Anatomy of Blood Flow in CNS and Consequences of Disruption Flashcards
Blood supply to the brain? (2)
Internal carotid and vertebral arteries
how many sources of blood supply are there to the brain
2
What is the blood supply to the face
External carotid
What part of the brain does the internal carotid supply
the anterior part of the brain
- Vertebral arteries come off the X, and pass up through the YY of the cervical Z
subclavian arteries
transverse foramen
vertebrae
Internal carotid branches into: (4)
Middle cerebral
Anterior cerebral
Posterior communicating
Opthalmic
Vertebral arteries X to form the YY
anastamose
basilar artery
The basilar artery bifurcates to form …
Posterior cerebral arteries
What is the advantage of the brain having such a branched blood supply
flow in one side is often able to compensate for flow in the other
Starting from the vertebral artery, what is the sequence of names for the circle of Willis
Vertebral artery -> basilar artery -> Posterior cerebral artery -> posterior communicating artery -> middle cerebral artery/Internal carotid -> anterior cerebral artery -> anterior communicating
anterior communicating artery connects …
the 2 anterior cerebral arteries
posterior communicating artery connects …
Posterior cerebral and internal carotid artery
- Venous sinuses are made from …
folds of the dura mater
Venous sinuses drain in towards… 1 -> 2 -> 3 -> and ultimately
back of the head (confluence of the sinuses), then transverse sinus, then sigmoid sinus and then to the internal jugular vein
What is the confluence of sinuses
Where all the venous sinuses drain into
What is the order of drainage thinking sinuses
SUPERIOR SAGITTAL SINUS, CONFLUENCE OF THE SINUSES, TRANSVERSE SINUS, SIGMOID SINUS, INTERNAL JUGULAR
Venous drainage of the brain? (4+4)
- Cerebral veins
- Venous sinuses (superior sagittal, confluence of sinuses, transverse, sigmoid)
- Dura mater
- Internal jugular venous
Internal carotid bifurcates at vertebral level …
C4
• The vertebral arteries join together to form the basilar artery at the level of the X
pons
middle cerebral arteries emerge through ….
the fissure between the frontal, parietal and temporal lobes
Stroke by definition is:
Rapidly developing focal disturbance of brain function of presumed vascular origin and lasting >24 hours’ duration
2 causes of stroke and their % incidence?
INFARCTION (85%) or HAEMORRHAGE (15%)
TRANSIENT ISCHAEMIC ATTACK (TIA) by definition is:
Rapidly developing focal disturbance of brain function of presumed vascular origin that resolves completely within 24 hours
INFARCTION by definition is:
Degenerative changes which occur in tissue following occlusion of an artery
CEREBRAL ISCHAEMIA by definition is:
Lack of sufficient blood supply to nervous tissue resulting in permanent damage if the blood flow is not restored quickly
THROMBOSIS by definition is:
Formation of a blood clot (thrombus)
EMBOLISM by definition is:
Plugging of a small vessel by material carried from a larger vessel e.g. thrombi from the heart of atherosclerotic debris from the internal carotid
RISK FACTORS FOR STROKE (5)
- Age
- Hypertension Obvious risk factor for haemorrhage (busting blood vessel in brain)
- Cardiac disease
- Smoking
- Diabetes mellitus
Middle cerebral artery supplies the X of the lateral part of the hemisphere
front 2/3
What parts of the brain does the Middle cerebral artery supply
• It supplies the front 2/3 of the lateral part of the hemisphere
What parts of the brain does the posterior cerebral artery supply
• The posterior cerebral artery supplies the medial and lateral parts of the posterior part of the hemisphere
What parts of the brain does the anterior cerebral artery supply
• The anterior cerebral artery supplies the medial part of the hemisphere
Disturbance of the Anterior Cerebral Artery results in: (3)
- Paralysis of contralateral leg (with relative sparing of the arm), face
- Disturbance of intellect, executive function and judgement (abulia)
- Loss of appropriate social behaviour
Disturbance of the Middle Cerebral Artery results in: (5)
- “Classic stroke”
- Contralateral hemiplegia Arm more than leg (complete hemiparesis can also be seen with middle cerebral artery stroke because the artery also supplies fibres in the core of the brain in the motor pathway)
- Contralateral hemisensory deficits
- Hemianopia (bilateral) (loss of half of the visual field in both eyes)
- Aphasia (Left sided lesion this is where speech and language centres are located) Expressive aphasia = understanding but lacking retrieval of appropriate words to answer, receptive aphasia = not understanding what you say (Wernicke’s region)
What will a left middle cerebral artery disturbance result in that the right won’t
Aphasia as the language centre is in the left
Disturbance of the posterior Cerebral Artery results in: (1 divided into 3)
• Posterior cerebral artery supplies the occipital lobe where you find the primary visual cortex
• This leads to visual defects:
o Homonymous hemianopia
o Visual agnosia
• Not being able to recognise things that you see
What are Lacunae
stroke often causes small holes to appear in brain tissue.
• These holes are called lacunae
Cause and onset of symptoms of an extradural haemorrhage?
Trauma, immediate effects (surgical emergency)
Cause and onset of symptoms of an subdural haemorrhage?
Trauma, delayed effects
Cause of a subarachnoid haemorrhage?
Ruptured aneurysms (can be trauma but less common)
Cause of an intracerebral haemorrhage?
Spontaneous hypertensive
Why does a subdural haemorrhage have delayed effects
is because lower pressure venous bleed
What’re the TWO layers of dura in the skull:
Periosteal
Meningeal
What is an emissary vein
one that comes through a hole in the skull, natural.
fold of dura extends between the medial surfaces of the two hemispheres called the XX
falx cerebri, and forms the superior saggital sinus
falx cerebri is …?
fold of dura that extends between the medial surfaces of the two hemispheres
