hormonal communication module 5 Flashcards
THE ENDOCRINE SYSTEM-
what is one of the homeostatic coordination systems?
what is a hormone?
what is a gland?
-the endocrine system
-a chemical messenger produced by an endocrine gland and carried in the blood = these chemicals transmit information to target organs and bring about a change
-a group of cells that produces and secretes one or more substances
what does each gland secrete?
thyroid?
pituitary?
pancreas?
adrenal?
testes?
ovaries?
-thyroxine
-the master gland
-insulin
-adrenaline
-testosterone
-oestrogen
explain how hormones work-
-endocrine glands have a good blood supply, so when they synthesise and secrete hormones, they go directly into the bloodstream
-the hormones are then transported around the body by the bloodstream to target cells to bring about a response
-target cells have specific receptors on their cell surface membranes which the hormone binds to as it has a complementary shape
-the receptors have to be complementary to the hormones for there to be an effect
what is the primary messenger?
what is the secondary messengers
-the hormone secreted by the endocrine gland that binds to the receptor on target
-cyclic AMP (cAMP), and is INSIDE THE CELL
describe what happens in the fight or flight response with adrenaline-
-adrenaline binds to specific receptors on the membrane of liver cells
-causes the enzyme adenylyl cyclase to change shape and become activated
-activated adenylyl cyclase catalyses the conversion of ATP to the second messenger molecule cyclic AMP (cAMP)
-cAMP binds to protein kinase A enzymes, activating them
-active protein kinase A enzymes initiate a series of enzyme activations that result in the breakdown of glycogen to glucose = glycogenolysis
-this enzyme cascade amplifies the signal from adrenaline and results in the release of extra glucose by the liver to increase blood glucose concentration
adrenal glands:
location?
structure?
what does the cortex produce? and what do they do?
what does the medulla do?
-above each kidney
-two main areas:
•central medulla
• outer cortex
-steroid hormones
•aldosterone = regulates levels of salts (potassium and sodium) and the water balance in the blood, impacting volume and pressure
•cortisol = the primary stress hormone which regulates metabolism of glucose, proteins and fats to release usable energy
- produces adrenaline, produced in stress or excitement and initiates flight or flight in body
what does the pancreas function as?
what is the exocrine function?
what is the endocrine function?
-an endocrine gland (secretes hormones directly into the blood)
-and an exocrine gland ( secretes substance via a duct)
-to produce pancreatic juice, containing digestive enzymes, to be delivered to the small intestine where it helps food digestion
-to produce glucagon and insulin
histology of pancreas:
look at pic in folder
what are the small sections of cells that are endocrine, called?
what do these contain and what do they do?
-islets of langerhans
-contain:
•alpha cells = secrete glucagon
•beta cells = secrete insulin
BLOOD GLUCOSE REGULATION-
what are the 3 ways in which glucose can enter the bloodstream?
-absorption in the gut after carbohydrate digestion
-hydrolysis of glycogen
-non-carbohydrates such as lipids, lactate and amino acids that have been converted to glucose
describe what happens if a decrease in blood glucose concentration occurs?
-detected by alpha and beta cells in the pancreas:
•alpha cells secrete glucagon
•beta cells stop secretion of insulin
-the decrease in blood insulin conc reduces the use of glucose by liver and muscle cells
-glucagon binds to receptors in the cell surface membrane of liver cells
-causing a conformational change in the receptor protein that activates a G protein
-the activated G protein activates the enzyme adenylyl cyclase
-active adenylyl cyclase catalyses the conversion of ATP into the secondary messenger, cAMP
-cAMP binds to protein kinase A enzymes, activating them
-active protein kinase A enzymes activate phosphorylase kinase enzymes by adding phosphate groups to them
-active phosphorylase kinase enzymes activate glycogen phosphorylase enzymes
-active glycogen phosphorylase enzymes catalyse the breakdown of glycogen to glucose = glycogenolysis
-this enzyme cascade amplifies the original signal from glucagon and results in the releasing of extra glucose by the liver to increase blood glucose conc back to a normal level
what does adrenaline do to blood glucose concentration?
