hormonal communication Flashcards
hormones, pancreas, regulation of blood glucose conc, diabetes,
4 steps
action of hormones
- secreted from endocrine glands
- transported in blood plasma and diffuses out of blood
- binds to receptors on membrane or in cytoplasm of target cells
- once bound, hormone stimulates target cell to produce a response
steroid hormones
- LIPID SOLUBLE
- pass through plasma membrane and bind to steroid hormone receptors in cytoplasm/nucleus
- forms hormone-receptor complex
- complex acts as a transcription factor either inhibiting or facilitating transcription of a specific gene
non steroid hormones
- HYDROPHILIC
- cant pass directly through cell membrane
- bind to specific receptors on cell surface of target cell
- binding triggers a cascade reaction mediated by chemicals called secondary messengers
adrenal gland
located at top of each kidney and has two parts:
- adrenal cortex
- adrenal medulla
adrenal cortex
outer region of glands, produces hormones vital to life such as cortisol and aldosterone
adrenal medulla
inner region of glands, produces non-essential hormones such as adrenaline
there are 3 types
which hormones are released from the adrenal cortex?
- glucocorticoids
- mineralocorticoids
- androgens
controlled by hormones from pituitary gland and are all steroid hormones
both regulate things…
glucocorticoids
cortisol - regulates metabolism, controls conversion of fats and proteins to energy
corticosterone - regulates the immune system (release controlled by hypothalamus)
controls blood…
mineralcocorticoids
aldosterone - controls blood pressure
regulated by signals from kidney
androgens
small amounts of male and female sex hormones
important in women after menopause
there are two hormones
which hormones are released from the adrenal medulla?
the ones released when body is stressed by SNS
- adrenaline
- noradrenaline
adrenaline
- increases heart rate and blood glucose
- stimulates conversion of glycogen to glucose in liver
noradrenaline
works with adrenaline in response to stress
effects:
- increased heart rate
- widening of air passages
- narrowing of blood vessels in non-essential organs which gives higher blood pressure
pancreas fucntion as two glands
- exocrine gland - contains cells that produce enzymes important for digestion and release them via a duct into duodenum
- endocrine gland - to produce and release important hormones (insulin and glucagon) into bloodstream
role as an exocrine gland
- made up of cells called acini which secrete sodium hydrogen carbonate which helps neutralise acid from stomach
- also secrete digestive enzymes into a tubule which join up to the pancreatic duct
e.g lipase, trypsin and amylase
role as an endocrine gland
islets of Langerhans are patches of endocrine tissue and they contain:
- alpha cells - larger and produce/secrete glucagon
- beta cells - smaller and produce/secrete insulin
- islets make up 15% of the pancreas.
internal structure of pancreas
acini - darker stained, small berry-like clusters (exocrine)
islets of Langerhans - lightly stained, large spherical clusters (endocrine)
things that increase blood glucose concentration
diet - when you eat carbohydrate rich foods, glucose is released when they are broken down so blood glucose conc increases
glycogenolysis - glycogen stored in the liver and muscle cells is broken down into glucose which is released into the bloodstream
gluconeogenesis - the production of glucose from a non-carb source e.g the liver can make glucose from glycerol and amino acids
things that decrease blood glucose concentration
respiration - the higher the level of physical activity, the higher the demand for glucose for respiration and the greater the decrease of blood glucose conc
glycogenesis - the production of glycogen - when blood glucose conc too high, excess glucose is converted to glycogen in the liver
role of insulin
- produced by beta cells in the iselts of Langerhans in pancreas
- detect rise in blood glucose conc and secrete insulin directly into blood
mechanism of insulin
- insulin binds to its glycoprotein receptor
- this causes a change in the tertiary structure of the glucose transport protein channels
- this causes the channels to open allowing more glucose to enter the cells
- insulin also activates enzymes within some cells to convert glucose to glycogen and fat
how does insulin lower blood glucose conc
- increase rate of absorption of glucose by cells, in particular skeletal muscle cells
- increasing the respiratory rate of cells - increases their need for glucose
- increasing rate of glycogenesis
- increasing rate of glucose to fat conversion
- inhibiting release of glucagon from alpha cells
role of glucagon
- proudced by alpha cells of the islets of Langerhans
- when blood glucose conc is too low, this fall is detected and glucagon is secreted into the bloodstream
receptors for glucagon only in liver cells and fat cells
how does glucagon raise blood glucose conc
- glycogenolysis - liver breaks down its glycogen store into glucose
- reducing amount of glucose absorbed by liver cells
- increasing gluconeogenesis - this is increasing the conversion of amino acids and glycerol into glucose in the liver
control of insulin secretion
- at normal blood glucose conncentrations,** potassium channels **in plasma membranes of *beta cells *are open and K+ ions diffuse out of cell
- when blood glucose conc rises, glucose enters cell by a glucose transporter
- glucose is metabolised inside mitochondria, resulting in production of ATP
- ATP binds to potassium channels and causes them to close - they are known as ATP-sensitive potassium channels
- K+ can no longer diffuse out of cell so the potential difference reduces to -30mV and depolarisation occurs
- depolarisation causes voltage-gated calcium channels to open
- calcium ions enter the cell and cause secretory vesicles to release the insulin they contain by exocytosis
type 1 diabetes
- cannot produce insulin
- beta cells in the islets of Langerhands do not produce insulin
- begins in childhood
type 2 diabetes
- either beta cells don’t produce enough insulin
- or body cells do not respond properly to insulin because glycoprotein receptors do not respond as effectively
- insulin receptors on surface of cells become less sensitive to insulin, leaving it in the bloodstream
treatment of type 1 diabetes
- insulin injections
- blood glucose conc monitored using a biosensor
treatment of type 2 diabetes
lifestyle changes:
- losing weight
- exercising more
- making sure energy intake matches the amount of energy burnt
- drugs can be used to slow down the absorption of glucose in the digestive system, they can also stimulate insulin production in the pancreas
medically produced insulin
1955 - insulin was the first recombinant human protein to be approved for use in diabetes treatment
- less likely to cause allergic reactions
- can be produced in much higher quantities
- production costs are much cheaper
- religious and ethical concerns about animal insulin are overcome
potential use of stem cells in diabetes treatment
- stem cells are differentiated into pancreatic beta cells to restore insulin production
- can come from embryos
- donor availability will not be an issue as it can produce unlimited source of new beta cells
- reduced likelihood of rejection issues
- people no longer have to inject themselves with insulin
- HOWEVER, uncontrolled growth and differentiation may result in formation of a tumour
