39 - Circulation of the CNS Flashcards
Proportion of cardiac output required by CNS
~10-20%
Broad layout of CNS vasculature
Dense network of small vessels.
Densest in the grey matter, less dense in the white matter
What form the Circle of Willis?
Formed by vertebro-basilar system and internal carotid system
What form the basilar artery?
Vertebral arteries fusing.
Vertebral artery
Formed by a branch of subclavian arteries.
Ascends through spine, enters foramen magnum
Internal carotid artery
Branch of the common carotid artery.
Ascends through neck.
Enters through foramen lacerum
What does the internal carotid form in the Circle of Willis?
Two branches: anterior cerebral artery
Middle cerebral artery
What does the basilar artery form in the Circle of Willis?
Posterior cerebral artery
What links the anterior, middle and posterior cerebral arteries?
Posterior and anterior communicating arteries
Path of anterior cerebral artery
Arches around the corpus callosum.
Projects branches to medial frontal and parietal lobes through longitudinal fissure.
EG motor, somatosensory cortices of lower limb
Possible appearances of a blockage of anterior cerebral artery
Contralateral hemianaesthesia of lower limbs.
Contralateral spastic paralysis of lower limbs
Origin of middle cerebral artery
Internal carotid
Path of middle cerebral artery
Travels through lateral fissure to supply lateral surface of the brain.
Parts of brain, functions, supplied by middle cerebral artery
Frontal, parietal, occipital
Superior surface of temporal lobe
Motor, sensory cortices for most of the body.
If person has language lateralised to left hemisphere, language areas.
Possible effects of blocking middle cerebral artery
Spastic paralysis to most of the body.
Language problems.
Posterior cerebral artery supply
Supplies inferior temporal lobe, all medial occipital lobe
Possible functions impaired by blocking posterior cerebral artery
Contralateral visual field affected
Small perforating arteries
Branch from Circle of Willis.
Supply deep structures of cerebrum near where they branch.
Things supplied by anterior-most perforating arteries
Optic chiasm, anterior hypothalamus
Things supplied by lenticulostriate arteries
Basal ganglia, internal capsule
Things supplied by ventral perforating arteries
Ventral midbrain, posterior hypothalamus and thalamus
Things supplied by pontine perforating arteries
Ventral pons
From where does the ophthalmic artery branch?
Internal carotid, before it branches into the anterior and middle cerebral arteries
From where does the choroidal artery branch?
Internal carotid, before it branches into the anterior and middle cerebral arteries
Things supplied by the ophthalmic artery
Passes into orbit: eye (including retina), top of nasal cavity and frontal scalp
Things supplied by the anterior choroidal artery
Structures in deep lateral hemispheres: Optic tract, lateral ventricles, hippocampus
Thing that the vertebro-basilar system broadly supplies
Brainstem
Branches of the basilar artery 1 2 3 4
Posterior cerebral artery
Superior cerebellar artery
Anterior inferior cerebellar artery
Posterior inferior cerebellar artery (variable, about 10% of the time)
Branches of the vertebral artery 1 2 3 4 5
Meningeal branches Posterior spinal Anterior spinal Posterior inferior cerebellar artery (variable. Originates here most of the time) Basilar artery
Supply of the midbrain
Posterior cerebral arteries (on the way to the occipital lobe) give branches into the midbrain.
Superior cerebellar artery gives branches to most-posterior part.
Supply of the pons
Basilar artery runs across anterior part, gives off pontine branches
Supply of the medulla
Posterior inferior cerebellar artery (most of the postero-lateral)
Anterior spinal artery (medial, anterior part)
Vertebral artery (anterolateral)
Effect of blocking anterior spinal artery
1
2
3
Damage to pyramids (corticospinal tract) leads to contralateral hemiparesis. Medial lemniscus (contralateral somatosensory deficit) Hypoglossal nucleus (ipsilateral flaccid paralysis, because affecting lower motor neurons).
Called ‘medial medullary syndrome’
Anterior spinal arteries
Runs in midline fissure through ventral spine.
Formed by branches of vertebral arteries fusing.
Posterior spinal arteries
Two, one on each side of dorsal spine.
Each formed by one vertebral artery.
Where do spinal arteries anastamose?
In circumferential arteries, which wrap around spine
Reinforcement of blood supply to spine
Segmental branches of the aorta feed into spinal blood supply thorough radicular arteries (EG intercostal or lumbar arteries)
