Questions and Answers
Intrinsic control mechanisms determine the distribution of blood to organs and the amount of blood directed to individual ______ beds.
capillary
If a tissue's metabolic need is low, intrinsic mechanisms will ______ the flow to that tissue.
decrease
If the metabolic need is high, intrinsic mechanisms will ______ the flow to that tissue.
increase
The flow of blood to any particular organ is determined by the ______ gradient and the resistance to blood in that organ.
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Mean arterial pressure provides the same driving ______ to all organs in the systemic circuit that receive blood in parallel.
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Any difference in blood flow to organs must be due to differences in ______.
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Organs can increase or decrease the amount of blood they receive by ______ or increasing resistance.
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Intrinsic control mechanisms ensure that all organs have an ______ supply of blood.
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Venoconstriction makes veins less ______, which increases pressure and facilitates venous return to the heart.
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Increased venous return to the heart results in increased ______ pressure, which increases end-diastolic pressure.
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Study Notes
Blood Flow Regulation
- When blood flow to one area of the body is decreased, it is redirected to other areas, commonly occurring between different organ systems.
- During exercise, blood flow increases to skeletal muscles, but is redirected from organs with low metabolic needs, such as the gut or kidneys.
Intrinsic Regulation of Blood Flow
- Intrinsic regulation occurs within organs to distribute blood according to metabolic needs.
- The brain is an example of intrinsic regulation, where blood flow is directed to specific areas depending on the activity being performed.
Types of Intrinsic Regulation
- There are four types of intrinsic regulation that act on blood vessels to change vessel diameter:
- Metabolic activity (active hyperemia): increased blood flow due to increased metabolic rate in tissues.
- Changes in blood flow (reactive hyperemia): increased blood flow in response to temporary blood flow reduction.
- Vasoconstriction: decreased blood flow due to increased vessel resistance.
- Vasodilation: increased blood flow due to decreased vessel resistance.
Mechanisms of Intrinsic Regulation
- Active hyperemia: increased oxygen consumption and carbon dioxide expulsion cause vasodilation, increasing blood flow and oxygen delivery.
- Reactive hyperemia: temporary blood flow reduction triggers vasodilation, increasing blood flow and oxygen delivery.
- Venoconstriction: increases pressure inside veins, pushing blood towards the heart, and increases venous return to the heart.
Intrinsic Regulation of Blood Flow to Organs
- Intrinsic control mechanisms determine the distribution of blood to organs and the amount of blood directed to individual capillary beds.
- Organs can increase or decrease blood flow by changing resistance.
- Organ blood flow is determined by the pressure gradient and resistance to blood in that organ.
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