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.
, Hayley Pearlman
November 2016
-The deep cerebral venous system and the superficial venous system drain the cerebral circulation into
the dural venous sinuses. The sinuses return blood to the heart through the internal jugular veins.
-The intracranial venous system has no valves and is dependent on internal pressure and gravity.
Intracranial pressure is briefly increased by coughing and performing the Valsalva manoeuvre. Because
the Valsalva manoeuvre increases ICP many strokes happen while having a bowel movement.
Anterior cerebral artery innervates the frontal lobe infarction resulting in paralysis of foot or leg,
altered gait, problems with decision making or performing arts, lack of spontaneity, easily distracted,
slowness of thought, incontinence, and affective disorders.
Middle cerebral artery innervates lateral hemisphere, deeper structures of the frontal, parietal, and
temporal lobes, internal capsule, and basal ganglia infarction resulting in hemiplegia of the face and
arm, sensory impairment, altered LOC,
Posterior cerebral artery innervates occipital lobes infarction causes visual disturbances
Basilar and vertebral arteries innervate the thalamus, cerebellum, and brain stem infarction
causes loss of sensory modalities, loss of purposeful movement
Describe the process of autoregulation with respect to cerebral blood flow and the implications in the
presence of a stroke.
-Cerebral autoregulation: The ability of the brain to maintain constant cerebral blood flow despite
changes in systemic arterial pressure.
-The brain requires a continuous blood supply of 750 to 1000 mL/min or 20% (1/6) of the cardiac output
for optimal brain functioning. Cerebral autoregulation is maintained within a MAP range of 60-
140mmHg.
-When cardiac output is reduced by 1/3 homeostatic mechanisms are overcome and cerebral
blood flow is reduced.
-Changes in blood viscosity (risk factors: smoking, obesity) alter cerebral blood flow. Decreased
viscosity increases cerebral pressure.
-When blood flow is interrupted neurological metabolism is altered within 30 seconds, metabolism
stops in 2 minutes, and cellular death occurs after 5 minutes.
-When oxygen is restricted anaerobic metabolism occurs resulting in the production of lactic
acid.
-Collateral circulation develops to compensate for decreased in cerebral blood flow. Collateral
circulation can be lifesaving when occlusions occur.
-Autoregulation utilizes metabolic factors to initiate constriction or dilation of cerebral vessels to
maintain a constant intracranial blood pressure.
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.
, Hayley Pearlman
November 2016
-The deep cerebral venous system and the superficial venous system drain the cerebral circulation into
the dural venous sinuses. The sinuses return blood to the heart through the internal jugular veins.
-The intracranial venous system has no valves and is dependent on internal pressure and gravity.
Intracranial pressure is briefly increased by coughing and performing the Valsalva manoeuvre. Because
the Valsalva manoeuvre increases ICP many strokes happen while having a bowel movement.
Anterior cerebral artery innervates the frontal lobe infarction resulting in paralysis of foot or leg,
altered gait, problems with decision making or performing arts, lack of spontaneity, easily distracted,
slowness of thought, incontinence, and affective disorders.
Middle cerebral artery innervates lateral hemisphere, deeper structures of the frontal, parietal, and
temporal lobes, internal capsule, and basal ganglia infarction resulting in hemiplegia of the face and
arm, sensory impairment, altered LOC,
Posterior cerebral artery innervates occipital lobes infarction causes visual disturbances
Basilar and vertebral arteries innervate the thalamus, cerebellum, and brain stem infarction
causes loss of sensory modalities, loss of purposeful movement
Describe the process of autoregulation with respect to cerebral blood flow and the implications in the
presence of a stroke.
-Cerebral autoregulation: The ability of the brain to maintain constant cerebral blood flow despite
changes in systemic arterial pressure.
-The brain requires a continuous blood supply of 750 to 1000 mL/min or 20% (1/6) of the cardiac output
for optimal brain functioning. Cerebral autoregulation is maintained within a MAP range of 60-
140mmHg.
-When cardiac output is reduced by 1/3 homeostatic mechanisms are overcome and cerebral
blood flow is reduced.
-Changes in blood viscosity (risk factors: smoking, obesity) alter cerebral blood flow. Decreased
viscosity increases cerebral pressure.
-When blood flow is interrupted neurological metabolism is altered within 30 seconds, metabolism
stops in 2 minutes, and cellular death occurs after 5 minutes.
-When oxygen is restricted anaerobic metabolism occurs resulting in the production of lactic
acid.
-Collateral circulation develops to compensate for decreased in cerebral blood flow. Collateral
circulation can be lifesaving when occlusions occur.
-Autoregulation utilizes metabolic factors to initiate constriction or dilation of cerebral vessels to
maintain a constant intracranial blood pressure.
