Functional Neuroanatomy Flashcards
What does stroke damage to anterior cerebral artery affect?
Lower limb
What does stroke damage to posterior cerebral artery cause?
Vision deficit
What does stroke damage to middle cerebral artery cause?
Loss of sensation + motor control of arm, hand, face + linguistic function on left
Why is the middle cerebral artery vulnerable to clots or emboli?
Continuation of internal carotid so clots likely to travel into it
What is the arterial supply of the brainstem?
- Internal carotid
- Basilar
- Vertebral x 2
What is meant by contralateral circulation?
If one vessel damaged and supply compromised, can be taken over by another
What can a brainstem stroke lead to?
- Involving vertebral + basilar arteries = high mortality
- Life support functions - breathing, chewing + swallowing via cranial nerves
- Coma due to damage to ARAS
What is seen in lateral medullary syndrome?
- Occlusion of PICA
- Contralateral loss of pain + temp on body (spinothalamic)
- Ipsilateral loss of pain + temp on face (trigeminal)
- Dysphagia, hoarseness, loss of gag reflex (nucleus ambiguous, roots of vagus + glossopharyngeal)
- Ipsilateral Horner’s syndrome (hypothalamopsinal fibres)
What is the arterial supply of the brainstem?
- Internal carotid
- Basilar
- Vertebral x 2
What is meant by contralateral circulation?
If on vessel damaged and supply compromised, can be taken over by another
What can a brainstem stroke lead to?
- Involving vertebral + basilar arteries = high mortality
- Life support functions - breathing, chewing + swallowing via cranial nerves
- Coma due to damage to ARAS
How are glial cells different from most neuronal cells?
Retain ability to divide throughout lifetime
What do brain tumours contrain?
Only glial cells (gliomas) or cells of meningeal coverings of brain (meningiomas)
What are the roles of astrocytes?
- Control extracellular ion concentrations (esp K)
2. Remove and deactivate transmitters (esp glutamate)
What do oligodendrocytes form?
Myelin sheath
What is necrosis?
- General cell injury
- Cell ruptures = inflam reaction
What is apoptosis?
- Programmed cell death
- Due to loss of trophic factors needed for cell to survive
- Via proteolytic enzymes (caspases) + DNAses
= Apoptotic bodies = phagocytosed by microglia - No inflam response
- Triggered by injury
Summarise axonal regeneration
- Triggered by IC Ca entering cytosol + activating protease which breaks down cytoskeleton
- Schwann cells phagocytose debris + secrete tropic factors > promoting axonal growth
- Schwann cells de-differentiate but stay within basal lamina
- Invading macrophages secrete factors = promote Schwann cell migration + axon growth
What is CNS response to injury?
- Blood borne monocytes + macrophages invade
- Microglia multiples + activate to remove debris
- 24hrs - oligodendrocyte precursors (OPCs) divide + hypertrophy - astrocytes follow
- Astrocyte process link together = barrier around lesion
- Meningeal like cells invade lesion forming plug
- Glial scar formation
Why is there a lack of axonal regeneration?
- Regrowth physically blocked by glial scar formation + chemically by inhibitory molecules:
1. Even small lesions that don’t seem to disrupt glial structure may inhibit
2. Regions of glial transitions may form barrier to regrowth
3. Inhibitory molecules block growth of adult axons but not embryonic (Nogo A)
4. Astrocytes produce inhibitors (CSPGs)
5. Macrophages produce molecules toxic to neurons
What is diffuse axonal injury associated with?
- Coup (injury under site of impact) + contracoup (injury on side opposite area hit)
- May remain comatose or go into persistent vegetative state (due to disturbance of ARAS in brainstem)
- Cerebral concussion = mild form
What is seen on the histology of DAI?
Damaged axons = brown using antibodies to B amyloid prescursor protein
What are petechial haemorhages?
- Often associated with DAI
- Indicate severe brain injury even in absence of any midline shift
What are coup and contracoup injuries associated with?
- Cerebral contusions (bruised brain)
- Rupture of bridging veins between brain surface + dural sinuses (slow subdural haemorrhage)
