BIOLOGY
UNIT 5: Human Biology and Health
🧬 1. The Hierarchy of Life
Our bodies are built in layers, starting from the invisible and moving to the visible:
• Atomic Level: Carbon, Oxygen, Hydrogen, and Nitrogen make up 96% of your body.
• Molecular Level: DNA (the blueprint), proteins (the builders), and lipids (the insulators).
• Cellular Level: The basic unit of life.
• Mitochondria: The power plant (creates energy).
• Nucleus: The "brain" containing your genetic code.
• Ribosomes: The factory that builds proteins.
• Tissue Level: Four distinct types:
• Epithelial: Your "wrapping" (skin and organ linings).
• Connective: The "glue" (bones, blood, and tendons).
• Muscle: The "motor" (skeletal, smooth, and cardiac).
• Nervous: The "wiring" (brain and nerves).
---
🧠 2. The Command & Control Systems
How the body communicates with itself:
• The Nervous System:
• Uses electrical impulses for instant reactions.
• Central (CNS): Brain and Spinal Cord.
• Peripheral (PNS): Nerves branching to your fingertips.
• The Endocrine System:
• Uses chemical messengers (hormones) for long-term changes.
• Insulin: Regulates blood sugar.
• Adrenaline: Prepares the "fight or flight" response.
• Cortisol: Manages stress levels.
---
🫁 3. The Life Support Systems
The "plumbing" and "ventilation" that keep cells alive:
• Cardiovascular System:
• The heart pumps ~2,000 gallons of blood daily.
• Arteries: Carry oxygen-rich blood away from the heart.
• Veins: Carry oxygen-poor blood back to the heart.
• Respiratory System:
• The lungs provide a massive surface area (size of a tennis court) for gas exchange.
• Alveoli: Tiny air sacs where Oxygen enters the blood and Carbon Dioxide leaves.
• Digestive System:
• Converts food into fuel through Metabolism.
• Small Intestine: Where 90% of nutrient absorption happens.
---
🛡 4. The Defense & Repair Mechanics
How the body stays healthy against threats:
• The Immune System:
• White Blood Cells: The "soldiers" that hunt pathogens.
• Antibodies: Custom-made "keys" that disable specific viruses.
• Lymphatic System: A drainage network that filters out toxins.
• Homeostasis:
• The body’s "Auto-Pilot."
• It keeps your temperature at 98.6°F (37°C).
• It balances water levels, pH levels, and blood pressure constantly.
---
🥗 5. The Pillars of Human Health
Biology is the "hardware," but health is the "software" and "maintenance":
• Nutritional Health:
• Macronutrients: Carbs (Energy), Proteins (Repair), Fats (Protection).
• Micronutrients: Vitamins (A, B, C, D, E, K) and Minerals (Iron, Calcium, Magnesium).
• Physical Health:
• Cardio: Strengthens the heart muscle.
• Resistance: Increases bone density and metabolic rate.
• Sleep Science:
• During sleep, the brain flushes out metabolic waste (toxins).
• Tissues repair themselves and memories are consolidated.
---
⚠️ 6. Common Biological Disruptors (Disease)
When the systems fail, health declines:
• Pathogenic: Caused by outside invaders (Bacteria, Viruses, Fungi).
• Genetic: Errors in the DNA code (e.g., Cystic Fibrosis).
• Lifestyle: Damage from external choices.
• High Sugar: Leads to insulin resistance (Type 2 Diabetes).
• Chronic Stress: Weakens the immune system via cortisol.
• Sedentary Life: Leads to atrophy (weakening) of the heart and muscles.
