Question

I. Visiting high mountains may cause altitude sickness in men living in plain areas. Prime cause of this is (a) excess of \(\mathrm{CO}_{2}\) in blood (b) decreased efficiency of haemoglobin (c) decreased partial pressure of oxygen (d) decreased proportion of oxygen in air.

Short answer

The prime cause of altitude sickness in men living in plain areas when they visit high mountains is (c) decreased partial pressure of oxygen.

Step-by-step solution

Understanding the condition of altitude sickness

Altitude sickness, also known as acute mountain sickness, is caused by reduced air pressure and lower oxygen levels at high altitudes. The decrease in air pressure means that there are fewer oxygen molecules for any given volume of air. Humans are adapted to live in the atmosphere of the plains, and when they move to high altitudes, the body may struggle to get enough oxygen.

Identifying the primary cause of altitude sickness

Among the given options, the prime cause of altitude sickness in people coming from lower altitudes is the decreased availability of oxygen. As altitude increases, the air pressure decreases, which leads to a decrease in the partial pressure of oxygen. This makes it more difficult for the body to absorb the oxygen necessary for efficient functioning.

Matching the correct option to the cause

Based on the understanding of how altitude sickness is caused, it is clear that the decrease in the partial pressure of oxygen at high altitudes is the most direct cause. Therefore, the correct answer is option (c) decreased partial pressure of oxygen.

Key concepts

Acute Mountain Sickness

Have you ever felt nauseous or dizzy after a rapid ascent to a high peak? That unsettling feeling could be acute mountain sickness (AMS), a condition affecting many mountain climbers, hikers, skiers, and travelers at high elevations. AMS occurs when the body does not acclimatize to the decreased supply of oxygen found at altitudes usually above 2,500 meters (8,200 feet). Symptoms range from headache, fatigue, stomach illness, to even sleep disturbances.

Due to lower atmospheric pressure at high altitudes, oxygen molecules spread out, meaning you inhale fewer of them with each breath, halting the body's normal function. If left untreated, AMS can progress to more severe conditions like High Altitude Pulmonary Edema (HAPE) or High Altitude Cerebral Edema (HACE). That's why slow and gradual ascent, along with acclimatization days, are highly recommended for high-altitude adventurers.

Partial Pressure of Oxygen

Let's delve into a concept vital to understanding how our bodies take in oxygen: the partial pressure of oxygen. At sea level, the air pressure is about 101 kPa, and oxygen makes up approximately 21% of the atmospheric gases. The partial pressure is the pressure that oxygen would exert if it occupied that space alone. But as you ascend higher, the total air pressure decreases, subsequently diminishing the partial pressure of oxygen.

This reduction makes it harder for your lungs to take in oxygen and for your blood to transport it to your organs. At high altitudes, this lower partial pressure of oxygen can lead to symptoms of AMS as the body struggles to maintain adequate oxygen levels in the bloodstream. Therefore, climbers and hikers often use breathing apparatus or take breaks during their ascent to adjust to the oxygen availability.

Haemoglobin Efficiency

Haemoglobin, the iron-containing protein in our red blood cells, has a star role in transporting oxygen from the lungs to tissues across the body. However, haemoglobin's ability to pick up and release oxygen is influenced by various factors, one being the partial pressure of oxygen. At high altitudes, the decreased partial pressure of oxygen means haemoglobin molecules have a tougher time grabbing onto oxygen molecules.

Yet our bodies have ways to compensate; for instance, the affinity of haemoglobin for oxygen increases, aiding in capturing as much oxygen as possible during inhalation. Over time, the body also produces more red blood cells to enhance oxygen transportation. Understanding haemoglobin efficiency is essential for preventing and treating altitude sickness, as well as for strategic planning of ascent profiles during high-altitude expeditions.

Adaptation to High Altitudes

Imagine moving from sea level to towering mountain tops. How does the body cope with the oxygen scarcity? This transition demands adaptation to high altitudes through physiological adjustments and changes in the way your body functions. Short-term responses include increased breathing and heart rate to boost oxygen intake and delivery. But the body doesn't stop there. Over days or weeks, it produces additional red blood cells, increases haemoglobin concentration, and enhances the efficiency of the muscles' mitochondria.

People living at high altitudes evolve exceptional long-term adaptations, such as larger lungs and a heart, increased blood flow, and a different haemoglobin structure for efficient oxygen transport. These amazing adaptative changes are the reason highlanders can thrive in low-oxygen environments that would make a sea-level dweller gasp for breath. The key to successful high-altitude ventures is allowing time for such adaptations to occur through gradual ascent and proper acclimatization.