Lesson 3: Blood Supply of the Nervous System Flashcards Preview

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Flashcards in Lesson 3: Blood Supply of the Nervous System Deck (77):

What do the paired internal carotid arteries supply in the brain?

Supply the anterior, lateral and medial (between the two cerebral hemispheres) aspects of the brain
(Sensory and motor cortices, medial surface, prefrontal cortex)


What do the paired vertebral arteries supply in the brain?

Supply the posterior and inferior surfaces, the cerebellum and the brain stem.
(Calcarine cortex, thalamus, upper midbrain, subthalamic nucleus, hippocampus)


What is a common location for strokes?

Internal capsule


Internal carotid artery system: What is their pathway?

Enters the cranium through the carotid foramen in the petrous bone and curves forward and medially to enter the cavernous sinus; joins Circle of Willis and divides to form anterior and middle cerebral artery


Internal carotid artery system: what happens when the artery reaches the cavernous sinus?
What does the ophthalmic artery supply?

At this point, two important arteries branch off the internal carotid: the anterior choroidal and ophthalmic.
Ophthalmic artery supplies blood to the eyeball and ocular muscles.


Internal carotid artery system: how is the anterior communicating artery related to the cerebral arteries? What does it do?

The artery connects the left and right anterior cerebral arteries. It supplies oxygenated blood to most midline portions of the frontal lobes and superior medial parietal lobes.


Internal carotid artery system: what do the left and right anterior cerebral arteries supply?

Supply the medial surface of the brain within longitudinal fissure.


Internal carotid artery system: what do the left and right middle cerebral arteries supply?

Supply the brain around the lateral fissure and internal capsule


Why are the left and right middle cerebral arteries important?

Important to communication disorders - can result in many clinical presentations; divides into smaller branches.
Supplies all of the cortical brain areas responsible for language - areas all supplied by different branches of artery, and not usually all damaged together.


What is the watershed area? What mechanism does it serve?
What occurs after a lesion?
What is an example of this?

Area of overlap is called the watershed area, which implies when there is good supply, it has more than enough, but when the vessels are poor, circulation is poor (named after alternate flooding or dry spells in a ‘watershed’ area in a river). Source of "back-up" supply if one is damaged.
Lesion: blood vessels from the nearby supply may grow to try to make up the loss.
Ex. Anterior cerebral artery reaches some of same area as branches of middle cerebral artery.


Vertebral artery system - What are the components left and right vertebral arteries? (3) What does each serve?

Anterior spinal artery - emerges from each vertebral artery and descends along midline (1)
Posterior spinal arteries - dorsal medulla(2)
-Posterior inferior cerebellar arteries - serves cerebellum (2) [often called PICA]


Vertebral artery system - what are the components of the basilar artery? What does each serve? (3)

-Posterior cerebral arteries (2): supplies most of temporal lobe, occipital lobe, interior surface of the brain, thalamus
-Superior cerebellar (2): pontine branches (many)
-Anterior inferior cerebellar arteries - anterior and lateral surfaces of the cerebellum (2) [often called AICA]


Vertebral artery system: what is the importance of the posterior communicating arteries?

Very important clinically – connects the internal carotid and vertebral systems


What is an anastomosis? What is an example and its components?

Anastomosis: branch connecting two arteries that provides an alternate path if one artery is blocked.
Ex. The circle of Willis - is formed by the paired anterior system (from the internal carotid arteries) and posterior system (from the paired vertebral arteries), linked by the posterior communicating arteries - left/right anterior cerebral arteries are linked by single anterior communicating artery


In the frontal lobe, what is the artery that supplies:
Lateral Surface
Medial Surface
Inferior Surface

Lateral: Middle cerebral artery
Medial: Anterior cerebral artery
Inferior: Middle and anterior cerebral arteries


In the parietal lobe, what is the artery that supplies:
Lateral Surface
Medial Surface

Lateral: Middle cerebral artery
Medial: Anterior cerebral artery


In the occipital lobe, what is the artery that supplies:
Lateral and Medial Surfaces

Lateral/Medial: Posterior cerebral artery


In the temporal lobe, what is the artery that supplies:
Lateral Surface
Medial Surface
Inferior Surface

Lateral: Middle cerebral artery
Medial: Jointly by middle cerebral, posterior cerebral, posterior communicating, and anterior choroidal arteries
Inferior: Posterior cerebral artery


What are the components of the Circle of Willis? (10)

Left internal carotid artery
Left anterior cerebral artery
Anterior communicating artery
Right anterior cerebral artery
Right internal carotid artery
Right posterior communicating artery
Right posterior cerebral artery
Basilar artery (end of)
Left posterior cerebral artery
Left posterior communicating artery


Why is PICA (posterior inferior cerebellar artery) important clinically?

