Neu 212 (Prelim) PDF

GENERAL ORGANIZATION OF THE NERVOUS SYSTEM Nervous System 1. CNS - Brain and Spinal Cord 2. PNS - ? Nerves and Ganglia - Peripheral nerves → Somatic and Autonomic Cells that make up the Nervous System 1. Neurons - Ba...

GENERAL ORGANIZATION OF THE NERVOUS SYSTEM Nervous System 1. CNS - Brain and Spinal Cord 2. PNS - ? Nerves and Ganglia - Peripheral nerves → Somatic and Autonomic Cells that make up the Nervous System 1. Neurons - Basic structural and functional unit - Capable of generating and conducting action potentials - Communication is by means of a chemical or electrical synapse 2. Neuroglia - Support/maintain neurons - Non-conducting - Not capable of communication through action potentials - Types: + CNS: - Ependymal Cells - Oligodendrocytes - Astrocytes - Microglia + PNS: - Satellite Cells - Schwann Cells Structure of Neuron: 1. Cell Body - Lacks centrioles; typical CNS neurons cannot divide - Neural stem cells persist but are inactive except those in the nose and in the hippocampus of the brain which are involved in memory storage - CNS : Nuclei; PNS : Ganglia 2. Dendrites - Branch & extend out from the cell body - Receive information from another cell and transmit the message to the cell body - Conduct action potentials towards the neuron cell body 3. Axon - Capable of propagating an AP at its initial segment of attachment to the cell body (Axon Hillock) - May be branched producing collaterals + Collaterals - enable a single neuron to communicate with several other cells - Nerve - bundle of axons  4. Synaptical Terminal - place where the electrical signal (the action potential) is converted into a chemical signal (neurotransmitter release) Classification of Neurons by Structure 1. Unipolar/Pseudounipolar - Unipolar Neurons - have only one structure extending from the soma - Pseudounipolar Cells - have 2 axons rather than an axon and dendrite + One axon extends centrally toward the spinal cord, the other axon extends toward the skin or muscle 2. Bipolar - have one axon & one dendrite extending from the soma 3. Multipolar - motor neurons having many processes extending from the cell body; has one axon Classification by Function 1. Sensory Neuron - deliver information from sensory receptors through action potentials - Somatic Sensory Neurons - monitor the outside world and body position - Visceral Sensory Neurons - monitor internal conditions and status of organs 2. Motor Neuron - Carry instructions from the CNS to peripheral effectors along efferent fibers also through action potentials - The ANS has sympathetic and parasympathetic divisions - Somatic Motor Neurons - under conscious control (voluntary). Its axon extends into the periphery to innervate skeletal muscle fibers at neuromuscular junctions - Visceral Motor Neurons - not under conscious control (involuntary). Part of the autonomic nervous system (ANS) that innervate smooth muscle, cardiac muscle, glands, and adipose.  - In the ANS there are preganglionic fibers that extend from the CNS to the autonomic ganglia and postganglioinic fibers that extend from the autonomic ganglia to the effectors 3. Interneuron - Located only in the CNS (numerous) - Outnumber all other types of neurons combined - Responsible for the distribution of sensory information & coordination of motor activity Axonal Transport - Process in which protein complexes and membranous organelles are transported within axons - Axons - capable of bidirectional transport - Anterograde - transport from the soma to the distal axon - Retrograde - transport from distal regions back to the soma Glial Cells or Neuroglia 1. Oligodendroglia - Responsible for the myelination of axons in the CNS - Schwann Cells - responsible for the myelination of axons in the PNS - Nodes of Ranvier - myelin sheath gaps along the axon; axonal membrane is uninsulated - Saltatory Conduction - action potentials jumping from node to node; possible along myelinated fibers that increases conduction velocity 2. Astroglia - Largest and most numerous neuroglia of the CNS 3. Microglia - Least numerous and smallest of all neuroglia - Phagocytic cells that patrol the CNS for foreign