5.3

• What is the name of the body’s coordination system which involves hormones?

  The endocrine system
• What is a hormone?


  A hormone is a chemical messenger secreted by a gland that travels in the blood to a target organ, causing a response.
• What type of organ secretes hormones?

  Glands
• Which gland controls many other glands in the body?

  The pituitary gland
• Why is the pituitary gland considered a ‘master gland’?


  It secretes a wide range of hormones, some of which may stimulate other endocrine glands.
• What is the role of the pituitary gland in the endocrine system?


  • Secretes human growth hormone (controls growth)
  • Stimulates the thyroid gland
  • Stimulates ovulation and oestrogen production in ovaries
  • Stimulates sperm production and testosterone in testes
• What is the role of the thyroid gland in the endocrine system?


  Secretes the hormone thyroxine, which controls metabolism, heart rate, and body temperature.
• What is the role of the pancreas in the endocrine system?


  Secretes the hormone insulin, which controls blood glucose levels.
• What is the role of the adrenal gland in the endocrine system?


  Secretes adrenaline, which controls the body’s ‘fight or flight’ response.
• What is the role of the ovaries in the endocrine system?


  Secrete oestrogen, which coordinates the menstrual cycle and the development of female secondary sexual characteristics.
• What is the role of the testes in the endocrine system?


  Secrete testosterone, which coordinates the production of sperm and the development of male secondary sexual characteristics.
• Which organ monitors and controls blood glucose concentration?

  The pancreas
• How does the pancreas respond when blood glucose levels are too high?


  The pancreas secretes insulin, which binds to receptors on the liver and muscles, converting excess glucose into glycogen for storage.
• How does the pancreas respond when blood glucose levels are too low?


  The pancreas secretes glucagon, which binds to liver cells, causing glycogen to be converted into glucose and released into the blood.
• How is blood glucose concentration controlled using a negative feedback loop?


  • When blood glucose concentration rises or falls below the optimum, a hormone is secreted by the pancreas.
  • The action of either insulin or glucagon helps restore the concentration to the correct level.
• What is Type 1 diabetes?


  Type 1 diabetes is an autoimmune disorder where the pancreas does not produce sufficient insulin, leading to high blood glucose levels.
• How can Type 1 diabetes be treated?


  • Insulin injections before meals
  • Limiting carbohydrate intake
  • Pancreas and pancreatic cell transplants
  • Investigations into genetic engineering of pancreatic cells
• What is Type 2 diabetes?


  Type 2 diabetes is a disorder where the body’s cells stop responding to insulin, leading to uncontrolled blood glucose concentration.
• How can Type 2 diabetes be treated?


  • Following a carefully-controlled diet
  • Doing regular exercise
  • Losing weight
  • Use of drugs that increase insulin production and effectiveness
• What is osmosis?


  Osmosis is the movement of water from a dilute solution to a concentrated solution through a partially permeable membrane.
• In what ways is water lost from the body?

  • During exhalation via the lungs
  • Sweating
  • Urine (some reabsorbed in the kidney)
• In what ways are ions lost from the body?


  • Sweating
  • Urine (some reabsorbed in the kidney)
• How are excess amino acids excreted from the body?


  • Deaminated in the liver to form ammonia
  • Ammonia is converted into urea (toxic)
  • Urea is excreted via sweat and urine
• How do the kidneys maintain the balance of water and other substances in the body?


  The kidneys filter blood, reabsorbing necessary substances and excreting waste products in urine.
• In what ways are ions lost from the body?


  Sweating and urine
• How are excess amino acids excreted from the body?


  They are deaminated in the liver to form ammonia, which is converted into urea.
• What is the toxic substance formed from excess amino acids?


  Ammonia
• How is urea excreted from the body?


  Urea is excreted via sweat and urine.
• How do the kidneys maintain the balance of water and other substances in the body?


  By filtering blood to remove waste products and selectively reabsorbing useful molecules.
• What waste product do the kidneys filter from the blood?


  Urea
• What is the full name of the hormone ADH?


  Anti-diuretic hormone
• Where is ADH secreted in the body?


  In the pituitary gland of the brain
• How does ADH affect the reabsorption of water in the kidneys?


  ADH increases the permeability of kidney tubules to water, leading to more water reabsorption.
• What happens when the blood is too concentrated regarding ADH secretion?


  The pituitary gland secretes more ADH.
• Why is kidney failure dangerous?


  It can lead to a build-up of toxic molecules and an uncontrolled ion and water balance.
• What are the two main ways of treating kidney failure?

  Dialysis and transplant
• What is kidney dialysis?


  It is the use of a specialist machine to carry out the function of kidneys.
• How does dialysis fluid work in kidney dialysis?


  It contains the same concentration of glucose and ions as healthy blood, allowing only excess and waste molecules to be lost.
• What is the function of reproductive hormones during puberty?


  They cause the development of secondary sexual characteristics and maturation of eggs in females.
• What is the main male reproductive hormone?

  Testosterone