Lecture Notes: Atmospheric Pressure, Oxygen, and Homeostasis

Importance of Oxygen

• Oxygen constitutes 21% of Earth's atmosphere, crucial for cellular respiration.
• Atmospheric pressure is vital for oxygen transfer into the blood.
• 78% of the air we breathe is nitrogen, which is not easily absorbed into the blood without high pressure.
• High-pressure scenarios, like deep-sea diving, can force nitrogen into the bloodstream, leading to 'the bends' if surfaced too quickly.

Atmospheric Pressure

• Humans evolved at sea level, relying on atmospheric pressure to facilitate oxygen absorption in the lungs.
• At higher elevations, atmospheric pressure decreases, making breathing more difficult.
• Mountain sickness can occur at high elevations due to reduced air pressure.

Sea Level vs. High Elevations

• At sea level: Highest atmospheric pressure facilitates easy breathing.
• At higher elevations: Reduced atmospheric pressure can lead to symptoms such as fatigue and confusion.
• Some human populations are naturally adapted to high elevations with anatomical and physiological changes.

Physiological Adaptations

• Acclimatization: Body adjusts to high elevations by increasing red blood cells and hemoglobin.
• Increased plasma volume to prevent blood from becoming too viscous.

Measuring Atmospheric Pressure

• Atmospheric pressure is measured in millimeters of mercury (mmHg) or atmospheres.
• Sea level pressure: 760 mmHg.
• Denver: 640 mmHg (higher elevation).
• Mount Everest: 250 mmHg (requires supplemental oxygen for most people).

Temperature Regulation

• Humans have a narrow thermal neutral zone where minimal energy is used to regulate body temperature.
• Thermal neutral zone is 25°C to 29°C.
• Outside this zone, metabolic rate increases to heat or cool the body through shivering or sweating.

Risks of Temperature Extremes

• Too cold: Brownian motion slows, affecting diffusion and nutrient delivery to cells.
• Too hot: Proteins denature, stopping cellular function.

Nutrients and Water

• Humans need macronutrients (carbohydrates, fats, proteins) and micronutrients (vitamins, minerals).
• Water is crucial for thermoregulation and diffusion.
• Overconsumption of sugar leads to health issues like type 2 diabetes.

Homeostasis

• Central to physiology; maintains a steady internal environment for cells to thrive.
• Internal environment includes blood plasma and extracellular fluid.
• Regulated variables include blood pH, CO2 levels, and require sensors, control centers, and effectors to maintain.
• Non-regulated variables, like heart rate and respiratory rate, can fluctuate widely.

Importance of Regulated Variables

• Blood pH must remain between 7.35 and 7.45.
• CO2 levels impact blood pH; lungs and kidneys act as effectors to maintain balance.

Key Concepts

• Different body systems work together to maintain homeostasis.
• Anatomical structures (effectors) are crucial in correcting physiological imbalances.
• Understanding homeostasis helps in identifying how diseases disrupt bodily functions.