particles by engulfing cellular debris, waste products, and pathogens 4. Ependymal Cells - Filled with cerebrospinal fluid, and lines the central canal of the spinal cord and the ventricles of the brain - Cerebrospinal Fluid - surrounds the brain & spinal cord; provides a protective cushion & transports dissolved gases, nutrients, and wastes White and Grey Matter 1. White Matter - Bundles of myelinated axons 2. Gray Matter - masses of the cell bodies, dendrites, neuralgia, and unmyelinated axons + Spinal Cord, white matter is at the surface while the gray matter is inside + Brain, white matter is inside, while the gray matter is outside and deep inside Terms to Describe Group of Neuronal Components 1. Nucleus - group of functionally related nerve cell bodies in the CNS 2. Column - In Cerebral Cortex, group of nerve cell bodies related in function that form a column perpendicular to the plane of the cortex  - In Spinal Cord, group of functionally related nerve cell bodies that form a longitudinal column extending through the spinal cord 3. Layer, lamina, stratum - form a layer oriented parallel to the plane of the larger neural structure that includes it 4. Tract, fasciculus, lemniscus - bundle of parallel axons in the CNS 5. Funiculus - group of several parallel tracts/fasciculi 6. Ganglion - located in a peripheral nerve or root; forms a visible knot 7. Nerve, ramus, root - peripheral structure consisting of parallel axons plus associated cells 8. Synapse - functional connection between a neuron & another cell 9. Chemical Synapse - neuromuscular junction and synapses between neurons; transmission through AP is one-way - Presynaptic Terminal/Membrane - contains synaptic vesicles with neurotransmitters - Synaptic Cleft - space between the presynaptic & postsynaptic terminal - Postsynaptic Terminal/Membrane - has receptor proteins where neurotransmitters will attach 10. Electrical Synapse - gap junctions that allow free movement of ions from the interior of one cell to the interior of the next cell; transmission through AP is in several directions Type of Synapses (CNS): Presynaptic Postsynaptic Type Element Function Element Axodendritic Axon Dendrite Usually terminal excitatory Axosomatic Axon Cell body Usually terminal inhibitory Axoaxonic Axon Axon Presynaptic terminal terminal inhibition Dendrodendritic Dendrite Dendrite Local interactions in axonless neurons Brain Directional Terms and Planes  DEVELOPMENT OF THE NERVOUS SYSTEM Week 3 Class Notes + 3 weeks after fertilization, nervous system forms + 2 weeks: primitive streak [bilevel → trilevel] a. Bilevel Structure or Bilaminar Disk (2 weeks) 1. Hypoblast → Endoderm 2. Epiblast → Mesoderm & Ectoderm b. Trilevel Structure or Trilaminar Embryonic Disk (3 weeks) 1. Endoderm - innermost 2. Mesoderm - middle 3. Ectoderm - outermost + 3 weeks (includes trilevel) a. Notochord - Formed sa mesoderm - Growth factor secretion stimulates Ectoderm forms Neuroectoderm forms Neural Plate (ectoderm) → forms neural tube and neural crest cells b. Neural Tube - Precursor to brain & spinal cord - Will form brain & spinal cord + Pag di nag-close and neural tube (cephalic), prosencephalon is affected = anencephaly (no brain/skull) + Pag di nag-close ang neural tube (codal end), rhombencephalon is affected = spina bifida + Spina Bifida: a. Occulta - normal b. Meningocele - cyst c. Myelomeningocele - cysts EMBRYONIC (4th week) SUBDIVISION (6th week) ADULT (11th week) Prosencephalon (Forebrain) Telencephalon Cerebrum Basal Ganglia Hippocampus Diencephalon Subthalamus Hypothalamus Thalamus Mesencephalon (Midbrain) Mesencephalon Crus cerebri Midbrain Rhombencephalon (Hindbrain) Metencephalon Pons Cerebellum Myelencephalon Medulla Oblongata Critical Development + In utero - during pregnancy + Perinatal - after birth 1. Neonatal - ¼ body length is head  - 10% body weight is head - 25% volume (birth); 75% (adult) - Sensory pathways myelinate first - Motor fibers myelinate later 2. Childhood - 90% adult size (5 yo) - 95% adult size (10 yo) - 100% adult size (17-18 yo) - 6 yo: 97.5% brain sa cranial activity - Adult: 92.5% brain sa cranial activity 3. Adulthood + Sensori → Motoric actions + 6 mos to 1 yo: rapid growth + 2 yo: slow development until 5 yo + 1 yo: brain; 2 yo: body; 2-3 yo: axons/dendrites + Myelination slows down at puberty + Neuro-plasticity - brain’s ability to adapt/adjust + Synapse - site of information transfer + White matter is required for learning  FUNCTIONAL NEUROANATOMY Week 4 Class Notes Outline: I. Meninges - Additional protection for the brain - Non-nervous connective tissue - Contains cerebrospinal fluid; lubricates the brain & spinal cord, acts as cushion for the brain - Brain floats - DAP: - Dura Mater (Pachymenix) - Outermost, toughest - Should be penetrated or broken - Houses CSF - Dito lang makikita traumatic brain injury, pag nasira to - Dural Folds - brain folds because of dura - Dural Sinuses - may CSF - Arachnoid - Middle layer - Between DM & A: Subdural Space - Subdural Hematoma - hindi nag penetrate sa brain because of the subdural space - Between A & PM: Subarachnoid Space (ends sa S2 and S3; for spinal tapping; location ng flow of CSF) - Both spaces: protects the brain from associated hemorrhagic injuries; extends to the whole cranial bone - Pia Mater - Fuses with the Ependyma to form the Choroid Plexus - Choroid Plexus - Produces CSF - Enters the 3rd and 4th ventricles through their roofs, and the lateral ventricles through the choroid fissure II. Ventricles & CSF Ventricles - “brain cavities”; fluid-filled (CSF = never stops being produced) + Pag walang CSF, brain continuously grows, di na kaya i-support ng neck a. 3 Main Ventricles 1. Lateral Ventricle (L & R) 2. 3rd Ventricle 3. 4th Ventricle b. CSF Functions - “PINCH” a. Protection - detection & removal of foreign substances; cushion b. Intracranial Pressure Regulation - c. Nutrition - mode of transportation ng nutrition to the brain d. Cushion - due to buoyancy; protection from head trauma e. Homeostasis - body’s state of balance c. CSF Flow 1. CSF produced in the choroid plexus in the lateral ventricle 2. CSF into the lateral ventricle → interventricular foramina (foramen of monroe) → 3rd ventricle (cavities) 3. CP in the 3rd ventricle produces more CSF 4. CSF → cerebral aqueduct (aqueduct of sylvius) → 4th ventricle 5. CP in the 4th ventricle adds more CSF in the 4th ventricle  6. CSF will flow out 2 lateral apertures (foramen of luschka) (openings) & 1 median aperture (foramen of magendie) 7. CSF flows to subarachnoid space (S2 - S3); distribute to the external surface of the brain & spinal cord 8. CSF → drained by the Arachnoid Villi → drained into the superior sagittal sinus for excretion (draining vessel) → blood (tapos iniihi natin CSF) III. Circle of Willis - Blood supply of the brain IV. Neurophysiology - Neuroglia or Glial Cells - Enhances, supports, protect neurons - In 1 neuron = 10 neuroglia - CNS: astrocytes; PNS: satellite cells V. Cerebrum - Contralateral - Dominant: Left (MALI: Math, Analytic, Language); Non-dominant: Right (HAM: Hemineglect Arts, Music) - Fiber Connections - to make connections with other parts of cerebrum a. Commissural Fibers - connect L&R structures; corpus colossum (example)(L&R hemis) b. Association Fibers - connects structures within the same hemisphere; arcuate fasciculus: conduction aphasia c. Projection Fibers - connects outside the brain; spinal cord - brain, brain - spinal cord, tracts - External Surface: a. Sulcus - fissures along the brain - Medial Longitudinal Fissure - divides L&R hemisphere - Central Sulcus (Rolandic Fissure) - divides pre & post central gyrus - Lateral Sulcus (Sylvian Fissure) - divides temporal lobe with other areas b. Gyrus 1. Frontal Lobe - BA 4: Primary Motor Area - execution of movement; pag may lesion: flaccicity - BA 6: Premotor/Precentral Area (Secondary Motor Area) - coordination of movement; spasticity - BA 8: Frontal Eye Field - conjugates eye movements; damage to L&R eye - BA 9-12: Prefrontal Area - higher cortical functions (behaviors); behavioral problems - BA 44: Broca’s Area - speech production; broca’s, motor, expressive, nonfluent aphasia 2. Parietal Lobe - BA 1, 2, 3: Primary Somatosensory Area - receives information - BA 5 & 7: Association Sensory - interprets