobe) lacks cartilage – directs sound waves into the: B. external auditory canal – wall of lateral 1/3 cartilagenous, medial 2/3 bony A B C – lining skin contains ceruminous & sebaceous glands which produce cerumen (earwax) C. tympanic membrane (ear drum) – separates external, middle ear Petrous part of temporal bone Ma18.9 – vibration of air (sound waves) causes vibration of the “ear drum” – thin skin externally, mucous membrane internally why mucous membrane internally? 6 The Middle Ear MIDDLE EAR INNER EAR A. consists of the tympanic cavity, an airfilled space within the petrous temporal bone containing auditory ossicles B. tympanic cavity opens to the mastoid air cells by many variable channels; AUDITORY OSSICLES middle ear infections can lead to mastoiditis C. opens to the nasopharynx by the auditory (pharyngotympanic, Eustachian) tube ∴lined by mucus membrane EXTERNAL AUDITORY CANAL – walls 1/3 bone, 2/3 cartilagenous A – latter closed at rest, opens with muscular contraction during swallowing, yawning… B C TO NASOPHARYNX Ma18.9 – equalizes P in middle ear with atmosphere – ∴ prevents distortion of tympanic membrane with changes in atmospheric pressure – route for spread of infection from pharynx to middle ear “otitis media” 7 The Auditory Ossicles FOOTPLATE OF STAPES • span tympanic cavity from the tympanic membrane to the oval window • oval window separates the air-filled middle ear and the fluid-filled inner ear • footplate of stapes fits in oval window, sealed and secured by annular ligament Malleus Incus TYMPANIC MEMBRANE Ma18.10 • vibration of tympanic membrane moves the auditory ossicles • mvt of ossicles ↑ force of sound waves, transfers them to the oval window Stapes TYMPANIC CAVITY • stapes moves like a piston in the oval window, initiating pressure waves in the fluid of the inner ear 8 MIDDLE EAR INNER EAR VIII VESTIBULAR DIVISION VIII COCHLEAR DIVISION CN VIII VESTIBULAR APPARATUS COCHLEA The Inner Ear I • contains 2 special sense organs innervated by the vestibulocochlear N. (CN VIII): A. the vestibular apparatus which senses “equilibrium”, or the position & acceleration of the head in space • served by the vestibular division of the vestibulocochlear N. (CN VIII) B. the cochlea which senses sound • served by the cochlear division of the vestibulocochlear N. (CN VIII) Ma 18.9 9 The Bony Labyrinth Cast of right labyrinth (lateral aspect) Frontal section through left temporal bone (posterior aspect) Rohen, J. W. Anatomy: A Photographic Atlas, 8e, © 2015, Wolters Kluwer Health. Cast of right labyrinth (posteromedial aspect) 10 Bony labyrinth Cochlea Membranous labyrinth Cochlear duct Vestibule Utricle & saccule Semicircular Semicircular canals ducts Senses: The Inner Ear II Hearing • bony labyrinth: interconnected, fluid-filled spaces within the petrous temporal bone Position, linear acceleration of head Angular acceleration of head Vestibular apparatus SEMICIRCULAR CANALS VESTIBULE: UTRICLE SACCULE COCHLEA SEMICIRCULAR DUCTS Ma18.12 – 3 subdivisions: the cochlea, vestibule & semicircular canals • membranous labyrinth: suspended within the bony labyrinth, also fluid-filled – consists of the cochlear duct, utricle & saccule and semicircular ducts – the sense organs of hearing and balance are epithelial specializations of the membranous labyrinth, and are illustrated in purple KEY COCHLEAR DUCT Membranous labyrinth Bony labyrinth 11 The Cochlea • a subdivision of the bony labyrinth • a coiled, tubular space; walls made of compact bone • spirals around a peg of bone, the modiolus which contains Ns & BVs VIII B C B B A C A C Ma18.17 • the membranous cochlear duct is suspended within the cochlea; its contained space is the scala media (B) A • the cochlear duct spans the cochlea from the bony spiral lamina (SL) to the opposite wall; B A • cochlear duct subdivides the cochlear space into the scala vestibuli (A) and the scala B tympani (C) C A C • cochlear duct ends at the apex of the cochlea • scalae vestibuli and tympani continuous at SL the apex of the cochlea via the helicotrema Ns, BVs 12 The Spiral Organ Ma18.17 • basilar membrane (BM) separates the scala media from the scala tympani SCALA MEDIA • sense organ of hearing, the spiral organ is located on the basilar membrane SCALA VESTIBULI • spiral organ contains hair cells and support cells BM SPIRAL GANGLION SCALA TYMPANI • afferent nerve fibres monitor hair cells • cell bodies of sensory afferents in the spiral ganglion SPIRAL ORGAN • axons join cochlear branch of CN VIII within modiolus HAIR CELLS AFFERENT NERVE FIBRES SUPPORT