basic topography of brain 2 Flashcards
what does the medulla continue as and where?
spinal cord at foramen magnum
what are the 4 surface features of the medulla?
- Pyramids and their decussation (crossing over)- crossing region of the cortical spinal fibres
- Olives laterally
- Connected to cerebellum by inferior cerebellar peduncle
- Cr N 9, 10, 11 and 12 from its surface
what are the cerebellar peduncles?
fibres that connect cerebellum to brainstem
how many cerebellar peduncles are there?
3 - superior, middle and inferior
where is the grey matter in the cerebrum and cerebellum?
on the surface
what is the reticular activating system and where is it found?
co-ordinates wakefulness and sleep-wake transitions through neurons being fired; sits in brainstem
what are the 2 surface features of the pons?
- middle cerebellar peduncle
- Cr N 5-8 originate from its surface
where does midbrain develop from?
mesencephalon
what are the 4 surface features of the midbrain?
- cerebral peduncle
- superior cerebellar peduncle
- origin of trochlear and oculomotor nerves
- corpora quadrigemina (superior and inferior colliculus)
label this:
1- Cerebral aqueduct
2- Red nucleus
3- Substantia nigra
4- Superior colliculus
where is CSF formed?
by choroid plexus in each ventricle
where is CSF absorbed?
by arachnoid villi
what are arachnoid villi?
finger like projections of arachnoid membrane that act as one way valves.
how do arachnoid villi work in absorbing CSF into venous circulation?
The pressure of the CSF is higher than venous system, so CSF flows through villi and granulations into blood
what are the 2 main branches of blood supply of the brain?
- The two Internal Carotid arteries enter the skull through the carotid canal
- The two Vertebral arteries also enter the skull through the foramen magnum to supply the brain.
Outline the Circle of Willis
what is the circle of willis a protective feature against?
vaso-occlusion of large arteries; even if deficit in one artery, brain will not suffer
what happens if there is occlusion in an end artery distal to circle of willis?
no more anastomosis of arteries as they are end arteries, which makes the brain more susceptible to stroke if the occlusion occurs there
what are the territories supplied by the cerebral arteries?
- Ant Cerebral arteries- medial surface of cerebral hemisphere
- Middle cerebral- lateral aspect of cerebral hemispheres
- Posterior cerebral- inferior aspect of cerebral hemispheres and occipital Lobe
where do superficial and deep veins of the brain drain into?
venous sinuses
where do venous sinuses lie?
between 2 layers of dura
where do the venous sinuses ultimately drain into?
internal jugular veins
what are 5 features of the cerebellum?
- right and left hemispheres separated by vermis
- each hemisphere has an anterior, posterior and flocculonodular lobe
- surface has sulci and folia (instead of being called gyri, are called folia- look like leaf)
- 3 cerebellar peduncles connect it to brainstem
- cerebellar tonsils sit just on top of foramen magnum
why are the cerebellar tonsils significant?
Sudden changes in intra cranial pressure can cause herniation of them out into foramen magnum
what are 2 things the cerebellum controls?
- posture maintenance
- fine tuning motor activity
how does info from the pyramidal tracts get to the cerebellum?
via superior cerebellar peduncles
what is the abnormality linked with the cerebellum?
ataxia
what is ataxia?
lack of voluntary coordination of muscle movements
how can you test for ataxia?
- finger-nose test
- knee-heel test
- walking in a straight line
