Spinal Cord Structure and Function
Overview of the Spinal Cord
- Ventral Root & Dorsal Root
- Dorsal Root Ganglion: A cluster of cell bodies where sensory information enters the spinal cord.
- Ventral Root: Carries motor information away from the spinal cord.
- Spinal Nerve: Formed from the merging of the dorsal and ventral roots.
- Sensory Information
- Entering through the dorsal root.
- Specifically associated with the posterior (back) horns of the spinal cord.
- Motor Information
- Exiting through the ventral root.
- Related to the lateral and anterior horns of the spinal cord.
Spinal Cord Tracts
- Definition: Collections of fibers (axons) in the Central Nervous System (CNS).
- Two Main Types:
- Ascending Tracts: Carry sensory information up the spinal cord to the brain.
- Descending Tracts: Carry motor information down the spinal cord from the brain.
Naming of Tracts
- Tracts are typically named based on their origin and termination.
- Examples:
- Ascending Tracts:
- Spinothalamic Tract: Originates in the spinal cord and terminates in the thalamus (relays sensory information).
- Lateral Spinocerebellar Tract: Originates in the spinal cord, terminates in the cerebellum (involved in proprioception).
- Descending Tracts:
- Corticospinal Tract: Originates in the cortex of the cerebrum, terminates in the spinal cord (responsible for voluntary motor control).
Neuronal Pathways
- Sensory Neuron Pathway:
- Sensory neurons enter through back of the spinal cord, travel up through ascending tracts to specific locations in the brain (e.g., cerebellum or thalamus).
- Motor Neuron Pathway:
- Motor commands originate from the cortex, descend through the corticospinal tract, exit the spinal cord via the ventral root to stimulate muscles.
Summary
- Sensory information is always ascending, while motor information is descending in the spinal cord.
- Understanding the organization of spinal cord tracts facilitates comprehension of how the body processes and responds to sensory and motor information.