cerebral blood flow

Examples of cerebral blood flow in the following topics:

• Blood Flow in the Brain

  • Cerebral circulation is the movement of blood through the network of blood vessels supplying the brain, providing oxygen and nutrients.
  • Cerebral circulation refers to the movement of blood through the network of blood vessels supplying the brain.
  • Since the brain is very vulnerable to compromises in its blood supply, the cerebral circulatory system has many safeguards.
  • The amount of blood that the cerebral circulation carries is known as cerebral blood flow (CBF).
  • Too little blood flow (ischemia) results in tissue death.

• Aging and the Heart

  • By the age 80, cerebral blood flow is 20% less, and renal blood flow is 50% less than at age 30.
  • The health of the myocardium depends on its blood supply, and with age there is greater likelihood that arthrosclerosis will narrow the coronary arteries.
  • Atherosclerosis is the deposition of cholesterol on and in the walls of the arteries, which decreases blood flow and forms rough surfaces that may cause intravascular clot formation .
  • High blood pressure (hypertension) causes the left ventricle to work harder.
  • It may enlarge and outgrow its blood supply, thus becoming weaker.

• Cerebrospinal Fluid and Its Circulation

  • It acts as a cushion or buffer for the cortex, providing a basic mechanical and immunological protection for the brain inside the skull and serving a vital function in cerebral autoregulation of cerebral blood flow.
  • CSF is reabsorbed into venous sinus blood via arachnoid granulations.
  • Chemical stability: CSF flows throughout the inner ventricular system in the brain and is absorbed back into the bloodstream, rinsing the metabolic waste from the central nervous system (CNS) through the blood-brain barrier.
  • When CSF pressure is elevated, cerebral blood flow may be constricted.
  • When disorders of CSF flow occur, they may therefore affect not only CSF movement but also craniospinal compliance and intracranial blood flow, with subsequent neuronal and glial vulnerabilities.

• Aging and the Cardiovascular System

  • Changes in blood vessels that serve brain tissue reduce nourishment to the brain, resulting in the malfunction and death of brain cells.
  • By the time we turn 80, cerebral blood flow is 20% less, and renal blood flow is 50% less than when we were age 30.
  • High blood pressure (hypertension) causes the left ventricle to work harder.
  • The ventricle muscle may enlarge and outgrow its blood supply, thus becoming weaker.
  • Atherosclerosis is the deposition of cholesterol on and in the walls of the arteries, which narrows the lumen, decreases blood flow, and forms rough surfaces that may cause intravascular clot formation .

• Anastomoses

  • A circulatory anastomosis is a connection or looped interaction between two blood vessels.
  • Such anastomoses occur normally in the body in the circulatory system, serving as backup routes for blood to flow if one link is blocked or otherwise compromised, but may also occur pathologically.
  • The arrangement of the brain's arteries into the circle of Willis creates redundancies for the cerebral circulation.
  • If one part of the circle becomes blocked or narrowed or one of the arteries supplying the circle is blocked or narrowed, blood flow from the other blood vessels can often preserve the cerebral perfusion well enough to maintain function.
  • Blood flows up to the brain through the vertebral arteries and through the internal carotid arteries.

• Ventricles

  • The cavities of the cerebral hemispheres are called lateral ventricles or first and second ventricles.
  • CSF flows from the lateral ventricles via the foramina of Monro into the third ventricle, and then into the fourth ventricle via the cerebral aqueduct in the brainstem.
  • The fluid then flows around the superior sagittal sinus to be reabsorbed via the arachnoid villi into the venous system.
  • CSF within the spinal cord can flow all the way down to the lumbar cistern at the end of the cord around the cauda equina.
  • Diseases of the ventricular system include abnormal enlargement (hydrocephalus) and inflammation of the CSF spaces (meningitis, ventriculitis) caused by infection or introduction of blood following trauma or hemorrhage.

• Veins of the Head and Neck

  • In the head and neck, blood circulates from the upper systemic loop, which originates at the aortic arch.
  • The deep-lying internal jugular vein receives blood from the dural venous sinuses in the brain as well as the cerebral and cerebellar veins.
  • The dural sinuses receive blood from the veins that drain the brain and skull.
  • As well as removing blood from the brain, the anterior retromandibular, facial, and lingual veins also drain into the internal jugular.
  • Outline the flow of blood in veins in the head and neck

• Blood Flow in the Skin

  • Blood flow to the skin provides nutrition to skin and regulates body heat through the constriction and dilation of blood vessels.
  • When vasoconstricted, blood flow through the skin is reduced, so less core heat is lost.
  • With restricted blood flow, the skin appears paler.
  • When vasodilated, blood flow through the skin is increased, meaning more core heat can be lost through radiation.
  • With increased blood flow, the skin appears red.

• Cerebrovascular Accident

  • This can be due to ischemia (lack of blood flow) caused by blockage (thrombosis, arterial embolism), or a hemorrhage (leakage of blood).
  • High blood pressure is the most important modifiable risk factor of stroke.
  • Systemic hypoperfusion is the reduction of blood flow to all parts of the body.
  • Hypoxemia (low blood oxygen content) may precipitate the hypoperfusion.
  • Cerebral venous sinus thrombosis leads to stroke due to locally increased venous pressure, which exceeds the pressure generated by the arteries.

• Syncope

  • Syncope, the medical term for fainting, is defined as a transient loss of consciousness and postural tone characterized by rapid onset, short duration, and spontaneous recovery due to global cerebral hypoperfusion that most often results from hypotension.
  • Vasovagal (situational) syncope, one of the most common types, may occur in scary, embarrassing or uneasy situations, or during blood drawing, coughing, urination or defecation.
  • In vasovagal syncope, the vagus nerve decreases blood flow to the brain.
  • There are many other causes of syncope, including low blood sugar levels and lung disease such as emphysema and a pulmonary embolus.
  • The vagus nerve, labeled at the top left and colored in yellow, may lower heart rate, reducing blood flow to the brain and causing vasovagal syncope.