Biology Topic 7

• Testosterone


  Hormone produced by testes, has effects of growing muscles, making voice and penis deeper/larger, increasing hair growth
• Adrenaline


  Hormone produced by adrenal glands, important for fight-or-flight response
• Thyroxine


  Hormone produced by thyroid, important for regulating metabolism
• Follicle Stimulating Hormone (FSH)


  Hormone produced by pituitary gland, job is to make small egg grow to larger egg
• Luteinizing Hormone (LH)


  Hormone produced by pituitary gland, job is to release the egg
• Contraception methods


  • Condom (barrier)
  • Pill (hormonal)
  • Coil/IUD (hormonal)
  • Diaphragm (barrier)
• Sterilization


  Surgical procedure to prevent pregnancy, tubes tied in women or vasectomy in men
• In Vitro Fertilization (IVF)

  • Advantages: Can result in a baby, helps those who can't conceive naturally
  • Disadvantages: Requires many drugs with side effects, very expensive, not always successful
• Homeostasis


  Maintenance of a constant internal environment to keep the body functioning properly
• Temperature regulation


  1. If too cold: Hairs stand up to trap air, blood vessels constrict, shivering to produce heat

  2. If too hot: Hairs lie flat, sweating, blood vessels dilate
• Ways the body can lose water

  • Urine
  • Sweat
  • Breathing out
• Kidney function


  1. Ultrafiltration: Blood enters kidneys under high pressure, water/ions/urea/glucose filtered out

  2. Reabsorption: Useful substances reabsorbed back into blood

  3. Release: Remaining waste excreted as urine
• Kidney dialysis


  Machine that takes over the filtering function of the kidneys, very time-consuming
• Blood glucose regulation


  1. After meal: Pancreas releases insulin, causes cells to take up glucose, lowers blood glucose

  2. If blood glucose too low: Pancreas releases glucagon, causes stored glycogen to be converted to glucose, raising blood glucose
• Symptoms of diabetes include increased urination, thirst, blurred vision, fatigue, hunger
• Homeostasis


  The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes
• The body has systems in place to keep the internal conditions optimum for the cells to function
• Internal conditions maintained by homeostasis

  • Blood glucose concentration
  • Body temperature
  • Water levels
• Automatic control systems


  • Involve the nervous system or hormones
  • Detect changes in the environment (internal or external) through receptor cells
  • Pass information to a Coordination Center (e.g. brain, spinal cord, pancreas)
  • Coordination Center processes the information and sends instructions to an effector (muscle or gland)
  • Effector carries out the response to maintain the optimum level
• Thermoregulatory center


  Part of the brain that monitors and controls body temperature
• How the body responds to high temperature

  1. Sweat glands produce sweat that evaporates, cooling the body

  2. Blood vessels in the skin dilate (vasodilation), allowing more blood flow and heat transfer out of the body
• How the body responds to low temperature

  1. Blood vessels in the skin constrict (vasoconstriction), reducing blood flow and heat loss

  2. Skeletal muscles contract and increase respiration to generate heat (shivering)

  3. Sweating stops
• Normal human body temperature is 37 degrees Celsius
• The thermoregulatory center contains receptors that detect temperature changes in the blood and skin
• Sensory neurons send electrical impulses from the skin's temperature receptors to the thermoregulatory center
• When body temperature changes from normal

  The thermoregulatory center detects the change and triggers responses to restore normal temperature
• Controlling body temperature is an example of homeostasis
• Endocrine system


  The system in the body that uses chemicals called hormones to control and coordinate the body's functions
• Endocrine system


  • Consists of a number of glands that secrete hormones directly into the bloodstream
  • Hormones are carried in the bloodstream and act on specific target organs
• Key endocrine glands


  • Pancreas
  • Ovaries
  • Testes
  • Thyroid
  • Adrenal
  • Pituitary
• Pituitary gland


  The "master gland" that releases hormones that act on other glands, triggering a range of effects in the body
• Insulin


  Hormone used to control the blood glucose concentration
• How insulin controls blood glucose concentration

  1. Pancreas senses rise in blood glucose after a meal

  2. Pancreas produces insulin

  3. Insulin triggers body cells to take up glucose from blood

  4. Insulin triggers liver and muscle cells to store excess glucose as glycogen

  5. Blood glucose concentration returns to normal level
• Type 1 diabetes


  Pancreas does not produce enough insulin
• Type 1 diabetes


  • Blood glucose concentration rises and stays high
  • Person with type 1 diabetes injects insulin to lower blood glucose
• Type 2 diabetes


  Body cells stop responding to insulin produced by pancreas
• Treatment of type 2 diabetes

  1. Diet with controlled carbohydrates

  2. Exercise
• Obesity is a major risk factor for type 2 diabetes
• Glucagon


  Hormone released by pancreas when blood glucose concentration falls
• How glucagon controls blood glucose concentration

  1. Glucagon triggers liver cells to convert glycogen to glucose

  2. Glucose is released into blood

  3. Blood glucose concentration rises