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How does blood flow inform us about brain function PowerPoint Presentation

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Description : Check out this medical presentation on Artery, which is titled "How does blood flow inform us about brain function?", to know about cerebrovascular anatomy and neural regulation of CNS blood flow.

Tags : Artery, blood flow, brain function, cerebrovascular anatomy, neural regulation, CNS blood flow

Published on : Jun 02, 2021 | Views : 1565 | Downloads : 2

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Slide 1-

How does blood flow inform us about brain function? Cerebrovascular anatomy & neural regulation of CNS blood flow Neurovascular coupling HST 583 Brad Dickerson, M.D. bradd@nmr.mgh.harvard.edu
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How does blood flow inform us about brain function? Cerebrovascular anatomy & neural regulation of CNS blood flow Cerebral blood flow: intro Cerebrovascular anatomy Neurotransmitter systems & neural regulation
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Blood flow and the organ of thought “…blood supply to any part of the cerebral tissue is varied in accordance with the activity of the chemiccal changes which underlie the functional action of that part…” -- Roy & Sherrington, 1890 “We must suppose a very delicate adjustment whereby the circulation follows the needs of the cerebral activity. Blood very likely may rush to each region of the cortex according as it is most active, but of this we know nothing.” -- W. James, 1890
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Blood flow and the organ of thought Slide courtesy of M. Raichle
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Blood flow and the organ of thought The brain requires blood for: General support of maintenance functions, like every organ - requires energy (ATP) Specific localized support of functional activity related to neural activity - requires energy (ATP) Blood supplies substrates for energy production: Glucose and oxygen ~750 ml/min
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The route of blood to the head
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The route of blood within the head
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Circle of Willis
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The route of blood within the head
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T1 T2
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The route of blood within the head
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The route of blood within the head
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Scale of the circulatory system Aorta: 2.5 cm (~1 in) Large arteries (e.g., carotid): .5 - 1 cm Arterioles: 10 - 50 um Capillaries: 5 - 10 um (RBC)
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Scale of the circulatory system Large arteries (e.g., carotid): .5 - 1 cm Arterioles: 10 - 50 um
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Scale of the circulatory system Capillaries: 5 - 10 um (RBC)
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Scale of the circulatory system Venules/veins
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The route of blood within the head
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The route of blood within the head
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The route of blood within the head
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The route of blood within the head
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Pial arteriolar anastomoses 1 mm From Edvinsson, 1993
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AP view: Vertebral artery angiogram
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5 mm Cortical capillary vasculature
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5 mm Cortical neural structure
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5 mm Cortical capillary vasculature Grey matter has 2-4 times the capillary density of white matter
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Cerebellar Vasculature
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Inferior Olivary Nucleus and Inferior Cerebellar Peduncle 2 mm From Duvernoy, 1995
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Cerebellar Histology Blue = myelin Pink = neuropil 1 mm From Duvernoy, 1995
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100 mm 500 mm From Duvernoy, 1995
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Cerebellar Cortical Histology
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Molecular Layer Purkinje Cells Granular Layer Cerebellar histology and vascularization From Duvernoy, 1995
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Capillary density in rat brain is proportional to metabolic rate Low levels of CBF Hypothalamus, cerebellum, medulla High levels of CBF Cochlear nucleus, mammillary body, cortex Low levels of CMRglu Hypothalamus, cerebellum, medulla High levels of CMRglu Cochlear nucleus, mammillary body, cortex From Edvinsson, 1993
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Flow of CSF
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CSF return to venous blood
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Large vessels in subarachnoid space
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Blood Brain Barrier What cerebral capillaries have: Tight continuous quintuple-layered intercellular junctions low wall thickness (0.2 um) higher mitochondrial content thick basement membrane What cerebral capillaries don’t have: fenestrations lots of vesicles fluid-filled bulk transport channels
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Blood Brain Barrier Allows passage/transport of small molecules (H2O, O2, CO2), lipophilic molecules (EtOH, heroin), passive transport of glucose, active transport of amino acids/NT precursors Prevents passage of larger molecules (dopamine), charged molecules, etc
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Measurement of blood flow to the brain Aorta 90cm/s, ICA 40cm/s, arterioles 10-250mm/s, capillaries 1mm/s Transcranial doppler ultrasound
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Cerebral autoregulation CBF remains constant over wide range of change in arterial pressure
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Flow is regulated by arteriolar smooth muscle Arterioles: 10 - 50 um
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Sites of CBF Regulation Large diameter vessels (ANS) Smaller diameter arterioles, venules (neurogenic) Must have smooth muscle with appropriate innervation and receptor site to act upon If signaling is at capillary level, message must move upstream to supplying arteriole
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Changes in cerebral blood flow can be prompted by Change in hemical mileu/blood gases Arterial hypercarbia/tissue acidosis/hypoxemia Neurotransmitter systems Autonomic nervous system Sympathetic (NE, Neuropeptide Y) Parasympathetic (ACh, VIP) Dopamine vs noradrenaline Serotonin Localized neural activity
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from hypothalamus and brain stem Global perfusion increase
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NE (fast, short acting) & NPY (slow, longer lasting) From Wilson-Pauwels, 1997 from hypothalamus and brain stem Sympathetic innervation of blood vessels
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Noradrenergic Dopaminergic from hypothalamus and brain stem Sympathetic innervation of cortical pial vessels
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Neurotransmitter systems