CELLS BASILAR MEMBRANE 13 + + Hair Cells + + • sensory cells of inner ear • transduce sound energy into APs in the afferent nerves Reticular lamina Depolarization • “hairs” are stereocilia on the apices of the hair cells Voltage-gated calcium channel Hair cell • membrane potential of hair cells determines rate of NT release from basal surface of hair cells • bending of hairs in one direction opens channels, depolarizes hair cell, ↑ NT release • bending of hairs in the other Vesicle filled direction closes channels, with excitatory hyperpolarizes hair cell, ↓ NT neurotransmitter release Spiral ganglion neurite B11.15 • pulsatile release of NT causes bursts of APs in afferent Ns 14 The Cochlea Uncoiled • the oval window / footplate of stapes are at the base of the scala vestibuli • the membrane-enclosed round window is at the base of the scala tympani • with vibration of the tympanic membrane, the stapes moves in and out of the oval window like a piston • pressure waves initiated in the fluid of the scala vestibule are relieved at the round window • the membranous labyrinth / basilar membrane vibrates in response to these pressure waves • hairs on the hair cells vibrate → pulsatile release of NT A Helicotrema Malleus Incus Stapes Oval window Scala vestibuli Scala media Tympanic membrane Scala tympani Round window with membrane B C 33 mm Tympanic membrane Round window Oval window Compression Rarefaction From Principles of Neural Science, 5e, by Kandel, et al., © 2014 by McGraw-Hill. Basilar membrane The Perception of Pitch LOW-FREQUENCY SOUNDS SCALA MEDIA SCALA VESTIBULI HELIOCOTREMA BASILAR MEMBRANE SCALA TYMPANI MEDIUM-FREQUENCY SOUNDS • BM is narrow and stiff at it’s base, wide and floppy at its apex • this is because the size of the spiral lamina decreases from base to apex HIGH-FREQUENCY SOUNDS Base Apex BASILAR MEMBRANE HIGH FREQ Mc19.29 MED FREQ Hz Hz 20,000 1500 (high notes) LOW FREQ Hz 500 • the BM is optimally displaced at a certain point along its length by a specific frequency; this activates the population of neurons monitoring the spiral organ at that point • thus, the spiral organ is organized “tonotopically” Hz • 20 (low notes) pitch coded by the pop’n of neurons firing in response to a given sound 16 Auditory Pathways Auditory pathways project bilaterally to primary auditory cortex. Auditory cortex (temporal lobe) Low-frequency sounds What is the clinical implication of this wrt a unilateral lesion? Low-frequency sounds Thalamus High-frequency sounds Medial geniculate nucleus (thalamus) Inferior colliculus High-frequency sounds Cochlear nuclei Ma18.18 Cochlear N. 17 Deafness Conduction Deafness • involves the external or middle ear • e.g. “swimmer’s ear”, otosclerosis • inner ear is intact, so hearing aids are effective Sensorineural Deafness • involves the inner ear or cochlear nerve • e.g. destruction of hair cells by exposure to loud sounds, ototoxic drugs, lesion of CN VIII 18 Bony labyrinth Cochlea Membranous labyrinth Cochlear duct Vestibule Utricle & saccule Semicircular Semicircular canals ducts Senses: The Inner Ear II Hearing • bony labyrinth: interconnected spaces within the petrous temporal bone Position, linear acceleration of head Angular acceleration of head Vestibular apparatus SEMICIRCULAR CANALS VESTIBULE: UTRICLE SACCULE COCHLEA SEMICIRCULAR DUCTS Ma18.12 – 3 subdivisions: the cochlea, vestibule & semicircular canals • membranous labyrinth: suspended within the bony labyrinth – consists of the cochlear duct, utricle & saccule and semicircular ducts – the sense organs of hearing and balance are epithelial specializations of the membranous labyrinth, and are illustrated in purple KEY COCHLEAR DUCT Membranous labyrinth Bony labyrinth 19 The Vestibular Apparatus I: the Otolith Organs • are the utricle and the saccule • each contains a macula, an area of epithelium with hair cells and support cells • tips of stereocilia embedded in a gelatinous matrix, the otolith membrane • otolith membrane contains calcium carbonate crystals called otoconia (statoconia) • therefore, the otolith membrane has a higher density than the surrounding fluid Otolith membrane Gelatinous material otoconia Hair cells Nerve fibers Ma18.15 20 The Otolith Organs: The Utricle & Saccule • fxn: detect the static position and linear acceleration of the head • macula of utricle oriented horizontally; macula of saccule oriented vertically • tilting of head (see below) causes otolith membrane to shift due to gravitational pull; this distorts stereocilia, alters NT release • linear acceleration of head