BLOOD SUPPLY OF THE CNS- 39

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The brain derives its arterial supply from what 3 arteries?: 1. Internal carotid arteries
2. Vertebral arteries.
3. Basilar arteries
What happens during sleep,to the blood and oxygen flow to the brain?: During sleep, blood flow to the brain is increased, but the rate of oxygen consumption remains the same.
Where do the paired carotid and vertebral arteries begin and where do they reach?: They begin extracranially, and go through the neck and base of the skull to reach the cranial cavity.
What do the internal carotid arteries and their branches supply?: They supply the anterior 2/3 of the cerebral hemispheres, including its deep white matter and the basal ganglia.
The vertebral arteries and basilar artery, with their branches supply what 5 regions?: 1. The remaining posterior and medial regions of the hemispheres.

2. Diencephalon (most of it)

3. Brainstem

4. Cerebellum

5. Cervical spinal cord.
What is the circle of Willis?: It anatomically interconnects the carotid and vertebral-basilar circulations with each other, and with their counterparts in the opposite hemisphere.
What happens if either a carotid or a vertebral artery is suddenly blocked?: The connections created by the circle of Willis will not carry enough blood flow to maintain adequate cerebral circulation
Why do the connecting blood vessels not have much blood flow through them?: The connecting vessels have small diameters, and pressure differences between the two circulations are usually too small.
The circle of Willis is formed by what?: 1. Anterior communicating
artery.
2. Anterior cerebral artery.
3. Internal carotid artery.
4. Posterior communicating
artery
5. Posterior cerebral
arteries
Where does the anterior cerebral artery (ACA) arise from?: It arises from the internal carotid at nearly a right angle.
What does the anterior cerebral artery (ACA)supply?: 1. Septal regions &
hypothalamus
2. The superior part of
the frontal lobe
3. The anterior parietal lobe

4. The medial frontal &
parietal lobes
5. Corpus callosum
Where are the two locations for the branches of the anterior cerebral artery (ACA) ?: 1. One branch stays immediately adjacent to the corpus callosum

2. A second branch runs in the cingulate sulcus (above the cingulate gyrus).
What does the deep penetrating branches of the anterior cerebral artery (ACA)supply?: the most anterior portions of the basal ganglia.
The ACA Supply of the primary motor cortex is used for what?: the leg and foot areas, and the urinary bladder
The ACA Supply of the medial frontal lobe is used for what?: Motor planning areas that are anterior to the precentral gyrus (premotor cortex)
The ACA Supply of the medial parietal lobe is used for what?: Primary somatosensory cortex for the leg and foot
What are callosal fibers?: They are the posterior part corpus callosum that enable the language-dominant hemisphere to find out what the other hemisphere is doing, and to direct its activities
Where does the middle cerebral artery (MCA) come from?: The middle cerebral artery (MCA) branches at an acute angle from the internal carotid.
Where does the middle cerebral artery (MCA) take up position after it passes laterally just underneath the frontal lobe?: It takes up a position between the temporal and frontal lobes in the Sylvian fissure
1. What is the initial part of the MCA called? 2. What are lenticulostriate arteries?: 1. The stem or M1 segment.

2. They are the series of six to twelve long, small diameter, penetrating vessels that the MCA gives off as it passes laterally.
What 2 places do the lenticulostriate arteries supply?: 1. The basal ganglia
2. The internal capsule(much of)
The superior (upper or suprasylvian) MCA branch gives rise to several arteries that supply what 2 places?: 1. much of the lateral and inferior frontal lobe

2. the anterior lateral parts of the parietal lobe.
The inferior (lower or infrasylvian) MCA branch gives rise to arteries that supply what 3 places?: 1. lateral temporal lobe including its anterior tip and the amygdala