information; hemianesthesia, gerstmann syndrome - BA 39: Angular Gyrus - visual interpretation; gerstmann syndrome - BA 40: Supramarginal Gyrus - proprioception; idiomotor aphasia - BA 43: Primary Gustatory Cortex - taste; ageusia 3. Occipital Lobe - BA 17: Primary Visual - receives visual input - BA 18, 19: Secondary Visual - supplementary functions (recognition of faces, colors, etc.); prosopagnosia, simultagnosia 4. Temporal Lobe - BA 41: Primary Hearing; loss of hearing - BA 42: Secondary Hearing; loss of hearing - BA 22: Wernicke’s Area; wernicke’s, fluent, comprehension aphasia 5. Insular 6. Limbic VI. Basal Ganglia (Basal Nuclei) - Monitors emotions; initiation of movement; smoothens muscle performance - Production of neurotransmitters (can be excitatory or inhibitory) (ex: acetylcholine = neuromuscular junction, norepinephrine = sympathetic nervous system, dopamine = motivation & mood, glycine = , gaba = brain inhibition)  - Structural Organization: to maintain structural integrity - Corpus Striatum: Centriform + Neostriatum - Centriform: Putamen + Globus Pallidus - Neostriatum: Putamen + Caudate Nucleus - Functional Organization: 1. Subthalamus 2. Subthalamic Nucleus 3. Substantial Nigra a. Pars Compacta b. Pars Reticulata VII. Diencephalon - Subparts: 1. Subthalamus - motor control 2. Hypothalamus - Suprachiasmatic Nucleus - sleep-wake cycle - Preoptic Nucleus - libido - Lateral Hypothalamus - hunger & thirst center - Medial Hypothalamus - satiety - Anterior Hypothalamus - alis-heat (sweat) - Posterior Hypothalamus - produce heat (shiver) 3. Epithalamus - Habenular Nuclei - olfaction - Pineal Body - induces sleep, secretes melatonin 4. Thalamus - sensory relay, except olfaction VIII. Cerebellum - “Little brain” - Ipsilateral functions - Vermis - maintains upright posture - Arbor Vitae - tree of life; for respiration - Ataxic Dysarthria - pag may lesion; incoordination and loss of balance - Lobes: a. Anterior Lobe or Paleocerebellum - Muscle tone b. Posterior Lobe or Neocerebellum - Coordination c. Flocculonodular Lobe or Archicerebellum - Balance IX. Brainstem - Bridges all of the tracts - Reflex center - 3 Structures: 1. Midbrain - CN 9 - 12 - Movement and motor control - Visual reflects (superior colliculi) and hearing reflex (inferior colliculi) 2. Pons - CN 5 - 8 - Bridges between L&R cerebellum - Vasomotor controls - Regulation of inspiration in breathing - Upper pons: - Pneumotaxic Center - inhibits inspiration - Lower pons: - Apneustic control - stimulates inspiration  3. Medulla Oblongata - CN 3 - 4 - Vasomotor center - Automatic respiratory reflex center - Junction between the spinal cord to the foramen magnum X. Spinal Cord - Starts at the foramen magnum - Connected by the medulla oblongata - Ends at: a. Adults: L1 b. Children: L3 - Conus Medullaris - where the spinal cord tapers off - Filum Terminale - Pia Mater prolongation - Length of Spinal Cord = M: 48 cm, F: 45 cm - Cervical Spinal Cord - branches off into the brachial plexus - Lumbar Spinal Cord - branches off into the lumbosacral plexus - Central part: gray matter (non-myelinated); peripheral part: white matter (myelinated) - Functions: - VEM - DAS - Ventral, Efferent (output info), Motor (Anterior) - Dorsal, Afferent (input info), Sensory (Posterior) a. Anterior - motor b. Posterior - sensory + CSF paikot ikot lang, pero drainage is through blood vessels na nasa SSS, pag nadrain, sa blood punta ng sobra = waste, so i-iihi mo sya + Hydrocephalus - inability of the brain to regulate amount of CSF; sumosobra yung CSF + Hemianesthesia - lack of sensation on one side of the body + Ageusia - loss of taste + Prosognosia - inability to recognize faces + Simultagnosia - inability to match an object through/in a picture + Conduction Aphasia - difficulty with repetition + Glutamate - most abundant in the nervous system + Gaba - most abundant in cerebral cortex + Glycine - most abundant in spinal cord + Dopamine - most abundant in striatum Area Specific Location Function FRONTAL LOBE 4 Precentral Gyrus Primary motor cortex 6 Premotor/Precentral Area or Secondary Motor Premotor or supplemental motor cortex Area 8 Frontal eye fields Eye movements