cerebral blood flow and brain metabolism Flashcards
what is the brain tissue dependant on for energy?
the brain requires significant amounts of ATP to be generated from glucose, neurons have an abundance of mitochondria and also require O2 in order to obtain maximal levels of ATP per glucose molecule
how does oxygen and glucose get into neurons?
O2 diffuses across the blood brain barrier, while glucose requires a specific transporter
describe the blood brain barrier
the blood brain barrier consists of brain capillary endothelial cells which are connected tightly to each other by tight junctions, permitting tight regulation of substances that might enter the brain tissues
what percentage of total blood flow and O2 consumption occurs within the brain
represents only 2% of total body weight
it receives 15% of total blood flow
20% O2 consumption
alterations to cerebral metabolism occur in
ischaemic or hypoxic events
- stroke
- haemorrhage
encephalopathy (an acute usually reversible global brain dysfunction which causes an altered mental state or altered state of consciousness)
- metabolic
- infective
- post-ictal
- drugs
- electrolyte disturbances
metabolic causes of encephalopathy include
- liver failure (excessive ammonia)
- kidney failure (excessive urea)
- hypoxia or hypercapnia
- diabetic hypoglycaemia
the circle of willis
is a six sided polygon shaped collection of arteries formed at the base of the brain at the suprasellar subarachnoid cistern (above the sella turcica), it passes above the optic nerve and oculomotor nerves but under the optic tracts
it contributes most of the blood supply to the brain
the left hemisphere is supplied by the left vertebral and left internal carotid arteries and vice versa
when there is a blockage the configuration of the Circle of Willis provides a means of collateral circulation
the basal ganglia and internal capsule are perfused by which arteries
the lenticulostriate arteries (a deep branch of the MCA) and the recurrent artery of Heubner (ACA)
The normal arrangement of the Circle of Willis looking inferiorly on the brain
ACA + AComm internal carotid + MCA PComm PCA + basilar Superior cerebellar artery AICA vertebral artery + anterior spinal PICA
the middle cerebral artery has two main cortical branches
a superior and inferior
