Spinal Cord Overview
Cross Section
I. Gray Matter (axons extend outside spinal cord to form spinal nerves)
a. Dorsal horn- somatic afferent (dorsal root)
b. Ventral horn- somatic efferent (ventral root)
c. Lateral horn (located at thoracic and upper lumbar)- ANS sympathetic
d. Gray Commisure
II. White matter
a. Types of white matter columns (funiculi)- dorsal, lateral, and ventral
b. Direction of white matter columns (tracts) in spinal cord
i. Decussation- crossing of nerves fibers to contralateral side
ii. Ipsilateral- fibers course on same side
Spinal Cord Ascending Tracts (fasciculi)
- naming convention “spino-“- carry sensory impulses up tract
iii. Multiple neuron pathways
1. 1st order neuron- detects stimulus at receptor and transmits to spinal cord or brain stem
2. 2nd order neuron- to thalamus
3. 3rd order neuron- to sensory cerebral cortex
iv. Types
1. Dorsal Column (Medial/lamniscal)
a. Gracile fasciculus- transmits sensory information on position and movement of lower trunk
b. Cuneate fasciculus- tranmits sensory information on position and movement of upper trunk
c. 3 neuron pathway
d. Decussation of in medulla oblongata
1. Anterolaterial System
a. Spinothalamic- pain, temp, pressure, tickle, itch in the skin
i. 3 neuron pathway
ii. Decussation in the spinal cord
b. Spinoreticular- pain in the skin
2. Dorsal and ventral spinocerebellar- proprioception in joints and tendons
a. 2 neuron pathway to cerebellum
b. No decussation of nerve fibers
a....