Not only do they supply the cerebellum but also, they supply the brain stem where the vital centres are found and lesions in them may be fatal.


What arteries is the spinal cord supplied by?
How is it supplemented with other structures?

Supplied by one anterior and two posterior spinal arterial branches from the vertebral arteries at the base of the brain AND that this circulation is backed up by additional small branches from the aorta throughout the length of the spinal cord.


How is paraplegia related to spinal cord injury?

Paraplegia may be due to damage to the circulation of the spinal cord without direct trauma to the spinal cord itself (e.g., drop in pressure to the branches during surgery for an aortic aneurysm).


What is the term for lack of oxygen?
What is the term for loss of blood supply?

Anoxia; ischemia


What is the role of cerebral veins?

Collect venous (deoxygenated) blood from brain tissue and conduct it to the venous sinuses to return the venous blood through veins in the neck to the heart.


Venous sinuses: what are the falx cerebri, falx cerebelli, and tentorium cerebelli?

Infoldings of inner layer of the dura mater are sheets of connective tissue that fold between the two cerebral hemispheres (falx cerebri), and the two halves of the cerebellum (falx cerebelli) and between the cerebrum ad cerebellum (tentorium cerebelli).


What do the falx cerebri, falx cerebelli and tentorium cerebelli form and what does the structure do?

Create spaces that form a series of venous channels called “venus sinuses”. Sinuses receive venus blood from the capillaries which flow into the cerebral veins that travel from deep in the brain to the surface, crossing briefly through the subarachnoid space to the subdural space and empty into the venous sinus system to be carried from the skull into the veins of the neck


Cerebral veins: what level of blood pressure vessels are they?
Where do the travel and where do they drain?

Round low pressure blood vessels that run only briefly in the subarachnoid space, and they then travel between the arachnoid and dura mater (in the subdural “space”) for some distance before draining into the venous sinuses


Where do the channels of the venus sinuses exit and terminate?

These series of channels converge and exit through the jugular foramen and brain into the internal jugular veins (left and right).


Where does the straight sinus come from, where does it empty and where does it run?

Comes from deep in the brain emptying the inferior sagittal sinus and runs directly backwards to the skull


Where does the transverse sinus travel and where does it exit and terminate?

Travel on the occipital bone laterally until they reach the point where the middle cranial fossa meets the posterior cranial fossa.
Run forward in the lateral floor of the posterior cranial fossa, exit the skull in jugular foramen and into internal jugular vein


Direction of flow of Venous sinuses: What are the 3 pathways?

1.Cerebral veins -> superior sagittal sinus drains to the right -> right transverse sinus -> right sigmoid sinus -> right internal jugular vein
2.Cerebral veins -> inferior sagittal sinus -> straight sinus -> left transverse sinus -> left sigmoid sinus -> left internal jugular vein
3.Cavernous sinus -> to sigmoid sinus


Mechanisms of Damage in TBI:
What are the 5 types?

-Coup Injury: Area where the skull impacts the brain – direct damage
-Contrecoup Injury: A backlash where the accelerating brains hits the opposite skull
-Pressure from space occupying lesions – tumours
-Uncal Hernation: Compression of the uncus (cerebrum and midbrain) on the medial temporal lobe against dura of the tentorial notch
-Tonsil Herniation: Compression of brainstem and medial cerebellum into foramen magnum


Non-Vascular Brain Injuries: what is the term for a pooling of blood that occupies space is more often associated with venous injury



Non-Vascular Brain Injuries: What is the term for higher pressure, rapid and more often associated with arterial bleeding, but the term is occasionally applied to venous bleeding too.



Epidural Haemorrage:
What is the mechanism?
Meningeal layers and spaces provided?
Arterial or venous blood?
Rapid or slow onset?
Vulnerable areas of the brain?

