Central Nervous System: The Spinal Cord

Spinal Cord It is about 18 inches long. Extends from the brain to the 1st or 2nd lumbar vertebrae. Long cylinder, 31 continuous segments. Each segment contains a pair of spinal nerves. Relay information from PNS to CNS. Cervical Enlargement: Swelling in the spinal cord that serves the upper appendages. Lumbrosacral Enlargement: Swelling in the spinal cord that serves the lower appendages.

Connective Tissue Coverings of the Spinal Cord Dura Matter: outer most covering of the spinal cord Not attached to the vertebral column, has a space(epidural block) filled with; connective tissue, blood vessel, and adipose tissue. Epidural Block: injection of anesthesia to the epidural space to block pain from spinal nerves in that area. Archnoid: Middle layer, contains collagen & elastic fibers. Pia Matter: Inner layer attached to the neural tissue, contains a network of blood vessels.

Structures of the Spinal Cord External Structures: Conus Medularis: Location where spinal cord tapers(L2). Caudia Equina: “Horse’s Tail”; collection of nerves that extend beyond the end of the spinal cord.

Structures of the Spinal Cord Internal Structures: Anterior & Posterior Medial Sulcus: Fissures(grooves) that divide the spinal cord into right and left halves. Central Canal: Narrow passageway filled with cerebrospinal fluid (center of cord). Gray Matter: Forms “H” or butterfly shape in the center of the cord. Contains unmyelinated fibers & neuroglia that “integrate” Contains; motor, sensory, & association neurons.

Structures of the Spinal Cord Internal Structures (cont.) White Matter Surrounds the gray matter. Contains mostly myelinated neurons that relay information from sensory to motor neurons. Contains two tracts that carry information to and from the brain.(Ascending Tract, Descending Tract)

Anatomical Structures of the Spinal Cord

Function of the Spinal Cord Conduction Pathways: Ascending Tract: Carries sensory information to the brain. Descending Tract: Conveys motor commands from the brain.

Function of the Spinal Cord Reflex Arc: Rapid way of responding to an emergency situation, impulse only travels through the spinal cord, not to the brain. Receptor: Sensory receptor end of dendrite that senses change. Sensory Neuron: Carries impulse to spinal cord. Association Neuron: Connects sensory neruron to motor neuron (carries out response) to illicit response.

Function of the Spinal Cord Reflex Arc: Somatic Reflex: Effect skeletal muscle (withdrawal reflex, patellar reflex). Visceral Reflex: Effects smooth or cardiac muscle (heart rate, breathing, vomiting, sneezing, coughing).

Reflex Arc

Damage & Disease Quadriplegia- Damage to the 4th or 5th cervical vertebrae that produces paralysis to the upper and lower limbs. Paraplegia- Damage to the thoracic vertebrae that produces paralysis to the lower limbs. Meningitis (spinal or cerebral)- Bacterial or viral infection of the coverings of the spinal cord or brain, affects the blood supply or cerebrospinal fluid resulting in the death of neurons.