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Brain and spinal nerve By: shirin Kashfi Nervous system: central nervous system (CNS) peripheral nervous system (PNS) Brain (cranial) nerves Spinal nerves Ganglions (dorsal root ganglions, sympathetic & parasympathetic ganglions) The difference between brain and spinal nerves • Cranial nerves supply the sensory and motor functions of the face and head and autonomic function of the body • Unlike the spinal nerves which supply all sensory and motor functions for a specific body segment, each cranial nerve is associated with a specific function or set of functions and may take in a larger territory Brain (cranial) nerves • There are 12 pairs • All of them originate from ventral surface of brain except for IV nerve Cranial nerve I: Olfactory nerve • Type: sensory • Function: carries sense of smell – The olfactory nerve is composed of axons from the olfactory receptors in the nasal sensory epithelium. It carries olfactory information (sense of smell) to the olfactory bulb of the brain Cranial nerve II: optic nerve • Type: sensory • Function: carries visual information – The optic nerve is composed of axons of the ganglion cells in the eye Cranial nerve III: oculomotor nerve • Type: motor • Function: It provides somatic motor innervation to four of the extrinsic eye muscles: the superior rectus, inferior rectus, medial rectus, and the inferior oblique muscles. Oculomotor nerve innervates the muscles of the upper eyelid. It also provides the parasympathetic innervation responsible for pupillary constriction in response to light and accomodation of the lens for near vision Cranial nerve IV: trochlear nerve • Type: motor • Function: The trochlear nerve provides somatic motor innervation to the superior oblique eye muscle Cranial nerve V: trigeminal nerve • Type: sensory & motor • Function: It provides sensory information from the face, forehead, nasal cavity, tongue, gums and teeth (touch, and temperature) and provides somatic motor innervation to the muscles of mastication or “chewing”, inner ear (tensor tympani) and upper neck – The trigeminal is the largest cranial nerve – This cranial nerve has 3 branches: the ophthalmic, maxillary and mandibular branches Cranial nerve VI: abducens nerve • Type: motor • Function: It carries somatic motor innervation to one of the extrinsic eye muscles, the lateral rectus muscle Cranial nerve VII: facial nerve • Type: sensory &motor • Function: It carries somatic motor innervation to the many muscles for facial expression. It carries sensory information form the face (deep pressure sensation) and taste information from the anterior two thirds of the tongue Cranial nerve VIII: vestibulocochlear nerve • Type: sensory • Function: sense of balance and sense of hearing – This cranial nerve branches into the Vestibular branch (balance) and the cochlear branch (hearing) Cranial nerve IX: glossopharyngeal nerve • Type: sensory & motor • Function: It carries sensory information (touch, temperature, and pressure) from the pharynx and soft palate. It carries taste sensation from the taste buds on the posterior one third of the tongue. It provides somatic motor innervation to the throat muscles involved in swallowing. It provides visceral motor innervation to the salivary glands. This cranial nerve also supplies the carotid sinus and reflex control to the heart Cranial nerve X: vagus nerve • Type: sensory and motor • Function: It provides sensory information (touch, temperature and pressure) from the external auditory meatus (ear canal) and a portion of the external ear. It carries taste sensation from taste buds in the pharynx. It also provides sensory information from the esophagus, respiratory tract, and abdominal viscera (stomach, intestines, liver, etc.). It provides visceral motor innervation to the heart, stomach, intestines, and gallbladder Cranial nerve XI: spinal accessory nerve • Type: motor • Function: The spinal accessory nerve has two branches. The cranial branch provides somatic motor innervation to some of the muscles in the throat involved in swallowing. The spinal branch provides somatic motor innervation to the trapezius muscles, providing muscle movement for the upper shoulders head and neck Cranial nerve XII: hypoglossal nerve • Type: motor • Function: It provides somatic motor innervation to the muscles of the tongue Spinal nerves • Mammals have 31 pairs spinal nerves – 8 pairs cervical, 12 pairs thoracic, 5 pairs lumbar, 5 pairs sacral and 1 pairs coccygeal Conus Medullaris Caudal end of spinal cord Cauda Equina (L1-L5, S1-S5, Co1) Filum Terminale a thickening of the pia and glial cell (anchors the spinal cord to the coccyx) Spinal nerves • Each of them have sensory and motor function • Each spinal nerves innervates certain area of body which is called dermatome