Hormones

• Major endocrine glands of the body

  • Pituitary gland
  • Thyroid
  • Pancreas
  • Adrenal glands
  • Testes (males)
  • Ovaries (females)
• Endocrine system


  Made up of endocrine glands that release chemical substances called hormones into the bloodstream
• Gland


  A group of cells that produces and releases one or more substances (a process known as secretion)
• Endocrine system vs nervous system


  • Effects of hormones are slower but act for longer, used to control functions that do not need instant responses
  • Nervous system provides instant responses
• Hormone


  A chemical substance produced by a gland, carried by the blood, and can alter the activity of specific target cells, tissues or organs
• Important hormones in humans

  • Adrenaline
  • Insulin
  • Testosterone
  • Progesterone
  • Oestrogen
• How adrenaline prepares the body for action


  1. Increases heart rate and breathing rate to ensure glucose and oxygen can be delivered to muscle cells and carbon dioxide can be taken away

  2. Other effects to prepare the body for movement (fight or flight)
• Hormone


  A chemical substance produced by a gland
• Hormones


  • Carried by the blood and can therefore circulate around the whole body
  • Transmit information from one part of the organism to another and bring about a change (they provide a signal that triggers a response)
  • Alter the activity of specific target cells, tissues or organs
• Important hormones in humans

  • Adrenaline
  • Insulin
  • Testosterone
  • Progesterone
  • Oestrogen
• Adrenaline


  The 'fight or flight' hormone, produced in situations where the body may be in danger
• How adrenaline prepares the body for action

  1. Increases heart rate and breathing rate to ensure glucose and oxygen can be delivered to muscle cells faster

  2. Diverts blood flow towards muscles and away from non-essential parts of the body to increase supply of reactants for respiration

  3. Dilates blood vessels inside muscles to allow more blood circulation and supply of glucose and oxygen

  4. Breaks down stored glycogen to glucose in the liver and muscle cells, releasing glucose to active muscle cells to provide greater energy for movement
• Blood glucose concentration


  Must be kept within a narrow range, an example of homeostasis
• Too high a level of glucose in the blood can lead to cells of the body losing water by osmosis, which can be dangerous
• Too low a level of glucose in the blood can lead to the brain receiving insufficient glucose for respiration, potentially leading to a coma or even death
• How the pancreas and liver control blood glucose levels

  1. Cells in the pancreas detect increased blood glucose levels

  2. The pancreas produces the hormone insulin, secreting it into the blood

  3. Insulin stimulates muscles and the liver to take up glucose from the bloodstream and store it as glycogen

  4. This reduces the concentration of glucose in the blood back to normal levels, at which point the pancreas stops secreting insulin

  5. Cells in the pancreas detect decreased blood glucose levels

  6. The pancreas produces the hormone glucagon

  7. Glucagon causes the glycogen stored in the liver to be converted into glucose and released into the blood

  8. This increases the concentration of glucose in the blood back to normal levels, at which point the pancreas stops secreting glucagon
• Testosterone


  Produced in the male testes, responsible for the development of secondary sexual characteristics in males
• Progesterone


  Produced in the female ovaries, responsible for maintaining the uterine lining during pregnancy
• Oestrogen


  Produced by the female ovaries, responsible for the development of secondary sexual characteristics in females and regulating the menstrual cycle
• Blood glucose concentration

  The amount of sugar in our bloodstream
• We need a decent amount of sugar in our blood so that our cells have a constant supply of glucose for respiration
• If the blood glucose concentration gets too high it can start to damage our tissues
• What happens when we eat a big meal with lots of carbohydrates

  1. Carbohydrates broken down in intestines into glucose

  2. Glucose absorbed into bloodstream

  3. Blood glucose concentration increases
• Pancreas


  • Organ that sits just behind the stomach
  • Releases insulin and glucagon hormones
• How insulin regulates high blood glucose

  1. Pancreas detects high glucose

  2. Releases insulin into bloodstream

  3. Insulin binds to cells (liver, muscle)

  4. Cells take up glucose from blood

  5. Blood glucose concentration decreases
• Glycogen


  Long-term storage form of glucose
• How glucagon regulates low blood glucose

  1. Pancreas detects low glucose

  2. Releases glucagon into bloodstream

  3. Glucagon binds to liver cells

  4. Liver breaks down glycogen into glucose

  5. Glucose released into blood

  6. Blood glucose concentration increases
• Insulin and glucagon


  Create a negative feedback loop to keep blood glucose at normal levels
• Our bodies constantly release insulin and glucagon to ensure blood glucose is kept at the right level
• Insulin


  A hormone released by the pancreas when glucose levels in the bloodstream are too high, which binds to cells and tells them to absorb excess glucose and turn it into glycogen
• Type 1 diabetes

  • Generally occurs in childhood or teenage years
  • Lifelong condition
  • Pancreas stops producing insulin or only produces tiny amounts
  • Can cause high blood glucose levels and illness or death
  • Main treatment is injecting insulin
• Insulin injection for type 1 diabetes


  1. Inject insulin after meals

  2. Amount depends on food eaten and exercise done
• People with diabetes are encouraged to eat less sugary food and exercise regularly
• Type 2 diabetes


  • Generally happens to older people with unhealthy diets
  • Cells become resistant to insulin, so they don't respond to it
  • Even with high insulin production, cells won't take in glucose
  • Main treatments are healthy low-sugar diet and regular exercise
  • Some drugs can also be given
• The key difference between type 1 and type 2 diabetes is the underlying problem and how they are treated