Term
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Definition
| Sloughing off of endothelial cells in capillary beds. |
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Term
| Origin of reserve blood needed in sympathetic response |
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Definition
| Comes from the veins and venules, function as capacitance vessels. |
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Term
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Definition
| Vessels branch off to form a larger cross sectional volume, slows down velocity of blood to facilitate exchange. |
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Term
| % of capillary perfusion at a given moment |
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Definition
| 25% of capillaries perfused at a given moment. If all capillaries perfused at the same time, CO, venous return, and BP will drop to zero, resulting in death (cardiac accident). |
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Term
| Kinds of molecular exchange in capillaries |
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Definition
1. Gases can freely diffuse through cell membranes of endothelial cells.
2. Polar molecules and ions cannot pass through cell membranes, need to diffuse between endothelial cells or through fenestrations.
3. High molecular weight proteins are severely impeded, results in osmotic pressure in capillary vessel. |
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Term
| Location of neuronal control in CV system |
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Definition
| Occurs in arteries and arterioles, mainly sympathetic innervation. Form of gross tuning, known as head pressure. |
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Term
| Location of local (paracrine) control in CV system |
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Definition
| Done in pre capillary sphincters, capillaries and veins for fine tuning resistance (through pericytes in capillaries and smooth muscle cells/pericytes in venules and veins). Amping up resistance in venules would increase pressure in capillary beds, want fine control, known as back pressure. |
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Term
| Modulation of arteriole lumen diameter |
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Definition
| Done through sympathetic innervation, NE would vasoconstrict. Have passive dilation through removal of sympathetic tone, there are very few examples of active parasympathetic or sympathetic dilators. |
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Term
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Definition
| Used in support and scaffolding around capillaries. Can also be used for local control of capillary diameter since they are contractile, can also release No to dilate capillary. Incompletely covers the capillary vessel. |
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Term
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Definition
Determines direction of fluid movement in capillaries.
Affected by water permeability of vessel, hydraulic pressure (major, forces material out of vessel) in capillary and in interstitial fluid (minor), and osmotic pressure in capillaries (major, forces materials back into vessel) and interstitial fluid (minor). |
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Term
| Sequence of exchange in capillaries. |
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Definition
1. Arteriole end: Blood flows under high pressure, the hydraulic pressure in the capillary exceeds that of the hydraulic pressure in the interstitial fluid and the osmotic pressure in the capillaries.
2. Venule end: hydrostatic pressure in the vessel now lower than osmotic pressure in vessel due to resistance in capillary vessels, materials get sucked backed into vessel. |
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Term
| Organ where reabsorption of materials into capillaries is crucial |
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Definition
| Lungs, need a dry interstitial space for gas exchange. Arteriole resistance would be high to limit hydraulic pressure in vessel. |
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Term
| Mechanisms for controlling regional blood flow |
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Definition
1. Local control, allows for fine tuning according to local needs.
2. Sympathetic neuronal control, has regional effects.
3. Hormonal Control, can be local or regional. |
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Term
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Definition
| Form of local control, achieved through stretch sensors, which activate Ca channels to depolarize cell and create vasoconstriction (myogenic response). Way of maintaining constant flow through arterioles. |
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Term
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Definition
| Flow increases to match metabolic requirements in real time, done through local control. Have metabolic regulation through signals such as lactate, pH, K, CO2, and Adenosine. Precapillary sphincters respond to metabolites. |
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Term
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Definition
| Flow increases to replenish tissue metabolic requirements after the fact. Form of local control. Have metabolic regulation through signals such as lactate, pH, K, CO2, and Adenosine. Precapillary sphincters respond to metabolites. |
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Term
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Definition
1. Autoregulation
2. Active hyperemia
3. Reactive hyperemia |
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Term
| Potassium metabolite pathway in local control of blood vessel diameter. |
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Definition
| K is high in cell normally. When there is extracellular K, this signals a low energy state, where the Na K ATPase is no longer transporting K into cell and is letting K leak out to generate ATP. Signal for the blood vessels to dilate. High K levels will result in spontaneous depolarization of nerves and myocardial cells. |
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Term
| Sympathetic innervation of arterioles |
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Definition
Skin and skeletal muscle is very highly innervated, have different receptors for different response to NE.
In skin, have alpha 1 receptors for vasodilation.
In skeletal muscle, have alpha 1 for vasoconstriction and beta 2 for vasodilation. |
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Term
| Local vasodilatory substances |
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Definition
Histamine, bradykinin, prostaglandin E
Want vasodilation in cases of minor injury to help the tissue heal faster.
Results in relaxation of arterioles and constriction of venules (inflammation). |
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Term
| Local vasoconstrictor substances |
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Definition
| Serotonin (major activator of platelets), Thromboxane A2, and Prostaglandin F. Used in times of severe tissue damage, release of vasoconstrictors limits blood loss. |
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Term
| Hormonal regulation of total peripheral resistance |
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Definition
| Done through RAAS pathway, covered in other lectures. Results in Angiotensin II, potent vasoconstrictor that raises BP, TPR, and MAP. Chronic hypertension many times results from overexpression of Angiotensin II. Must take ACE inhibitors and angiotensin II receptor blockers. |
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