Central Nervous System Plus Spinal and Cranial Nerves

Central Nervous System Plus Spinal and Cranial Nerves

Central Nervous System n Consists of Brain and Spinal Cord

Spinal Cord Protection and Covering n Vertebral Colum – Ring of bone formed by vertebral foramina protect the spinal cord

Spinal Cord Protection and Covering n Meninges – connective tissue covering that protect the spinal cord. They are found in 3 layers

Meninges n Dura Mater – outer layer of meninges – Composed of tough connective tissue

Meninges n Arachnoid meninges Mater – middle layer of – Composed of collagen and elastic fibers that resemble a spider’s web

Meninges n Pia Mater – inner layer of meninges – Composed of transparent collagen and elastic fibers that adhere to the spinal cord and brain

Subarachnoid Space n Area between the arachnoid mater and pia mater containing CSF – Spinal Tap (lumbar puncture) – a long needle is inserted into the subarachnoid space (generally between L 3 & L 4 or L 4 & L 5) to withdraw CSF for diagnostic purposes or to introduce medication.

External Structure n The adult spinal cord is only about 16 -18 inches long…it ends around L 2

Cauda Equina n Nerves on the lower portion of the cord angled downward through the vertebral canal.

Enlargements n Cervical Enlargement – contains nerves that supply the upper limbs n Lumbar Enlargement – contains nerves that supply the lower limbs

Indentations/divisions n Anterior Median Fissure & Posterior Median Sulcus – divide the cord into right and left halves

Central Canal n Space down the center of the spinal cord containing CSF

Internal Structure n Gray Matter – Anterior Horns – contain cell bodies of somatic motor neurons – Posterior Horns – contain cell bodies of somatic and autonomic sensory neurons – Lateral Gray Horns – present only in lower portion of the spinal cord. Contains cell bodies of autonomic nervous system

Ventral Horn Lateral Horn Dorsal Horn

White Matter n Organized into columns containing myelinated and unmyelinated axons of sensory and motor neurons Posterior White Column Lateral White Column Anterior White Column

White Matter n Tracts – bundles of axons having a common origin or destination carrying similar information – Sensory (ascending) tracts – consist of axons that conduct nerve impulses toward the brain – Motor (descending) tracts – consists of axons that carry nerve impulses down the spinal cord

Tracts

Spinal Nerves n Paths of communication between the spinal cord and the nerves that serve the specific regions of the body

Roots n Connect each spinal nerve segment to the spinal cord – Posterior (dorsal) root – contains only sensory axons § Dorsal Root Ganglion – swollen area containing sensory cell bodies – Anterior (ventral) root – contains both somatic motor and autonomic motor neurons

Spinal Reflexes n. A fast, involuntary sequence of actions that occurs in response to a particular stimulus in which integration takes place in the gray matter of the spinal cord

Reflex Arc n Sensory Receptor n Sensory Neuron n Integrating Center n Motor Neuron n Effector