Topography of the Brain Flashcards
What arteries supply the brain?
Internal carotid arteries and vertebral arteries (branches of subclavian)
What is the benefit of the circle of willis?
This is a protective feature against vaso-occulsion of large arteries. It provides a reservoir so that it is not fatal if an artery on one side of the circle in blocked.
What is dangerous about the branches off of the circle of willis?
Branches supplying the cerebral hemispheres, distal to the Circle are effectively ‘end arteries’. This is dangerous as if an embolus travels there, it will occlude that artery and block the brain supply to that region of the brain that it supplies.
What branches come off of the ICA?
The anterior (ACA), middle cerebral (MCA) and posterior communicating arteries (PComA)
What does the vertebral-basilar system supply?
Its branches supply the brainstem and cerebellum
Describe the blood supply of the cerebral arteries
- Anterior cerebral – medial aspect of cerebral hemispheres excluding occipital lobe
- Middle cerebral – lateral aspect of cerebral hemispheres
- Posterior cerebral – inferior aspect of cerebral hemispheres and occipital lobe
Describe the venous drainage of the brain
Superficial and deep veins of the brain drain into venous sinuses which lie between two layers of dura mater. They are enlarged spaces between the dura mater which are lined with endothelium. These then drain into the IJV.
What is the function of the brainstem?
- Pathway for fibre tracts running between higher and lower centres
- Brainstem nuclei are involved with 10 of the 12 cranial nerves, so innervation of head and neck
Name the different features of the medulla?
• Contains the 4th ventricle
• Continues as the spinal cord at foramen magnum of the cranium
• Surface features:
o Pyramids (tract) and their decussation (area where fibres cross over)
o Olives laterally
o Connected to the cerebellum by the inferior cerebellar peduncle
o Cranial nerves IX, X, XI and XII from its surface
What are the surface features of the pons?
- Middle cerebellar peduncle
* Cranial nerve V, VI, VII and VIII originate from its surface
What are the features of the midbrain?
• Develops from the metacephalon • Central cavity – cerebral aqueduct • Surface features: o Cerebral peduncle o Superior cerebellar peduncle o Colliculi (superior and inferior) o Origin of oculomotor (CN III) and trochlear (CN IV)
Describe the different parts of the cerebellum
- Right and left hemispheres are separated by Vermis
- Each hemisphere has an anterior, posterior and flocculonodular lobe
- Surface has sulci and folia
- Three cerebral peduncles connect it to the brainstem
- Two cerebellar tonsils
Why is the foramen magnum and cerebellum clinically important?
Foramen magnum leaves a groove in the cerebellum and inside the groove lies the tonsils.
If a tumours grows which increases intracerebral pressure or in trauma during surgery causing leaking of CSF which will decrease the pressure –> causes tonsillar herniation.
Name two function of the cerebellum?
- Posture maintenance
* Fine tuning motor activity
Where does the cerebellum receive information from?
- From pyramidal tracts (moto intention of brain)
- Ipsilateral proprioceptors from periphery
- Vestibular nuclei about balance and posture
It calculates the best way to coordinate force, direction, extent of muscle contraction to maintain posture prevents overshoot and ensures smooth coordinated muscle contraction
