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There are 12 pairs of cranial nerves, numbered with Roman numerals. I Olfactory II Optic III Occulomotor IV Trochlear V Trigeminal VI Abducens VII Facial VIII Vestibulocochlear IX Glossopharyngeal X Vagus XI Accessory Nerve XII Hypoglossal 1 I. OLFACTORY nerves Transmits the sense of smell. II. OPTIC NERVE: Transmits visual information from the eye’s retina. III Occulomotor Nerve: this controls most of the extrinsic muscles of the eye (that move the eyeball). They also have parasympathetic innervation in the iris (pupil) and cilliary (controls the lens). 2 IV. Trochlear Nerve: supplies one of the extrinsic eye muscles V. Trigeminal Nerve: This is the main sensory nerve of the face. It has a large branch that passes through the foramen ovale of the skull. Problems with CN-5 are called TRIGEMINAL NEURALGIA, which is excruciating pain in the face from nerve inflammation. 3 VI: Abducens controls one of the eye muscles (lateral rectus). VII Facial Nerve: This innervates the muscles of facial expression and salivary glands. A person who cannot blink or smile may have damage to what nerve? VII Facial Nerve A person who cannot easily taste sweet, sour, or salty substances has damage to what nerve? VII Facial Nerve BELL’S PALSY is damage of the facial nerve Needs to be distinguished from a stroke. 4 VIII. VESTIBULOCOCHLEAR nerve transmits hearing and balance. IX: GLOSSOPHARYNGEAL a) signals the pharynx to constrict (along with X) during swallowing. b) Innervates top of tongue c) Has baroreceptors 5 X Vagus Nerve a) Parasympathetic supply to organs b) Moves the larynx during speech c) Signals pharynx to constrict during swallowing (with CN IX) . This is the only cranial nerve that travels into the abdomen. The majority of the parasympathetic outflow from the head is by the vagus nerve. 6 XI: ACCESSORY NERVE enters the skull through foramen magnum and leaves through the jugular foramen. It just supplies the shoulder muscles. XII. HYPOGLOSSAL NERVE (hypo=under; glossal=tongue) - supplies the under surface of the tongue. Damage causes impairment of speech. 7 FORAMEN MAGNUM. It goes to L1-2. In infants, it ends at L4-5, because it doesn’t grow as fast as the rest of the body. 8 CAUDA EQUINA (“Horse’s tail”), which exit through the intervertebral foramina. 9 The SACRAL PLEXUS is made up of the spinal nerves exiting the spinal cord from the level of L4 to S5. 10 There is a spinal nerve C8, although there is no C8 vertebrae. 11 CENTRAL CANAL, GREY MATTER, WHITE MATTER, POSTERIOR MEDIAN SULCUS, ANTERIOR MEDIAN FISSURE, DORSAL HORN, VENTRAL HORN, DORSAL ROOT, DORSAL ROOT GANGLION, VENTRAL ROOT, and SPINAL NERVE 12 Ganglion = a group of neuron cell bodies. Some are motor, some are sensory. The ganglions in the dorsal root are always sensory. All ganglia are in the PNS only 13 Posterior root ganglion 14 Most synapses are in the CNS 15 SENSORY NEURONS come in through the posterior root, their cell body is in the posterior root ganglion, and its axon goes into the posterior horn and synapses in the grey matter. It also sends a branch to an area of the white matter called the DORSAL COLUMN PATHWAY, which goes into the brain (thalamus). 16 Thalamus 17 LMN’s have their cell body in the anterior horn (of the gray matter), and their axon goes out the anterior root, and synapses in a muscle. 18 Their cell bodies are in the dorsal half of the gray matter in the spinal cord. They receive signals from the sensory neuron and then synapse on the cell body of the motor neuron. In this way, the interneurons (sometimes called association neurons) transmit signals from the sensory pathways to the motor pathways. 19 The complexity of the CNS can be attributed to Interneurons 20 Pain and temperature 21 Sensory, lower motor, and interneuron forms the SIMPLE REFLEX ARC. 22 If you touch a hot stove, the sensory input comes into the spinal cord, the association neurons send the information to the lower motor neurons, the muscle contracts, and you take your hand off the stove before your brain even knows it. Simple reflex behavior involves three nerves, and no brain involvement. Reflexes are automatic events. 23 They involve both motor and sensory neurons, they are rapid, involuntary, and they involve multiple synapses. 24 KNEE-JERK REFLEX 25 SENSORY TOUCH SPINAL NERVE POSTERIOR ROOT GANGLION POSTERIOR ROOT POSTERIOR HORN TRACT THALAMUS 26 Inside the brain nerves are called tracts; outside the brain, they are called called nerves (ie optic nerve and optic tract, olfactory nerve and olfactory tract) 27 Upper motor neuron: cell body is in the brain, synapses on a lower motor neuron (in the spinal cord) Lower motor neuron: cell body is in the spinal cord, and synapses on skeletal muscle. 28 a plexus. One of these is known as the brachial plexus (in the armpit; innervates the muscles of the arm). 29 rami, trunks, divisions, cords 30 PROPRIOCEPTION neurons measure the amount of force and movement in muscles and joints Proprioception nerves travel up the spinocerebellar tract. Close eyes and touch finger to nose. 31 Cannot move hand on own (paralysis) but reflexes work 32