Spinal Cord

• Foramen Magnum  L1 – L2
• SkullL 1-2
• -Spinal Cord growth stops at 4years old
• -Vertebral column grows until full height reached
• - About 18 inches long
• -End of cord = conus medullaris

• 1.Cauda Equina (“horse’s tail”)
• -Spinal nerves are pulled with growing vertebrae.
• -Exit sacral foramina.
• 2. Filum Terminale tethers conusmedullaris to the sacral vertebrae, via coccygealligament.a.
• -Prevents superior movement.
• 3. Laterally, denticulate ligament anchors cord
• -Composed of Pia Mater attached to Arachnoid
• -Prevents lateral movement

• 1. Done between L3 & L4, or L4 & L5.
• 2. Reduce chance of spinal cord injury because it is BELOW tip of cord.
• 3. Sample of CSF taken from Sub-arachnoid space

• 1. Catheter inserted intoepidural space.
• 2. Left in place with continuous infused analgesic.
• 3. Long-term pain relief

• carries SENSORY impulses up towards brain,
• and MOTOR impulses down from the brain (TRACTS).

Motor/Efferent (Descending)

Sensory/Afferent(Ascending) --

Can act as an integration center!

1. Sensory input received

2. Signal travels down a sensory neuron

3. Info integrated by interneuron (NOT BRAIN)

4. Motor signal sent out by motor neuron

5. Motor signal travels to EFFECTOR and appropriate reaction occurs

• 1. Central in the spinal cord.
• 2. Contains Mostly cell bodies & unmyelinatedinterneurons.
• 3. Central Canal (CSF) surrounded by gray commissure.a. Neuron crossover site.

• 3. Arranged in 3 Horns
• a. Posterior (Dorsal) Horn
• b. Anterior (Ventral) Horn
• c. Lateral Horn

• Arranged in 3 Horns
• a. Posterior (Dorsal) Horn
• - Somatic & VisceralSensory fibers
• b. Lateral Horn
• - Visceral motor
• c. Anterior (Ventral) Horn
• - Somatic motor cell bodies
• Grey commisures
• - axons of interneurons

• 1. Peripheral in the spinal cord.
• 2. Contains Myelinated & unmyelinated axon.
• 3. Arranged in 3 Columns (Funiculi)
• a. Lateral Column
• b. Anterior Column
• c. Posterior Column

• 4. Each column contains “Tracts”:
• a. Axons that share structural or functional similarities.
• b. Tracts may travel in 3 directions…

• 1. Branch from spinal cord.
• 2. 31 pairs.
• 3. Carries BOTH sensory & motor neurons
• 4. Formed through fusion of ventral & dorsal ROOTS.
• 5. Innervates (connect with) muscles, skin, and glands of neck & body

• 6. Nerve splits to form:
• a. Dorsal Ramus
• 1) Innervating back!
• 2) T1-L2, only

• b. Ventral Ramus
• 1) Innervating sides & front!
• 2) Includes all plexuses!

• • Lumbar leads anterior
• • Sacral leads posterior

Nerve Plexuses (4)

• a. Nerve Network.
• b. All from ventral rami.
• c. Thoracic nerves don’t form plexus

• a. The area of the body that is monitored by a specific sensory nerve.
• b. Map of Somatic Sensory Innervation.
• c. Doctors use this to determine damage to nerves.

• 1. Mechanoreceptor
• a. Detect mechanical or physical change.
• b. Touch, vibration, pressure, stretch.

c. PROPRIOCEPTOR• detect position of body in space.

Detects heat or cold within range.

a. Detects chemical change.

b. Molecules dissolved in fluid

.c. Taste, smell, etc

Detect photons (light).

Detects tissue damage and pain.