Blood supply to the CNS Flashcards
What proportion of the CO, oxygen consumption, and liver glucose does the Brain demand
10-20% CO
20% O2 consumption
66% liver glucose
What are the two sources of blood supply to the brain
Interbal carotid arteries
Vertebral arteries
(Circle of Willis -> Cerebral arteries)
What is the venous drainage system for the brain
Cerebral veins drain into Venous sinuses from Dura mater at the back of the head
Drainage into the Internal jugular vein
Define stroke
rapidly developing focal disturbance of brain function of presumed vascular origin and of >24 hours duration
What are the causes of stroke
Infarction (85%)
Haemorrhage (15%)
Define Transient Ischaemic attack (TIA)
rapidly developing focal disturbance of brain function of presumed vascular origin that resolves completely within 24 hours
Define infarction
Degenerative changes which occur in tissue following occlusion of an artery
Define cerebral ischaemia
Lack of sufficient blood supply to nervous tissue resulting in permanent damage if blood flow is not restored quickly
What are the causes of occlusions
Thrombosis (formation of a blood clot)
Embolism (plugging of small vessel by material carried from larger vessel)
What are the risk factors for stroke
Age Hypertension Cardiac disease Smoking Diabetes mellitus
What occurs if stroke occurs due to the anterior cerebral artery
Paralysis of contralateral leg > arm, face
Disturbance of intellect, executive function and judgement (abulia)
Loss of appropriate social behaviour
What occurs if stroke occurs due to the middle cerebral artery
“Classic stroke” Contralateral hemiplegia: arm > leg Contralateral hemisensory deficits Hemianopia Aphasia (L sided lesion)
What occurs if stroke occurs due to the posterior cerebral artery
Visual deficits
homonymous hemianopia
visual agnosia
What is a lacune
Small cavity
What is a lacunar infarct
Appear in deep structures as a result of small vessel occlusion
Deficit is dependent on anatomical location
generally associated with hypertension
What are the three layers of the meninges from the outermost layer and describe them
Dura mater - tough and protective, adherent to bone, space between forms sinuses
Arachnoid mater - thin membrane attached to the dura
Pia mater - delicate membrane closely adherent to the brain and spinal cord
Which layer of the meninges contains CSF
Subarachnoid space between arachnoid mater and Pia mater contains the CSF
Describe epidural haemorrhage
arterial bleeding
headache, drowsiness, vomiting, seizure
promptly after injury
between dura mater and skull
Describe subdural haemorrhage
between Pia mater and dura mater
venous bleeding
headache, drowsiness, vomiting, seizure
symptoms delayed by days or weeks
Describe extradural haemorrhage
Trauma, immediate effects
What are subarachnoid haemorrhages often due
Often due to ruptured aneurysms (Berry aneurysms)
Describe intracerebral haemorrhage
spontaneous hyper-tensive
Describe the circle of willis
Basilar artery sits in front of the pons
Basilar splits to give the two posterior cerebral artery
Middle cerebral artery is the largest form the internal carotid -> anterior cerebral artery
Small anterior communicating artery between two anterior cerebral artery
Compensatory flow means that it can supply blood even when a carotid artery is blocked
Which parts of the brain do the cerebral arteries supply
Anterior cerebral artery perfuses frontal lobe and strip across top
Middle cerebral artery supplies lateral part of brain
Posterior cerebral artery supplies occipital lobe and inferior part of the temporal lobe
