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Autoregulation of perfusion

As the name would suggest, autoregulation mechanisms require neither specialized nervous stimulation nor endocrine control. Rather, these are local, self-regulatory mechanisms that allow each region of tissue to adjust its blood flow—and thus its perfusion. These local mechanisms include chemical signals and myogenic controls.

Chemical signals involved in autoregulation

Chemical signals work at the level of the precapillary sphincters to trigger either constriction or relaxation. As you know, opening a precapillary sphincter allows blood to flow into that particular capillary, whereas constricting a precapillary sphincter temporarily shuts off blood flow to that region. The factors involved in regulating the precapillary sphincters include the following:

  • Opening of the sphincter is triggered in response to decreased oxygen concentrations; increased carbon dioxide concentrations; increasing levels of lactic acid or other byproducts of cellular metabolism; increasing concentrations of potassium ions or hydrogen ions (falling pH); inflammatory chemicals such as histamines; and increased body temperature. These conditions in turn stimulate the release of NO, a powerful vasodilator, from endothelial cells (see [link] ).
  • Contraction of the precapillary sphincter is triggered by the opposite levels of the regulators, which prompt the release of endothelins, powerful vasoconstricting peptides secreted by endothelial cells. Platelet secretions and certain prostaglandins may also trigger constriction.

Again, these factors alter tissue perfusion via their effects on the precapillary sphincter mechanism, which regulates blood flow to capillaries. Since the amount of blood is limited, not all capillaries can fill at once, so blood flow is allocated based upon the needs and metabolic state of the tissues as reflected in these parameters. Bear in mind, however, that dilation and constriction of the arterioles feeding the capillary beds is the primary control mechanism.

The myogenic response

The myogenic response    is a reaction to the stretching of the smooth muscle in the walls of arterioles as changes in blood flow occur through the vessel. This may be viewed as a largely protective function against dramatic fluctuations in blood pressure and blood flow to maintain homeostasis. If perfusion of an organ is too low (ischemia), the tissue will experience low levels of oxygen (hypoxia). In contrast, excessive perfusion could damage the organ’s smaller and more fragile vessels. The myogenic response is a localized process that serves to stabilize blood flow in the capillary network that follows that arteriole.

When blood flow is low, the vessel’s smooth muscle will be only minimally stretched. In response, it relaxes, allowing the vessel to dilate and thereby increase the movement of blood into the tissue. When blood flow is too high, the smooth muscle will contract in response to the increased stretch, prompting vasoconstriction that reduces blood flow.

[link] summarizes the effects of nervous, endocrine, and local controls on arterioles.

Questions & Answers

respiration is not just taking in of oxygen and bringing out Co2. that is called INHALATION AND EXHALATION. BUT RESPIRATION IS THE BREAKDOWN OF LARGE MOLECULES OF GLUCOSE OR OTHER SUBSTRATES IN THE PRESENCE OF OXYGEN AND SUBSEQUENT REMOVAL OF WASTE PRODUCT
Osuji Reply
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esther Reply
to know the detailed functioning of the internay body organs
Jam
we study anatomy to know about the structure of the organs which in turn help to study physiology which is the knowledge related to function of the vital organ,and when we know the normal functionality we can understand the abnormalities in that organ,and the study of disease is called pathology
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the study of structure and function of internal body parts
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is a branch of biology which describes the structures of the body and relationship from one part to another
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mwitwa Reply
Anatomy is the study of structures of the body
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Physiology the study functions of the body
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anatomy is the study of internal body structures and physiology is the functioning of these structures in the body
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it an organ found in our thoracic cavity
Richard
lungs are spongy organs where our respiration takesplace
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Lungs is a spongy organs located in the chest , is an a primary organs of respiration in human body and other Animals
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lungs thorex me present hote hai ye organ hai and gas exchange (o2,co2 exchange)inka inka function hai.
PRIYANKA
lungs ka function hai
OM
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main function is respiration
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respiration is the taking ing of oxygen by the body tissues and the removal of carbondioxide from the body tissues
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heart beat is the process briting
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To circulate the blood
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it pump blood to the lungs
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very twiest
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Cells die and reproduce
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knuckle of the middle finger
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because of the gases (nitrogen, oxygen)
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To prevent collision with the lungs, lubricates the heart, protects the heart from infection in the event a peripheral organ is effected, and stabilizes the heart within the mediastinum.
Jeremiah
This app should be updated too much as there is very little information for some topics.I hope you will consider my information....
aman Reply
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motor root of the trigeminal nerve
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muscular system
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nucleus ribosome Golgi body call membrane cytoplasm
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Organelles of the cell are: Mitochondria,Ribosome,golgi apparatus, nucleus, secretory granules, nuclear e t c
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Richard
Local hormones are hormones that effect the cell that released them or cells near the releasing cell and they do not circulate within the blood stream.
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the trachea bifurcated into how many branches on the right lung
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three lobes
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Explain the normal flow of blood.
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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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