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34 Cards in this Set
- Front
- Back
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What 2 sources does the brain receive its blood supply from?
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internal carotid arteries and vertebral arteries
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The left and right vertebral arteries join to form what?
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the basilar artery
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What is the Circle of Willis?
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The basilar artery joins the blood supply from the internal carotid arteries in an arterial ring. Other arteries arise from this circle, so if one of the main arteries are blocked the smaller arteries of the brain can still receive blood from the circle of willis.
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What percentage of the oxygen cardiac output does the brain consume?
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20% (approx 750 ml/min)
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What has higher cerebral blood flow, grey or white matter?
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Grey matter, 4 times more
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what is normal cerebral blood flow?
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45 - 50ml/ 100g/ min
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What regulates CBF?
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MABP, partial pressure of arterial CO2 and O2, Neural activity, Blood viscosity
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What effect does carbon dioxide have on CBF?
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vasodilator- increases flow
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Endothelial cells have very tight junctions, why is this?
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prevents movement of large molecules across, protection of potentially toxic molecules
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Entry of molecules to brain is dependant on what?
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lipid solubility or presence of specific transporter
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What transports glucose to the brain across the blood brain barrier?
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the glucose transporter GLUT-1 present on endothelial cells of BBB
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How much cerebrospinal fluid is in human brain?
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150 ml
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What is the function of cerebrospinal fluid (CBF)?
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Bouyancy, shock absorber, removal of waste, reglutes intracranial pressure when blood volume rises
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where does CBF flow?
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In the subarachnoid space (between arachnoid and pia matter)
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Where is the subarachnoid space?
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between arachnoid and pia matter
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what produces CSF?
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the choroid plexus
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CSF is reabsorbed by what?
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the arachnoid villi
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There are two types of stroke, what are these?
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ischeamic stroke (85%) and haemorrhagic stroke (15%)
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In Ischeamic stroke, a blood clot stops flow to an area of the brain. This is happens in two ways, what are these?
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Thrombotic stroke- when a blood clot blocks an artery supplying the brain. and Embolic stroke- when a blood clot, formed somewhere else in body, travels to brain and blocks flow
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What happens in haemorrhagic stroke?
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blood vessel within the brain ruptures
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What type of stroke has higher mortality?
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haemorrhagic
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In ischaemic stroke two types of tissues arise, what are these?
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Ischaemic core (irreversibly damaged) and ischaemic Penumbra (tissue that is not normal- but may recover if blood flow is restored or correct drugs are given)
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After a stroke, as time goes on what happens?
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the reversible deficit ( the ischaemic Penumbra) is reduced. More tissue becomes permanently damaged (Infarction). must act quickly
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Thrombolysis is used when?
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In ischaemic stroke after haemorrhagic stroke has been excluded by CT scan
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How would you image brain after a stroke?
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CT scan or MRI
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Why would you image brain after stroke?
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to exclude haemorrhage, to discriminate between infarction tissue and reversible tissue, to identify location
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What type of scan detects early brain damage?
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MRI
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What type of scan detects ischaemic damage after only 5 minutes of stroke?
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Diffusion weighted imaging (DWI)- allows non-invasive measurement of the translational motion of water molecules in living tissue
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Why does diffusion decrease in stroke?
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There is an influx of water due to energy failure inhibiting Na/K pumps promoting accumulation of Na. The cell swells causing a reduction of extracellular space causing diffusion rate to decrease
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Do males or females have worse outcome after stroke?
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males
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perfusion weighted imaging can be combined with DWI to do what?
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determine what patients will benefit from thrombolysis
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What is perfusion?
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Delivery of blood to capillary bed for supply of nutrients and oxygen
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what does DWI/PWI mismatch reveal?
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penumbra (area of salvageable tissue) - where DWI is not
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Why are neurones more sensitive to oxygen deprivation?
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high metabolic rate and low energy reserve
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