Transcript Functional Organization of the Spinal Cord

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 L2 where the dorsal and
ventral roots fan out like a
horse’s tail (cauda equina).
Spinal Cord Protection
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 L3) 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
• 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