Blood supply to the Brain Flashcards
what is the circle of willis officially referred to as?
Circle of willis= cerebral arterial circle
blood flow in the brain is regulated by autoregulation; what increases ‘flow’
- CBF (cerebral blood flow) is autoregulated - chemoreceptors on carotid body measure O2/CO2 and feeding back to brain to modulate dilation/constriction of cerebral vasculature
- Normotensive cerebral blood flow (CBF) ~ 50mL per 100g of brain tissue per min if cerebral perfusion pressure is 50-150 mmHg
- Blood flow doesn’t change until PO2 falls below ~ 50mmHg then it increases if hypoxia further PO2 decreases happens and CBF can increase up to 400% above resting levels
FLOW INCREASES IF= O2 DECREASES, CO2 INCREASES
what are the main branches of internal carotid (in individuals that have norm circle of willis formation)
internal carotid main branches :
- ophthalmic- supplies the orbit + retina. n.b. Within cavernous part it crosses foramen lacerum + it also connects to external carotid
*posterior communicating artery; connects carotid and vertebral artery system
*middle cerebral artery - it supplies basal ganglia + internal capsule, + lateral 2/3rds of cortex
*anterior cerebral which supplies internal capsule (white matter tract), medial side of frontal + parietal lobes. The anterior cerebral anastomoses with middle cerebral artery
which white matter tract connects wernickes and broca’s area
Arcuate fasciculus
connect Werknicke’s and Broca’s areas
What is the most commonly blocked artery in ischemic stroke?
middle cerebral artery (MCA) is the most common artery involved in acute stroke
*specifically the lenticulstriate vessels (these branch off the middle cerebral artery)
locate on a brain; cadaver the following areas:
*primary motor cortex
*primary somatosensory cortex
*primary auditory cortex
*primary visual cortex
*Broca’s
*Wernicke’s
what is Broca’s vs Wernicke’s areas responsible for?
Broca’s area (Broca’s expressive speech) is associated with language production, while Wernicke’s area (Wernicke’s receptive speech) is associated with language comprehension
what are the main branches of the posterior circulation to the brain?
bilateral vertebral arteries (come from subclavian).
The posterior circulation derives blood from the bilateral vertebral arteries (VA). It supplies the brainstem, cerebellum, occipital lobes, medial temporal lobes and posterior part of the deep hemisphere, mainly the thalamus.
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Vertebral (comes from subclavian) artery - comes through transverse process of cervical foramen - enters skull via foramen magnum - gives rise to
-Spinal cord - anterior/posterior spinal arteries
-Dorsal medulla of brainstem - PICA (posterior inferior cerebellar artery) -
Basilar - formed by both vertebral arteries coming together - (lies on ventral surface of pons)
-lies on ventral surface of Pons
-Cerebellum (Anterior inferior cerebellar artery and superior cerebellar artery - both supply cerebellum)
*posterior cerebral artery
-Inferior and medial aspects of temporal and occipital cortex
-Thalamus and posterior internal capsule
-Midbrain
-Anastomose with Middle Cerebral Artery
which artery in the brain supplies the area of the brain responsible for leg movement?
Anterior Cerebral Artery (ACA): This vessel supplies blood to the front part of your brain, knows as your frontal lobe. There is a right sided ACA and a left sided ACA. If a stroke occurs in this area, you may see leg weakness and/or difficulty thinking and making decisions.
which artery in the brain supplies the visual cortex
posterior cerebral artery supplies the visual cortex
which 2 arteries is the oculomotor (CN III) nerve ‘sandwiched’ between
the occulomotor nerve (CN III) is sandwiched between posterior cerebral and superior cerebellar
what do we mean by a stenotic artery
a narrowing or constriction of the diameter of a bodily passage or orifice
/abnormally constricted body canal or passage. synonyms: stenosed/constricted
where is venous drainage in the brain?
The cerebral veins empty into the dural venous sinuses (found in subarachnoid space). The superficial system drains into the superior sagittal sinus, while the deep system drains into transverse, straight and sigmoid sinuses
n.b. the superior sagittal sinus is the biggest venous drainage vein; it’s a midline vein without valves or tunica muscularis that courses along the falx cerebri, draining many of the cerebral structures surrounding it
Arachnoid granulations (broccoli things) allow _________ to flow into venous blood of sinuses but prevent backflow of blood into subarachnoid space
- Arachnoid granulations (broccoli things) allow CSF to flow into venous blood of sinuses but prevent backflow of blood into subarachnoid space
- Allows constant flow of CSF being made/replaced
Some drain into jugular and facial veins - most drain into dural sinuses (see previous lecture)
