hormonal communication Flashcards
what is the difference between exocrine and endocrine glands?
exocrine secretes into ducts whereas endocrine secretes straight into blood
what is a hormone?
chemical messenger
how are hormones transported?
blood
where do hormones travel to?
target cells
how are hormones specific?
only activate cells with appropriate target receptors
what are the 7 main endocrine glands?
- pineal
- pituitary
- thyroid
- adrenal
- pancreas
- ovaries
- testes
what does the pineal gland secrete and where does it work?
melatonin targets many organs and acts as a body clock
what does the pituitary gland secrete and where does they work?
- FSH/LH work in the ovaries in menstrual cycle
- ADH works in the kidneys in osmoregulation
what does the thyroid gland secrete and where does it work?
thyroxine works in the liver and controls metabolism
what does the adrenal gland secrete and where does it work?
adrenaline and cortisol work everywhere and control the fight or flight response
what does the pancreas secrete and where does it work?
insulin and glucagon work in the liver to regulate glucose levels
what are the 3 types of hormones?
- steroid
- peptide
- amino acid derivates
how do steroid hormones work?
- lipophilic so diffuse freely through the phospholipid bilayer
- bind to receptors in cytoplasm or nucleus of target cell to form an active receptor-hormone complex which acts as a transcription factor for gene expression
- moves into nucleus and binds directly to DNA leading to stimulation or inhibition of transcription of a specific gene
- eg. oestrogen, progesterone, testosterone
what does the first messenger do?
- the hormone brings the information/signal from endocrine gland
- binds to a receptor on cell surface membrane
what does the second messenger do?
causes the effect in the cell eg. fight or flight
how do peptide hormones work?
- hydrophilic so cannot cross the phospholipid bilayer
- binds to receptors on surface of cell which are usually coupled to internally anchored proteins (G proteins)
- the receptor complex activates a series of second messengers which initiate cell activity
what are the differences between hormonal and neuronal?
- chemicals vs electrical impulses
- blood vs nerves
- hormonal slower
- response widespread vs localised
what are the two parts of the adrenal glands?
- adrenal cortex
- adrenal medulla
what happens in the adrenal cortex?
- outside
- produces steroid hormones that are vital for life
- -mineralcorticoids eg alodsterone
- glucocorticoids
- controlled by pituitary glands
what happens in the adrenal medulla?
- inside
- produces amine based hormones that are non essential
- controlled by stress (sympathetic stimulation)
- adrenaline and noradrenaline
what does the exocrine tissue of the pancreas do?
secretes a variety of digestive enzymes and alkaline pancreatic juice via the pancreatic duct into duodenum
what does the endocrine tissue of the pancreas do?
the islets of langerhans secrete glucagon and insulin
how do islets of langerhans appear under a microscope?
- lighter stains
- large spherical clusters
how do pancreatic acini (acinus) appear under a microscope?
- darker stains
- small berry like clusters
what are pancreatic acini?
glands which are the secretory unit of the pancreas
what % of the pancreatic tissue is exocrine?
98%
what are pancreatic islets?
spherical clusters of polygonal endocrine cells
how is the blood supply specialised in the islets?
permeated by fenestrated capillaries which allow quick entry of pancreatic hormones into blood
what % of pancreatic cells are endocrine?
2%
how many islets (roughly) are there in the pancreas?
1-2 million
what are the 4 types of pancreatic islet cells?
- alpha
- beta
- delta
- pancreatic polypeptide cells
what do beta cells do?
secrete insulin
what % of islet cells are beta cells?
70%
where in the islets are beta cells commonly located?
centre
what do alpha cells do?
secrete glucagon
what % of islet cells are alpha cells?
15-20%
where in the islet are alpha cells commonly located?
peripherally
why does blood glucose constantly fluctuate?
- negative feedback loop so fluctuates in a narrow range
- regulation after meals and exercise
what two antagonistic hormones are involved in blood glucose regulation?
glucagon and insulin
what happens when blood glucose is low?
glucagon is release from alpha cells and cause an increase in blood glucose concentration
where are glucagon receptors found?
ONLY on liver and fat cells
what is glycogenolysis?
stimulating glycogen breakdown in the liver which promotes glucose release by the liver and adipose tissue
what is gluconeogenesis?
glucose being made from non carbohydrate stores eg. glycerol and amino acids
what is glycogenesis?
the formation of glycogen from sugar
how does glucagon increase blood glucose levels?
- glycogenolysis
- gluconeogenesis
- reducing absorption of glucose into liver cells
- decreasing rate of glucose breakdown by reducing cell respiration rate
what role does adrenaline play in increasing blood glucose?