Result of a blow to the side of the head.
Bleeding between the skull and its periosteal dura. Commonly from the middle meningeal artery
Arterial bleed
Rapid onset
Somewhat confined by close attachments to the skull; injured middle meningeal artery; pressure on the brain


Subdural Haematoma:
What is the mechanism?
Meningeal layers and spaces provided?
Arterial or venous blood?
Rapid or slow onset?
Vulnerable areas of the brain?

Associated with head trauma
Bleeding in the "potential space"; between the dura mater and arachnoid mater - where cerebral veins travel to reach the venous sinuses.
Venous blood
Slow onset - spreads widely, shifts and is slow to form
Increased pressure on the brain; veins between dura are torn; dura and arachnoid membrane; oculomotor nerves


Subarachnoid Haemorrhage:
What is the mechanism?
Meningeal layers and spaces provided?
Arterial or venous blood?
Rapid or slow onset?
Vulnerable areas of the brain?

Cause of a congenital defect during contact sports - head injury
Defect and ballooning of the artery wall, aneurysm presses on the brain, eventually bleeds. Bleeds into subarachnoid space and mixes with CFS
Frequently in the Circle of Willis
Arterial blood
Rapid onset
Affects CSF - blood vessels in brain, brainstem and spinal cord; torn vessels in arachnoid mater in subarachnoid space


Intracerebral Haemorrhage:
What is the mechanism?
Meningeal layers and spaces provided?
Arterial or venous blood?
Rapid or slow onset?
Vulnerable areas of the brain?

Commonly from strokes, caused by blockage of blood vessels (interrupts blood supply), or rupture of arteries in the brain tissues - can be in brainstem, basal ganglia, cerebellum, cortex.
Arterial blood
Rapid onset
Causes ischemia to tissue.


Non-vascular head injuries: What are some examples and what do they do?

Direct damage to the brain, space occupying lesions, which in turn causes compression of the brain tissue or brain stem and cranial nerves against the dura infoldings and compression of the cerebellum and brain stem into the foramen magnum.


What are the most common non-vascular causes of space-occupying lesions?

Swelling, and tumours are the most common non-vascular causes of space occupying lesions.


What is the difference between a non-vascular and vascular head injury?

Non-vascular: Trauma to the blood vessels in the skull and they can cause a space-occupying lesion
Vascular: Loss of circulation to the tissue itself


What is the purpose of the pupillary light reflex?

An important test for expanding pressure in the brain


Where does the brain receive its arterial supply and where does it end up?

-The brain receives its arterial supply from two paired arteries, which enter the skull and form an anastomosis, the circle of Willis.


Where is venous blood collected and drain?

Collected into cerebral veins, drains into the venous sinus system.
Drains from the skull and into the internal jugular vein


What carries oxygenated blood to the brain, what returns deoxgenated blood back to the heart?

Arteries; veins


What do arterioles do?
What do capillaries do?

Deliver blood to the capillaries
Connect arterioles with venules


What are the two divisions of the carotid artery and what do they serve in the body?

External and its branches supply blood to the facial muscles and forehead as well as to the oral, nasal and orbital cavities. Internal enters the cranium through the carotid foramen in the petrous bone and enters the cavernous sinuses.


Why is the Circle of Willis an important point?

Willis is an important anastomotic point that serves to equalize the vascular blood supply to both sides of the brain


What two structures arise from the Circle of Willis and what do they serve?

Cortical branches are major arteries that supply external brain structures Central branches are small arteries that penetrate the ventral surface of the brain to supply the internal and subcortical brain structures


Anterior Cerebral Artery (ACA): Where does it travel? What does it supply?

-Travels rostrally in the interhemispheric fissure along the midsagittal surface of the brain.
Supplies the orbital and medial cortical surfaces of the prefrontal, frontal and parietal lobes.


What does the anterior cerebral artery anastomose with?

Anastomose with the branches of the PCA. Terminal branches also cross over to the lateral cortical surface and develop anastomosing continuity with the branches of the MCA in the watershed area


What is the result of blood flow interruption in the ACA?

Decreased blood supply to the midsaggital extension of the sensory and motor cortices, causing sensory loss and paralysis in legs, feet and toes


Middle Cerebral Artery: What is it a direct continuation of?

