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