in plane of macula (not shown) causes otolith membrane to shift due to inertia; this also distorts stereocilia, alters NT release • popn of hair cells activated, 1° sensory neurons firing APs codes for head position, linear acceleration Head in Neutral Position Ma18.15 Gravity Head Tilted Posteriorly Receptor output increases Gravity Otolith moves “downhill,” distorting hair cell processes 21 The Vestibular Apparatus II: The Semicircular Ducts Semicircular ducts Ampulla • three arranged at right angles to each other • each has an ampulla containing the crista ampullaris with hair cells Utricle Saccule • tips of hair cells embedded in the gelatinous cupola • no otoconia, so density of cupola is the same as the surrounding fluid • ∴ cupola moves with fluid Ampulla filled with endolymph Cupula Anterior semicircular duct Hair cells Lateral semicircular duct Crista Supporting cells Ma18.13 Sensory nerve Ma18.14 Posterior semicircular duct 22 The Semicircular Ducts Detect Rotation • fxn: detect rotation of the head • with rotation of the head in the plane of a given duct, endolymph and cupola lag behind due to inertia, bending the hairs • this alters AP traffic along vestibular division of CN VIII • since at right angles to each other, each optimized to detect mvt around a different axis Direction of relative endolymph movement Direction of duct rotation Direction of duct rotation Semicircular duct Ampulla Ma18.13 Cupola At rest 23 Pathways for Equilibrium Sensations Information used to coordinate head mvt with eye, neck, trunk and limb mvt. To thalamus and cerebral cortex for conscious sensation Vestibular ganglion Semicircular canals N III Vestibulo -ocular reflex Vestibular branch N IV Vestibular nuclei N VI To cerebellum Vestibule Cochlear branch Rotate your owl Ma18.16 N XI Vestibulocolic reflex Vestibulocochlear nerve (N VIII) Vestibulospinal tract 24 The End Rohen, J. W. Anatomy: A Photographic Atlas, 8e, © 2015, Wolters Kluwer Health. 25 The Eye Images from Human Anatomy 8th ed., © 2015, by Martini, Timmins and Talitsch, denoted by “Ma”. Images from Human Anatomy, 2nd ed., © 2008 by McKinley & O’Loughlin, denoted by “Mc”. 1 The Orbit • a pyramidal space • base located anteriorly • apex located posteromedially at the optic foramen • contains eyeballs, muscles, Ns, BVs, lacrimal apparatus and orbital fat Orbits, superolateral view The medial walls are parallel. Orbits, superior view 2 The Orbit: Bones Roof A. frontal bone B. sphenoid bone C. fossa for lacrimal gland A J C Medial wall I D. ethmoid bone E. lacrimal bone F. fossa for lacrimal sac B Lateral wall D E G. zygoma F G B. sphenoid bone Floor H. maxilla K H G. zygoma Orbital openings I. optic canal J. superior orbital fissure Ma6.15 K. inferior orbital fissure 3 Surface Anatomy of the Eye A. palpebral fissure C B. medial and lateral angles H C. palpebrae superioris and inferioris G D. pupil B E. iris F F. sclera covered by conjunctiva; conjunctivitis E G. eyelashes with sebaceous and apocrine glands D C’ Ma18.19 covered by cornea A B’ H. in medial angle, the lacrimal lake 4 The Eye & Eyelids A. orbicularis oculi B. sup., inf. tarsal plates F D C’ E C G A B – tarsal glands are large sebaceous glands – often implicated in styes C. medial, lateral palpebral ligaments D. levator palpebrae superioris C. orbital fat D. lacrimal gland Ma18.19 E. lacrimal sac 5 The Eye in Sagittal Section Ma18.21 D C B. palpebral conjunctiva B A C. conjunctival sac D. conjunctival fornix E K J G F I A. orbital conjunctiva H E. sclera F. cornea G. iris H. pupil I. lens J. suspensory ligaments K. ciliary body 6 The Lacrimal Apparatus A B E C F D G H Ma18.19 • fossa for lacrimal gland (A) in superolateral orbit • gland secretes lacrimal fluid into conjunctival sac via ~12 lacrimal ducts (B) that open into the superior conjunctival fornix • lacrimal fluid collects in lacrimal lake (C) • drains via lacrimal puncta (D), lacrimal canaliculi (E) to the lacrimal sac (F) • drains via nasolacrimal duct (G) into nasal cavity (H) 7 The Globe Consists of Three Layers Fibrous Vascular Neural tunic tunic tunic (sclera) (choroid) (retina) The three layers, or tunics, of the eye Ma18.21 The Fibrous Layer: The Sclera & Cornea Visual axis A. opaque sclera covers post. 5/6 of eyeball D B C C B. ant. portion visible through orbital conjunctiva C. insertion of the six extraocular eye muscles, which position the eye in the orbit A D. transparent cornea covers ant. 1/6 of eyeball, bends light to focus it on the fovea (E) Ma18.21 E 9 G The Extraocular Eye Muscles Trochlea A D II B E C • insert into the sclera • position the eye in the orbit F A. Superior rectus B. Inferior rectus C. Medial rectus D. Lateral rectus E. Superior oblique F. Inferior oblique G. LPS Why two muscles elevate, and two muscles depress? Balance out unwanted mvts ELEVATION A Trochlea E Frontal bone LPS E Trochlea Optic nerve A C D ABDUCTION D ADDUCTION B F Ma10.5 B DEPRESSION F Maxilla Lateral view 10 Movements of the Eye are Balanced In the neutral position the eye is adducted relative to the orbital axis: Depression: • superior oblique: depression (and intorsion & abduction) • inferior rectus: depression (and extortion & adduction Elevation: • inferior oblique: elevation (and extorsion & abduction) • superior rectus: elevation (and intorsion & adduction) ELEVATION A Trochlea E C D ABDUCTION F Orbits, superior view ADDUCTION B DEPRESSION Ma10.5 From Moore’s Essential Clinical Anatomy, 7e, © 2023 by Wolters Kluwer 11 Clinical Testing of Extraocular Muscles • abduction aligns angle of gaze with pull of sup., inf. rectus • adduction aligns angle of gaze with pull of sup., inf. oblique From Moore’s Essential Clinical Anatomy, 7e, © 2023 by Wolters Kluwer 12 Innervation: LR6, SO4, AO3 IV III G A D II B F VI E C A. Superior rectus B. Inferior rectus C. Medial rectus D. Lateral rectus E. Superior oblique F. Inferior oblique G. Levator palpebrae superioris Ma10.5 13 Nerve Palsies Oculomotor nerve palsy • only lateral rectus, inferior oblique spared • inc. paralysis of levator palpebrae superioris • inc. paralysis of sphincter pupillae • Presentation: – eye “down and out” – ptosis (droopy eyelid) – mydriasis (large pupil) Abducens nerve palsy • paralysis of lateral rectus • eye adducted at rest due to unopposed medial rectus • when asked to look toward lesioned side, only contralateral (unaffected) eye moves 14 The Pigmented (Vascular) Layer Fornix Levator palpebrae superioris Upper eyelid muscle Posterior cavity Retina Ethmoidal labyrinth Sclera Lacrimal gland Medial rectus muscle Optic nerve (N II) Trochlear nerve (N IV) Lateral rectus muscle Ma18.21 Horizontal section, superior view A The Pigmented (Vascular) Layer Ma18.22 A H F B Ma18.21 G A. choroid ends anteriorly as the: ciliary body (B) & iris (C) C C. iris a contractile diaphragm extending anterior to lens with a central aperture, the pupil • size of pupil controlled by constrictor (D) & dilator (E) pupillae muscles within the iris… D F. ciliary processes secrete aqueous humor, provide attachment for suspensory ligaments of lens (G) H. ciliary muscle, within ciliary body, adjusts thickness of lens to further refract light • controlled by the accommodation reflex... E B 16 Control of Pupillary Size Constrictor pupillae (circular) Pupil Constrictors contract with PSy input Dilator pupillae (radial) Ma18.22 Ma18.21 Dilators contract with Sy input 17 The Accommodation Reflex: Far and Near Vision • lens transparent, biconvex • enclosed in a highly elastic capsule – isolated lens spherical • held in place by suspensory ligaments • ciliary muscle relaxed • suspensory ligaments taut • lens flattened • less refraction of light • tension in suspensory ligaments adjusts shape, convexity of lens The eye accommodates for close vision by tightening the ciliary muscles, allowing the pliable crystalline lens to become more rounded. • ciliary muscle contracted • suspensory ligaments slack • lens rounded • more refraction of light – controlled by ciliary muscle • convexity of lens varies continuously to fine-tune focus of objects on retina Light rays from distant objects are nearly parallel and don’t need as much refraction to bring them into focus. Light rays from close objects diverge and require more refraction to bring them into focus. 18 The Lens and Chambers of the Eye Ma18.22 Vascular tunic Choroid Ciliary body Iris Posterior cavity Neural tunic (retina) Neural layer Pigmented layer Anterior cavity Fibrous tunic Cornea Sclera The lens is suspended between the posterior cavity and the anterior cavity. The Circulation of Aqueous Humour Ciliary process • anterior cavity divided into anterior and posterior chambers, separated by the iris Suspensory ligaments • epithelial cells covering the ciliary body secrete aqueous humor into the Anterior cavity: Posterior chamber posterior chamber Anterior chamber Posterior cavity (vitreous chamber) Pupil Cornea Lens Body of iris Ciliary body Canal of Schlemm Conjunctiva Sclera Choroid Retina Ma18.22 • aqueous humor flows from the posterior chamber through the pupil, into the anterior chamber • nourishes the avascular cornea • at