- binds to different receptors on surface of liver
- activates same enzyme cascade and leads to breakdown of glycogen by glycogen phosphorylase
- stimulates muscle breakdown where needed for respiration
what happens when blood glucose is high?
detected by beta cells which release insulin
which cells have insulin receptors?
almost all
how does insulin cause a decrease in blood glucose levels?
- increased absorption (especially in skeletal muscle) as when insulin binds to receptor it leads to a change in its tertiary structure so channels open and cell becomes more permeable to glucose
- activates enzymes within liver and adipose cells which converts glucose to glycogen
- increase the rate of glucose breakdown by increasing respiration rates
how is insulin released from beta cells?
- when glucose concentration is high it enter the cell by facilitated diffusion (large and polar)
- ATP is produced as the cell respires
- high conc of ATP means they bind to potassium ion channels and close them which causes a change in membrane potential
- depolarisation causes voltage gated Ca2+ channels to open
- influx of calcium ions cause beta cells to secrete insulin
- insulin-containing vesicles move towards the membrane and are released via exocytosis
what is the action of insulin once it has been released?
- muscle cells, fat storage cells , adipose cells and liver contain glucose transporter proteins (GTP) which are insulin sensitive in phospholipid bilayer
- allows for uptake of glucose via facilitated diffusion
- rate of uptake is limited by the number of GTPs
- insulin binds to specific receptors on the membrane of target cells
- this stimulates them to activate/add more GTPs to their bilayer which increases their permeability to glucose so rate of diffusion increase
what does aldosterone do?
control body temp and water concs
what is type 1 diabetes?
beta cells cant produce insulin
what is the treatment for t1d?
- insulin injections
- monitor glucose levels
what is type 2 diabetes?
body has reduced sensitivity to insulin due to the glycoprotein receptors not working properly
what is the treatment for t2d?
- diet and exercise
- insulin injections
what is the cause t1d?
autoimmune disease
what is the cause of t2d?
- excess weight
- habitual overeating of refined carbs
- inactivity
what are the symptoms of t1d and why?
- frequent urination
water moves into blood to increase water potential - increased thirst
replace water that moves out of cells - loss of consciousness
glucose not being used in muscles for resp
what are downsides to pig/cow insulin?
- expensive
- difficult
- allergic reactions to non-self antigen
what are the benefits to GM human insulin?
- cheaper
- overcome ethical issues with animals
- less allergic reactions
- mass produce
what are the advantages to stem cell treatment in diabetes?
- overcome organ donor problems
- less likelihood of rejection
- insulin injections not required
what are the disadvantages to stem cell treatment in diabetes?
- destruction of human embryos
- could become cancerous
- immunosuppressants
why must insulin be injected rather than taken orally?
insulin is a protein that will get broken down by protease in the mouth
what are the reactions in fight or flight?
- Hr increases to pump more oxygenated blood around the body
- pupils dilate to take in light
- arterioles in skin constrict to get more blood to major muscle groups eg heart
- blood glucose level increases for respiration
- smooth muscle in lungs relax to allow more oxygen in
- non essential systems eg digestion shut down to focus on emergency function
what is the fight or flight repsonse?
- autonomic nervous system detects a threat
- hypothalamus communicates with sympathetic nervous system, adrenal cortical system and the pituitary gland
- nervous impulses causes the adrenal medulla to secrete adrenaline and noradrenaline
- pituitary gland secretes ACTH which stimulates the adrenal cortex to release cortisol and corticosterone
what does adrenaline do in the fight or flight response?
- increased HR to pump more oxygenated blood around the body
- stimulates glycogenolysis to make glucose for resp
what does noradrenaline do in the fight or flight response?
- widening of pupils to let light in
- dilation of bronchioles to allow more oxygen in
- vasoconstriction to get more oxygen to muscle
what does cortisol do in the fight or flight response?
- increase blood pressure to maintain ion levels
- increased blood glucose for respiration
what does corticosterone do in the fight or flight response?
- suppress the immune system to save energy for more important processes
- reduce inflammatory response
how does adrenaline work?
- binds to complementary receptors (glycoproteins) in cell surface membrane
- activates enzyme adenyl cyclase via anchored G proteins on livers surface
- catalyses conversion of ATP to cyclic AMP which acts as a second messenger
what is the action of adrenaline for glycogenesis?
(see how does adrenaline work flashcard)
- after cAMP formation it activates protein kinases to phosphorylates other enzymes and results in glycogen breakdown
what 2 nerves are connected to the medulla oblongata and what do they do?
- sympathetic nerve releases noradrenaline to increase HR by stimulating the SAN
- vagus nerve (parasympathetic) releases acetylcholine to decrease HR
what do chemoreceptors do?
