Endocrine system

  • endocrine and exocrine gland
  • pancreas
  • the regulation of blood glucose
  • regulation of insulin levels
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Endocrine gland

  • Endocrine gland- secretes hormones into the blood there are no DUCTS
  • Exocrine gland- secretes molecules into a duct which carries the molecules to where they are used.
  • Target cell- they possess specific receptors on their plasma membrane. The shape of the receptor is Complementary to the shape of the hormone molecule.

2 types of hormones

  • protein and peptide hormones and derivatives of amino acids e.g. (adrenaline, insulin and glucagon).  Protein's are insoluble in the Phospholipid membrane and don't enter the cell.
  • Steroids hormones e.g sex cells.Steroids can pass through the membrane- enter's cell-->direct effect on DNA
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Adrenaline is an amino acid derivative and is unable to enter a target cell. It causes an effect inside the cell without entering it.

  • Adrenaline in the blood (1st messenger) binds to the specific receptor site on the cell surface membrane
  • When adrenaline binds to the receptor  (adrenaline receptor complex) adenyl cyclase enzyme is activated.
  • The adenyl cyclase converts ATP to cyclic AMP (cAMP). cAMP is the second messenger inside the cell  which can activate other enzymes inside the cell
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Function of adrenal glands

ADRENAL MEDULLA - in the centre of adrenal gland

manufacture and release adrenaline in response to shock or pain.

Adrenaline can cause;

  • relax smooth muscle in the bronchioles
  • increase heart rate and stroke volume of heart
  • vasoconstriction to raise blood  pressure
  • stimulate conversion of glycogen to glucose
  • dialate pupils
  • increase mental awareness
  • inhibit action of gut
  • body hair to errect
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Adrenal cortex

Adrenal cortex uses cholesterol to produce certain steroid hormones


  • Mineralcorticoids (e.g aldosterone) help to control the concentrations of NA and K in the blood


  • Glucocorticoids (e.g. cortisol) help to control the metabolism of carbohydrates and proteins in the liver.
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Exocrine function on pancreas

Secretion of enzymes

Cells in pancreas manufacture and release digestive enzymes - EXOCRINE FUNCTION

Tubules join to make a pancreatic duct with fluid which contains;

  • enzymes; Amylase, trypsinogen and lipase
  • contains NaCO3 which makes it alkali due to the acidic environment in the stomach
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Secretion of hormones - Endocrine function

Certain areas in the pancreas - ISLET OF LANGERHANS -The islet are well supplied with blood capillaries and these hormones are secreted directly into the blood.  ISLET OF LANGERHANS  - contain 2 different cells

  • a cells - manufacture and secrete GLUCAGON (hormone) which causes blood glucose levels to rise
  • B cells - manufacture and secrete INSULIN (hormone) which causes the blood glucose levels to go down            



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When blood glucose too too high

If blood glucose too high the B CELLS detect this and secretes INSULIN;


  • the target cells- e.g liver cells, hepatocytes, muscle cells and other cells in the brain posses the specific membrane bound receptors for insulin..............
  • when blood passes these cells insulin binds to the receptor...........................
  • Then Adenyl cyclase is activated ---> atp ---> cAMP ---> activates a series of enzyme controlled reactions


b cells secrete insulin---> insulin detected by receptor cells---> liver and muscle cells remove glucose from blood and convert glucose to glycogen---> glucose conc lowered.

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How insulin effects blood glucose levels

Insulin has several effects;



  • more glucose channels are placed into the cell surface membrane.
  • Glucose converted to glycogen for storage GLYCOGENESIS
  • more glucose converted to fats and used in respiration
  • Increased entry of glucose through specific channels, reduces the blood concentration. 


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When blood glucose concentration low

If blood glucose concentration too low it's detected by a CELLS and in response secrete GLUCAGON. 



  • Glucagon detected by receptors on liver cells.................................................
  • liver cells convert glycogen to glucose and releases glucose into the blood...
  • glucose concentration then rises
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Effects of Glucagon

Effects of glucagon


  • use more fatty acids in respiration
  • Production of glucose by conversion from amino acids and fats - GLUCONEOGENESIS
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Type 1

  • insulin dependent
  • starts in childhood
  • the body misidentifies B cells the immune system thinks their foreign and destroys them
  • Body can't manufacture insulin or store excess glucose as glycogen
  • may be cause by a viral attack or inflammation of pancreas



  • insulin injections, careful monitoring, and control of diet
  • slow down the absorption of glucose from the digestive system
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Type 2

  • insulin independent
  • body cells unable to respond to insulin maybe due to age or obesity
  • cell receptors on liver and muscle cells decline and lose ability to respond to insulin
  • level of insulin secreted by B cells decline

Factors that bring on type 2 obesity - family history , or being asian or afro Caribbean



  • careful monitoring, control of diet
  • Drugs which boost insulin production or help cells absorb glucose
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Source of insulin

Insulin either taken from pigs or manufacture by bacteria that is called GENETICALLY ENGINEERED.

Advantages of genetically engineered insulin;

  • exact copy of human insulin therefore works faster and more effective
  • less chance of rejection due to the immune system
  • less chance of developing tolerance to insulin
  • lower risk of infection
  • cheaper to manufacture than extracting from animals
  • manufacturing process more adaptable to demand
  • less moral objections due to ethical reasons
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New way to treat diabetes


  • stems cells are not differentiated and can be induced to develop a variety of cell types
  • stem cells are normally taken from bone marrow


But scientist's have found precursor cells in the pancreas of mice that can develop into a variety of cell types.

If similar cells can be found in the human pancreas this can be used to produce B CELLS in patients with TYPE 1 diabetes.

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