- 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
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
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.
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
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
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.
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.
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
Effects of Glucagon
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
- 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
- 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
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
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.