Compared with the interstitial fluid that bathes active muscle cells, blood reaching these cells in arterioles has a a. higher PO2. b. higher PCO2. c. greater bicarbonate concentration. d. lower pH.

Verified step by step guidance

1. Step 1: Understand the question. The question is asking you to compare the composition of blood in arterioles to the interstitial fluid that surrounds active muscle cells. Specifically, it wants to know which of the given options is true.
2. Step 2: Recall what you know about the circulatory system and gas exchange. Blood in arterioles is oxygenated because it has just left the lungs, where oxygen (O2) enters the blood and carbon dioxide (CO2) leaves the blood. This is due to the difference in partial pressures of these gases in the lungs and the blood.
3. Step 3: Consider the state of active muscle cells. When muscle cells are active, they are undergoing cellular respiration at a high rate, consuming O2 and producing CO2 as a waste product. This means that the interstitial fluid around active muscle cells will have a lower PO2 and a higher PCO2 compared to the blood in arterioles.
4. Step 4: Apply this knowledge to the answer choices. The blood in arterioles will have a higher PO2 (option a) compared to the interstitial fluid around active muscle cells. Options b, c, and d are incorrect because they describe conditions that would be true of the interstitial fluid, not the blood in arterioles.
5. Step 5: Choose the correct answer. The correct answer is a. higher PO2.

Key Concepts

Partial Pressure of Gases

Partial pressure refers to the pressure exerted by a single type of gas in a mixture of gases. In the context of oxygen (O2) and carbon dioxide (CO2), the partial pressures in blood and interstitial fluid influence gas exchange. Active muscle cells consume oxygen and produce carbon dioxide, leading to differences in partial pressures that drive diffusion across membranes.

Bicarbonate Buffer System

The bicarbonate buffer system is a crucial physiological mechanism that helps maintain pH balance in the blood and interstitial fluid. It involves the equilibrium between carbonic acid (H2CO3), bicarbonate ions (HCO3-), and carbon dioxide (CO2). Changes in bicarbonate concentration can affect pH levels, which is important for muscle function and metabolic processes.

Acid-Base Balance

Acid-base balance refers to the regulation of pH levels in the body fluids, which is vital for normal cellular function. Active muscle metabolism produces acids, leading to a decrease in pH (acidosis) in the interstitial fluid. Understanding how blood and interstitial fluid differ in pH and gas concentrations is essential for comprehending muscle physiology and metabolic responses.