Circulation of CNS Flashcards
Why does the CNS need efficient delivery of nutrients and removal of metabolic byproducts?
High metabolic requirements
What is the percentage of cardiac output that’s needed by the CNS?
10-20%
What does autoregulation of cerebral blood flow do?
Maintain adequate perfusion when arterial BP changes or if blood gases change
Which area of the brain has more blood vessels: cortex or white matter?
Cortex
What does the circle of Willis do?
Provide arterial supply to brain
What two systems form the circle of Willis?
Vertebro-basilar
Internal carotid
What does the circle of Willis allow if one of the blood vessels becomes blocked?
Blood to reach brain still
Where is the circle of Willis?
Around optic chiasm and hypothalamus
In which direction do the internal carotid arteries more?
Laterally
In which direction do the vertebro-basilar arteries move?
Over brainstem
What forms the vertebro-basilar system?
Two vertebral arteries join to form basilar artery medially
Through which foramen do the vertebral arteries enter the skull?
Foramen magnum
Through what does the internal carotid enter the skull?
Carotid canal in base of skull
Which artery is the vertebral artery a branch of?
Subclavian
How does the vertebral artery travel up the spine?
Through transverse foramina
What brain structure does the vertebral artery associate with before joining the circle of Willis?
Brainstem
Which system forms the posterior circulation of the circle of Willis?
Vertebro-basilar system
Which system forms the anterior circulation of the circle of Willis?
Internal carotid
What are the main arteries supplying the cerebrum?
Anterior cerebral artery
Middle cerebral artery
Posterior cerebral artery
How is the loop in the circle of Willis closed?
Via communicating arteries
What gives off the anterior cerebral artery?
Internal carotid artery
In which direction does the anterior cerebral artery run?
Anteriorly and medially
What joins the two anterior cerebral arteries?
Anterior communicating artery
What is the posterior cerebral artery a branch of?
Basilar artery
What does the posterior communicating artery join?
Posterior cerebral and internal carotid arteries
What does the anterior cerebral artery supply?
Medial part of
- Frontal lobe
- Parietal lobe
Up to parieto-occipital sulcus
What functional territories are supplied by the anterior cerebral artery?
Motor and sensory cortices for lower limb
In what structure does the anterior cerebral artery run?
Longitudinal fissure
What is the relationship between the anterior cerebral artery and corpus callosum?
Hooks around front of corpus callosum > arches over
What clinical signs do you see with a cerebrovascular event in an anterior cerebral artery?
Contralateral hemiparesis with spastic paralysis of lower limb
Contralateral hemianaesthesia of lower limb
What does the middle cerebral artery supply?
Lateral surface of brain including parts of
- Frontal lobe
- Parietal lobe
- Superior and lateral parts of temporal lobe
- Occipital lobe
Insula
What are the functional territories supplied by the middle cerebral artery?
Motor and sensory cortices for body except lower limb
Parieto-occipital association areas
Language areas
What is the middle cerebral artery a branch of?
Internal carotid artery
In which direction does the middle cerebral artery run?
Directly laterally
In which structure does the middle cerebral artery run?
In lateral fissure between temporal lobe, and frontal and parietal lobes
Where does the middle cerebral artery externalise in the brain?
On lateral surface of cerebrum
What clinical signs do you see with a cerebrovascular accident in a middle cerebral artery?
Contralateral hemiparesis associated with upper limb and face
Contralateral hemianaesthesia associated with upper limb and face
If on language dominant side, aphasia
What does the posterior cerebral artery supply?
Medial and inferior surfaces of
- Temporal lobe
- Occipital lobe
What functional territories does the posterior cerebral artery supply?
Visual cortex
Where does the posterior cerebral artery come off the basilar artery?
At level of medulla
In which direction does the posterior cerebral artery move?
Laterally and posteriorly
What clinical signs do you see with a cerebrovascular event in a posterior cerebral artery?
