Hormonal communication

• Endocrine gland 


  group of cells specialised to secrete chemicals
• Pituitary gland 


  Growth hormone
• thyroid gland


  produces thyroxine - controls rate of metabolism
• adrenal gland 


  produces adrenaline - increases heart and breathing rate
• testis 


  produces testosterone - controls sperm production
• pineal gland 


  produces melatonin - affects reproductive development
• thymus 


  produces thyroxin - matures white blood cells
• pancreas 


  produces insulin - converts excess glucose into glycogen
• Ovary 


  Produces oestrogen and progesterone - controls ovulation
• Functions of hormones 


  Regulate processes such as growth, metabolism and homeostasis
• steroid hormones

  • lipid soluble
  • pass through lipid component of cell membrane and bind to steroid hormone receptor to form hormone-receptor complex
  • hormone-receptor complex acts as transcription factor - can inhibit transcription
• non steroid hormones

  • hydrophilic - cannot pass directly through cell membrane
  • binds to receptor on cell surface membrane of target cell - triggers cascade reaction
• hormones compared to neurones

  • slower and less specific form of communication
  • not broken down as quickly as neurotransmitters - longer lasting and more widespread effect
• Adrenal cortex

  • Outer region of the glands
  • produces cortisol
• Adrenal medulla

  • Inner region of glands
  • produces adrenaline - increases heart and breathing rate
  • produces noradrenaline - works with adrenaline during stress e.g. increased heart rate and widening pupils
• exocrine glands


  produces enzymes and releases them through a duct
• endocrine glands 


  produces hormones and releases them into the blood
• Exocrine functions

  • Produces digestive enzymes that are secreted through a duct
  • produces protease (break downs proteins into amino acids)
  • produces lipase ( breaks down lipids into fatty acids)
  • produces amylase (breaks down starch into sugars)
• endocrine functions

  • produces hormones that regulate blood glucose levels
  • produces insulin ( lowers blood glucose levels)
  • produces glucagon (raises blood glucose levels)
• islets of langerhans

  • clusters of endocrine cells scattered throughout the pancreas
  • types of islets : alpha cells - produce glucagon (pink stain) , beta cells - produce insulin (blue stain)
• ways to increase blood glucose concentration

  • diet - eating carbohydrate rich foods can increase blood glucose due to glucose being absorbed into the bloodstream
  • glycogenolysis - glycogen stored in the bloodstream is broken down into glucose and released into bloodstream
  • glucagoneogenesis - production of glucose from non carbohydrate sources e.g. amino acids
• ways to decrease blood glucose concentration

  • respiration - glucose is used by cells to release energy e.g. during exercise more glucose is needed as more energy is being used up
  • glycogenesis - production of glycogen - when blood glucose is too high, excess glucose is converted into glycogen
• How insulin lowers blood glucose concentration

  1. Increasing rate of absorption of glucose by cells
  2. increasing respiratory rate of cells - increasing their need for glucose
  3. increasing rate of glycogenesis
  4. increasing rate of glucose to fate conversion
  5. inhibiting release of glucagon from alpha cells
• ways glucagon increases blood glucose concentration

  1. glycogenolysis
  2. reducing amount of glucose absorbed by liver cells
  3. increasing glucagoneogenesis
• What happens when blood glucose level falls?

  1. Fall detected by alpha cells which produce glucagon
  2. glycogen is converted to glucose
  3. amino acids are converted to glucose
  4. glucose enters from intestines
  5. blood glucose level rises
• what happens when blood glucose rises?

  1. detected by beta cells which produce insulin
  2. cellular respiration increases
  3. glucose is converted to glycogen
  4. glucose converted to fat
  5. glucose absorbed into cells
  6. blood glucose level falls
• type 1 diabetes

  • where patients are unable to produce insulin (beta cells in islets of langerhans don’t produce insulin)
  • controlled by regular insulin injections
• type 2 diabetes

  • when patients can’t effectively use insulin or control their blood sugar levels
  • control by regulating carbohydrate intake through their diet
  • overweight people also encouraged to lose weight
  • drugs can also be used to slow down rate at which body absorbs glucose if diet and excessive are not enough to control levels