Spinal Cord Structure and Function

Spinal Cord Structure

• The spinal cord is a long, slender column of nervous tissue, extending from the medulla oblongata of the brainstem to the lumbar region of the vertebral column.
• It's roughly cylindrical, but slightly flattened in anterior and posterior directions.
• It's divided into 31 segments (cervical, thoracic, lumbar, sacral, and coccygeal).
• Each segment gives rise to a pair of spinal nerves.

Gray Matter vs. White Matter

• The spinal cord's internal structure is composed of gray and white matter.
• Gray matter forms an H-shaped region centrally, with anterior and posterior horns. It contains neuron cell bodies, dendrites, and glial cells. Sensory and motor functions originate and terminate here.
• White matter surrounds the gray matter and contains myelinated axons (nerve fibers). These axons form ascending sensory and descending motor tracts that transmit signals to and from the brain.

Protective Structures

• The spinal cord is encased and protected by several layers:
  • Vertebral column: The bony structure that houses and supports the spinal cord.
  • Meninges: Three layers of protective membranes (dura mater, arachnoid mater, and pia mater) that surround the cord and fill the space between the cord and the vertebral column.
  • Cerebrospinal fluid (CSF) fills the subarachnoid space (between the arachnoid and pia mater) cushioning the spinal cord against impact.
• These structures work together to physically protect the spinal cord from damage.

Functions of Spinal Tracts

• Spinal tracts are bundles of axons that carry signals between the brain and the rest of the body.
• Sensory tracts (ascending) transmit information from the periphery to the brain.
• Motor tracts (descending) transmit signals from the brain to the muscles and glands.
• Different tracts have specific functions, such as carrying signals for pain, temperature, touch, or motor commands.

Spinal Cord Segments

• Each segment corresponds to a region of the body served by the spinal nerves emerging from that segment.
• Spinal nerves carry sensory and motor information to/from the body region they innervate.
• The spinal cord's segmental organization is crucial for its function, allowing for precise nerve innervation based on location.