Human Body Systems Overview

Respiratory System

• Function: Provides oxygen to the body and removes carbon dioxide.
• Main Organs:
  • Lungs: Main organ where gas exchange occurs.
  • Trachea: Air passes through to reach the lungs.
  • Bronchi & Bronchioles: Tubes that direct air into the lungs.
  • Alveoli: Tiny air sacs where oxygen enters the blood and carbon dioxide leaves.
    • Adaptations: One cell thick for easy gas exchange, blood capillaries for diffusion, large surface area for fast exchange.
  • Diaphragm: Muscle that helps in breathing.
• Process:
  • Oxygen is inhaled into the lungs.
  • Oxygen diffuses into the blood at the alveoli.
  • Carbon dioxide is removed from the blood and exhaled.
• During Exercise:
  • Breathing rate increases to supply more oxygen.
  • More carbon dioxide is removed.
  • Deep breathing improves oxygen intake.

Digestive System

• Function: Breaks down food into nutrients the body can use.
• Main Organs:
  • Mouth: Breaks down food using teeth and saliva.
  • Esophagus: Moves food to the stomach.
  • Stomach: Uses acid and enzymes to digest food.
  • Small Intestine: Absorbs nutrients into the blood.
    • Villi adaptations: Thin walls, large surface area, blood capillaries for absorption.
  • Large Intestine: Absorbs water and forms waste.
  • Liver & Pancreas: Help digest fats and regulate blood sugar.

Circulatory System

• Function: Transports oxygen, nutrients, and waste around the body.
• Main Organs:
  • Heart: Pumps blood around the body.
  • Blood Vessels:
    • Arteries: Thick walls, carry oxygen-rich blood away from the heart.
    • Veins: Thin walls, carry oxygen-poor blood back to the heart.
    • Capillaries: Tiny network of vessels for gas exchange, connect veins to arteries.
• Blood Components:
  • Red Blood Cells: Carry oxygen.
  • White Blood Cells: Fight infection.
  • Platelets: Help with blood clotting.
  • Plasma: Carries nutrients and waste.
• During Exercise:
  • Heart rate increases to pump more oxygen to muscles.
  • More carbon dioxide is removed through the lungs.

Endocrine System

• Function: Produces hormones to regulate body functions.
• Main Glands & Hormones:
  • Pancreas: Produces insulin to control blood sugar.
  • Adrenal Glands: Produce adrenaline for the "fight or flight" response (excited, scared). Increases heart rate, boosts energy supply.
  • Thyroid: Produces thyroxin, regulates metabolism.
  • Pituitary Gland: Controls other glands, produces growth hormone and antidiuretic hormone.
  • Reproductive Glands:
    • Ovaries (females): Produce estrogen and progesterone.
    • Testes (males): Produce testosterone.

Nervous System

• Function: Controls body movements and responses.
• Main Parts:
  • Brain: Processes information and controls actions.
  • Spinal Cord: Sends signals between the brain and body.
  • Nerves: Carry messages to and from the brain.
• Neurons:
  • Cell body, dendrites (receive signals), axon (carry signals), myelin sheath.
  • Dendrites connect neurons.
  • Myelin sheath speeds up signal transmission.
• Types of Responses:
  • Voluntary: Controlled movements (e.g., catching a ball).
  • Reflexes: Automatic responses (e.g., pulling hand away from heat).
• Reflex Arc Response (Steps):
  • Stimulus detected by receptor cells in skin.
  • Sensory neurons carry impulse to spinal cord.
  • Spinal cord relays the response which generates signal.
  • Motor neurons send the message to muscles.
  • Muscles contract, resulting in response.