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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
What is tone?
- ***Generally all vessels have a normal state of tone
What autonomics innervate arteries and arterioles?
What is the diff. b/t basal tone and resting state?
Resting State takes into consideration minor help from SNS
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
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
What is the role of SNS and Adenosine in vessel tone?
- SNS: active vasoconstriction/passive vasodilation
- Adenosine: active vasodilation/passive vasoconstriction
What is the role of Vasopressin and Angiotensin II?
- ***increased resistance, decreased flow
What happens to vessels in warm/cold states?
- Warm: Vasodilation
- Cold: Vasoconstriction
What is the role in increased endothelin?
What is the role of Nitric Oxide?
- ***decreased resistance, increased flow
What are the three intrinsic factors of vascular tone?
- Reactive hyperemia
- Active hyperemia
What are the two extrinsic factors of vascular tone?
- Hormonal influence
- Neural Influence
What do extrinsic factors affect most, pressure or flow?
Pressure > flow
What is active hyperemia?
Increased metabolites = vasodilation = increased blood flow = high oxygen = vasoconstriction
What causes Reactive Hyperemia?
Occlusion (clot, block, pinch, etc.)
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
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
What are 5 important vasodilators?
K, H, Adenosine, NO, CO2, Lactic Acid
What gases are important in vasoconstriction?
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
What organs participate in Autoregulation?
Brain, Heart, Kidney, Skeletal muscle
Out of the smooth muscles around vessels and the precapillary sphinctors, which ones are affected by the SNS?
Smooth muscles around vessels
What are three reasons for why capillaries are good for diffusion?
- Surface Area
- Slow velocity of flow
What is the main hormone that widens capillaries and relaxes precapillary sphinctors?
What vessel contains precapillary sphinctors?
Where do the movements of filtration and reabsorption go?
- Filtration: out of capillaries
- Reabsorption: into capillaries
What is the Pc at the arteriole/venous end?
- Arteriole: 37 mmHg
- Venous: 17 mmHg
What does a negative and positive number tell us when caculating capillary fluid movement?
- Negative = reabsorption (in)
- Positive = filtration (out)
Where will fluid flow in case of hemorrhage and why?
Reabsorb into capillaries to replace lost fluid
What is the general net outward/infward capillary filtration?
- Outward = 11 mmHg
- Inward = 9 mmHg
- ***2 leftove for Lymphatic system
Is there more lymph return in the pulmonary or systemic circulation?
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)