Blood flow to a tissue will increase if the
a) Level of carbon dioxide at the tissue increases.
b) PH rises.
c) Level of oxygen at the tissue increases.
d) Vessel constricts.
e) both A and C
The Correct Answer and Explanation is:
The correct answer is a) Level of carbon dioxide at the tissue increases.
Here’s a detailed explanation:
Blood flow to a tissue is regulated by a combination of factors, including the levels of carbon dioxide (CO2), oxygen (O2), and the pH of the blood. This regulation is part of a process called local autoregulation, which ensures tissues receive an adequate blood supply according to their metabolic needs. When tissue activity increases, the demand for oxygen rises, and carbon dioxide levels increase due to cellular respiration.
Explanation of Answer Choices:
- a) Level of carbon dioxide at the tissue increases:
- When tissues become more metabolically active, such as during exercise or increased cellular activity, the production of carbon dioxide (CO2) increases. This rise in CO2 causes a drop in local pH, making the surrounding environment more acidic.
- Blood vessels respond to this by dilating (vasodilation), increasing blood flow to the tissue in order to remove excess CO2 and bring in more oxygen. This is a key factor in regulating tissue perfusion based on metabolic demand. Increased CO2 levels stimulate chemoreceptors in blood vessels to induce vasodilation, which enhances blood flow to the area.
- b) pH rises:
- A rise in pH typically indicates a decrease in CO2 levels, leading to alkalosis (a more basic environment). This would have the opposite effect on blood flow; it would lead to vasoconstriction, reducing blood flow to the tissue. Therefore, this answer is incorrect for increasing blood flow.
- c) Level of oxygen at the tissue increases:
- When oxygen levels in tissues rise, blood flow is generally not increased. High oxygen concentrations indicate that the tissue does not require as much oxygen, which would typically result in vasoconstriction rather than vasodilation. This would reduce blood flow rather than increase it.
- d) Vessel constricts:
- If a vessel constricts, blood flow is reduced, not increased. This is the opposite of what occurs when tissues require more oxygen and need increased perfusion.
- e) both A and C:
- While CO2 increase does promote vasodilation, an increase in oxygen would not lead to increased blood flow, making this answer incorrect.
Conclusion:
Thus, blood flow to a tissue will increase if the level of carbon dioxide at the tissue increases. This is due to the body’s physiological response to remove excess CO2, which promotes vasodilation and improves tissue perfusion.