Loss of vision in contralateral visual field
What is homonymous hemianopia?
Loss of vision in visual field of one side
What is the role of the small perforating branches?
Supply deep structures where they com off main arteries
What does the anterior group of small perforating branches come off?
Anterior communicating artery
What does the anterior group of small perforating branches supply?
Optic chiasm
Anterior parts of hypothalamus
What does the posterior group of small perforating branches come off?
Posterior cerebral artery
What does the posterior group of small perforating branches supply?
Ventral parts of midbrain
Posterior parts of hypothalamus
Thalamus
What do the pontine branches come off?
Basilar artery before it terminates
What do the pontine branches supply?
Pons
What does the lateral group of small perforating branches come off?
Middle cerebral artery as it projects laterally
What does the lateral group of small perforating branches supply?
Basal ganglia
Internal capsule
What else is the lateral group of small perforating branches called?
Lenticulostriate arteries
Which artery is the ophthalmic artery a branch of?
Internal carotid artery
Where does the ophthalmic artery branch from the internal carotid?
Just before anterior and middle cerebral arteries
What structure does the ophthalmic artery enter?
Orbit
What does the ophthalmic artery supply?
Eye, including retina
Top of nasal cavity
Frontal scalp
Which artery is the anterior choroid artery a branch of?
Internal carotid artery
What structure does the anterior choroid artery follow?
Lateral ventricle all the way around - forms C shaped hook
What structures does the anterior choroid artery supply?
Structures in deep lateral hemispheres
- Optic tract
- Lateral ventricles
- Hippocampus
What does the posterior inferior cerebellar artery branch off?
Vertebral artery
What does the posterior inferior cerebellar artery supply?
Posterior part of inferior surface of cerebellum
What are the branches of the basilar artery, in order?
Anterior inferior cerebellar artery
Superior cerebellar artery
Posterior cerebral artery
What does the anterior inferior cerebellar artery supply?
Anterior part of inferior cerebellum
What does the superior cerebellar artery supply?
Superior cerebellum
In which direction do cerebellar arteries project?
Posteriorly
What are the spinal arteries?
One anterior spinal artery
Two posterior spinal arteries
Where does the anterior spinal artery run?
In ventral longitudinal fissure in spinal cord
How is the anterior spinal artery formed?
One branch from each vertebral artery meet
What do branches from the superior cerebellar artery supply?
Posterior part of midbrain, in particular colliculi
Where does most of the midbrain that is not supplied by branches of the superior cerebellar artery get its blood supply from?
Some posterior perforating branches of posterior cerebral artery
Where does the medulla get its blood supply from?
Medially from anterior spinal artery
Posterolaterally from posterior inferior cerebellar artery
In between where olives are from vertebral artery
What is the medial medullary syndrome?
Group of signs associated with cerebrovascular accident of anterior spinal artery
What are the clinical signs of medial medullary syndrome?
Pyramids - Contralateral hemiparesis - UMN signs - Spastic paralysis - Hyper-reflexia Medial lemniscus - Contralateral hemianaesthesia Hypoglossal nucleus - Ipsilateral paralysis - Ipsilateral atrophy of some tongue muscles
What is the lateral medullary syndrome?
Group of signs associated with cerebrovascular accident of posterior inferior cerebellar artery
What is the origin of the posterior spinal arteries?
Vertebral arteries
Where do the posterior spinal arteries run?
Posterolateral aspect of spinal cord
What reinforces the spinal arteries?
Radicular arteries
What is the origin of radicular arteries?
Branches of some of segmental arteries of aorta
What forms the anastomosis between the anterior and posterior spinal arteries?
Circumferential branches
Where do the cerebral veins run?
In subarachnoid space
What do the cerebral veins drain into?
Venous sinuses
Where do the venous sinuses drain to?
Jugular venous system
Between which layers of the meninges are the venous sinuses located?
Two layers of dura
