Cerebral Circulation and Stroke

A set of vocabulary flashcards that cover the major vessels, measurement techniques, regulatory mechanisms, and clinical aspects of cerebral circulation and stroke.

Cerebral circulation

The movement of blood through the brain’s arterial, capillary, and venous systems to supply oxygen and nutrients and remove waste.

Normal cerebral blood flow (CBF)

Approximately 750–800 mL of blood per minute, equal to ~15–16 % of cardiac output or 50–55 mL/100 g of brain tissue per minute.

Basilar artery

A major artery formed by the union of the vertebral arteries that supplies the brainstem, cerebellum, and posterior cerebral regions.

Internal carotid artery

One of the brain’s two primary inflow vessels; contributes to the Circle of Willis and supplies anterior and middle cerebral territories.

Circle of Willis

An arterial ring at the brain’s base formed by branches of the basilar and internal carotid arteries, providing collateral blood flow.

Cranial venous sinuses

Endothelial-lined channels that drain cerebral venous blood into the internal jugular veins.

Internal jugular vein

The main venous outflow pathway that receives blood from cranial sinuses and returns it to the systemic circulation.

Kety and Schmidt Nitrous Oxide Method

An indirect CBF measurement technique using inhaled nitrous oxide as a diffusible indicator, based on the Fick principle.

Fick principle

Physiological concept stating that blood flow to an organ equals the uptake (or release) of a substance divided by the arteriovenous concentration difference.

Radioactive tracer method (CBF)

Technique in which a radioactive substance (e.g., xenon, 2-deoxyglucose) is injected and regional brain blood flow is calculated from detected radioactivity.

Radioactive xenon

Inert gas tracer commonly used to assess regional cerebral blood flow via external detectors.

2-Deoxyglucose (radioactive)

Glucose analogue labeled with a radioisotope; accumulates in metabolically active brain areas to map regional perfusion.

Scintillation counter

Device that detects gamma radiation from radioactive tracers to quantify their concentration in tissue.

Computed (Computerized) Axial Tomography (CT)

X-ray–based imaging technique that can estimate cerebral blood flow and identify structural brain lesions.

Positron Emission Tomography (PET)

Imaging method using positron-emitting tracers to visualize metabolic activity and regional cerebral perfusion.

Magnetic Resonance Imaging (MRI)

Imaging modality employing magnetic fields and radio waves; specialized sequences (e.g., perfusion MRI) assess cerebral blood flow.

Autoregulation (cerebral)

Intrinsic ability of the brain to maintain nearly constant blood flow when mean arterial pressure ranges between ~60 and 140 mm Hg.

Effective perfusion pressure

Difference between mean arterial pressure and cerebral venous pressure (≈0 mm Hg); primary determinant of cerebral blood flow.

Cerebral vascular resistance

Opposition to blood flow in cerebral vessels, influenced by vessel caliber, intracranial and CSF pressures, and blood viscosity.

Intracranial pressure (ICP)

Pressure within the skull; elevated ICP compresses cerebral vessels and increases vascular resistance.

Cerebrospinal fluid (CSF) pressure

Hydrostatic pressure of CSF that can compress cerebral vessels when elevated, reducing blood flow.

Cushing reflex

Protective response to cerebral ischemia: elevated ICP triggers systemic hypertension via vasomotor center activation to restore brain perfusion.

Blood viscosity (effect on CBF)

Inverse relationship: higher viscosity (e.g., polycythemia) increases resistance and lowers CBF; lower viscosity (e.g., anemia) does the opposite.

Chemical regulation of CBF

Adjustment of cerebral blood vessel diameter in response to PaO₂, PaCO₂, and pH/H⁺ levels.

Carbon dioxide (hypercapnia)

Most potent physiological vasodilator in the brain; PaCO₂ >45 mm Hg dilates vessels and elevates CBF via formation of carbonic acid and H⁺.

Hypoxia (low O₂)

Stimulus that increases cerebral blood flow through vasodilation to maintain oxygen delivery.

Sympathetic vasoconstrictor fibers (brain)

Nerves that can constrict cerebral vessels during extreme hypertension, limiting blood flow to prevent hemorrhage; minimal effect under normal conditions.

Stroke

Sudden loss of neurological function due to inadequate cerebral blood supply, leading to reversible or irreversible deficits; also called cerebrovascular accident (CVA).

Ischemic stroke

Stroke subtype caused by arterial occlusion from thrombus or atherosclerotic embolus, resulting in localized brain ischemia.

Hemorrhagic stroke

Stroke subtype resulting from rupture of a cerebral vessel and bleeding into brain tissue.

Stroke risk factors

Conditions that raise stroke likelihood: heart disease, hypertension, hypercholesterolemia, diabetes mellitus, heavy smoking, and excessive alcohol use.

Common stroke symptoms

Dizziness, loss of consciousness, weakness or paralysis (often unilateral), numbness, speech impairment, emotional changes, poor coordination, memory loss.