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.