Functional Organization of the Spinal Cord Chapter 12

Spinal Cord Landmarks The adult spinal cord is 18 inches long and.5 inches wide. It has cervical and lumbar enlargements of the innervation of the limbs. The spinal cord terminates at L 2 where the dorsal and ventral roots fan out like a horse’s tail (cauda equina).

Spinal Cord Protection

Meninges and cerebrospinal fluid (CSF) protect and stabilize the spinal cord. CSF fills the subarachnoid space between the arachnoid and pia matter meninges. Lumber puncture: diagnostic procedure (performed at L 3 ) to test CFS. Epidural space: located between bony vertebrae and dura matter. Filled with a soft padding of fat.

Spinal Bifida

Labeled Spinal Cord Cross-section

Spinal Cord Cross-section Landmarks Gray matter: cell bodies of multipolar neurons – Dorsal horns: sensory nuclei (visceral and somatic) – Ventral horns: motor nuclei (visceral and somatic) – Commissure: cross over White matter: myelinated axons of ascending and descending pathways – Posterior column: ascending (sensory) tracts – Anterior column: descending (motor) tracts

Paralytic Poliomyelitis Occurs in 1% of all poliovirus infections. Virus uses retrograde axonal transport to infect neuron cell bodies. In spinal polio, the virus invades the neurons of the anterior horn. What type of paralysis occurs?

Spinal Nerves

Spinal nerves: contain the axons of both sensory and motor neurons. Spinal nerve numbering: – Spinal nerves are numbered after the adjacent vertebrae Dorsal root: – Contain axons of sensory neurons – Ganglion: cell bodies of sensory neurons Ventral root: – Contain axons of motor neurons

Motor and Sensory Innervation Ramus: branch of spinal nerve Motor commands: – Dorsal ramus: Contain somatic and visceral fibers that innervate the back. – Ventral ramus: Contain somatic and visceral fibers that innervate body wall, surface, and limbs. – White ramus Contain motor preganglionic fibers that innervate the sympathetic ganglion. – Gray ramus: Contain postganglionic fibers that innervate glands and smooth muscles of the body wall and limbs.

Motor Fibers

Motor and Sensory Innervation Ramus: branch of spinal nerve Sensory information: – Dorsal ramus: Carries sensory info skin and muscles of the back. – Ventral ramus: Carries sensory info from body wall, surface, and limbs. – White ramus Carries sensory info from visceral organs.

Sensory Fibers

Dermatome The specific bilateral region of the skin surface monitored by a single pair of spinal nerves. Shingles: – viral infection (VZV) of the dorsal root ganglion. – The distribution of painful sores corresponds to the sensory nerve that is infected.

Nerve Plexus Complex network of interwoven nerves. There are 4 major plexuses in the human body: -Cervical -Brachial -Lumbar -Sacral