the iridocorneal angle aqueous humor drains through the trabecular meshwork into the scleral venous sinus (canal of Schlemm) and is thus returned to venous blood • glaucoma occurs with increased intraocular pressure • usually caused by decreased 20 Glaucoma • aqueous humor produced / removed at same rate to maintain intraocular pressure, IOP • in glaucoma, IOP rises due to accumulation of aqueous humor • increased pressure on retina, optic nerve inhibits blood flow • causes ischemic damage of retina Open-angle glaucoma most common • slowly developing • age-related changes in the trabecular meshwork increases resistance to aqueous humor outflow • initially peripheral vision loss, eventually blindness • screening for glaucoma part of eye exam • tx medication, laser trabeculoplasty 21 The Inner (Neural) Layer A. the retina B. the ora serrata separates the visual and nonvisual parts of the retina B C. macula lutea A D. fovea centralis E. optic disc: the “blind spot” E F. optic nerve C G. central A & V Ma18.21 F G D 22 Macula Fovea lutea Ma18.23 Optic disc Central retinal artery (blind spot) and vein emerging from center of optic disc A photograph taken through the pupil showing the retinal blood vessels, the origin of the optic nerve, and the optic disc The Retina Has Four Cell Layers 1. ganglion cells: axons form optic N 2. horizontal, bipolar & amacrine cells process visual signal 3. photoreceptors (rods & cones) transduce light energy into a change in membrane potential 4. pigmented layer absorbs XS light Horizontal cell Cone Rod Choroid Pigmented layer of retina Rods and cones Amacrine cell Bipolar cells Ganglion cells Nuclei of Nuclei of rods Nuclei of ganglion cells and cones bipolar cells LM x 75 Ma18.23 LIGHT The retina 24 Why is Resolution Highest in the Fovea? 1. types of photoreceptors • there are two kinds of photoreceptors: rods and cones • cones are specialized for: – high temporal resolution due to fast response time – low sensitivity ∴ only saturate in intense light – colour vision due to the presence of three types of cones with different pigments • rods are specialized for: – low temporal resolution due to slow response time – high sensitivity saturates in daylight – achromatic as there is only one kind of rod pigment • cones are concentrated at the fovea, rods in the periphery of the retina 25 Why is Resolution Highest in the Fovea? cont. 2. ratio of photoreceptors to ganglion cells • average for entire retina 137:1 • in periphery 1000:1 ∴pixel size large • at the fovea 1:1 ∴pixel size small 3. anatomically adapted for light sensitivity • light passes through fewer cell layers to reach photoreceptor cells Rods and cones Fovea Bipolar cells Ganglion cells 26 The End Ma18.23 Blood Supply of the CNS Images from Human Anatomy 6th ed., © 2009, by Martini, Timmins and Talitsch, denoted by “Ma”. Images from Human Anatomy, 2nd ed., © 2008 by McKinley & O’Loughlin, denoted by “Mc”. Images from Grant’s Atlas, 11th ed., by A. Agur, © 2009 denoted by “GA” 1 Intracranial Blood Supply • Ma22.13 intracranial structures receive blood from two sources: the paired internal carotid As and the paired vertebral As 1. the internal carotid As are branches of the common carotid As • they enter the cranium through the carotid canal Internal carotid A External carotid A Vertebral A 2. the vertebral As are branches of the subclavian As Common carotid A Subclavian A • they ascend in the neck through the foramina transversaria and enter the cranium through the foramen Brachiocephalic trunk magnum alongside the spinal cord 2 These Four Major Arteries Anastomose* at the * flow together: capillary beds may Base of the Brain receive arterial blood from > 1 source FRONTAL LOBE ANTERIOR CEREBRAL A. PITUITARY GLAND INTERNAL CAROTID A. (CUT) MIDDLE CEREBRAL A. TEMPORAL LOBE POSTERIOR CEREBRAL A. POSTERIOR CEREBRAL A. BASILAR A. CEREBELLUM VERTEBRAL A. OCCIPITAL LOBE Mc23.11 ARTERIES OF THE BRAIN INFERIOR VIEW 3 The Circle of Willis ANTERIOR COMMUNICATING A. ANTERIOR CEREBRAL A. • at a branch point, blood flow into each artery is determined by their relative resistance • vascular caliber can change over time in response to changes in vascular resistance INTERNAL CAROTID A. POSTERIOR CEREBRAL A. Mc23.11 • blood does not “circle” in the Circle of Willis POSTERIOR COMMUNICATING A. • this may lead to clinically significant changes in the flow pattern of the Circle 4 Cerebral Vascular Territories Medial surface PCA branches If the cerebral hemispheres are considered to have three surfaces (inferior, medial, & superolateral) and