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Why is arteriole systole and recoil important?
- Systole: allows for distension during systole
- Recoil: pushes blood through the body during relaxation
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What is tone?
- Contraction
- ***Generally all vessels have a normal state of tone
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What autonomics innervate arteries and arterioles?
SNS
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What is the diff. b/t basal tone and resting state?
Resting State takes into consideration minor help from SNS
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What is the diff. b/t active vasoconstriction/vasodilation?
- Active vasodilation: increase in diameter due to SNS
- Active vasoconstriction: decrease in diameter due to SNA
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What is the diff. b/t passive vasodilation/vasoconstriction?
- Passive vasodilation: return to state after active vasoconstriction
- Passive vasoconstriction: return to state after active vasodilation
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What is the role of SNS and Adenosine in vessel tone?
- SNS: active vasoconstriction/passive vasodilation
- Adenosine: active vasodilation/passive vasoconstriction
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What is the role of Vasopressin and Angiotensin II?
- Vasoconstriction
- ***increased resistance, decreased flow
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What happens to vessels in warm/cold states?
- Warm: Vasodilation
- Cold: Vasoconstriction
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What is the role in increased endothelin?
Vasoconstriction
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What is the role of Nitric Oxide?
- Vasodilation
- ***decreased resistance, increased flow
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What are the three intrinsic factors of vascular tone?
- Reactive hyperemia
- Active hyperemia
- Autoregulation
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What are the two extrinsic factors of vascular tone?
- Hormonal influence
- Neural Influence
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What do extrinsic factors affect most, pressure or flow?
Pressure > flow
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What is active hyperemia?
Increased metabolites = vasodilation = increased blood flow = high oxygen = vasoconstriction
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What causes Reactive Hyperemia?
Occlusion (clot, block, pinch, etc.)
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After an occlusion is removed, what happens to blood flow in Reactive Hyperemia?
Blood flow is greater than before because of the vasodilation that occured to compensate for the occlusion
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What happens to the hyperemic response if you have an occlusion present for longer?
It is longer and the peak of Blood flow is higher
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What are 5 important vasodilators?
K, H, Adenosine, NO, CO2, Lactic Acid
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What gases are important in vasoconstriction?
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What is Autoregulation?
- Changes that automatically occur when BP changes
- BF drop: Vasodilation to increase flow and decrease resistance
- BF Increase: Vasoconstriction to decrease flow and increase resistance
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What organs participate in Autoregulation?
Brain, Heart, Kidney, Skeletal muscle
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Out of the smooth muscles around vessels and the precapillary sphinctors, which ones are affected by the SNS?
Smooth muscles around vessels
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What are three reasons for why capillaries are good for diffusion?
- Surface Area
- Slow velocity of flow
- porous
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What is the main hormone that widens capillaries and relaxes precapillary sphinctors?
Histamine
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What vessel contains precapillary sphinctors?
Metarterioles
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Where do the movements of filtration and reabsorption go?
- Filtration: out of capillaries
- Reabsorption: into capillaries
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What is the Pc at the arteriole/venous end?
- Arteriole: 37 mmHg
- Venous: 17 mmHg
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What does a negative and positive number tell us when caculating capillary fluid movement?
- Negative = reabsorption (in)
- Positive = filtration (out)
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Where will fluid flow in case of hemorrhage and why?
Reabsorb into capillaries to replace lost fluid
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What is the general net outward/infward capillary filtration?
- Outward = 11 mmHg
- Inward = 9 mmHg
- ***2 leftove for Lymphatic system
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Is there more lymph return in the pulmonary or systemic circulation?
Systemic
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What are the five systems that increase venous return? (BRSSP)
- Blood volume
- Respiratory pump
- Skeletal muscle pump
- Sympathetic vasoconstriction (kinins)
- Pressure from cardiac contraction (CO)
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