Medulla Oblongata Lecture Notes

Overview

• Medulla Oblongata: One of the three sections of the brainstem.
  • Most inferior section; continuous with the pons (above) and spinal cord (below).

External Anatomy

Anterior Surface

• Anterior Median Fissure: Midline feature, continuous along the spinal cord.
• Sulci:
  • Ventral Lateral Sulcus
  • Posterolateral Sulcus
• Pyramids: Contain motor fibers (corticospinal tract).
• Olives: Lateral to the pyramids.
  • Contain olivary nuclei for movement coordination and movement-related learning.
• Inferior Cerebellar Peduncles: Connect medulla to the cerebellum.
• Cranial Nerves: IX, X, XI, XII emerge from this area.

Posterior Surface

• Posterior Median Sulcus: Midline structure, continuous with the spinal cord.
  • Conveys sensory input from below the neck.
• Gracilis & Cuneatus Tubercles: Lateral from the midline, carry sensory information (mainly touch) to the brain.

Internal Anatomy

Levels of the Medulla (Cross Sections)

1. Level of Decussation of the Pyramids

• Transition to the spinal cord.
• Decussation: Major crossing point for descending motor fibers.
  • Motor fibers from brain to periphery.
  • Includes tracts such as: Spinocerebellar, Lateral Spinothalamic (temperature, pain), and spinal tract for cranial nerve V.

2. Level of Decussation of the Medial Lemniscus

• Major crossing point for sensory fibers (touch, vibration).
• Fibers synapse at nucleus gracilis and nucleus cuneatus, then cross.
• Tracts Present: Spinocerebellar, Lateral Spinothalamic, and spinal tract for cranial nerve V.
• Nuclei:
  • Nucleus Gracilis
  • Nucleus Cuneatus
  • Spinal nucleus of cranial nerve V
  • Accessory nucleus
  • Hypoglossal nucleus (cranial nerve XII)

3. Level of the Olives and Inferior Cerebellar Peduncles

• Central canal expands into the fourth ventricle.
• Sensory & Motor Tracts: Medial Longitudinal Fasciculus, Spinocerebellar, Lateral Spinothalamic, Pyramidal
• Important Nuclei:
  • Olivary nucleus
  • Glossopharyngeal nucleus
  • Vagal nucleus
  • Spinal nucleus of cranial nerve V
  • Continuation of hypoglossal nucleus (cranial nerve XII)

Function

• Houses nuclei controlling vital functions: heart rate, breathing, blood pressure.
• Respiratory Center: Located in the pons and medulla.
• Vasomotor Center: Controls blood pressure, collects information influencing heart rate.

Blood Supply

• Vasculature varies by level.
• Major arteries: Vertebral, Posterior/Anterior Spinal, Posterior Inferior Cerebellar.

Summary

• Medulla Oblongata: Part of brainstem and continuous with spinal cord.
• Three levels: Olives, Medial Lemniscus Decussation, Pyramid Decussation.
• Functions: Motor command transmission, sensory information processing, vital function regulation.