Neuro 4: Anatomy of blood flow in CNS + Consequences of disruption Flashcards
The brain uses up _____% of cardiac output
10-20%
What are the 2 sources of blood supply to the brain?
- internal carotid arteries (front)
- vertebral arteries (back)
The 2 sources of blood supply to brain gives rise to network of cerebral arteries called _________
cerebral arteries come off the circle
Circle of Willis.
External carotid supplies the ______
Internal carotid supplies the _______
External carotid supplies the face
Internal carotid supplies the cerebral hemispheres
Vertebral arteries branch off the ________
and make their way through the _______ ________ (in the cervical vertebrae)
and through the ______ _____ into the brain
Vertebral arteries branch off the subclavian arteries
and make their way through the TRANSVERSE FORAMINA
and through the ________ _______ into the brain
What is the ventral view of the brain?
- from underneath
the two vertebral arteries at the bottom join together to form the _______ _____
the two vertebral arteries at the bottom join together to form the Basilar Artery
The basilar artery bifurcates –> to form the ____ ______ _____
The basilar artery bifurcates –> to form the posterior cerebral arteries
The internal carotid arteries travel superiorly, then heads laterally —> forming the ______ _____ ______
and
they also branch to form the ______ ______ _____
The internal carotid arteries travel superiorly, then heads laterally —> forming the middle cerebral arteries
((They emerge through the fissure btw frontal, parietal + temporal lobes))
and they also branch to form the anterior cerebral arteries
Why is the arrangement of arteries circular?
- if one side gets occluded, there is still another route for blood to travel.
What are the 4 main veins that drain the cerebral hemispheres via the jugular system?
- cerebral veins
- venous sinuses
- dura mater
- internal jugular vein
Dural Venous sinuses:
Running along the top, housed between the 2 folds of dura –>
at bottom of dural fold –>
Dural Venous sinuses:
Running along the top, housed between the 2 folds of dura –> Superior Sagittal Sinus
at bottom of dural fold –> Inferior Sagittal Sinus
The superior + inferior sagittal sinus runs backwards to form a large blood filled space called –>
The superior + inferior sagittal sinus runs backwards to form a large blood filled space called –> CONFLUENCE OF THE SINUSES
DEFINE stroke:
DEFINE stroke:
- rapidly developing focal disturbance of brain function of presumed vascular origin, lasting more than 24 hours
(85% due to infarction, 15% due to hemorrhage)
Define Transient Ischemic Attack (TIA)
Define Transient Ischemic Attack (TIA):
- rapidly developing focal disturbance of brain function of presumed vascular origin that resolves completely within 24 hrs
What is an infarction?
- degenerative changes that occur in tissues following occlusion of an artery
What is Cerebral Ischaemia ?
- lack of sufficient blood supply to the nervous tissue
- -> resulting in permanent damage if blood flow is not restored quickly.
–> due to hypoxia/anoxia
What are 2 major causes of Occlusions?
- Thrombosis
- Embolism
What are 5 main risk factors for stroke?
- age
- hypertension
- cardiac disease
- smoking
- diabetes mellitus
Middle cerebral artery extends laterally
–> supplies __ of the lateral hemisphere
Middle cerebral artery extends laterally
–> supplies 2/3 of the lateral hemisphere
The posterior cerebral artery supplies the ____ and ____ parts of the posterior part of the hemisphere.
The posterior cerebral artery supplies the MEDIAL and LATERAL parts of the posterior part of the hemisphere.
The anterior cerebral artery supplies the _____ part of the hemisphere
The anterior cerebral artery supplies the medial part of the hemisphere
What might happen in disturbance of the anterior cerebral artery?
- paralysis of contralateral leg more common than arms
- disturbance of intellect, executive function + judgement
- loss of appropriate social behavior
What might happen in disturbance of the middle cerebral artery?
- “classic stroke”
- contralateral hemiplegia (arm >leg)
- contralateral hemisensory deficits
- hemianopia
- aphasia (L-sided)
- -> can’t speak
What might happen in disturbance of the posterior cerebral artery?
PCA supplies the occipital lobe (which has the primary visual cortex)
- this leads to visual defects
- -> homonymous hemianopia
- -> visual agnosia
- -> can’t recognize things you see
What is a lacunar infarct?
- stroke causes small holes (lacunae) as brain tissue dies
- occurs due to small vessel occlusion.
- may also occur due to hypertension
- symptoms = dependent on anatomical location of vessel that has been occluded
What are the different classifications of haemorrhagic stroke?
- extradural
- subdural
- subarachnoid
- intercerebral
How do the different subtypes of hemorrhagic stroke differ?
- extradural
- subdural
- subarachnoid
- intercerebral
EXTRADURAL
- from trauma
- immediate effects
SUBDURAL
- from trauma
- has delayed effects
SUBARACHNOID
- due to ruptured aneurysms
INTRACEREBRAL
- due to spontaneous hypertensive rupture of small vessels
What is the difference between dura in the skull and in the vertebral column.
in the VERTEBRAL COLUMN:
- single layer of dura with fat btw bone + the dura
in the SKULL:
- 2 layers of dura
What are the 2 layers of dura ?
- periosteal
- meningeal
What is the Falx Cerebri
- fold of dura extends between the medial surfaces of the 2 hemisphere.
peeling apart of the 2 layers of 2 layers of dura at the top forms the ______ ______ ______
peeling apart of the 2 layers of 2 layers of dura at the top forms the superior sagittal sinus
in the superior sagittal sinus, you find the arachnoid granulation which are:
in the superior sagittal sinus, you find the arachnoid granulation which are:
- bursts of subarachnoid space
- that protrudes into the superior sagittal sinus
- CSF leakes through the holes in the arachnoid memb
- and enters the superior sagittal sinus
Extradural hemorrhages have a rapid onset due to the rupture of a _____ artery.
Extradural hemorrhages have a rapid onset due to the rupture of a meningeal artery.
What is an extradural haematoma?
- high pressure arterial supply to the brain –> leads to splitting of arteries in the meninges themselves
- leads to compression of the skull underneath
- potential space in periosteal dura –> can be filled with blood in extradural hemorrhage
Why is subdural hemorrhagic stroke delayed?
- has slower development because:
- it is a lower pressure venous bleed
skull isn’t completely closed they might have veins through them e.g
- emissary vein
why is antibiotics given in scalp laceration?
there is a chance of infection passing into brain via the emissary vein
