Hormonal communication

• How does the endocrine system communicate?

  Via hormones released by endocrine glands and circulate in the blood
• What are endocrine glands?

  Ductless glands that secrete hormones directly into the bloodstream
• What are exocrine glands?

  Secrete substances into a tube or duct, like enzymes
• Give four examples of protein hormones

  ADH, adrenaline, insulin and glucagon
• Give two examples of steroid hormones

  Testosterone and Oestrogen
• How do hormones work?

  - Reach all cells of body but only act on the target cells

  - Binds to the receptor that is specific to the hormone on the target cell

  - Usually grouped together to form a target tissue
• Protein hormones

  - Bind to receptors on membrane causing a response in the cell
• Steroid hormones

  - Lipid soluble

  - Pass through phospholipid bilayer and nucleus to have a direct effect on DNA
• First messengers

  Protein hormones binds to receptors on target cell membrane to as a first messenger

  
• Second messenger

  Many first messengers activate a g protein in the membrane, when binding to a receptor.

  
  

  G protein activates an enzyme ,often adenyl cyclase, within cell

  
  

  Converts ATP into cyclic AMP

  
  

  cAMP acts as a second messenger and activates a cascade of enzyme-controlled reactions within the cell

  
• Amplification effect

  1 primary messenger can make 1000s of secondary messengers, as long as the hormone is still binded to the receptor
• What are the two layers of an adrenal gland, if dissected transversely?

  Adrenal cortex and adrenal medulla
• What does adrenal cortex do?

  Produce steroid hormones using cholesterol, like mineralcorticoids and glucocorticoids
• Mineralcorticoids (aldosterone)

  Help control concentration of sodium and potassium , which affects blood pressure, in the blood
• Glucocorticoids (cortisol)

  Help control metabolism of carbohydrates, fats and proteins in liver
• What does cortisol do?

  Stimulate liver cells and encourage glycogenolysis
• Adrenal medulla

  Manufactures and releases adrenaline and (noradrenaline) in response to stress (flight or fight response)
• Zona glomerulosa

  In cortex

  Secrete mineralcoticoids
• Zona Fasciculata

  In cortex

  Secrete glucocorticoids
• Zona Reticularis

  Secrete precursors to all sex hormones
• Labelled diagram of an adrenal gland

  
• Give five examples of responses to adrenaline

  - Smooth muscles in bronchioles relax - wider lumen

  - Increased heart and stroke volume

  - Vasoconstriction

  - Convert glucogen into glucose in liver

  - Dilated pupils
• Physical changes in a cat when experiencing adrenaline

  Hair on top

  Dilated pupils

  Panting/hissing

  Stood upright

  Ears' straight up
• What is in a pancreas?

  Islets of Langerhans and pancreatic cells with digestive enzymes

  
• What makes the pancreas an endocrine gland?

  Islets of Langerhans cells secrete insulin or glucagon into blood

  
  

  Blood with insulin or glucagon goes back into the bloodstream
• What makes the pancreas an exocrine gland?

  Pancreatic cells secrete pancreatic juice which drains in the duct

  
  

  Pancreatic duct carries pancreatic juice to small intestine

  
  

  Secretion of pancreatic juice into small intestine
• Alpha cell

  Secretes glucagon

  Stained lighter

  
• Beta cell

  Secretes insulin

  Stained darker

  
• Acinus

  A group of lots of pancreatic cells

  
• What organelles does the alpha and beta cell have in common?

  Many vesicles containing their respective hormones

  Golgi apparatus

  Extensive RER

  Nucleus
• What is the normal blood glucose levels?

  90mg/100cm³
• What happens if there's a rise in glucose level?

  Beta cells of Islets of Langerhans detect the rise in glucose level

  
  

  Release insulin

  
  

  Liver take more glucose and convert it into glycogen (GLYCOGENESIS)

  
  

  NEGATIVE FEEDBACK
• What happens if there's a decrease in glucose level/

  Alpha cells of Islets of Langerhans detect the decrease in glucose level

  
  

  Release glucagon

  
  

  Liver cells breaks glycogen int glucose

  (GLYCOGENOLYSIS)

  
  

  NEGATIVE FEEDBACK

  
  

  NEGATIVE FEEDBACK
• Main target cells of insulin

  Hepatocytes and muscle cells with the receptors
• What happens when insulin binds to these receptors?

  Activates tyrosine kinase inside the cell, causing phosphorylation of inactive enzymes in cell.

  
  

  A cascade of enzyme-controlled reactions
• What are the "cascade of enzyme controlled reactions" for insulin?

  1. An increase in the number of glucose transporter proteins in cell membranes, leading to an increased uptake of glucose into cells.

  2. An increase in the rate of cellular respiration

  3. An increase in the rate of conversion of glucose to fat in adipose cells (fat storing cells).

  4. An increase in the rate of conversion of glucose to glycogen in the liver and muscle cells (GLYCOGENESIS).
• Main target cells of glucagon

  Hepatocytes
• What happens when glucagon binds to these receptors?

  Stimulates a G protein

  and activates adenyl cyclase inside the cell, which converts ATP to cAMP (cyclic AMP).
• What does cAMP activate?

  1. The breakdown of glycogen to glucose (GLYCOGENOLYSIS).

  2. The conversion of amino acids and glycerol into glucose-6-phosphate.

  This synthesis of glucose from non-carbohydrate sources is called

  GLUCONEOGENESIS.

  3. More fatty acids are used as a respiratory substrate.
• Diabetes mellitus

  Thirst, thin, tired, toilet

  Lose water via osmosis in blood

  Urinate more