three poles (occipital, frontal and temporal), then their vascular supply can be summarized as follows: ACA and branches Basilar A ACA branches Vertebral A Lateral surface MCA branches Basilar A Artery Surface Pole ACA medial frontal MCA superolateral temporal PCA inferior occipital Think about the functional localization within these vascular territories. Stroke in which vascular territory would lead to: PCA branches Vertebral A • aphasia? • paralysis of the contralateral leg? • paralysis of the contralateral face and arm? 5 Vascular Supply of the Brainstem and Cerebellum • the midbrain is supplied by the PCAs • the pons is supplied by the BA PCA • the cerebellum is supplied by branches of the vertebral and basilar As • the medulla is supplied by the VAs and their branches • a stroke in which vascular territory might lead to: BASILAR A. VERTEBRAL As Mc23.11 – strabismus, diplopia, enlarged pupil and ptosis? – difficulty with speech and swallowing? • the vertebral arteries give rise to the unpaired anterior spinal artery and the CEREBELLAR As paired posterior spinal arteries….. 6 Blood Supply of the Spinal Cord POST. SPINAL As Branches of the vertebral arteries form: 1. the single midline anterior spinal artery located in the ventral median fissure • it supplies the ventral and lateral columns of white matter and the ventral grey horns • What pathways would be affected by a stroke in the anterior spinal artery territory? 2. the bilaterally paired posterior spinal arteries located in the dorsolateral sulcus ANT. SPINAL A Mc16.T1 • they supply the dorsal white columns and the dorsal grey horns • What pathways would be affected by a stroke in a posterior spinal artery? 7 Spinal Cord Blood Supply is Reinforced • at cervical levels by branches of the vertebral As • at thoracic levels by branches of the intercostal As • at lumbar levels by branches of the lumbar As B These form: A. radicular As which supply the spinal nerve roots B. anterior and posterior segmental medullary As, which feed into the anterior and posterior spinal As A GA4.47 8 Meninges & Intracranial Bleeds A. Extradural hematoma • torn meningeal A. usually with head trauma • blood btw periosteum & bone GA7.13 B. Subdural hematoma • torn cerebral vein as it crosses from subarachnoid space to dural venous sinus • blood btw dura & arachnoid C. Subarachnoid hemorrhage A B • ruptured cerebral A. • blood in subarachnoid space C 9 Meninges & Intracranial Bleeds: CT extradural hematoma • lens-shaped • respects suture lines Case courtesy of Dr Sandeep Bhuta subdural hematoma subarachnoid hemorrhage • crescent-shaped • gyral enhancement • does not respect suture lines Case courtesy of Dr Andrew Dixon Case courtesy of Prof Peter Mitchell 10 Aneurysm and Embolism Aneurysm: dilation of vessel wall • cerebral aneurysms within skull • may compress adjacent structures (such as a cranial nerve), causing mass effects • ruptured aneurysm 2nd most common cause of subarachnoid hemorrhage • frequently located at branch points Embolism: occlusion of A by material flowing in blood Case courtesy of Dr Bruno Di Muzio (clot, tumor cells, clump of bacteria, air, plaque fragments) • cerebral embolism within the skull • leads to infarction, ischemia, necrosis • deficits reflect location of infarct • thrombus: embolism composed exclusively of blood products • transient ischemic attack (TIA) result in no lasting deficit • ischemic stroke vs. hemorrhagic stroke 11 The Brainstem and Cranial Nerves Images from Human Anatomy 6th ed., © 2009, by Martini, Timmins and Talitsch, denoted by “Ma”. Images from Human Anatomy, 2nd ed., © 2008 by McKinley & O’Loughlin, denoted by “Mc”. 1 BRAINSTEM CERVICAL CORD SENSORY NUCLEI MOTOR NUCLEI The Brainstem vs. the Spinal Cord • in both, the grey matter is deep and the white matter is superficial • in both, the white matter consists of axons carrying sensory information rostrally, and motor information caudally • while grey matter in the spinal cord is a continuous column, grey matter in the brainstem is broken up into a discontinuous series of functionally specialized nuclei • both subserve somatic and autonomic functions • unlike the spinal cord, the brainstem: LUMBAR CORD – subserves “special senses”: hearing and balance – contains a “reticular formation” responsible for the maintenance of vital functions and one’s level of arousal 2 Brainstem: White Matter Tracts Descending fibre tracts • UMNs carrying voluntary output from the cerebral cortex to the spinal cord, controlling the body; “corticospinal tract” • UMNs carrying