CNS Study Guide Part 2

Flow of Cerebrospinal Fluid (CSF)

• Pathway:
  • Lateral Ventricles
  • Interventricular Foramen
  • Third Ventricle
  • Cerebral Aqueduct
  • Fourth Ventricle
  • Lateral (Luschka) & Medial (Magendie) Apertures
  • Subarachnoid Space
  • Arachnoid Granulations (resorption)
• Production: CSF is produced in the choroid plexus.
• Functions:
  • Buoyancy: Reduces the net weight of the brain.
  • Chemical Buffer: Maintains stable chemical environment.
  • Physical Protection: Cushions the brain against trauma.
• Clinical Relevance:
  • Hydrocephalus: Condition characterized by excess CSF due to:
  • Overproduction
  • Blockage
  • Poor absorption

Internal Carotid Artery Branches

• Anterior Cerebral Artery (ACA):
  • Branches: Pericallosal, Callosomarginal
  • Supplies: Medial aspects of frontal & parietal lobes
• Middle Cerebral Artery (MCA):
  • Branches: Superior/Inferior divisions, Sulcal arteries, Lenticulostriate arteries
  • Supplies: Lateral aspects of hemispheres, Broca's & Wernicke's areas
  • Strokes:
  • ACA Stroke: Leg weakness
  • MCA Stroke: Face/arm weakness, aphasia

Vertebral Artery Branches

• Pathway:
  • Vertebral arteries merge to form Basilar artery
  • Basilar artery gives rise to Posterior Cerebral Arteries (PCA)
• Branches of PCA:
  • Calcarine artery
  • Medial occipital artery
  • Parieto-occipital artery
• Supply: PCA supplies occipital lobe, midbrain, and visual cortex
• Cerebellar Arteries:
  • Superior Cerebellar Artery (SCA)
  • Anterior Inferior Cerebellar Artery (AICA)
  • Posterior Inferior Cerebellar Artery (PICA)
• Spinal Cord Supply:
  • Anterior & Posterior spinal arteries
• Clinical Relevance:
  • PCA Stroke: Visual loss
  • Cerebellar Infarcts: Ataxia, vertigo

Circle of Willis

• Components:
  • Anterior Communicating Artery
  • Anterior Cerebral Arteries (ACA)
  • Internal Carotid Arteries
  • Posterior Communicating Arteries
  • Posterior Cerebral Arteries (PCA)
  • Basilar Artery
• Function: Provides collateral blood flow at the base of the brain
• Mnemonic: "A Communicates, Carotids Curve to Middle, Posterior Communicates to Posterior Cerebral"

Practice Questions

1. Trace the flow of CSF through its pathway.
2. Identify the arteries supplying the primary motor cortex.
3. Which structure connects the third and fourth ventricles?
4. What deficits are associated with an MCA stroke?
5. Draw and label the Circle of Willis.
6. Which artery is implicated in Wallenberg syndrome?