Oxygen, nutrients, and temperature regulation are vital for human survival. Our bodies require a constant supply of oxygen for energy production, while nutrients fuel cellular processes. Maintaining a stable body temperature is crucial, as extreme heat or cold can lead to life-threatening conditions.

Pressure and homeostasis play key roles in our body's function. Changes in atmospheric pressure affect oxygen availability, while osmotic pressure influences cellular water balance. Maintaining stable pH, water, and electrolyte levels is essential for optimal physiological processes and overall health.

Essential Requirements for Human Life

Oxygen and nutrients for life

• Oxygen
  • Cellular respiration
    • Aerobic respiration requires oxygen to produce ATP (adenosine triphosphate)
    • ATP is the primary energy currency of cells used for various cellular processes
  • Oxygen delivery
    • Respiratory system takes in oxygen from the air through breathing
    • Circulatory system transports oxygen to tissues via hemoglobin in red blood cells
• Nutrients
  • Macronutrients
    • Carbohydrates provide energy (glucose) and structural components (cellulose)
    • Proteins are essential for growth, repair, and maintenance of tissues (muscles, organs)
    • Lipids serve as energy storage (triglycerides), insulation, and cell membrane components (phospholipids)
  • Micronutrients
    • Vitamins act as cofactors in enzymatic reactions (vitamin C) and regulate various bodily functions (vitamin D)
    • Minerals are necessary for proper enzyme function (iron), bone formation (calcium), and fluid balance (sodium)
  • Nutrient absorption
    • Digestive system breaks down food into absorbable components (amino acids, fatty acids, simple sugars)
    • Circulatory system delivers nutrients to cells for utilization in metabolic processes (metabolism)

Effects of extreme temperatures

• Hyperthermia (overheating)
  • Heat exhaustion
    • Symptoms include heavy sweating, rapid pulse, dizziness, and fatigue
    • Occurs when the body overheats and cannot cool itself effectively through sweating and vasodilation
  • Heat stroke
    • Severe condition characterized by body temperature above 40℃
    • Can lead to organ damage (liver), brain dysfunction (confusion), and death if untreated
• Hypothermia (overcooling)
  • Mild hypothermia
    • Body temperature drops below 35℃
    • Symptoms include shivering, confusion, and loss of coordination (difficulty walking)
  • Severe hypothermia
    • Body temperature falls below 28℃
    • Can result in organ failure (heart), irregular heartbeat (arrhythmia), and death
• Thermoregulation
  • Hypothalamus regulates body temperature by balancing heat production and loss
  • Mechanisms for heat loss include vasodilation (increased blood flow to skin), sweating, and behavioral changes (seeking cool environments)
  • Mechanisms for heat conservation include vasoconstriction (reduced blood flow to skin), shivering (muscle contractions), and seeking warm environments (shelter)

Gas and fluid pressure impacts

• Atmospheric pressure
  • Normal atmospheric pressure at sea level is 1 atm (760 mmHg)
  • Decreased pressure at high altitudes
    • Reduced partial pressure of oxygen leads to hypoxia (low oxygen levels in tissues)
    • Altitude sickness symptoms include headache, nausea, and fatigue
  • Increased pressure in deep-sea diving
    • High partial pressures of gases can lead to nitrogen narcosis (impaired judgment) and oxygen toxicity (seizures)
    • Rapid changes in pressure can cause barotrauma (ear pain) and decompression sickness (joint pain, paralysis)
• Osmotic pressure
  • Osmosis is the movement of water across a semipermeable membrane from a region of low solute concentration to a region of high solute concentration
  • Osmotic pressure is the pressure required to stop osmosis and maintain equilibrium
  • Cells maintain osmotic balance through the transport of ions (sodium, potassium) and water
    1. Hypertonic solutions cause cell shrinkage (crenation) as water moves out of the cell
    2. Hypotonic solutions cause cell swelling and potential lysis (rupture) as water moves into the cell
  • Osmotic imbalances can lead to dehydration (excessive water loss) or edema (fluid accumulation in tissues)
• Hydrostatic pressure
  • Pressure exerted by a fluid due to gravity, increases with depth in a fluid column
  • Affects blood pressure and circulation
    • Orthostatic hypotension occurs when blood pools in the lower extremities upon standing, causing dizziness
    • Venous return is aided by skeletal muscle pumps (calf muscles) and respiratory pump (diaphragm contraction)

Homeostatic Balance

• pH balance
  • The body maintains a narrow pH range (7.35-7.45) in blood and tissues
  • Buffer systems, including bicarbonate and phosphate buffers, help regulate pH
• Water balance
  • Maintaining proper hydration is crucial for cellular function and overall health
  • Regulated by hormones such as antidiuretic hormone (ADH) and the renin-angiotensin-aldosterone system
• Electrolyte balance
  • Proper concentration of ions (sodium, potassium, calcium) is essential for nerve conduction and muscle contraction
  • Regulated by the kidneys and endocrine system to maintain homeostasis