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44 Cards in this Set
- Front
- Back
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Flow Rate (of blood through a vessel) |
- Directly proportional to the pressure gradient and inversely proportional to vascular resistance. - Force = Pressure gradient / Resistance |
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Pressure Gradient |
- The difference in pressure at the beginning and end of the vessel. - Blood flows from high to low pressure (same as garden hose at home) - Pressure is highest close to the heart and drops as you get further away. |
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Resistance |
- Measure of hindrance to blood flow. - The higher, the more difficult it is for blood to flow, flow rate will decrease. - The heart must pump blood harder to compensate for high friction - This is directly proportional to viscosity (thickness) of blood and vessel length, inversely proportional to vessel radius. |
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Resistance ( FC #2) |
- Your heart will pump harder - "Clogged Arteries" could be an increase in resistance - If a vessel is short it won't have friction for that long. |
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Viscosity |
- How much friction occurs between molecules of a fluid - Greater = greater resistance to flow |
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Blood Viscosity |
- Determined by how many RBC - RBC concentration can be altered by drugs and altitude (below oxygen concentration, being higher than sea level). |
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Vessel Length |
- Longer the vessel, the greater the surface area. - Our vessels are always the same length - The larger the blood vessel radius, the lower the surface area in contact with the blood. - low surface area = low resistance - radius of the arterioles (change in size the most) are constantly adjusting |
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Vessel Length (FC #2) |
- The length can change when we grow, but during adulthood they do not change. - We are always micromanaging vessels in our body ( always changing size {not length}) - Less resistance = not many blood cells touching |
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Arteries |
- Large radius and low resistance - Allows blood to be quickly sent to organs - They have elastic walls (stretch & rebound) - They stretch when the heart pumps and contract when the heart is at rest. - Blood is kept flowing through vessels at the same rate at all times. |
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Arteries (FC #2) |
- Really big - Have to be able to accept large amounts of blood -Diastolic (resting) the artery walls recoil and squeeze blood forward. - Systolic (flowing) blood is flowing forward |
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Blood Pressure |
- The force exerted by the blood against vessel walls - Depends on the volume of blood and the compliance (stretch-ability) of the vessel - arteries (highest pressure) - How much force blood is pushing on the walls - Blood pushes out and forward |
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Systolic Pressure |
- Max pressure exerted in arteries blood is ejected from the heart - about 120 mm Hg - When heart is pushing blood out |
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Diastolic Pressure |
- Minimum pressure exerted in arteries as the heart relaxes - About 80 mm Hg - Amount of pressure pushing on arterial walls. |
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Mean Arterial Pressure (MAP) |
- Mean = average - Must be high enough to maintain adequate blood flow to the tissues - Must not be so high to stress the heart or cause vascular damage - Systolic & diastolic |
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High Blood Pressure |
- A lot of stress on the heart - Can lead to ruptures and aneurisms |
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Low Blood Pressure |
- Tissues are not being fed - Stress on the whole body |
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Mean Arterial Pressure (MAP) |
- Measured by baroreceptors within the circulatory system |
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Short - Term Control Measures |
- Alters cardiac output and total peripheral resistance - Autonomic nervous influence on heart, veins, and arterioles. - How frequent and how hard the heart beats |
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Long - Term Control Measures |
- Adjust total blood volume by changing salt/water balances - Kidneys (renal system) - Changes take time |
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Changes in MAP |
- Triggers an autonomic baroreceptor reflex - The heart and blood vessels adjust to correct cardiac output and total peripheral resistance - Carotid sinus (brain needs blood up the neck) and aortic arch (The spot that has the highest pressure) baroreceptors are mechanoreceptors (monitors changes in size in the cell) |
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Increasing MAP |
- Baroreceptors fire action potentials at faster rates - The cardiac control center in the brain stem integrates inputs - Sympathetic and parasympathetic activities are controlled - Sympathetic dominance = BP increases - Parasympathetic dom. = BP decreases |
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Arterioles |
- When an artery reaches an organ, it branches which spreads throughout the organ. - The radius (can be adjusted) is much smaller - Resistance is increased and pressure decreases.
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Adjustment of Arterioles
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- Helps to regulate arterial pressure |
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Arteriole Smooth Muscle
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- Vascular tone - Allows for vessel enlargement or narrowing - Control of contraction of arteriolar smooth muscle comes from intrinsic and extrinsic factors. |
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Intrinsic Control of Arterioles
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- Comes from within the organ they reside in - Chemical influences: - Metabolic changes, histamine release - Physical influences: - Stretch response, heat/cold |
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Arterioles perform Active Hyperemia
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- Contracting skeletal muscle reduces local O2 concentrations and increases ATP and CO2 concentrations. - Relaxation of arterioles is triggered - Blood flow is increased |
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Vasoconstriction
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- Blood flow is reduced |
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Adjustments of Size to Arterioles
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- The paracrines act upon the smooth muscle beneath the endothelium. - EX: Nitric Oxide (NO) is a vasodilator, Endothelin is a vasoconstrictor. |
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Long-Term Vascular changes in Arterioles
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- Angiogenesis is triggered - Histamine can be released from damaged connective tissue or WBCs - Histamine causes local vasodilation (Redness and swelling will result. |
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Passive Stretch in Arterioles
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- This auto regulation is a safety mechanism to protect organs from high BP - Local physical changes also affect arteriolar smooth muscle |
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What causes local vasodilation?
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Heat |
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What causes local vasoconstriction?
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Cold
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Extrinsic control of Arteriolar radius
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- Increased sympathetic activity results in widespread vasoconstriction - Parasympathetic neurons do no innervate most arterioles |
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How does the endocrine system affects the arteriole radius?
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- Epinephrine reinforces sympathetic signals - vasoconstricts - Vasopressin and Angiotensin II - Increased water and salt retention by kidneys - Vasocontstrictors |
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Capillaries (Capillaries -> Venules -> Veins -> Heart) |
- There are many of these branches to supple all cells with blood flow - Almost all cells are within 0.01cm from this - Most materials are exchanged across these walls via diffusion |
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Capillary Walls
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- Faster diffusion - A single layer of endothelial cells about 1uM thick - No smooth muscle or connective tissue |
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Movement of materials in Capillaries
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- Concentration gradients drive most movement across capillary walls - Bulk flow of all materials dissolved in plasma also occurs |
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Bulk Flow of Capillaries
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- Water and solutes move as one - Not driven by a concentration gradient - Occurs due to a combination of all 4 factors |
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Ultrafiltration
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- Normally occurs at the beginning of the capillary |
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Reabsorption
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- Normally occurs at the end of the capillary |
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Veins
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- Which then returns to the heart - A large radius which causes little resistance - Blood flow speeds up as it gets closer to the heart - Able to act as capacitance vessels (blood reservoir) - They can hold large volumes of blood by easily expanding their walls - They lie between skeletal muscles which can act as a pump |
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Sympathetic Nervous System (methods on returning blood to the heart) |
- Stimulates venous vasoconstriction - Increases venous return of blood to the heart - Also increases cardiac output - When skeletal muscle contracts it increases venous return - Makes vessels smaller - When venous return is high so is the cardiac output |
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Venous Valves
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- These prevent backflow of blood once it has been squeezed closer to the heart - Blood is moving up one step at a time (it fights gravity) |
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Pressure Gradient in Veins
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- This is between the lower limbs and the chest aids in venous return - This is known as the respiratory pump |
