Blood Supply to the CNS Flashcards
How much CO goes to the brain?
10-20%
How much glucose consumption is done by the brain?
66%
2 sources of blood supply to the brain?
Internal carotid arteries
Vertebral arteries
Path of the internal carotid arteries?
(internal branch of CC)
Goes through carotid canal in base of skull
Path of the vertebral arteries?
(branch of the SCV artery)
Goes through the foramen magnum (as associated w. cervical vertebrae) to fuse and form the basilar artery
What protects the vertebral arteries?
Vertebral transverse foramina
What part of the brain circulation do the vertebral arteries form?
Posterior circulation (of the brain)
What do the internal carotid arteries and vertebral arteries give rise to?
Circle of Willis - anastomotic circuit of vessels that supplies the brain
What comes off the Circle of Willis?
Cerebral arteries
LOOK AT ONENOTE PICTURE!!!
What part of the brain circulation do the internal carotid arteries form?
Anterior circulation (of the brain)
What do the internal carotid arteries go on to become?
Middle cerebral artery
What does the basilar artery spilt into to form?
Posterior cerebral artery
What does the basilar artery sit infront of?
Pons
Which artery goes into the longitudinal fissure between the hemispheres?
Anterior communicating artery
connects L and R anterior cerebral artery across the L.F
4 things that mediate venous drainage of the brain
Cerebral veins
Venous sinuses
Dura mater
IJV
What forms the venous sinuses?
Falx
Folds of the dura mater (as 2-layers)
Where is the blood from the brain drained into?
Into the BACK of the head to the IJV
Stroke (or CVA) definition?
Rapidly developing focal disturbance of brain function of presumed vascular origin
AND
of >24 hours duration
Two reasons for why a stroke can happen?
Infarction (85%)
Haemorrhage (15%)
TIA?
Transient Ischaemic Attack
TIA definition?
Rapidly developing focal disturbance of brain function of presumed vascular origin that resolves completely within 24 hours
(temporary blockage - warning of a stroke)
2 causes of occulusions?
Thrombosis
OR
Embolism
5 main risk factors for stroke?
Age Hypertension Cardiac disease Smoking Diabetes mellitus
Part of brain middle cerebral artery is supplying?
Lateral parts of the brain - frontal lobe (large part) and temporal & parietal lobes (lateral surface)
Also supplies sub-cortical grey matter towards centre of brain
Part of brain anterior cerebral artery is supplying?
Mid-saggital part of brain - frontal lobes (midline) and parietal lobes (superior medial) [uptil parieto-occipital fissure]
Part of brain posterior cerebral artery is supplying?
Occipital lobes
What happens if ACA is occluded?
Paralysis of contralateral leg > arm, face (as supplies motor cortex)
Disturbance of intellect, executive function & judgement
Loss of appropriate social behaviour
What happens if MCA is occluded?
'’Classic stroke’’
Contralateral hemiplegia: arm>leg
Contralateral hemisensory deficits (behing central gyrus have 1o sensory cortex)
Hemianopia & aphasia
What happens if PCA is occluded?
Visual deficits!!!
Homonymous hemianopia
Visual agnosia
Where does lacunar infarcts happen?
Lacune is a small cavity - forms after a stroke as causes these small holes to form in the brain tissue
Explain how lacunar infarcts appear
Appear in deep structures as a result of small vessel occlusion
Results of a lacunar infarction?
Deficit depends on anatomical location
Happens during life - area has often been infarcted and then cleared away (via phagocytosis) leaving a lacuna
What are lacunar infarcts associated with?
Hypertension
4 different types of haemorrhagic strokes?
Extradural - trauma, immediate effects
Subdural - trauma, delayed effects
Subarachnoid - ruptured aneurysms
Intracerebral - spontaneous hypertensive
Extradural bleed?
Due to rupture of meningeal artery - arterial bleed
Subdural bleed?
Due to rupture of veins - venous bleed
Superior sagittal sinus?
Biggest sinus - CSF leaks into here