voluntary output from the cerebral cortex to the brainstem, controlling the face; “corticobulbar tract” • involuntary descending fibre tracts that modulate & coordinate: – posture, muscle tone, balance (e.g. vestibulospinal tract) – autonomic functions (e.g. from the hypothalamus) Ascending fibre tracts • from the spinal cord to the thalamus – e.g. SS input destined for conscious appreciation in the cerebral cortex • from the spinal cord to the cerebellum – e.g. subconscious proprioceptive input from muscles and joints Peduncles: white matter bundles • paired cerebral peduncles join the midbrain & cerebral hemispheres • 3 paired cerebellar peduncles join the brainstem & cerebellar hemispheres 3 The Brainstem in Context Diencephalon Midbrain Pons Brainstem Medulla Ma15.1 4 The Brainstem: Ventral View A B D C E F H I J K M N O G P L Q Ma15.20 A. diencephalon (thalami and hypothalami) B. optic nerves C. Midbrain D. cerebral peduncles E. occulomotor nerves (CN III) F. trochlear nerves (CN IV) G. Pons H. I. J. K. trigeminal nerves (CN V) abducens nerves (CN VI) facial nerves (CN VII) vestibulocochlear nerves (CN VIII) L. Medulla M. N. O. P. Q. R. glossopharyngeal nerves (CN IX) vagus nerves (CN X) accessory nerves (CN XI) pyramids hypoglossal nerves (CN XII) olives 5 The Cerebellum must be Removed to view the Dorsal Brainstem FOURTH VENTRICLE A C. The inferior cerebellar peduncles connect the medulla and cerebellum B C The cerebellum overlies the fourth ventricle. MEDULLA CEREBELLUM MIDSAGITTAL SECTION thru the CBLM, cutting left cblr peduncles, brainstem intact Ma15.19 A. The superior cerebellar peduncles connect the midbrain and cerebellum B. The middle cerebellar peduncles connect the pons and cerebellum MIDBRAIN PONS Three paired masses of white matter connect the cerebellum and brainstem: Once the peduncles are cut, one sees the floor of the fourth ventricle on the dorsal aspect of the brainstem. 6 The Brainstem: A. thalami Dorsal View B. pineal gland A B C. Midbrain D. superior colliculus (vision) E. inferior colliculus (hearing) D E C F. trochlear nerve (CN IV) F H. Pons G H I I. middle cerebellar peduncle L J. floor of IVth ventricle J O K K. Medulla L. inferior cerebellar peduncles M. posterior median sulcus N M Ma15.16 G. superior cerebellar peduncle N. gracile tubercle O. cuneate tubercle 7 The Cerebellum D • connected to the brainstem by the (A, B, C) superior, middle & inferior cerebellar peduncles E MIDBRAIN D. cortical grey matter PONS B • two bilaterally paired cerebellar hemispheres E. subcortical white matter A C F. cerebellar nuclei Functions of the Cerebellum MEDULLA F Sagittal section Ma15.19 • control of posture, balance • coordination of motor function 8 Inputs to the Cerebellum Frontal lobe Include: • spinocerebellar proprioceptive info. re. ipsilateral body position, muscle tone Thalamus Cerebellum • vestibulo-cerebellar input re. position and acceleration of the head in space Midbrain Pons Medulla CN VIII Cervical cord Vestibular apparatus • contralateral corticopontocerebellar afferents re. movement planning 9 Outputs from the Cerebellum Frontal lobe • motor, premotor ctx via VA, VL thalamus • motor cortex controls mvt of contralateral body…. Thalamus Cerebellum • what an elegant system for control of body movement! Midbrain Pons Medulla CN VIII Cervical cord Vestibular apparatus 10 BRAINSTEM CERVICAL CORD SENSORY NUCLEI MOTOR NUCLEI The Cranial Nerves & their Nuclei • like the body, the head has both: • sensory & motor components • voluntary & involuntary (autonomic) components SOMATIC (VOLUNTARY) MOTOR VISCERAL (AUTONOMIC) MOTOR SOMATIC SENSORY VISCERAL SENSORY • unlike the spinal cord, functional columns disperse into a series of longitudinally arranged, distinct nuclei • unlike spinal nerves, CNs may carry a single modality • unlike the spinal cord, the brainstem and cranial nerves subserve the “special” visceral sensation, taste and the “special senses” of hearing and balance LUMBAR CORD VISCERAL SENSORY INCLUDING TASTE HEARING AND BALANCE Note: for clarity, motor columns are shown on one side and sensory columns are shown on the other. 11 Both, however, are bilateral. Functional Approach to Learning Cranial Nerves 1. Cranial nerves that convey special senses – – – I (the olfactory N.) II (the optic N.) VIII (the vestibulocochlear N.) 2. Cranial nerves that control skeletal muscle – – – – – III (the oculomotor N.)