Blood supply to CNS Flashcards
How large is the brain and how much body ressources does it use?
2% of body mass by 20% of CO, 20% of O2 consumption, and 68% of glucose
So need a large blood supply
What arteries go to the brain?
Internal carotid arteries and Vertebral arteries
They anastamose at the base of the brain to form the circle
Where does the internal and external arteries branch?
Around the adams apple-
External goes to face and neck blood supply
Internal Goes uninterupted to the brain-arrive laterally to the brain and join with circle of willis
Where does the vertebal arteries lie?
exit as first branch of subclavian-throught the cervical and exit by the magnum foramen. Join back at circle
Describe the circle of willis
Vertebral artery arrives posteriorly, and forms the basilar artery-sits right in front of pons
Splits each side in Posterior cerebral artery
Internal carotid becomes middle cerebral artery-communicates with posterior cerbral with posterior communicating
Also anterior communicating bewteen two anterior cerebral artery (which connect with middle cerebral artery)
What are the main venous drainages of the brain?
Cebreral veins join back up in numerous venous sinus-made by fold of dura mater (epidural)-then all collect at back of the head
Main one, along top is superior saggital sinus
Inferior saggital sinus becomes straight sinus and then join
exit via transverse sinus, then sigmoid sinus and then the carotid veins
What is a stoke?
Also called CVA-rappidly developmig focal disturbance of brain function
85%-clot
15% - artherosclerosis
What is a TIA?
Transient Iscaemic attack
Rapidly developing focal distrubance of brain function
BUT FULLY RESOLVE in 24H
Temporary blockage-bit of block but cleared
But suggest risks of stroke
Define infarction
Degenerative changes in a tissue, following loss of blood supply-dead
Define ischaemia
Lack of sufficient blood supply resulting in permanent damage - hypoxia/anoxia (only oxy) but ischeamia causes a lot more
What are the 2 causes of occulusions
thrombosis-static blood anywhere starts thrombus and can migrate
Embolism-Plugging of small vessel by material (anything-like thrombi)-like heart artherosclerosis debros
What changes could you observe on a patient with a vascular problem
Vascularture can be blown appart, yellow (fatty deposits) or can see infacted tissue (blacker) in brain
What are the main risk factors for stroke?
Age, Hypertensions (hemorhagic stroke), Cardiac disease, Smoking, diabetes miellitus
Mostly lifestyle
Which parts of the brain are perfused by which arteries?
Anterior cerebral artery does the top and front of brain and back until occipital lobe–supplies lower limbs
Middle cerebral artery-lateral fields and central brain (exept top strip)-torso, etc, and other
Posterior cerebral-mostly occipital and goes down and does part of temporal lobes
What issues do you expect to see with some one with an anterior cerebral artery issue?
Paralysis of contralateral legs (over arms)
Distrubance of intellect, executive and function and judgment (front brain)
Loss of appropriate social behavior (front brain)
What issues do you expect to see with some one with an middle cerebral artery issue?
“classic stroke”-Contralateral hemiplegia (arm>leg)
Contralateral hemisensory deficits
hemianopia (as eye fibers pass through)
Aphasia (On the L side only)
What issues do you expect to see with some one with an posterior cerebral artery issue?
Visual deficits- Homymous (both sides in both eyes) Hemianopia (loss of visal field) Visual agnosia (recognising what is in front of you)
What issues do you expect to see with some one with an lacunar infarcts?
Lacunar infarcts represent strokes happening in life
associated with hypertension but not always symptomatic
What are the 4 types of haemorrhagic stroke?
Extradural, subdural, subarachnoid, intracerebral
What issues do you expect to see with some one with an haemorrhagic stroke?
Extradural-trauma-immediate-arterial-rupturing of bridging veins-blood creates the space.often central to where bone joint-increase of brain pressure until death
Subdural-venous-(already space there-where the blood accumulates)-Trauma-delayed. again rupture of bridging veins but sub dura. Often presents quite a while after head injury + loss of conciousness
Subarachnoid-where all the arteries vessels are-ruptured aneurysm (often born with weaknesses in vessels)
Intracerebral-spontaneous due to hypertension
