Cerebral blood flow, or CBF, is the amount of blood that enters the brain. The adult human brain uses about 20% of the blood put out by the heart at rest (Orlando Regional Healthcare, 2004), and blood normally takes up about 10% of the intracranial space (Sanders and McKenna, 2001; Walters, 1998). Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte. ... In animals, the brain, or encephalon (Greek for in the head), is the control center of the central nervous system. ... A sketch of the human brain by artist Priyan Weerappuli, imposed upon the profile of Michaelangelos David. ... The heart and lungs, from an older edition of Grays Anatomy. ... The cranial cavity is the relatively large space formed inside the skull. ...

CBF is tightly regulated to meet the brain's metabolic demands, and on the average must be maintained at a flow of 50 milliliters of blood per 100 grams of brain tissue per minute (Orlando Regional Healthcare, 2004). It is important to maintain CBF within narrow limits because too much blood can raise intracranial pressure (ICP), which can compress and damage delicate brain tissue, and too little blood causes ischemia, or inadequate blood supply. Ischemia results if blood flow to the brain is below 18 to 20 ml per 100 g per minute, and tissue death occurs if flow dips below 8 to 10 ml per 100 g per minute. In brain tissue, a biochemical cascade known as the ischemic cascade is triggered when the tissue becomes ischemic, potentially resulting in damage to and death of brain cells. Medical professionals must take steps to maintain proper CBF in patients with conditions like shock, stroke, and traumatic brain injury. Cerebral blood flow in excess of 55 to 60 ml per 100 g per minute, called hyperemia, is more than the brain needs and can contribute to an increase in intracranial pressure. Overview of the citric acid cycle The citric acid cycle, one of the central metabolic pathways in aerobic organisms. ... Intracranial pressure, (ICP), is the pressure exerted by the cranium on the brain tissue, cerebrospinal fluid (CSF), and the brains circulating blood volume. ... In medicine, ischemia (Greek ισχαιμία, isch- is restriction, hema or haema is blood) is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. ... A Biochemical Cascade is a series of chemical reactions in which the products of one reaction are consumed in the next reaction. ... The ischemic cascade is a series of biochemical reactions that take place in the brain after seconds to minutes of ischemia (inadequate blood supply) (Arnold, 2003). ... Drawing by Santiago Ramón y Cajal of neurons in the pigeon cerebellum. ... Shock is a serious medical condition where the tissue perfusion is insufficient to meet the required supply of oxygen and nutrients. ... A stroke, also known as cerebrovascular accident (CVA),[1] is an acute neurological injury in which the blood supply to a part of the brain is interrupted. ... Traumatic brain injury(like james mousdell) (TBI), traumatic injuries to the brain, also called intracranial injury, or simply head injury, occurs when a sudden trauma causes brain damage. ... Hyperaemia (AmE hyperemia) is the medical condition in which blood congests in a part of the body. ...

Cerebral blood flow is determined by a number of factors, such as viscosity of blood, how dilated blood vessels are, and the net pressure of the flow of blood into the brain, known as cerebral perfusion pressure, which is determined by the body's blood pressure and intracranial pressure. Cerebral blood vessels are able to change the flow of blood through them by altering their diameters in a process called autoregulation; they constrict when systemic blood pressure is raised and dilate when it is lowered (Kandel, 2000 p.1305). Arterioles also constrict and dilate in response to different chemical concentrations. For example, they dilate in response to higher levels of carbon dioxide in the blood (Kandel, 2000 p.1305). The pitch drop experiment at the University of Queensland. ... The arterial system The blood vessels are part of the circulatory system and function to transport blood throughout the body. ... Cerebral perfusion pressure, or CPP, is the net pressure of blood flow to the brain. ... A sphygmomanometer, a device used for measuring blood pressure. ... Autoregulation is a specific form of homeostasis used to describe the tendency of the body to keep blood flow constant when blood pressure varies. ... Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms. ...

Functional magnetic resonance imaging and positron emission tomography are neuroimaging techniques that can both be used to measure CBF. These techniques are also used to measure regional CBF (rCBF) within a specific brain region. Functional magnetic resonance imaging (fMRI) is the use of MRI to measure the hemodynamic response related to neural activity in the brain or spinal cord of humans or other animals. ... Image of a typical positron emission tomography (PET) facility Positron emission tomography (PET) is a nuclear medicine medical imaging technique which produces a three dimensional image or map of functional processes in the body. ... Neuroimaging includes the use of various techniques to either directly or indirectly image the structure, function, or pharmacology of the brain. ...

See also

• Cerebral perfusion pressure
• Cerebral circulation

Cerebral perfusion pressure, or CPP, is the net pressure of blood flow to the brain. ... Cerebral circulation refers to the blood vessels, arteries and veins, carrying blood to and away from the brain, respectively. ...

References