Circulatory System

The given question tests our understanding of the concept of double circulation in the cardiovascular system. Let's evaluate the assertion and the reason step-by-step:

1. Understanding Double Circulation: Double circulation is a characteristic feature of the cardiovascular system in mammals, including humans. It involves a two-loop system where blood passes through the heart twice during each complete circuit. This type of circulation ensures that oxygenated and deoxygenated blood are kept separate and allows for efficient transport of oxygen and nutrients.
2. Assertion [a]: "The cardiovascular organization called double circulation provides vigorous flow of blood to the brain, muscles, and other organs."
   • This statement is true. Double circulation ensures that oxygen-rich blood is pumped with high pressure from the heart to various body organs, supporting their high metabolic demands efficiently. The systemic circulation carries oxygenated blood to vital organs and helps maintain optimal physiological function.
3. Reason [r]: "The blood is pumped a second time after it loses pressure in the capillary beds of the lungs or skin."
   • This statement is also true. In double circulation, blood first travels to the lungs (pulmonary circulation) where it loses carbon dioxide and picks up oxygen. After losing pressure in the lung capillaries, the blood returns to the heart where it is pumped again with renewed pressure into the systemic circulation.
4. Correlation between Assertion and Reason:
   • The reason correctly explains the assertion. The second pumping helps in regaining the pressure lost in the capillaries, thereby ensuring vigorous and efficient blood flow to all organs, satisfying their metabolic needs.
5. Conclusion: Based on the above analysis, both the assertion and the reason are true, and the reason correctly explains why the assertion is true.

Thus, the correct option is: Both [a] and [r] are true and [r] is the correct reason for [a].

Hyperventilation, which involves rapid and deep breathing, affects the components of arterial blood. Let's break down the physiological changes that occur:

1. Decrease in CO₂ Concentration:
   • During hyperventilation, increased breathing removes CO₂ from the blood faster than it is produced by the body's metabolism.
   • This leads to a decrease in arterial CO₂ concentration (hypocapnia).
2. Decrease in Proton (H⁺) Concentration:
   • CO₂ is in equilibrium with carbonic acid (H₂CO₃) in the blood, which dissociates to form bicarbonate ions (HCO₃^-) and protons (H⁺).
   • When CO₂ levels drop, the reversible reaction shifts to reduce the concentration of H⁺, thereby decreasing proton concentration.
3. Increase in pH:
   • The decrease in H⁺ concentration leads to an increase in blood pH, causing alkalosis (the blood becomes more alkaline).
   • This is a direct result of reduced CO₂ levels due to hyperventilation.
4. O₂ Concentration:
   • Although hyperventilation increases the air exchange in the lungs, the arterial O₂ concentration does not significantly increase, as hemoglobin is nearly saturated with oxygen under normal conditions.

The correct events occurring due to hyperventilation in arterial blood are:

• Decrease in CO_2 concentration
• Decrease in proton concentration
• Increase in pH

Conclusion: The provided correct answers match the physiological effects of hyperventilation on arterial blood, confirming that the Increase in O₂ concentration is not significant.