Cerebral circulation
Cerebral circulation | |
---|---|
Identifiers | |
MeSH | D002560 |
Anatomical terminology |
Cerebral circulation is the movement of
The following description is based on idealized human cerebral circulation. The pattern of circulation and its nomenclature vary between organisms.
Anatomy
Blood supply
Blood supply to the brain is normally divided into anterior and posterior segments, relating to the different arteries that supply the brain. The two main pairs of arteries are the
Anterior cerebral circulation
The anterior cerebral circulation is the blood supply to the anterior portion of the brain including eyes. It is supplied by the following arteries:
- Internal carotid arteries: These large arteries are the medial branches of the common carotid arteries which enter the skull, as opposed to the external carotid branches which supply the facial tissues; the internal carotid artery branches into the anterior cerebral artery and continues to form the middle cerebral artery. [4]
- Anterior cerebral artery (ACA)
- Anterior communicating artery: Connects both anterior cerebral arteries, within and along the floor of the cerebral vault.
- Middle cerebral artery (MCA)
Posterior cerebral circulation
The posterior cerebral circulation is the blood supply to the posterior portion of the brain, including the occipital lobes, cerebellum and brainstem. It is supplied by the following arteries:
- cranium the two vertebral arteries fuse into the basilar artery.
- Basilar artery: Supplies the midbrain, cerebellum, and usually branches into the posterior cerebral artery
- Anterior inferior cerebellar artery (AICA)
- Pontine branches
- Superior cerebellar artery (SCA)
- Posterior cerebral artery (PCA)
- Posterior communicating artery
Venous drainage
The venous drainage of the cerebrum can be separated into two subdivisions: superficial and deep.
- The superficial system
The superficial system is composed of
- The deep venous system
The deep venous system is primarily composed of traditional
Physiology
Cerebral blood flow (CBF) is the blood supply to the brain in a given period of time.[6] In an adult, CBF is typically 750 millilitres per minute or 15.8 ± 5.7% of the cardiac output.[7] This equates to an average perfusion of 50 to 54 millilitres of blood per 100 grams of brain tissue per minute.[8][9][10]
The radio index of cerebral blood flow/cardiac output (CCRI) decreases by 1.3% per decade, even though cardiac output remains unchanged.[7] Across the adult lifespan, women have a higher CCRI than men.[7] CBF is inversely associated with body mass index.[7]
CBF is tightly regulated to meet the brain's
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. Cerebral perfusion pressure (CPP) is defined as the mean arterial pressure (MAP) minus the intracranial pressure (ICP). In normal individuals, it should be above 50 mm Hg. Intracranial pressure should not be above 15 mm Hg (ICP of 20 mm Hg is considered as intracranial hypertension). [12] Cerebral blood vessels are able to change the flow of blood through them by altering their diameters in a process called cerebral autoregulation; they constrict when systemic blood pressure is raised and dilate when it is lowered.[13] 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 and constrict in response to lower levels of carbon dioxide.[13]
For example, assuming a person with an arterial partial pressure of carbon dioxide (
CBF is equal to the cerebral perfusion pressure (CPP) divided by the cerebrovascular resistance (CVR):[16]
- CBF = CPP / CVR
Control of CBF is considered in terms of the factors affecting CPP and the factors affecting CVR. CVR is controlled by four major mechanisms:
- Metaboliccontrol (or 'metabolic autoregulation')
- Pressure autoregulation
- Chemical control (by arterial pCO2 and pO2)
- Neuralcontrol
Role of intracranial pressure
Increased intracranial pressure (ICP) causes decreased blood perfusion of brain cells by mainly two mechanisms:
- Increased ICP constitutes an increased interstitial hydrostatic pressure that, in turn, causes a decreased driving force for capillary filtrationfrom intracerebral blood vessels.
- Increased ICP compresses cerebral arteries, causing increased cerebrovascular resistance (CVR).
Cerebral perfusion pressure
Cerebral perfusion pressure is the net
Imaging
References
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- ^ Cipolla, Marilyn J. (2009). "Anatomy and Ultrastructure". National Center for Biotechnology Information, U.S. National Library of Medicine. Morgan & Claypool Life Sciences. Retrieved June 22, 2021.
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- ^ "Carotid Arterial System". The Lecturio Medical Concept Library. Retrieved 2021-06-22.
- ^ Hufnagle, John J.; Tadi, Prasanna (2022). "Neuroanatomy, Brain Veins". StatPearls. StatPearls Publishing. Retrieved 28 February 2023.
- ^ Tolias C and Sgouros S. 2006. "Initial Evaluation and Management of CNS Injury."[full citation needed] Archived March 2, 2007, at the Wayback Machine Emedicine.com. Accessed January 4, 2007.
- ^ PMID 27789785.
- ^ a b Orlando Regional Healthcare, Education and Development. 2004. "Overview of Adult Traumatic Brain Injuries." Archived February 27, 2008, at the Wayback Machine Accessed 2008-01-16.
- ^ Shepherd S. 2004. "Head Trauma." Emedicine.com. Shepherd S. 2004. "Head Trauma." Emedicine.com. Accessed January 4, 2007.
- ^ Walters, FJM. 1998. "Intracranial Pressure and Cerebral Blood Flow." Archived May 14, 2011, at the Wayback Machine Physiology. Issue 8, Article 4. Accessed January 4, 2007.
- ^ Singh J and Stock A. 2006. "Head Trauma." Emedicine.com. Accessed January 4, 2007.
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- ^ a b Kandel E.R., Schwartz, J.H., Jessell, T.M. 2000. Principles of Neural Science, 4th ed., McGraw-Hill, New York. p.1305
- ^ Hadjiliadis D, Zieve D, Ogilvie I. Blood Gases. Medline Plus. 06/06/2015.
- ^ a b Giardino ND, Friedman SD, Dager SR. Anxiety, respiration, and cerebral blood flow: implications for functional brain imaging. Compr Psychiatry 2007;48:103–112. Accessed 6/6/2015.
- ^ AnaesthesiaUK. 2007. Cerebral Blood Flow (CBF) Archived September 18, 2010, at the Wayback Machine. Accessed 2007-10-16.
- ^ P. Vajkoczy, H. Roth, P. Horn, T. Lucke, C. Thome, U. Hubner, G. T. Martin, C. Zappletal, E. Klar, L. Schilling, and P. Schmiedek, “Continuous monitoring of regional cerebral blood flow: experimental and clinical validation of a novel thermal diffusion microprobe,” J. Neurosurg., vol. 93, no. 2, pp. 265–274, Aug. 2000. [1]