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Lecture

Feb 29th_2012_PhysioII.docx

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Department
Kinesiology & Health Science
Course Code
KINE 2011
Professor
Gillian Wu

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Feb 29 ,2012 Lecture Notes Composition of Arterioles The SEM of arterioles Endothelial cells are in direct contact with the blood (thin layer of cells) Smooth muscle cells form layers around the endothelial cells Arteriole is a nice long tube, endothelial cells run lengthwise along the surface , smooth muscle cells are circumferentially around it. Wrapping around allows the smooth muscle to control the diameter of the arteriole. The smooth muscle cells can change capacity, contract and relax. If they are fully contracted, they are going to squeeze the arteriole to smaller diameter which will create A HIGH RESISTANCE FLOW PATHWAY (more difficult for blood to enter and pass through this arteriole). If Smooth Muscle small relax then arteriole can take a larger circumference , and a lot more blood can pass through it. That is whats going on in order to mainupulate blood flow through arteriole Endothelial cells, they are the inner lining of all the blood vessels, cardiac chambers, & arterioles. Endothelial cells were recognized to play major role in preventing blood cells and platelets from globing on to the sides. Endothelial cells keep the blood cells & platelets from adhering to the surface, which prevents the clots from occurring at random locations throughout the blood vessels. Thrombus that can form on the inner side of atherscelotic plaque, because it can fill up blood vessel with the clot, IT HAPPENS IF THE ENDOTHELIAL CELLS GET DAMAGED. The endothelial cells are not creating smooth layer therefore a LARGE CLOT is formed. Endothelial cells structure is imp in controlling exchanging fluids and nutrients from within the plasma compartment to Extracellular compartment and other cells. Important substances are produced by endothelial cells, and have direct effect on smooth muscle cells, .. Nitric oxide is a vasodilator(dilation to enlarge) vasodilator increases the diameter of blood vessel, meaning it increases flow. Endothelin (produced in large quantities, for people that have high blood pressure) very powerful vasoconstrictor and causes the smooth muscles to contract and reduce the diameter of the arteriole. Endothelial cells within the capailiers through the process of angiogenesis. They also have effect on smooth muscle cells, Also effect if cells will be proliferate (multiply) NORMALLY YOU DON’T WANT SMOOTH MUSCLE CELLS TO MULTIPLY YOU WANT IT TO CONTINUE, iTS BAD, but it happens in atherscelorsis. Endothelial cells regulate inflammatory responses because they are the cell layer that immune cells have to interact with in order for immune cells to exit the blood and get to the side of infection, .. There are specific interactions that need to occur…Endothelial cells make sure they occur. Function of Smooth Muscle cells. Wrapping around the exterior Provide statbility and strength to the arteriole, Arteriole cells are very thin and can’t support and on their own they cannot support a lot of pressure, so smooth muscle cells make them stable. Smooth muscle cells main job is setting the blood vessel diameter in doing so they regulate blood flow. They can contract and relax, but they are normally operating at a level of partial contraction (unlike striated muscle all or none response). Smooth muscle will be partial contracted in NORMAL conditions this is called vascular tone . Because the smooth muscle cells can hold this for hours and hours, and they can do this because they have diff structure of actin and myosin inside them and different myosin ATPases. Major point is that they can hold partial contraction for a LONG time, (under normal conditions) By operating at partial contraction, they have max felxibaility to whatever signals they recived, it’s the vascular tone, that is set by arterioles, THAT DETERMINES WHAT YOUR MEAN ARTERIAL PRESSURE IS. Smooth muscle cells it helps regulate blood flow and establish mean arterial pressure. Smooth muscle cells can also be a big player in hypertension ( high blood pressure).Smooth muscle cells will spend more time in constricted state so there is more resistance. Nitric Oxide (NO) POSTED ON MOODLE Nitric oxide is major VASODILATOR in endothelial cells. Nerves can also make it This process involves using an amino acid, called L-Arginine which is the substrate for the enzyme that makes nitric oxide which is called nitric oxide synthase, Nitric oxide is a gas, (NO) Nitrous gas ( laughing gas) Nitric oxide is lipid soluable which means that its not going to just stay in endothelial cells , its freely diffusible so it can diffuse across the endothelial cell membrane, across the space that seperates endotheliam and smooth muscle cells, and right into the smooth muscle cells. Does not require receptor because it just moves freely through lipid memembrane. Once its inside the smooth muscle will cause activation of an enzyme Guanlate cyclase (responsible for producing secondary messenger called cGMP) ---increases in the cGMP causes the relaxation of the smooth muscle cells, coz the myosin and actin cross bridges break apart allowing the cell to relax. When the smooth muscle cell relaxes and dimater of the arteriole increases and more blood flow is coming through the arterial. 2 step process. (i) the cell that makes the nitric oxide (endothelial cells) (ii) the cell that actually have to react to the nitric oxide respond to it Endothelial cells have no capacity to change the diameter on their own, OR cause the blood vessel to change the shape on its own, we need to have smooth muscle cell reacting to a stimulus in order to get change in blood flow. But the endothelial provides this signal to the smooth muscle cells. Endothelial cells constantly produce low level of nitric oxide, and so you always have smooth muscle cells having nitrix oxide coming to them which maintains a healthy (VASCULAR SYSTEM) Nitric oxide gas is very unstable, doesn’t last it gets broken into nitrates. So you cant get it to go very far, since it breaks down fast. Nitric Oxide (PRACTICAL APPLICATIONS) Exercise physiology; nitric oxide production is enhanced in the body , taken the pill prior to workout so you since more blood will be rushing to muscle so you get much stronger muscle pumpe will be able to work out more extremely and develop more muscle mass and work out more extremely. Pill is L-arginine that will help you produce more nitric oxide will active gynalate cyclase wwhich will activate cGMP which will get hyper activation of nitric oxide OR relaxation of smooth muscle so there is more blood flowing. There are NO SCIENTIFIC studies that show that in healthy individuals that taking in more L-arginine will produce more nitric oxide. Since L-arginine is not a limiting factor of Nitric Oxide so taking in more L-arginine will not produce Nitric oxide. The limiting factor in this process is
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