Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Cranial nerves 5 sensesRelated movements SmellI - olfactory – sensory VisionII - optic – sensoryEye ball movement (all motor) III - oculomotor IV - trochlear VI - abducens Hearing and equilibrium VIII – vestibulocochleal - sensory TasteVII - facial - taste (sensory), facial expression (motor) IX - glosopharengial taste (sensory), swallowing (motor) X - vagus taste (sensory), speech and swallowing (motor)* V - trigeminal – chewing – mixed XII - hypoglossal– tongue muscles – motor XI – spinal accessory – neck muscles (help in swallowing - motor * the only cranial nerve that extend to lower parts of the body

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Gray Matter and Spinal Roots Figure 12.31b

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings The sensory neurons cell bodies are found in the dorsal root ganglion and their axons travel through the dorsal root into the gray matter of the cord The axons of the motor neurons travel away from the spinal cord through the ventral roots

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings White Matter in the Spinal Cord Composed of both myelinated and unmyelinated fibers that run in three directions Ascending – to higher centers; sensory Descending – to lower levels from brain or higher places in the cord; motor Transversely – from one side of the cord to the other Divided into three funiculi (columns) – posterior, lateral, and anterior Each funiculus contains several fiber tracks with similar destination and function Fiber tract names reveal their origin and destination Fiber tracts are composed of axons with similar functions

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Spinal nerves Spinal nerves consist of the sensory nerve roots (dorsal) and the motor roots (ventral) All spinal nerves are mixed nerves (both sensory and motor) Spinal nerves split into 2 main branches immediately after emerging: Dorsal ramus – innervate skin of the back and deep back muscle Ventral ramus – form plexuses. The ventral rami of T2-T12 do not form plexuses and innervate intercostal spaces and muscles of the trunk

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Complex interwoven network of nerves Four large plexuses Cervical plexus Brachial plexus Lumbar plexus Sacral plexus Nerve plexus

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings PlexusMain spinal nerves Regions innervatedMajor nerves CervicalC1-C5Skin and muscles of head & neck. Superior chest and shoulder Phrenic (diaphragm) BrachialC5-C8, T1Shoulder and upper limbsAxillary Musculocutaneous Radial Median Ulnar LumbarL1-L4Antero-lateral abdominal wall, external genitalia, part of lower limbs Femoral SacralL4-L5, S1-S4Buttocks, perineum, lower limbs Sciatic

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Reflex Rapid (and unconscious) response to changes in the internal or external environment needed to maintain homeostasis Reflex arc - the neural pathway over which impulses travel during a reflex. The components of a reflex arc include: receptor - responds to the stimulus afferent pathway (sensory neuron) - transmits impulse into the spinal cord Central Nervous System - the spinal cord processes information efferent pathway (motor neuron) - transmits impulse out of spinal cord effector - a muscle or gland that receives the impulse from the motor neuron & carries out the desired response