Neuroanatomy High-Yield Reference
1. Medulla (Internal & Clinical)
Key Concept: The Medulla controls autonomic functions and contains the lower cranial nerve nuclei (IX, X, XI, XII).
| Structure | Detail & Clinical Relevance |
|---|---|
| Nucleus Solitarius | Visceral Sensory for Taste (VII, IX, X) and Baroreceptors (Carotid Body-IX, Aortic Arch-X). |
| Nucleus Ambiguus | Branchial Motor to Pharynx/Larynx (IX, X, XI). Lesion = Dysphagia, Hoarseness, Uvula deviates away. |
| Dorsal Motor Nucleus (X) | Parasympathetic output to heart/lungs/GI. |
| Pyramids | Contains Corticospinal Tract. Decussation marks the border between Medulla and Spinal Cord. |
2. Pons (Internal & Eye Movements)
Key Concept: The Pons is the bridge for Cerebellar communication and horizontal eye movements.
| Structure | Detail & Clinical Relevance |
|---|---|
| Medial Longitudinal Fasciculus (MLF) | Connects CN VI (Pons) to CN III (Midbrain). Allows conjugate gaze. Lesion (INO): Looking Left -> Right eye frozen. Convergence intact. |
| PPRF | Horizontal Gaze Center. Signals the ipsilateral VI nucleus to "Look out". |
3. Midbrain (The "Rule of 4" Top)
| Structure | Detail & Clinical Relevance |
|---|---|
| Superior Colliculus | Receives visual input for reflexive eye movements. Problem = Parinaud Syndrome (Cannot look up). |
| Substantia Nigra | Pars Compacta: Dopamine production. Depigmentation = Parkinson's. |
| Red Nucleus | Rubrospinal tract (Flexor tone). Lesion below = Decerebrate (Extension). |
4. Major Tracts (Exhaustive)
Corticospinal
Spinothalamic
DCML (Medial Lemniscus)
Horner's Pathway
| Tract | Function | Decussation Point |
|---|---|---|
| Dorsal Column (DCML) | Vibration, Proprioception. | Medulla (Internal Arcuate Fibers). |
| Spinothalamic (LSTT) | Pain, Temperature. | Spinal Cord (Anterior White Commissure, 1-2 levels above entry). |
| Lat. Corticospinal | Voluntary Motor. | Medullary Pyramids (Lower Medulla). |
| Spinocerebellar | Unconscious Proprioception. | Does NOT cross (Ipsilateral Ataxia). |