Chapter 13 Spinal Cord Spinal Nerves and Somatic Reflexes Functions of the Spinal Cord Conduction carries information up and down the cord Neural Integration receives input from many places coordinates that with cerebral input Locomotion repetitive movements of walking or coordinated by the cord Reflexes involuntary stereotyped response involving the brain spinal cord and peripheral nerves 45 cm long Diameter of your pinky Contains cervical and lumbar enlargements Adults spinal cord stops at L1 birth L3 L2 S5 is the Cauda Equina 31 pairs of spinal nerves Divided into regions Cervical Thoracic Lumbar Sacral Spinal Tracts Ascending Tracts carries sensory information First order neuron transmits to brain or spinal cord Second order transmit to thalamus Third order carries to the cerebral cortex Descending Tracts conducts motor impulses down Upper motor neuron transmits from cerebral coretex ot brain stem to Lower motor neuron Decussation crossing over to the other side of the body Ipsilateral origin and destination on same side of body Contralateral origin and destination of opposite sides Nerves contains numerous neurons nerve fibers Encases in Schwann Cells in the PNS Afferent carry sensory information to CNS Efferent carry motor information from CNS to effectors Somatic innervate skin skeletal muscles bones joints Visceral innervate blood vessels glands viscera Nerves 31 pairs 8 cervical C1 8 12 thoracic T1 12 5 lumbar L1 5 5 sacral S1 5 1 coccygeal Co1 Plexuses Merged web like areas of nerves Cervical plexuses C1 C5 Brachial plexuses C5 T1 Lumbar plexuses L1 L5 Sacral plexuses L4 S4 Coccygeal plexuses S4 Co1 Dermatone an area of skin that is supplied with the nerve fibers of a single posterior spinal root Myotome a group of muscles that are innervated by a single spinal nerve root Reflexes Quick involuntary stereotyped reactions of glands or muscles to stimulation Somatic Reflex somatic receptors in skin muscles tendon are stimulated Afferent fibers carry info from receptors to posterior horn of spinal cord of brain stem Integrating center a point of synaptic contract between neurons in gray matter of cord and brain stem Efferent nerve fibers carry motor impulses to muscles Efferent carry out the response