* IV (the trochlear N.) VI (the abducens N.) XI (the accessory N.) XII (the hypoglossal N.) 3. Mixed cranial nerves – – – – V (the trigeminal N.) VII (the facial N.) IX (the glossopharyngeal N.) X (the vagus N.) 12 Cranial Nerves that Convey Special Senses I the olfactory nerve (covered with the nose / respiratory system) • conveys smell from the olfactory epithelium in the roof of the nasal cavity • nerves enter cranium by passing through the cribriform plate of the ethmoid II the optic nerve (covered with the eye) • conveys visual input from the retina • nerve enters cranium through optic foramen VIII the vestibulocochlear nerve (covered with the ear) • conveys auditory sensations from the cochlea via its cochlear division • conveys balance information from the vestibular apparatus via its vestibular division • nerve enters cranium through the internal auditory (acoustic) foramen 13 Cranial Nerves that Control Skeletal Muscle I III the oculomotor nerve* IV the trochlear nerve • exit cranium through superior orbital fissure to enter orbit • control extraocular eye muscles that position the eye in the orbit • nerve damage causes VI the abducens nerve • strabismus (misaligned eye) and • diplopia (double vision) * also controls the levator palpebrae superioris muscle – paralysis causes ptosis (a droopy eyelid) * also conveys parasympathetic preganglionic fibres destined for the eye – nerve damage causes mydriasis (enlarged pupil) 14 Cranial Ns that Control Skeletal Muscle II Jugular foramen Foramen magnum Cervical spinal cord Accessory N. (CN XI) SCM XI the accessory nerve • emerges as a series of rootlets from the lateral aspect of upper cervical segments • coalesce to form the accessory N. which enters the cranium through the foramen magnum • exits via jugular foramen with CN IX & X • controls the sternocleidomastoid (SCM) and trapezius muscles • SCM turns the head to the opposite side • trapezius elevates the shoulder • nerve damage causes……. XII the hypoglossal nerve • exits the cranium via hypoglossal canal Trapezius • controls the shape and position of tongue via its intrinsic and extrinsic muscles McT15.8 • nerve damage causes….. 15 A C Mixed Cranial Nerves 1: The Trigeminal Nerve B D A. the trigeminal nerve • conveys somatic sensation from the face E • consists of three divisions: B. ophthalmic division via superior orbital fissure (with which other three CNs?) C. maxillary division via foramen rotundum B C McT15.7 D D. mandibular division via foramen ovale E. the trigeminal ganglion contains the cell bodies of these pseudounipolar 1° somatic sensory neurons (like a DRG) • mandibular division also voluntary motor to the four muscles of mastication 16 Mixed Cranial Nerves 2: The Facial N (CN VII) pterygopalatine G. greater petrosal N. geniculate G. • exits cranium via internal auditory (acoustic) foramen 1. voluntary motor fibres exit skull via stylomastoid foramen to innervate muscles of facial expression 2. special visceral sensory (taste) from anterior 2/3 of tongue – 1° sensory axons in chorda tympani, cell bodies in geniculate ganglion 3. parasympathetic preganglionic via: stylomastoid foramen chorda tympani submandibular G. – the chorda tympani to submandibular ganglion: postganglionic fibres distributed to the submandibular and sublingual glands, oral mucosa below oral fissure – the greater petrosal nerve to the pterygopalatine ganglion: postganglionic fibres distributed to the lacrimal gland, nasal mucosa, oral mucosa above oral fissure – Nerve damage causes Bell Palsy 17 Mixed Cranial Nerves 3: The Glossopharnygeal N Pons (CN IX) Otic ganglion Pharyngeal branches CN IX Lingual branch Medulla Parotid gland • exits the cranium via the jugular foramen (other nerves?) 1. somatic sensory from post 1/3 of tongue, oropharynx 2. special visceral sensory (taste) from post 1/3 of tongue 3. visceral sensory from carotid body (chemoreceptors) and carotid sinus (baroreceptors) 4. parasympathetic preganglionic fibres to otic ganglion; postganglionic fibres innervate the parotid gland Carotid body Ma15.28 Common carotid A. Carotid sinus 5. voluntary motor to a single pharyngeal muscle 18 Pharyngeal branch Mixed Cranial Nerves 4: The Vagus N (CN X) CN X Laryngeal nerves Cardiac branches Cardiac plexus Right lung Left lung Liver Celiac Stomach plexus Pancreas Spleen Colon Small intestine Ma15.29 • exits the cranium via the jugular foramen 1. voluntary motor to the pharynx and larynx 2. general sensory from laryngopharynx, larynx 3. visceral sensory from chemoreceptors in the aortic body, baroreceptors in the aortic arch, thoracic and abdominal viscera 4. parasympathetic preganglionic fibres to intramural ganglia of thoracic and abdominal viscera 19