and visual reflexes along with pupil dilation & constriction 9 Dorsolateral prefrontal cortex Collectively known as the PREFRONTAL AREA - Cognitive processes (reasoning & judgment) and 10 Anterior prefrontal cortex executive function - Higher cortical functions (behaviors) 11 Orbital gyri or Orbitofrontal area 44 Inferior frontal gyrus (Broca’s Area) Speech production PARIETAL LOBE 1 Post central gyrus (Primary Somatosensory Receives information (touch and kinesthesia Area) - Kinesthesia - awareness of the position & movement 2 of the parts of the body 3 5 Superior parietal lobule (Association Sensory) Interprets information 7 40 Supramarginal Gyrus Proprioception - lets us perceive the location and movements of our body parts 39 Angular Gyrus Visual interpretation, language, number processing & spatial cognition, memory retrieval, attention, and theory of mind  TEMPORAL LOBE 21 Middle temporal gyrus Auditory association areas; comprehension and/or understanding of language 22 Superior temporal gyrus (Wernicke’s Area) 37 Fusiform gyrus/Occipitotemporal gyrus Lesions can cause anomia 41 Superior temporal gyrus (Auditory Cortex) Primary auditory area 42 Secondary auditory area OCCIPITAL LOBE 17 Occipital Gyri/Primary visual cortex Primary visual area 18 Occipital Gyri/Secondary visual cortex Secondary visual areas where visual processing occurs 19 Occipital Gyri/Associate visual cortex  CRANIAL NERVES Week 5 Class Notes Cranial Nerve - 12 nerves that sends electrical signals between your brain & different parts of your body - Relays sensory and/or motor/movement information Origin of the Cranial Nerves A. Motor Function (Efferent) - may effect - Arise from collections of cells that lie deep within the brain stem - Homologous to the anterior horn cells of the spinal cord B. Sensory Function (Afferent) - papunta - Their cells of origin outside the brain stem, usually in ganglia that are homologous to the dorsal root ganglia of the spinal nerves. - Second-order: lie within the brain stem CRANIAL NERVES Only One Of The Two Athletes Felt Very Good Victorious And Healthy Some Say Marry Money But My Brother Says Big Brains Matter Most I. Olfactory - Sensory - Origin and Course: - Arise from olfactory receptor cells located in olfactory epithelium of nasal cavity and pass through cribriform plate of ethmoid bone to synapse in olfactory bulb - Fibers of olfactory bulb neurons extend posteriorly a olfactory tract, which runs beneath frontal lobe to enter cerebral hemispheres and terminates in primary olfactory cortex as well as entorhinal cortex and amygdala - Originates from olfactory epithelium (upper nasal cavity) - Olfactory nerve → olfactory bulb → cerebral hemispheres → primary olfactory cortex → entorhinal cortex and amygdala - Function: - Carry afferent impulses for sense of smell - Clinical Testing: - Person is asked to sniff aromatic substances such as oil of cloves and vanilla, and to identify each II. Optic - Sensory - Origin and Course: - Retina of the eye to form the optic nerve, passes through the optic canal of orbit. The optic nerves converge to form the optic chiasma where fibers partially cross over, continue on as optic tracts, enter thalamus, and synapse  there. Thalamic fibers run to the primary visual cortex - Optic nerve → optic chiasma → thalamus → primary visual cortex - Function: - Carry afferent impulses for vision - Clinical Testing: - Eye chart, object (finger) moving into the visual field III. Oculomotor - Motor - Origin and Course: - Fibers extend from ventral midbrain (near its junction with pons) and pass through bony orbit, via superior orbital fissure, to eye - Function: a. Somatic efferent portion: 1. Levator palpebrae superioris muscle that raises the upper eyelid 2. Superior rectus, medial rectus, inferior rectus muscles and inferior oblique muscle are involved in movement of eye in different directions/hazes b. Parasympathetic fibers innervate two smooth intraocular muscles: 1. Ciliary Muscle - controls lens shape for focusing 2. Sphincter Pupillae - causes the pupil to constrict - Clinical Testing: - Pupils are examined for size, shape, and equality. Pupillary