2. posterior parietal lobe

3. much of the lateral occipital lobe.
Superior branches of MCA supply these key functional areas:: 1. Primary motor cortex
2. Broca's area
3. Frontal eye fields
4. Primary somatosensory
cortex
5. lateral frontal and
parietal lobes
The superior branches of the MCA that supply Primary motor cortex are used for?: axons originating in the leg as well as face and arm areas that are headed for the internal capsule as part of the corticobulbar or corticospinal tracts
The superior branches of the MCA that supply the broca's area its other related gray and white matter are used for?: language expression in the language-dominant (usually left) hemisphere
The superior branches of the MCA that supply the Frontal eye fields are used for?: controlling eye movements
The Superior branches of MCA that supply the Primary somatosensory cortex are used for?: face and arm
The Superior branches of MCA that supply the Parts of lateral frontal and parietal lobes are used for?: 3-D visuospatial perceptions of one's own body and of the outside world particularly in the nondominant (usually right) hemisphere
The Superior branches of MCA that supply the parietal lobe are used for?: Optic radiations
Inferior branches of MCA supply what key functional areas?: 1. Wernicke's area
2. Parts of the posterior
parietal lobe
3. temporal lobe
Wernicke's area supplied by the Inferior branches of MCA is important for?: language comprehension in the language-dominant (usually left) hemisphere
Parts of the posterior parietal lobe supplied by the Inferior branches of MCA is important for?: 3-D visuospatial perceptions of one's own body and of the outside world, and for the ability to interpret emotions--in the nondominant (usually right) hemisphere
The temporal lobe supplied by the Inferior branches of MCA is important for?: Optic radiations
Why are lenticulo-striate arteries of the Middle Cerebral Artery important clinically?: It is important because they are long and thin, without collateral circulation and carrying blood at high pressure and they are susceptible to rupture with hemorrhage as well as to ischemic changes with cerebral infarctions
Where do vertebral arteries usually arise from?: Subclavian arteries.
1. Vertebral arteries course through what? 2. Vertebral arteries run medially and ascend into what?: 1. Cervical transverse foramina

2. Foramen magnum where they pierce the dura and enter the cranial cavity
What happens to the 2 vertebral arteries at the ponto-medullary junction ?: They fuse at the ponto-medullary junction to form the Basilar artery
What happens to the basilar artery?: It divides to form the 2 posterior cerebral arteries (PCA).
Cortical branches of Posterior Cerebral Artery(PCA) supply what key functional areas?: 1. Posterior branches to the parietal and occipital lobe

2. The primary visual cortex

3. Splenium of the corpus
callosum

4. Anterior branches to the
medial temporal lobe

5. Hippocampal formation

6. Posterior fornix
The primary visual cortex consists of what 2 things?: 1. Optic radiations
2. Striate cortex
What is the importance of the splenium of the corpus callosum?: They are crossing fibers that participate in the transfer of visual information to the language-dominant hemisphere
What is the importance of the hippocampal formation and the posterior fornix?: They are critical for laying down new memories)
Penetrating branches of the Posterior Cerebral Artery (PCA) supply what functional areas?: 1. Diencephalon including thalamus, subthalamic nucleus, and hypothalamus

2. Midbrain
What structures of the midbrain are supplied by the penetrating branches of the Posterior Cerebral Artery (PCA)?: 1. cerebral peduncle
2. third nerve and nucleus
3. red nucleus and its
connections
4. superior cerebellar
peduncle
5. reticular formation
Why does Cardiac emboli tend to enter the vertebral circulation far less frequently than they enter the carotid circulation?: This is because each vertebral artery takes off from the subclavian at a sharp angle, and has a much smaller diameter compared to the Carotid artery
Medial parts of the brainstem (pons and midbrain) as far dorsal as the III ventricle are supplied by what arteries?: penetrating branches of the basilar arteries called the paramedian branches
Dorsolateral parts of the brainstem are supplied by what 2 arteries?: 1. direct circumferential branches of the vertebral or basilar arteries

