**Question:** Which of the following may be the effect of positive 'g' acceleratory force on the body of an astronaut?

**Core Concept:** The effect of positive 'g' acceleratory force on the human body, particularly on astronauts in space, is important to understand as space travel is becoming more prevalent. This concept involves the understanding of the human body's response to changes in gravity, specifically the effect of acceleration on blood flow, fluid balance, and the cardiovascular system.

**Why the Correct Answer is Right:**

**Correct Answer: C (Optional)**

The correct answer, Option C, is "Increased blood volume due to compression of the splanchnic bed." When an astronaut is subjected to positive 'g' acceleratory force, their blood flow distribution changes. The splanchnic bed, which includes organs such as the liver, spleen, and stomach, is compressed, causing an increase in blood volume. This is an adaptive response to counteract the decreased blood volume in the extremities due to the redistribution of blood to these vital organs.

**Why Each Wrong Option is Incorrect:**

**Option A (Incorrect):** The incorrect answer, "Decreased blood flow to vital organs," does not accurately describe the response of the body to positive 'g' acceleratory force. Instead, blood flow to vital organs is increased to ensure adequate perfusion during the acceleration.

**Option B (Incorrect):** "Increased blood flow to the limbs" is not the primary response to positive 'g' acceleratory force. While blood flow to the limbs may increase slightly, the primary focus is on ensuring adequate perfusion of vital organs, leading to an increase in blood flow to these organs at the expense of the limbs.

**Option D (Incorrect):** "Increased cardiac output" is a general concept and does not specifically address the effect of positive 'g' acceleratory force. While increased cardiac output occurs as a result of acceleration, the correct answer focuses on the redistribution of blood flow to vital organs.

**Clinical Pearl:** The increased blood volume due to compression of the splanchnic bed is an important adaptation for astronauts during spaceflight as it helps maintain perfusion and organ function when exposed to positive 'g' acceleratory forces. This understanding is crucial for medical professionals and students preparing for medical examinations like NEET PG, USMLE, AIIMS, and FMGE.