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Biology 201 Study Guide: Chapter 13 - Spinal Cord Functions and Anatomy

Functions of the Spinal Cord

  • The spinal cord serves as a major conduit for information traveling between the brain and the body. It coordinates reflexes and various body functions.

Gross Anatomy of the Spinal Cord

  • Regions:

    • Cervical Region: Supports the neck and upper limbs.
    • Thoracic Region: Corresponds to the chest area, connected to the ribs.
    • Lumbar Region: Relates to the lower back and legs.
    • Sacral Region: Relates to the pelvic area.

  • Enlargements:

    • Cervical Enlargement: Innervates the upper limbs.
    • Lumbar Enlargement: Innervates the lower limbs.

  • Special Structures:

    • Medullary Cone: The tapered end of the spinal cord.
    • Cauda Equina: A bundle of spinal nerves and spinal nerve rootlets.

Meninges

  • Three protective membranes covering the spinal cord:

    • Dura Mater: The outermost tough layer.
    • Arachnoid Mater: The middle layer; web-like.
    • Pia Mater: The innermost thin layer that directly covers the spinal cord.

  • Subarachnoid Space:

    • Contains cerebrospinal fluid (CSF), which cushions the spinal cord.

  • Epidural Space:

    • Area outside the dura mater, important for epidural anesthesia.

Key Ligaments

  • Terminal Filum: Anchors the spinal cord to the coccyx.
  • Coccygeal Ligament: A continuation of the terminal filum; provides stability.
  • Denticulate Ligaments: Help anchor the spinal cord laterally.

Spina Bifida

  • A congenital condition where the spinal cord fails to close properly.
    • Role of Folic Acid:
    • Vitamin B is crucial in preventing spina bifida during pregnancy.

Cross-Sectional Anatomy of the Spinal Cord

  • Fissures and Sulci:

    • Anterior Median Fissure: A deep groove on the anterior side.
    • Posterior Median Sulcus: A shallow groove on the posterior side.

  • White Matter vs. Gray Matter:

    • White Matter: Contains myelinated axons; organized into columns/funiculi.
    • Gray Matter: Contains neuron cell bodies; divided into:
    • Posterior (Dorsal) Horns: Houses sensory neurons.
    • Anterior (Ventral) Horns: Contains motor neurons.
    • Gray Commissure: Connects both sides of the gray matter.
    • Central Canal: Hollow center filled with CSF.

Neural Pathways

  • Sensory (Afferent) Fibers:

    • Located in the posterior (dorsal) root; carry sensory information to the spinal cord.

  • Motor (Efferent) Fibers:

    • Located in the anterior (ventral) root; send motor commands from the spinal cord to the body.

  • Neuron Somas:

    • Motor Neuron Somas: Located in the anterior (ventral) horn.
    • Sensory Neuron Somas: Located in the posterior (dorsal) root ganglion (unipolar neurons).

Spinal Cord Tracts

  • White Matter Columns/Funiculi:
    • Posterior Columns (Funiculi): Ascending tracts; carry information to the brain.
    • Lateral and Anterior Columns (Funiculi): Various tracts for motor and sensory relay.

Important Terms

  • Decussation: Crossing over of nerve fibers from one side of the body to the other.
  • Contralateral: Refers to the opposite side of the body.
  • Ipsilateral: Refers to the same side of the body.

Information Transfer

  • Understanding how information passes between the brain and spinal cord is crucial for grasping spinal cord functionality.