reflex is tested with penlight. Convergence for near vision is tested, as is the subject's ability to follow objects with the eyes. + Pupils should constrict when illuminated IV. Trochlear - Motor - Origin and Course: - Fibers emerge from dorsal midbrain and course ventrally around midbrain to enter orbit through superior orbital fissure along with oculomotor nerves - Function: - Supply somatic motor fibers to one of the extrinsic eye muscles, the superior oblique muscle - Clinical Testing: - Testen in common with CN III V. Trigeminal - Sensory & Motor - Largest and is the general sensory nerves of the face - Innervates most of the chewing muscles, and the tensor tympani - Afferent axons for the corneal blink reflex are carried in ophthalmic branch of nerve V while the efferent limb is through VII - Origin and Course: - Cell bodies are located in large trigeminal ganglion (semilunar or gasserian) - Fibers extend from the pons to the face forming three divisions - Function: - Transmits touch, temperature, sense, and pain from the face - Three Divisions: 1. Ophthalmic Division (V1) - Origin and Course: from face to pons via superior orbital fissure - Function: conveys sensory impulses from skin of anterior scalp, upper eyelid, nose, and from nasal cavity mucosa, cornea, and lacrimal gland - Clinical Testing: cornea reflex tested (touching cornea with wisp of cotton should elicit blinking) 2. Maxillary Division (V3) - Origin and Course: from pons via foramen rotundum - Function: conveys sensory impulses from nasal cavity mucosa, palate, upper teeth, skin of cheek, upper lid, lower eyelid - Clinical Testing: sensations of pain, touch, and temperature are tested with safety pin and hot & cold objects 3. Mandibular Divisions (V2)  - Origin and Course: pass through skull via foramen ovale - Function: conveys sensory impulses from anterior tongue, lower teeth, skin of chin, temporal region of scalp, supplies motor fibers to and carries proprioceptive fibers from, muscles of mastication - Clinical Testing: assessed by asking person to clench his teeth, open mouth against resistance, and move jaw side to side VI. Abducens - Motor - Origin and Course: - Fibers leave inferior pons and enter orbit via superior orbital fissure to run to eye - Function: - Supply somatic fibers to lateral rectus muscle, an extrinsic eye muscle; convey proprioceptor impulses from the same muscle to the brain - Levator palpebrae superioris muscle - lifts the upper eyelid - Orbicular Muscle - closes the eyelids (VII) - Clinical Testing: - Tested in common with CN III VII. Facial - Sensory & Motor - Origin and Course: - Fibers issue from pons, just lateral to abducens nerves, enter temporal bone via internal acoustic meatus, and run within bone before emerging through stylomastoid foramen nerve then course to lateral aspect of face - Pons → temporal bone → stylomastoid foramen → face - Function: - Has 5 branches: temporal, zygomatic, buccal, mandibular, and cervical - Conveys motor impulses to skeletal muscles of face, platysma, and stapedius; also transmits proprioceptor impulses from the same muscles to the pons - Transmit parasympathetic motor impulses to lacrimal glands, nasal & palatine glands, and submandibular & sublingual salivary glands. Some of the cell bodies are in pterygopalatine & submandibular ganglia on the CN V - Convey sensory impulses from taste buds of anterior 2?3 of tongue: cell bodies of these sensory neurons are in geniculate ganglion - Clinical Testing: - Anterior ⅔ of the tongue is tested for ability to taste, salty, sour, and bitter substances - Symmetry of the face is checked. Subject is asked to close eyes, smile, whistle, and so on - Tearing is assessed with ammonia fumes - Lesion rostral to the facial nucleus = paralysis of the contralateral facial muscles VIII. Vestibulocochlear - Sensory - Origin and Course: - Double nerve that arises from spiral & vestibular ganglia in the labyrinth of the inner ear - Cochlear nerve is connected with hearing - Vestibular nerve is part of the system of equilibrium (position sense) - Function: - Vestibular branch: afferent impulses for equilibrium and sensory nerve