Hayley Pearlman
November 2016
PAT 20 Week 8: Stroke
-Stroke is the number one cause of adult disability in Canada and the third leading cause of death
-Stroke occurs with inadequate blood flow, a condition referred to as ischemia.
Characterize the role of excitatory amino acids as a common pathway for neurologic disorders.
-Neurons become ischemic and depolarize after 5 minutes of occlusion resulting in the opening of
sodium/potassium pumps and calcium channels.
-Sodium moves into the cell and pulls water with it causing an increase in intracranial pressure.
-Because of depolarization calcium enters the cell but does not leave causing calcification of the
mitochondria. The presence of calcium triggers the release of glutamate from the post-synaptic area.
Glutamate, an excitatory neurotransmitter, triggers the entry of more calcium in the cell and more
depolarization. This cycle causes the release of free radicals and other harmful toxins as the ischemic
cells begin to die. This is the calcium cascade.
-Calcification of the mitochondria causes them to break down and for apoptosis (cell suicide) to occur.
-Cytokines are released and the inflammatory process begins increasing intracranial pressure and
ultimately accelerating cell death.
-Nitric oxide is released in compensation and increases perfusion. The reperfusion of injured areas can
be detrimental and cause further injury.
List the major vessels in the cerebral circulation and state the contribution of the internal carotid
arteries and vertebral arteries and the circle of Willis to the cerebral circulation.
-2 internal carotid arteries which supplement the anterior circulation.
-Branch into the middle cerebral and anterior cerebral arteries.
-Supply the frontal, parietal, and temporal lobes, the basal ganglia and sections of the thalamus
and hypothalamus.
-2 vertebral arteries which supplement the posterior circulation.
-Branch into the basilar artery posterior cerebral artery circle of Willis
-Supply the middle and lower temporal lobes, the occipital lobes, the cerebellum, brainstem,
and sections of the thalamus and hypothalamus.
-The distal ends of the internal carotid and vertebral arteries communicate at the base of the brain at
the circle of Willis. This anastomosis of arteries can provide lifesaving perfusion if one of the main
vessels becomes occluded.