-increases blood glucose concentration by binding to different receptors on the liver cell surface membranes = activating the same enzyme cascade = leading to the breakdown of glycogen by glycogen phosphorylase
-also stimulates hydrolysis of glycogen stores in the muscle during exercise and then men the glucose remains in muscle cells when it is needed for increased respiration
what happens when there is an increase in blood glucose concentration?
-when above normal range, it is detected by beta cells in the pancreas
-glucose molecules enter the beta cells by facilitated diffusion
-the beta cells respire this glucose and produce ATP
-high concentrations of ATP cause the potassium channels in the beta cells to close, causing a concentration gradient in the membrane
-this change in membrane potential causes voltage-gated calcium channels to open
-in response to the influx of calcium ions, the beta cells secrete the hormone insulin
-insulin-containing vesicles move towards the cell surface membrane where they can release insulin into the capillaries
-it then stimulates the uptake of glucose by muscle cells, fat cells and the liver
action of insulin-
what are the target cells of insulin?
what do these proteins allow?
what are these proteins?
-muscle cells, fat storage cells, adipose tissue and liver cells contain glucose transporter proteins in their cell surface membranes = target cells for insulin
-for the uptake of glucose molecules via facilitated diffusion
•the rate of glucose uptake for these cells is limited by the number of glucose transporter proteins present
-the glucose transporter proteins on target cells are insulin-sensitive
-insulin binds to specific receptors on the cell surface membranes of target cells
-this stimulates then to activate and add more glucose transporter proteins to their cell surface membranes = increasing the permeability of the cells to glucose
-as a result, the rate of facilitated diffusion increases
what does insulin also stimulate?
-increased uptake of glucose in the liver by stimulating glycogenesis
-once glucose has entered a liver cell, it is rapidly converted to glucose phosphate
-glucose phosphate converted into glycogen
-lowering glucose concentration within the liver cell
-a steep diffusion gradient is maintained between the blood in capillaries and the liver cells
negative feedback control-
overall?
-receptors detect whether a specific level of blood glucose concentration is too high or too low = alpha and beta cells in pancreases are receptors
- they release glucagon (alpha) and insulin (beta)
-liver cells act as the effectors in response to glucagon and liver; muscle and fat cells act as the effectors in response to insulin
the roles of the liver-
what does the liver convert?
how?
-glycogen to glucose, regulating blood glucose concentration
-insulin and glucose have specific receptors on the membranes of liver cells
-when these hormones bind to their receptors, they trigger either glycogenesis or glycogenolysis
what is glycogenesis?
-the synthesis of glycogen from glucose molecules
-triggered by insulin after it detects an increased blood glucose concentration
-the synthesis of glycogen removes glucose molecules from the bloodstream and decreases blood glucose concentration to within normal range
-glycogen acts as a compact and efficient carbohydrate storage molecule
what is glycogenolysis?
-the breakdown of glycogen to produce glucose molecules
-triggered by glucagon after it detects a decreased blood glucose concentration
-it activates enzymes in the liver that breakdown glycogen molecules into glucose
-releasing more glucose molecules into the bloodstream and increases blood glucose concentration to within normal range
what is gluconeogenesis?
-the synthesis of glucose from non-carbohydrate molecules
-triggered by glucagon by activating enzymes within the liver
-enzymes convert other molecules such as fatty acids and amino acids into glucose molecules
-glucose molecules are released into the bloodstream, increasing glucose concentration to within normal range
DIABETES
where does excess glucose go?
-the kidneys are unable to filter out this excess glucose in the blood so appears in urine
-lots of glucose = lots of urine = thirsty due to dehydration
DIABETES- type I diabetes mellitus
what is it?
what causes it?
what can the lack of insulin also affect?
what happens if blood glucose is too high?
-where the pancreas fails to produce sufficient insulin to control blood glucose levels
-an autoimmune response where T cells attack the beta cells of the islets of Langerhans in the pancreas = the beta cells detect high blood sugar and synthesise insulin
-glycogen stores = person feels fatigued
-organ damage can occur
how is type I normally treated?
-regular blood tests
-insulin injections
-diabetes appropriate diet = should consume more polysaccharides than mono/disaccharides
