b5 homeostasis and response YouTube video

• Homeostasis is the maintenance of a constant internal environment and keeps your body functioning properly
• Homeostasis


  • Controlling blood glucose levels
  • Controlling water levels
  • Controlling temperature
• Brain


  The control center that sends signals to various parts of the body
• Nervous system


  1. Receptors pick up stimuli

  2. Signal travels to central nervous system

  3. Response sent back
• Reflex


  Signal travels from receptors to spinal cord and back without going to the brain
• Nerve cells


  • Cell body is long to send fast electrical signals
  • Signals slow down when transferring between nerve cells due to chemical signalling across synapses
• Parts of the brain


  • Cerebral cortex
  • Cerebellum
  • Medulla
• Eye


  • Sclera
  • Retina
  • Optic nerve
  • Ciliary muscles
  • Cornea
  • Lens
  • Suspensory ligaments
• Short-sightedness


  Image focuses before the retina
• Long-sightedness


  Image focuses behind the retina
• Thermoregulation


  1. Hairs stand up to trap air when cold

  2. Sweating and vasodilation when hot

  3. Shivering to produce heat when cold
• Endocrine system glands


  • Pituitary
  • Thyroid
  • Adrenal
  • Pancreas
  • Ovaries
  • Testes
• Insulin


  Produced by pancreas, lowers blood glucose levels
• Glucagon


  Produced by pancreas, raises blood glucose levels
• Glycogen


  Stored form of glucose
• Type 1 diabetes is caused by the pancreas not producing enough insulin, type 2 is caused by cells becoming insensitive to insulin
• Diabetes symptoms


  • Loss of weight
  • Increased urination
  • Increased thirst
  • Blurry vision
  • Fatigue
  • Hunger
• Kidney functions


  • Remove urea
  • Control ion content
  • Control water content
• Kidney filtration


  1. Blood enters under high pressure

  2. Water, ions, urea, glucose filtered out

  3. Useful substances reabsorbed

  4. Remaining waste excreted as urine
• Antidiuretic hormone (ADH)


  Controls how much water is reabsorbed by the kidneys
• Kidney dialysis is a time-consuming process that has to be done 3 times a week
• Kidney transplants have long waiting lists and risk of rejection
• Hormones involved in the menstrual cycle


  • Follicle stimulating hormone (FSH)
  • Luteinizing hormone (LH)
  • Estrogen
  • Progesterone
• Contraception methods


  • Condoms
  • Hormonal pills/coils
  • Diaphragms
  • Sterilization
• About 1 in 6 people experience infertility, with roughly equal male and female causes
• IVF


  Involves taking many drugs with side effects, is very expensive, and has around 40% success rate per cycle
• Plant growth responses


  • Phototropism (growth towards light)
  • Geotropism/gravitropism (growth towards gravity)
  • Gibberellins (promote growth)
  • Ethylene (promotes ripening)
  • Auxins (promote growth in right direction)