Cranial Nerves - Cerebral Lateralization Left hemisphere -...

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Unformatted text preview: Cerebral Lateralization Left hemisphere - categorical hemisphere – specialized for spoken and written language, sequential specialized and analytical reasoning (math and science), analyze data in linear way in Right hemisphere - representational hemisphere – perceives information more holistically, perception of spatial perceives relationships, pattern, comparison of special senses, imagination and insight, music and artistic skill imagination Highly correlated with handedness Highly – 91% of people right-handed are left side dominant Lateralization develops with age – females have more communication between hemispheres females (corpus callosum thicker posteriorly) (corpus 14-1 14- Cranial Nerves 12 pair of nerves 12 – arise from brain arise – exit through foramina leading to muscles, glands and exit sense organs in head and neck sense Input and output ipsilateral except CN II and IV 14-2 14- 12 Cranial Nerves How do you remember which nerve is which number? – Here is a G-rated mnemonic devices: Old Opie occasionally tries trigonometry and feels very gloomy, vague, and hypoactive. – There are also several R-rated ones Some cranial nerves are sensory, some motor, and some are both (mixed)? – Some say marry money but my brother says big butts matter more. How many noses do you have? Sensory, motor, or mixed? Run from the nasal mucosa to the olfactory bulb. Extend thru the cribriform plate. Lesion to these nerves or cribriform plate fracture may yield anosmia – loss of smell. CN1 Olfactory nerves How many eyes do you have? Sensory, motor, or mixed? Begin at the retina, run to the optic chiasm, cross over, continue as the optic tract and synapse in the thalamus. Optic nerve damage yields blindness in the eye served by the nerve. Optic tract damage yields partial visual loss. Visual defects = anopsias CN2 Optic Nerves “Eye mover” Sensory, motor, or mixed? Originate at the ventral midbrain. Synapse on: – Extraocular muscles Inferior oblique; Inferior, medial, and superior rectus – Iris constrictor muscle – Ciliary muscle Disorders can result in eye paralysis, diplopia or ptosis. CN3 Oculomotor Nerves How Do I know If the Nerve is Motor, Sensory or Mixed? There are a couple that are in dispute. The There book says one thing our notes say another. Yes, as they are primarily sensory or primarily motor. SO….for our test, let’s go with the silly sayings. For example, CN 8, silly For vestibularcochlear, is predominately SENSORY anyway so it’s O.K . It memorize it that way. Controls the superior oblique muscle which depresses the eye via pulling on the superior oblique tendon which loops over a ligamentous pulley known as the trochlea. Originates on the dorsal midbrain and synapses on the superior oblique Sensory, motor, or mixed? Trauma can result in double vision. Why? CN4 Trochlear Nerves Trochlear Nerve Eye movement (superior oblique muscle) Damage causes double vision and inability to Damage rotate eye inferolaterally rotate 14-10 14- CN5 Trigeminal Nerves Sensory, motor, or mixed? Biggest cranial nerve Originates in the pons and eventually splits into 3 divisions: – Ophthalmic (V1), Maxillary (V2), & Mandibular (V3). Sensory info (touch, temp., and pain) from face. Motor info to muscles of mastication Damage? Sensory, motor, or mixed? Runs between inferior pons and lateral rectus. CN5 Abducens Nerves Abducens Nerve Provides eye movement (lateral rectus m.) Damage results in inability to rotate eye Damage laterally and at rest eye rotates medially laterally 14-14 14- Sensory, motor, or mixed? Originates at the pons Convey motor impulses to facial skeletal muscles – except for chewing muscles. Convey parasympathetic motor impulses to tear, nasal, and some salivary glands. Convey sensory info from taste buds on anterior 2/3 of the tongue. Facial nerve damage may yield Bell’s palsy, total ipsilateral hemifacial paralysis CN7 Facial Nerves Branches of Facial Nerve Clinical test: Test anterior 2/3’s of tongue with substances such as sugar, salt, vinegar, and quinine; test response of tear glands to ammonia fumes; test motor functions by asking subject to close eyes, smile, whistle, 14frown, raise eyebrows, etc. 14-16 CN8 Auditory/Vestibulocochlear Nerves Sensory, motor, or mixed? Originates at the pons 2 divisions: – Cochlear Afferent fibers from cochlea in the inner ear HEARING – Vestibular Afferent fibers from equilibrium receptors in inner ear BALANCE Functional impairment? Glossopharyngeal Nerve Swallowing, salivation, gagging, control of BP and Swallowing, respiration respiration Sensations from posterior 1/3 of tongue Damage results in loss of bitter and sour taste and Damage 14impaired swallowing 14-19 impaired CN9 Glossopharyngeal Nerves Sensory, motor, or mixed? Fibers run emerge from medulla and run to the throat. Motor Functions: – Motor fibers to some swallowing muscles – Parasympathetic fibers to some salivary glands Sensory Functions: – Taste, touch, heat from pharynx and posterior tongue. – Info from chemoreceptors on the level of O2 and CO2 in the blood. Info from baroreceptors on BP. Chemoreceptors and baroreceptors are located in the carotid sinus – a dilation in the internal carotid artery. CN10 Vagus Nerves Sensory, motor, or mixed? Only cranial nerves to extend beyond head and neck. – Fibers emerge from medulla, leave the skull, and course downwards into the thorax and abdomen. Motor Functions: – Parasympathetic efferents to the heart, lungs, and abdominal organs. Sensory Functions: – Input from thoracic and abdominal viscera; from baroand chemoreceptors in the carotid sinus; from taste buds in posterior tongue and pharynx Vagus Nerve Swallowing, Swallowing, speech, regulation of viscera viscera Damage causes Damage hoarseness or loss of voice, impaired swallowing and fatal if both are cut cut 14-22 14- Sensory, motor, or mixed? Formed by the union of a cranial root and a spinal root. – CR arises from medulla while SR arises from superior spinal cord. SR passes thru the FM and joins with CR to form the accessory nerve. They then leave the skull via the jugular foramen. – Cranial division then joins vagus and innervates larynx, pharynx, and soft palate. – Spinal division innervates sternocleidomastoids and trapezius. CN11 Accessory Nerves CN12 Hypoglossal Nerves Sensory, motor, or mixed? Arise from the medulla and exit the skull via the hypoglossal canal and innervate the tongue. Innervate the intrinsic & extrinsic muscles of the tongue. – Swallowing, speech, food manipulation. Damage? Hypoglossal Nerve Tongue movements for speech, food Tongue manipulation and swallowing manipulation – iif both are damaged – can’t protrude tongue f – iif one side is damaged – tongue deviates towards f injured side; see ipsilateral atrophy injured 14-25 14- Cranial Nerve Disorders Trigeminal neuralgia (tic douloureux) – recurring episodes of intense stabbing pain in recurring trigeminal nerve area (near mouth or nose) trigeminal – pain triggered by touch, drinking, washing face – treatment may require cutting nerve Bell’s palsy – disorder of facial nerve causes paralysis of facial disorder muscles on one side muscles – may appear abruptly with full recovery within 3-5 may weeks weeks 14-26 14- ...
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