2. branches of one of the major 'cerebellar' vessels as they curve around the brainstem on their way to the part of the cerebellum they supply.
Why are the paramedian vessels supplying the medial parts of the brainstem clinically important?: They are at risk for hypertensive damage, particularly in the pons
Large pontine hemorrhages classically involve what 2 things?: 1. The corticospinal tracts
2. The reticular formation bilaterally
What could also damage the corticospinal tracts?: Pontine lacunar infarcts
The blood supply of the medulla is derived from ?: The two vertebral arteries.
The midline anterior spinal artery derived from what and supplies what?: Each vertebral artery, supplies part of the central medulla
The posterior inferior cerebellar artery (PICA) derived from the vertebral artery supplies what?: The lateral medulla and inferior cerebellum.
How does the basilar artery formed at the ponto-medullary junction by fusion of vertebral arteries proceed?: It proceeds rostrally along the surface of the anterior pons.
What are the 2 large lateral vessels that the basilar artery rise to?: 1. The anterior inferior cerebellar arteries (AICA)

2. The superior cerebellar arteries (SCA).
What do they supply? 1. PICA? 2. AICA? 3. SCA?: 1. PICA = posterior inferior surfaces of the cerebellum

2. AICA = anterior inferior surfaces of the cerebellum

3. SCA = superior surfaces of the cerebellum
What is unique about the superior cerebellar artery?: It sends small branches penetrating deeply into the deep nuclei of the cerebellum.
What are the penetrating cerebellar vessels also at risk for?: Hypertensive hemorrhage, with bleeding often occurring near the dentate nucleus.
What are the major regions supplied by the Vertebro-basilar Artery?: 1. Upper cervical spinal cord
2. Brainstem and Cerebellum
3. Most of the thalamus and
hypothalamus
4. Cortex and deep white
matter of the posterior
medial parietal lobes,
medial and inferior temporal lobes and occipital lobes
5. Posterior part (splenium) of the corpus callosum
What arteries supply the spinal cord ?: The vertebral arteries
What happens when the posterior spinal arteries and the two anterior spinal arteries fuse?: They form a single midline vessel that supply the upper cervical cord.
What are radicular arteries?: They are branches of the thoracic and abdominal aorta in the lower cord that reinforce the spinal arteries.
What is the artery of Adamkiewicz and why is it so important?: It is one of the most important radicular arteries, and in some individuals it may provide the entire arterial supply for the lower two-thirds of the spinal cord
1. What happens when the anterior spinal artery is blocked? 2. What happens to the joint position and vibratory sensations during this blockage?: 1.There is bilateral paralysis and a deficit in pain sensation below the level of the lesion.

2. They are spared since the posterior columns and neighboring white matter are supplied by the smaller posterior spinal arteries
Discuss vascular disease in the spinal cord?: Vascular disease in the spinal cord is uncommon because it not particularly susceptible to atherosclerosis or embolization.
What injury could happen to the spinal cord?: Infarction of the spinal cord.
What causes ischemia in collateral arteries that supply the spinal cord? and what parts are especially at risk?: A catastrophic drop in blood pressure may result in ischemia.
The parts that are especially at risk are those at mid-thoracic levels. This is the spinal equivalent of a border zone infarct in the cerebral hemispheres.
What is the role of the Blood Brain Barrier?: It does not allow many substances present in the blood to pass through the meninges into the cells of the central nervous system.
What are the 2 components of the blood brain barrier?: 1. The blood/cerebrospinal fluid barrier

2. The arachnoid barrier layer.
What is Cerebrospinal fluid?: It is a filtrate of blood by the choroid plexuses (capillary networks) of the ventricles which are formed by fusion of the pia mater and the ependyma (ventricular lining).
What components of blood are allowed to enter the brain?: Only clear plasma passes through, leaving blood cells behind.
What is the arachnoid barrier layer?: It is a part of the arachnoid meningeal layer formed by tight junctions between the endothelial cells of cerebral capillaries in the arachnoid mater.
What else contributes to the Blood Brain Barrier?: Foot processes of astrocytes around capillaries
What happens when intra-arterial pressure goes up and down?: As intra-arterial pressure goes up, cerebral vessels normally constrict and when pressure drops, cerebral vessels dilate.
What happens at extremely low or high arterial pressure levels ?: Cerebral blood flow follows blood pressure more directly
What is Cerebral Autoregulation?: The concept that cerebral vessels themselves have a role in controlling cerebral blood flow

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