Internal carotid artery.


Middle Cerebral Artery: Where does it run laterally?
And what does it serve in the brain?

Runs laterally and emerges through the sylvian fissure on the lateral brain surface - divides into the temporal, frontal and parietal branches.
Speech, language and large part of sensorimotor areas


What are the two branches that the MCA gives off?

Lateral and medial lenticulostriate branches that supply the basal ganglia and diencephalon.


What occurs when there is impaired vascular circulation to the middle cerebral artery?

Contralateral hemiplegia and impaired sensory functions - discriminative touch, tactile agnosia, and reduced pain and temperature


Central Arteries: what does the anteromedial artery serve?

Supplies the hypothalamus and subrachiasmatic regions of the brain


Central Arteries: what does the medial striate artery arise from and supply?

Arise from ACA and supply blood to parts of caudate nucleus, putamen internal capsule.


Central Arteries: what does the anterior choroidal supply?

Choroid plexus, hippocampus, and portions of globus pallidus, posterior internal capsule, putamen, and geniculate bodies.


Central Arteries: what does the posterior choroidal artery supply?

Choroid plexus of the third ventricle, tectum in midbrain, and pineal gland


Central Arteries: where does the posteromedial artery supply blood?

Red nucleus, substantia nigra, medial cerebral peduncle, subthalamic nucleus, midbrain reticular formation, and superior cerebellar peduncle.


How can the anterior communicating artery connect the blood supply for the hemispheres?

By linking the two anterior cerebral arteries


What is an alternate feed for the vertebral basilar system?

Through posterior communicating artery, if there is a significant vascular insufficiency involving the internal carotid artery.


What can be triggered if there is thromboembolic involvement of the internal carotid artery?

Retrograde blood flow from external carotid, through ophthalmic artery branches in the eye


What three areas can anastomose in the watershed area?

Anterior, middle and posterior cerebral arteries


What are the two types of cerebrovascular accidents?

Occlusive vascular (thrombosis or embolism) Hemorrhagic (aneurysm, arteriovenous malformations) strokes


Occlusive Vascular Pathology: What is the primary cause of arterial occlusion? What is a transient ischemic attack and why could it occur?
Are all strokes preceded by a TIA?

Atherosclerosis (hardened arterial walls) is primary cause.
Transient ischemic attack (TIA) is temporary interruption of blood circulation to the brain - occlusive carotid disease


What is an embolism?

Clot that breaks free from a thrombus and enters the blood stream, eventually blocking a small end artery.


What is thrombosis?

Local build up of fatty substances and blood platelets in a cerebral vessel that is caused by an atherosclerotic plaque - degeneration of the vessel wall


What is an extradural hematoma?
What happens to the dura?

Blood vessel ruptures between the dura mater and skull.
Extravasated blood separates the dura from inner skull and forms a large lens-shaped accumulation of blood.


What is an aneurysm? How is it caused?

Dilation of an artery that occurs at points of bifurcation of major cerebral arteries. Due to weakness in vessel wall or congenital arterial defect. Ruptures and releases blood into the brain or onto its surface


What is an arteriovenous malformation?
Where does arterial blood travel?

Tangled dilated artery or vein becomes connected in a local area; thus arterial blood bypasses cortical tissue and directly drains into veins, depriving underlying tissue of oxygen.


What is the pathway that blood takes to the dural sinuses?

First happens at capillary level, where intracerebral capillaries unite to form small veins (venules). Venules collect the blood and transfer it to veins. Veins that drain surface and deep brain structures empty blood into dural sinuses (in the cranium)


What is the pathway of the superior sagittal sinus? Where does it receive blood from and where is it drained?

Runs along dorsomedial line on vertex in falx cerebri, receives blood from superior cerebral veins and CSF drained through the arachnoid villi.


What is the pathway of the inferior sagittal sinus?

Runs in inferior margin of falx cerebri over dorsal edge of corpus callosum.


Which type of vein collects circulated blood from the neocortex and subcortical white matter and drain it into superior sagittal sinus?.

Superficial cerebral


Which type of vein drains blood from subcortical structures and empty into the great cerebral vein of Galen?

Deep cerebral