cell bodies are located in vestibular ganglia - Cochlear branch: afferent impulses for sense of hearing, and sensory nerve cell bodies are located in spiral ganglion within cochlea. Some motor fibers from the pons innervate the outer hair cells of the cochlea - Clinical Testing: - Hearing is checked by air and bone conduction using tuning fork IX. Glossopharyngeal - Sensory & Motor - Origin and Course:  - Fibers emerge from medulla and leave the skull via jugular foramen to run to the throat - Function: - Tongue receives its sensory innervation through CN VII, IX, X, and the general sensory afferent fibers are mediated by V - Visceral afferent axons: supply general sensation to the pharynx, soft palate, posterior ⅓ of tongue, fauces, tonsils, auditory tube, and tympanic cavity - Sinus nerve: supply special receptors in the carotid body and carotid sinus that are concerned with reflex control of respiration, blood pressure, and heart rate - Clinical Testing: - Position of the uvula is checked. Gag and swallowing reflexes are checked. Subject is asked to speak and cough. Posterior ⅓ of tongue may be tested for taste - Clinical Correlations - Generally involved with CN X (motor) & IX (sensory) X. Vagus - Sensory & Motor - Origin and Course: - Only CN that extend beyond head and neck region - Fibers emerge from medulla, pass through the skull via jugular foramen and descend through neck region into thorax and abdomen - Function: - Parasympathetic motor fibers supply heart, lungs, and abdominal viscera and are involved in regulation of heart rate, breathing, and digestive system activity - Transmit sensory impulses from thoracic & abdominal viscera, from the aortic arch baroreceptors and the carotid and aortic bodies and taste buds of posterior tongue and pharynx - Carry proprioceptive fibers from the muscles of larynx and pharynx - Clinical Testing: - CN IX & X are tested in common since they both innervate muscles of throat and mouth - Clinical Correlations: - Lesions may be intramedullary or peripheral - Often involve CN IX & XI, sometimes the XII - Complete bilateral transection: fatal - Unilateral lesions: widespread dysfunction of the palate, pharynx, larynx - Vocal cord weakness/paralysis: hoarseness - Recurrent laryngeal nerve: result of invasion or compression by a tumor or as a complication of thyroid surgery XI. Accessory - Motor (lowk mixed) - Origin and Course: - Cranial Root: emerges from the lateral aspect of medulla - Spinal Root: emerges from the superior region (C1-C5) of spinal cord - The spinal portion passes upward along the spinal cord, enters the skull via foramen magnum, and temporarily joins the cranial root. The resulting accessory nerve exits from the skull through the jugular foramen. Cranial and spinal fibers then diverge - Function: - Cranial division joins the fibers of vagus nerve to supply motor fibers to larynx, pharynx, and soft palate - Spinal root supplies motor fibers to trapezius and sternocleidomastoid muscles which together move head and neck, and conveys proprioceptor impulses from the same muscles - Clinical Testing: - Sternocleidomastoid and trapezius muscles are checked for strength by asking person to rotate head and shrug shoulders against resistance - Clinical Correlations:  - Interruption of the spinal component leads to: - Paralysis of sternocleidomastoid muscle, causing the inability to rotate the head to the contralateral side - Paralysis of the upper portion of trapezius muscle; wing-like scapula, inability to shrug the ipsilateral shoulder XII. Hypoglossal - Motor - Origin and Course: - Fibers arise by a series of roots from medulla and exit from skull via hypoglossal canal to travel to tongue - Mainly serve the tongue - Hypo = beneath; glossal = tongue - Function: - Carry somatic motor fibers to intrinsic and extrinsic muscles of the tongue, and proprioceptive fibers from same muscles to brain stem - Controls not only food mixing and manipulation by tongue during chewing, but also tongue movements that contribute to swallowing and speech - Clinical Testing: - Subject is asked to protrude and retract tongue. Any deviations in position are noted