Endocrine system

• 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

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

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

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.

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
  

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            

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.

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. 

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
• 

Effects of glucagon

• Conversion of GLYCOGEN to GLUCOSE - GLYCOGENOLYSIS

• use more fatty acids in respiration

• Production of glucose by conversion from amino acids and fats - GLUCONEOGENESIS

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

Treatment

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

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

Treatments

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

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

STEM CELLS!

• 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.