endocrine system Flashcards
what is endocrine communication?
a communication system using hormones as signalling molecules
what is a hormone ?
molecules releases by a gland into the blood to carry a signal to target tissue
what are the 2 types of hormone?
protein and steroid
describe the protein hormone
not soluble in membrane, so therefore binds to plasma membrane onto a complementary site and causes a release of secondary messenger inside the cell
describe the steroid hormone
is lipid soluble so can pass through the membrane so can have a direct effect on target
why are steroid hormones lipid soluble ?
synthesised from lipid-based molecules like cholesterol so soluble in fats and dissolve in the lipid bilayer
what is an endocrine gland?
ductless group of cells that secreates hormone straight into the bloodstream
what is an exocrine gland?
group of cells around a small duct that secrete products into the duct leading to the site requiring the substance
why do hormones have specific targets ?
to produce a specific response in specific places
why is each hormone different?
so it doesn’t react to everything whilst travelling around the body and only reacts with the target cells
what is a first messenger ?
non-steroid hormone - causes release of secondary
explain the path of a non steroid hormone binding to target cell
binds to plasma membrane- activates G protein- which activates an effector molecule - which converts ATP to cyclic AMP which is the secondary messenger- this will act on another protein to activate enzyme controlled reactions to alter cell activity
where is adrenal gland found?
anterior to kidneys
why do the adrenal glands have a good blood supply ?
hormones travel in the blood so their transport network needs to be available near the production site
name the outermost layer of the adrenal cortex
zona glomerulosa
name the middle layer of the adrenal cortex
zona fasciculata
name the innermost layer of the adrenal cortex
zona reticularis
state what the zona glomerulosa secretes
mineralocorticoids - aldosterone
state what the zona fasciculata secretes
glucocorticoids - cortisol
state what the zona reticularis secretes
precursor molecules (androgens)
what is the function of mineralcortiocoids?
control concentration of Na and K ions in blood so maintains blood pressure
what is the function of aldosterone ?
targets cells of DCT and collecting duct by increaseing absorbency to Na and water and decreasing to K. so therefore increasing blood pressure
what is the function of glucocorticoids?
control metabolism of carbohydrates, fats and proteins in liver
what is the function of cortisol ?
response to stress or lowered blood glucose so therefore stimulates production of glucose from stored compounds
what is the function of precursor molecules ?
targets sex organs to be converted into sex hormones to develop 2nd sexual characteristics and regulate production of gametes
what type of hormone does the cortex produce ?
steroid based
what do steroid based hormones act upon ?
cause protein synthesis
outline the mechanism for steroid hormones causing protein synthesis ?
hormone passes through cell membrane and binds to complementary receptors in cytoplasm- a receptor-steroid complex is formed and travels to nuclear and binds to chromosomal material which stimulates production of mRNA so codes for protein synthesis
what type of hormones do the medulla secrete and give 2 examples ?
adrenaline and noradrenaline
is adrenaline steroid/non? why?
non steroid - polar and derived from AA tyrosine
why do many cells have adrenaline receptors?
effects of flight or fight need to be widespread as different parts of the body will have different but equally important responses
state 8 responses of the body to adrenaline
relaxes smooth muscle in lungs, increases stroke volume, vasoconstriction therefore increases blood pressure, glycogen to glucose, pupils dilate, increase in mental awareness, inhibits digestion, hair erects
why does adrenaline increase stroke volume in response to adrenaline ?
increase in blood pumped per min so increase blood flow round so increase in oxygen and glucose to muscle so increased activity for flight/fight
what are the exocrine cells of the pancreas called?
acinus cell
what do the acini make and secrete ?
digestive enzymes including pancreatic amylase, trypsinogen and lipase
what is the function of pancreatic enzymes ?
amylase to maltose wha
what is the function of lipase ?
digest lipids
outline the pathway of an enzyme synthesised in an exocrine gland?
mad win the acinus cell, travels down tubule at centre of acini, down interlobular duct, into pancreatic duct, then enters duodenum
what is the purpose of sodium hydrogen carbonate being produced in the exocrine gland ?
is an alkali so neutralises acid coming through duodenum therefore creates optimum environment for enzymes
where in the pancreas does the endocrine function take place ?
islets of langerhan
what do alpha cells of the islets of langerhan secrete ?
glucagon
what do beta cells of the islets of langerhan secrete ?
insulin
describe the mechanism for releasing insulin
in the membrane Ca channels shut, K open so K diffuses out therefore inside cell is more negative.
when glucose concentration outside increases glucose enters cell and glucose is used in respiration and ATP is produced through use of enzyme glucokinase. extra ATP causes K channels to close so the inside is more positive. therefore the change in charge opens Na channels and therefore Na flows in and causes vesicles containing insulin to move to PM ready for exocytosis
what is the role of the enzyme glucokinase?
acts as a glucose sensor and triggers a change in metabolism of glucose
how are the acini cells are specialised ?
They need many ribosomes to synthesise proteins: these ribosomes will be on the rough endoplasmic reticulum. They will also have a lot of Golgi apparatus as these are involved with packaging the enzymes into secretory vesicles. Many mitochondria will be present to supply ATP for the active processes
why is trypsinogen released in the inactive form ?
It is activated in the intestines so that Active trypsin would digest any proteins in the intestines only, so won’t digest anything needed in the pancreatic duct and cells when created if it was activated
