Chapter 13-The Spinal Cord, Spinal Nerves, And Somatic Reflexes

Contains nerve fiber bundles connecting areas of the body with the brain

Walking requires repetitive coordinated muscle contractions, brain initiates walking but central pattern generators (groups of neurons) in the spinal cord coordinate it

Involuntary responses to certain stimuli

Arises at brain stem, extends to about L1, gives rise to 31 pairs of spinal nerves, pair 1 between skull and C1, rest through intervertebral foramina, divided into regions (cervical, thoracic, lumbar and sacral)

Gives rise to nerves of the upper limbs

Gives rise to nerves of the pelvic region and lower limbs

Just below lumbar enlargement, gives rise to Cauda Equina

Bundle of nerve roots occupies vertebral canal from L2 to S5, nerves arising innervate pelvic region and lower extremities

3 layers of connective tissue coverings that enclose the brain and spinal cord, brain and spinal meninges are continuous with one another

Outermost layer made of dense irregular connective tissue, ends at 2nd sacral vertebrae, epidural space is outside and contains fat, connective tissue, blood vessels, epidural anesthesia

Middle layer, collagen and elastic fibers, subdural space which contains interstitial fluid between dura & arachnoid layers, subarachnoid space contains the CSF

Innermost layer, thin layer adheres to brain and spinal cord, contain blood vessels that supply the spinal cord

Extensions of the pia mater, suspend the cord in the dural sheath, extend laterally attach the pia and dural layers, function to protect the cord against sudden displacement

Contains somas, dendrites, proximal axons of neurons, little myelin, contains all synapses in CNS

Abundance of myelin, composed of bundles of axons called tracts