- detect chemical changes such as oxygen concentration, carbon dioxide levels and the pH of the blood
- increased carbon dioxide means decreased pH which stimulates sympathetic nervous system and vice versa
what do baroreceptors do?
- detect changes in blood pressure
- found in the carotid arteries and aorta
what type of diabetes is likely to form in adults due to foetal undernutrition and why?
type 2 as it causes a change in metabolism and is not a autoimmune condition
how would a delay in emptying of the stomach could improve management of t2d?
- feel more full for longer
- prevent rapid glucose absorption
- eat less so less risk of obesity
which type of diabetes is gestational diabetes closest to?
type 2 as insulin is still being produced but the liver cells dont respond to it
describe when and how insulin is administered and how it acts to reduce blood glucose conc
- administered with a pump prior to meals
- bind to receptors in cell surface membrane of liver cells
- it promotes uptake of glucose
- triggers conversion of glucose to glycogen in glycogenesis
how does adrenaline bind to cardiac cells?
binds to glycoprotein receptors on the cell surface membrane
why don’t hormones act on individual muscle cells instead of SAN?
individual muscle cells would contract out of sync and so HR wouldnt increase
how does adrenaline bring about a response inside SAN cells?
binds to receptors on cell surface membrane which triggers adenyl cyclase which converts ATP to cAMP which acts as a secondary messenger which depolarises the SAN
what is the effect of long term stress on the body?
- prolonged high BP can lead to cardiovascular problems
- suppressed immune system leads to increased susceptibility to infections
how could injury to the hypothalamus and the pituitary gland cause many different symptoms?
they produce a wide range of hormones which signal to other endocrine glands so many symptoms appear
describe the function of the liver in urea production
combines ammonia and carbon dioxide as part of the ornithine cycle
how are monoclonal antibodies produced for pregnancy tests?
- mouse is injected with hCG to make correct antibody
- the B cells that make the antibody are removed from the spleen and fused with a myeloma to form a hybridoma
- divides rapidly and produce millions of the antibody
how do pregnancy tests work?
- urine on the wick moves down the stick
- if it contains hCG then it can binds to receptors on free hCG antibodies that have coloured beads attached
- this forms an hCG/antibody complex
- moves to the first window where there are immobilised monoclonal antibodies that only bind to hCG/antibody complexes
- this triggers the dye to show as a line
- the solution moves to the second window where there a re a line of antibodies that bind to the mobile antibodies even if the don’t have hCG
- if this line doesn’t show the test is faulty
how do scientists test for anabolic steroids?
urine sampled in gas chromatography and mass spectrometry
what are the effects of kidney failure?
- protein in the urine if the podocytes or basement membrane in the bowmans capsule are damaged then larger molecules can pass into the urine
- blood in urine
- electrolyte imbalance and urea as kidneys cant filter out excess ions
- high blood pressure as water potential cannot be controlled
what are the two types of dialysis?
haemodialysis and peritonial dialysis
why should there be no glucose in the urine?
reabsorbed by the proximal convoluted tubule
why might there be proteins in the urine?
- blood pressure too high
- kidney infection
- fault with filtration
how is glomerular filtration rate affected by kidney failure?
less blood filtered by the glomerulus causing GFR to decrease and toxins build up in blood
how is GFR measured?
- blood test measures creatine levels
- breakdown product in muscles give estimated GFRcm^3/min
what factors affect GFR?
- age
- gender
- diet
- ethnicity
- pregnancy
- fitness
how does haemodialysis work?
- partially permeable membrane separates blood from dialysate
- blood passes through tubes surrounded by dialysate
- dialysate contains substances needed in the blood (glucose, Na2+)
- as the conc of substances that are needed are in the right quantities in the dialysate, substances only move in or out when the blood has incorrect concs
- dialysate is constantly refreshed so conc grad is maintained
- contains no urea so it moves out of the blood
how does peritoneal dialysis work?
- makes use of the natural lining of the peritoneum so active transport can occur
- dialysate is introduced into the abdomen through a catheter
- drained out to maintain conc grad so urea can move out
what are the differences in haemodialysis and peritoneal dialysis?
- passive vs active transport and facilitated diffusion
- removes more waste (more effective) vs less effective
- fluid constantly refreshed vs not constant so conc grad less
- countercurrent flow vs not
what are the advantages of a kidney transplant?
- quality of life
- less restrictive diets
- less expensive
- long term
what are the disadvantages of a kidney transplant?
- immunosuppressants
- long term side effects
- not enough donors to cope with demand
- risk of rejection
- organ needs to be replaced after 10 years
