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Physiology II-1
Vascular System
| Question | Answer |
|---|---|
| Blood flow equation? | Change in pressure (delta P)/Resistance (R) |
| Pressure gradient across systemic circuit? | 90 mm Hg |
| Aortic (MAP) pressure? | 90 mm Hg |
| Venous (CVP) pressure? | 0 mm Hg |
| Pressure gradient across pulmonary circuit? | 15 mm Hg |
| Pulmonary arterial pressure? | 15 mm Hg |
| Pulmonary venous pressure? | 0 mm Hg |
| Factors affecting blood flow resistance? | Viscosity, vessel length, vessel radius |
| Define: total peripheral resistance | Combined resistance of all blood vessels within the systemic circuit |
| Cardiac output (CO) is equal to? | Blood flow |
| Change in pressure (delta P) is equal to? | Mean arterial pressure (MAP) |
| Resistance (R) is equal to? | total peripheral resistance (TPR) |
| Flow=delta P/R is equal to which equation? | CO=MAP/TPR |
| What are characteristics of arteries? | Thick, elastic, large radius, rapid transport, pressure reservoir - contain collagen and elastin |
| What are characteristics of microcirculation? | Site of exchange, small radius, thin walls |
| What are characteristics of veins? | Thin walls, large radius, highly distensible, blood reservoir |
| What blood vessels have endothelial layer? | Inner layer of all blood vessels |
| How does the arterial pressure reservoir work? | Expand during systole and recoil during diastole - low compliance |
| Why is diastolic pressure 80 mm Hg? | Due to elastic recoil - min pressure is not 0 |
| What is used to measure blood pressure indirectly? | Sphygmomanometer, listen for turbulent blood flow sounds |
| Which blood vessel provides greatest resistance to blood flow? | Arterioles |
| What is active hyperemia? | Increased blood flow in response to increased metabolic demands - intrinsic chemical regulation of vascular resistance |
| What is reactive hyperemia? | Increased blood flow in response to previously decreased blood flow - intrinsic chemical regulation of vascular resistance |
| What does Nitric Oxide (NO) cause in a blood vessel? | Vasodilation |
| What does Endothelin cause in a blood vessel? | Vasoconstriction |
| What does Histamine cause in a blood vessel? | Vasodilation - released during inflammatory response/anaphylaxis - intrinsic chemical regulation of vascular resistance |
| What does local heat application cause in a blood vessel? | Increased blood flow due to local vasodilation - intrinsic physical regulation of vascular resistance |
| What does local cold application cause in a blood vessel? | Decreased blood flow due to local vasoconstriction - intrinsic physical regulation of vascular resistance |
| What is shear stress? | Friction of blood on vessels |
| What is the vascular response to an increase in shear stress? | Release NO - vasodilation - decrease shear stress |
| What is the myogenic response to blood vessel stretch? | Change in vascular resistance to counteract changes in resistance - autoregulate blood flow |
| How does the regulation of blood flow change during exercise? | Cardiac output increases, skeletal muscle vessels vasodilate, GIT & kidneys vasoconstrict |
| Which nervous system(s) control arterial radius? | Sympathetic only except in penis & clitoris |
| Which brain structure regulates arterial radius? | Medulla |
| What is the purpose in the sympathetic response for vasoconstriction? | Increases MAP and TPR |
| What are the receptors for norepinephrine and what is its role in the blood vessels? | a1 andrenergic receptors - vasoconstriction |
| What are the receptors for epinephrine and what is its role in the blood vessels? | B2 andrenergic receptors - vasodilation - in skeletal & cardiac muscle ONLY |
| What is the hormonal regulation of arterial radius? | Vasoconstrictors are released following decreases in blood volume - vasopressin and angiotensin II |
| What are the properties of capillaries? | exchange material between blood and cells, slow velocity, maximize diffusion |
| What are continuous capillaries? | Small molecules can move through (not proteins), most common |
| What are fenestrated capillaries? | Large gaps between cells allow proteins and/or blood cells through - found in kidneys, liver, intestines, and bone marrow |
| How is blood flow regulated through capillary beds? | Precapillary sphincters |
| Where does mediated transport occur? | Brain |
| What is bulk flow? | Movement of water and solutes as a unit |
| What is a hydrostatic pressure gradient? | Force due to a fluid - capillary and interstitial |
| What net movement does capillary hydrostatic pressure (Pcap) favor? | Filtration |
| What net movement does interstitial fluid hydrostatic pressure (Pif) favor? | Absorption |
| What is osmotic pressure gradient? | Water moves to high [solute] area to balance concentration gradient |
| What net movement does capillary oncotic pressure (∏cap) favor? | Absorption (attractive force for water to move into capillary) |
| What net movement does interstitial fluid oncotic pressure (∏if) favor? Filtration | |
| What is net filtration pressure? | Filtration pressure - absorption pressure... NFP=(Pcap+∏if)-(∏cap+Pif)... if NFP negative, filtration is more than absorption |
| Does standing on your feet favor filtration or absorption? | Increase of Pcap favors filtration |
| Is the lymphatic system open or closed? Open, starts at capillaries and drains into right thoracic duct into right atrium | |
| What is movement of the lymphatic system due to? | Skeletal muscle pump |
| What effect does high compliance have on veins? | Can handle large volumes of blood with little change in pressure |
| What is central venous pressure? | The pressure in the vena cava leading to the right atrium |
| What is venous return? | The volume of blood entering each atrium per minute |
| What effect does sympathetic stimulation have on venous return? | Vasoconstriction increases venous return |
| What effect does the skeletal muscle pump have on venous return? | Muscle contracting & relaxing pumps blood through veins, valves create unidirectional flow |
| What effect does the respiratory pump have on venous return? | Inspiration decreases thoracic pressure and increases abdominal pressure - favors blood movement to thoracic cavity |
| What effect does cardiac suction have on venous return? | Ventricular contraction and relaxation increase atrial & ventricular volume - increase venous return |
| What effect does blood volume have on venous return? | Blood volume impacts CVP and therefore increases or decreases venous return |
| What is the long-term regulation of blood pressure? | Blood volume |
| How is MAP determined? | MAP=HRxSVxTPR |
| Why is the regulation of MAP important? | Critical for homeostasis - need enough driving force to pump blood around body |
| What is the short-term regulation of MAP? | Neural control regulates CO and TPR - involves heart and blood vessels |
| What is the long-term regulation of MAP? | Hormonal control regulates blood volume through thirst and urine output via kidneys |
| What is the MAP baroceptor reflex? | Stretch receptors drop HR, SV, CO, and TPR and increase vasodilation until BP returns to normal |
| What role does epinephrine play in the hormonal regulation of MAP? | Increases HR, SV, TPR, and tone |
| What role does vasopressin play in the hormonal regulation of MAP? | Increases TPR and MAP |
| What role does angiotensin II play in the hormonal regulation of MAP? | Increases TPR and MAP |
Created by:
ugrn
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