5.4 hormonal communication Flashcards
exocrine glands
secrete substances into a duct
exocrine cells arrangement in pancreas
in small groups called ACINI (acinus), surrounding a tubule at the centre
role of acinus cell
- synthesise enzymes (amylase, lipase, trypsinogen)
- secrete into the tubule at the centre of the group
tubules in the acini
- join to form INTRALOBULAR ducts that combine to form pancreatic duct
role of pancreatic duct
- carries the fluid containing the enzymes into the first part of the small intestine (duodenum)
- SECRETES the fluid into the duodenum
what is in the fluid from the pancreatic duct
- pancreatic amylase (amylose to maltose)
- trypsinogen (inactive protease that is converted to active trypsin when it enters duodenum)
- lipase (digests lipids)
- sodium hydrogencarbonate to neutralise the system coming from acidic stomach
which are the endocrine glands in the pancreas
islets of langerhans
describe arrangement of islets of langerhans
- alpha cells
- beta cells
how to recognise alpha and beta cells
- alpha light stain
- beta dark stain
alpha cells purpose
secrete glucagon
beta cells purpose
secrete insulin
how is insuliin released from beta cells
- potassium ion channels in CSM usually open (and ca2+ closed), so k+ flow out of cell
- when blood glucose conc high, glucose diffuses into cell
- glucose metabolised to produce ATP
- ATP closes k+ ion channel
- accumulation of k+ inside cell alters PD; inside cell is less negative
- change in PD opens Ca2+ chanells, so calcium ENTERS the cell
- ca2+ cause the vesicles of insulin to fuse with the CSM, releasing insulin by exocytosis
normal conc. blood glucose
4-6 mmol / dm3
hypoglycaemia
low blood sugar
hyperglycaemia
high blood sugar
probelms associated with hypoglycaemia
- glucose too low
- tiredness
- irritiability
what happens if blood glucose is too high (not full thing)
- beta cells secrete insulin
- travel in blolod to target cells (liver, muscle)
insulin is a … (hormone)
peptide based hormone
so cant diffuse across cell surface membrane
describe how insulin enters cells
- insulin binds to sepcific completmentary insulin receptor on CSM of target (muscle/liver) cells
- activates enzyme tyrosine kinase
- causes phosphorylation of inactive enzymes in the cell, activating them
- cascade of enzymes
- vesicles containing glucose transproter protein inserted into CSM
- extra glucose can now enter cell for 1. glycogenesis 2. respiration 3. conversion to fats
what happens if blood glucose too low
- alpha cells secrete glucagon into the blood
- GLUCAGON ONLY ACTS ON HEPATOCYTES
- Binds to specific comp receptors in hepatocytes
- stimulates a g protein , which activates adenyl cyclase, which catalyses ATP-> cAMP, which actives a series of enzyme contrilled reactions
- glycogenolysis (glycogen to glucose) 2. more fatty acids used in respiration (instead of glucose) 3. gluconeogenesis
gluconeogenesis
formation of NEW glucose
- from amino acids and fats
what mechanism controls the blood glucose
NEGATIVE FEEDBACK
endocrine glands
- SECRETE chemical messengers called hormones
- travel in blood
- bind to specific complementary receptors on target cells
2 types of hormones
PEPTIDE (protein based)
steroid (lipid soluble, non polar)
list the endocrine glands (head to toe)
pituitary
thyroid
adrenal
pancreas
testes
ovary
nervous system vs endocrine system
ENDOCRINE IS:
- slower to bring an effect
- longer lasting
- chemical messengers vs electrical impulse
- endocrine tracles in blood vs neevous via neurones
when a hormone binds to a receptor this activates
G PROTEIN
activates adenyl cyclase
which does ATP to cAMP [SECONDARY MESSENGER]
camp activates protiens/enzymes by phosphorylating them
Where are the adrenal glands found
just on top of the kidneys
2 parts of the adrenal glands
cortex (outer)
medulla (inner)
adrenal cortex releases:
- mineralocorticoids eg aldosterone
- glucocorticoids eg cortisol
adrenal medulla releases:
- noradrenaline
- adrenaline
how do STEROID hormones work?
- lipid soluble so are able to diffuse through phospholipid bilayer
- binds to a specific receptor in the CYTOPLASM
- receptor-steroid complex enters nucleus of target cell and binds to another specfic receptor on the DNA
- stimulates the production of mRNA, coding for the protein
- THEREFORE ACTING AS A TRANSCRIPTION FACTOR
mineralocorticoids
- eg aldosterone
- controlls conc na+ k+ in blood
- controls blood pressure
- produced in CORTEX
glucocorticoids
-eg cortisol
control metablism in the liver, also stimulates production of glucose from glycogen , in the liver
is adrenaline steroid or peptide
peptide
so requires specfiic complementary GLYCOPROTEIN receptors on the CSM of its target cells
glucocoricoids and mineralocorticoids are hwat type of hormone
steroid
released in time of stress
can increase BP and cause gluconeogenesis
endocrine function of the pancreas:
- islets of langerhans
- control of blood glucose: alpha cells release glucagon, beta cells release insulin
exocrine function of the pancreas
- acini release enzymes (amylase, lipase, trypsinogen) into tubule at centre
- join to form intralou=bular duct, join to form pancreatic duct
- enzyme fluid carried to SMALL INTESTINE
type 1 diabetes
- autoimmune
- beta cells destroyed
- cant produce enough insulin and cant store excess as glycogen
type 2 diabetes
- resistance to insulin
risk factors of type 2 diabetes
- obesity
- lack of exercise
- high sugar carb diet
type 1 diabetes typical treatments
- indulin injections
- insulin pump
- ISLET CELL TRANSPLANT
- pancreas transplant
- FUTURE: GM insulin, stem cell transplant to produce beta cells
type 2 diabetes treated
- lifetsyle
- less sugar carb diet
- more exercise
how did they used to get insulin
from pigs
how do they currently get insulin
GM bacteria to produce human inuslin
advantaged of using the GM bacteria to produce human insulin vs pig insulin
- exact copy, more effective
- less chance of rejection
- cheaper
- less moral objections
- less chance of allergy
role of androgens
regulation of sexual characteristics and cell growth
(released from cortex)
