communication and the hormonal system Flashcards
what is the difference between endocrine and exocrine glands
endocrine= glands made up of groups of cells that manufacture and release hormones directly into the blood via capillaries that run through the glands e.g adrenal glands are ductless
exocrine glands= glands made up of groups of cells surrounding a small duct (tube), manufacture and release their products into the duct leading to the site where secretion is required e.g salivary glands secrete saliva into the mouth
what are target cells
-only cells that respond to hormone as they have specific receptors with complementary shape to the hormone
where can target cells be found
-grouped together in target tissue such as the epithelium of collecting duct in the nephron
-or found in several tissues e.g adrenaline receptors in CNS and tissue under PNS control such as the heart, smooth and skeletal muscles
what are the two types of hormones
-protein hormones
-steroid hormones
explain the mechanism of action of protein hormones
- Hormone binds to cell surface receptor
- binding induces a change in the shape of the receptor which activates a G protein located on the inner surface of the membrane
- The G protein activates the enzyme Adenyl Cyclase
- Adenyl cyclase converts ATP into cyclic AMP (cAMP) which is a secondary messenger
- cAMP activates enzymes required for specific biochemical reactions
- activated enzymes produce specific changes in the cell (hormone induced change)
explain the mechanism of action of steroid hormones (and thyroxine)
- pass through the phospholipid bilayer and bind to specific receptors with complementary shape in the cytoplasm
- the steroid hormone receptor complex enters the nucleus and binds to another receptor on chromosomal material
- this binding stimulates production of mRNA triggering protein synthesis (usually enzymes)
- activated enzymes produce a response
compare protein and steroid based hormones
protein based hormones:
-polar (water soluble) so can’t pass across plasma membrane
-binds to specific complementary receptor on plasma membrane
-binding causes change in the shape of the receptor activating G protein
-G protein activates adenyl cyclase etc.
-activated enzymes produce specific change in the cell
steroid based hormone:
-lipid soluble and can pass through plasma membrane
-binds to specific receptor in the cytoplasm
-steroid hormone-receptor complex enters the nucleus and binds to another receptor on chromosomal material
-binding stimulates production of mRNA triggering protein synthesis
-activated enzymes produce a response
what are examples of steroid and protein hormones
protein:
-insulin, glucagon, adrenaline (first messengers) trigger release of second messenger = response
steroid:
-oestrogen, testosterone
what is the structure of adrenal glands and where are they found
-located above the kidney
-medulla, cortex and capsule
= cortex and medulla both well supplied with capillaries into which hormones are directly secreted
what hormones are secreted in the cortex of the adrenal glands
outer cortex= mineralocorticoids e.g aldosterone
middle cortext= glucocorticoids e.g cortisol
inner cortex= precursors for sex hormones (androgens)
what hormone is secreted from the medulla
adrenaline and noradrenaline
what is the role of mineralocorticoids e.g aldosterone
control concentrations of sodium and potassium in the blood, and so maintain blood pressure. Aldosterone acts on distal tubules and collecting ducts of the kidney.
what is the role of glucocorticoids e.g cortisol
Glucocorticoids control the metabolism of carbohydrates, fats and protein in the liver. Cortisol is produced in response to stress and low blood glucose, stimulating production of glucose (by glycogenolysis and gluconeogenesis).
what is the role of precursors for sex hormones (androgens)
Precursors for sex hormones (androgens) are taken up by the testes and ovaries for production of testosterone and oestrogen which control fertility
how do adrenaline and noradrenaline hormones work
behave like protein hormones
they bind to complementary receptors on the surface membranes of target cells (Adrenaline molecule is the first messenger) which activates a G protein.
G protein activates Adenyl cyclase which converts ATP to cyclic AMP (cAMP) which acts as a second messenger and then causes an effect inside the cell by activating enzymes in the cell.
what affect does adrenaline and noradrenaline have
Adrenaline:
Increases heart rate
Increases blood glucose
Increased mental awareness
Noradrenaline:
Increased heart rate
Widening of pupils
Widening of air passages
Narrowing of other blood vessels
