Hormonal Communication Flashcards
The endocrine communication system uses hormones as signalling molecules: what is the process of this system
- Secretion (production & release) of hormones into the bloodstream
- Hormones transported by blood
- Hormone detected by target cells / tissues / organs
How do endocrine hormones move vs exocrine ones
Secreted directly into the blood versus secreted via a duct
What are the 2 types of hormones
Protein (non steroid) & steroid
Protein (non-steroid hormones) Vs Steroid hormones
How do hormones work on target cells / tissues
- specific receptor on cell-surface membrane
(Receptor made of glycoproteins)
-> complementary to shape of hormone molecule
-> hormone binds to receptor & changes initiated in the cells
1st vs 2nd messenger
How is the second messenger activated process
- 1st non steroid messenger binds to receptor on cell surface membrane
- G protein activated
- Adenyl cyclase - effector molecule - activated
- ATP converted to cAMP (2nd messenger)
- cAMP acts directly on another protein (e.g, ion channel) or may initiate a cascade of enzyme controlled reactions, which alter cell activity
What organ functions as an endocrine and exocrine gland
The pancreas
Exocrine function of pancreas
-> secrete pancreatic juices into pancreatic duct (delivered to small intestine)
Pancreas juices made up of
- digestive enzymes (amylase, trypsin, lipase)
- sodium hydrogencarbonate (neutralises contents of digestive system, which has left the acidic stomach)
Endocrine function of pancreas
- secrete hormones from the islets of langerhans
+ endocrine tissues are made up of these islets
-> alpha & beta cells are found in these island
Alpha vs beta cells in pancreas
Key processes in Pancreas (glycogenolysis, glycogenesis, gluconeogenesis, lipogenesis)
What does glucagon do
- stimulate glycogenolysis
- stimulate gluconeogenesis
# released if blood glucose concentration too low
-> glucose conc in blood increases, as glucose conc in cell e.g. muscles / hepatocytes increases
What does insulin do
- released if blood glucose too high
- stimulates glycogenesis
-glucose concentration of cells e.g. muscles / hepatocytes decreases therefore in blood decreases
What mechanism regulates blood glucose conc (normally 4-6 mol/dm3)
Negative feedback
This is as it’s insulin versus glucagon (antagonistic as they have the opposite effects)
What happens in hypoglycaemia & how is it detected (when too low blood glucose conc)
When not enough glucose is delivered to the body tissues & brain
This can lead to seizures, unconsciousness / death
-> detected in alpha cells in the islet of langerhans
Glucagon is secreted into bloodstream
Receptors on the outside of hepatocytes & muscle cells detect glucagon
-> activates gluconeogenesis, glycogenolysis & decreased rate of respiration
-> concentration of glucose in cells increases and so concentration of glucose in blood increases as glucose diffuses into blood from cells
What happens in hyperglycaemia& how is it detected (when too high blood glucose conc)
-> detected by beta cells in the islet of langerhans
- insulin secreted into the bloodstream!
- receptors on outside of hepatocytes & muscle cells detect insulin
- activates glycogenesis & increased rate of respiration & lipogenesis
Glucose concentrate decreases in cells & blood as glucose diffuses into cells from blood, down the concentration gradient by facilitated diffusion
Mechanism of insulin secretion
What ion channels are open & closed @ a normal blood glucose level
- ca2+ closed
- K+ open
How is insulin secrete when BGC is high (steps)
- Glucose molecules move into the beta cells by a glucose transported
- Glucose metabolised in mitochondria via glucokinase to form ATP
- Extra ATP binds to K+ channels & causes their closure
- K+ can’t diffuse out of cell / builds up / inside less negative / P.D reduced / depolarised membrane
- Voltage gated Ca2+ ion channels open
- Ca2+ enter cells
- Secretion of insulin (vesicles contains it move towards & fuse with the cell surface membrane)
- Insulin released by Exocytosis
Insulin action in hepatocytes
Glucagon action to do with hepatocytes
Type 1 diabetes (insulin dependent) cause
& typical onset
- in childhood
Cause = autoimmune response or viral infection, in which the immune system destroys beta cells OR physical trauma
Type 1 diabetes symptoms
Weight loss (less glucose converted into glygogen, lipids etc & stored - lost in urine instead)
More urine produced (less water reabsorbed in the collecting duct, due to high glucose conc
Effects of type 1 diabetes on the body
- insulin can no longer be synthesised by beta cells in the pancreas to control blood glucose concentration
- excess glucose can’t be stored as glycogen
- excess glucose not removed quickly: prolonged periods of high b.g.c. especially after meals
-> no store of glycogen, which can be used to release glucose -> blood g.c. falls too low
Type 1 diabetes: typical treatment vs in severe cases vs potential treatments
Type 2 diabetes (non-insulin dependent) onset & causes?
Over 40, but many children getting it now
Beta cells still produce insulin, but it’s ineffective
-> specific receptors on cell surface membrane of liver & muscle cells = less responsive to it
- cells lose ability to respond to insulin in blood
Risk factors for type 2 diabetes
- obesity
- lack of regular exercise
- high blood pressure & cholesterol
- ethnicity (Asian & Afro-Caribbean)
- family history
Type 2 diabetes: typical vs severe treatment
Alternate insulin sources & evaluation of them?
- Pig Insulin ( 🐷 pancreas = matches human close, but some = ethical or religious objections)
- Genetically modified bacteria producing insulin
Adrenal glands structure
What does the adrenal cortex secrete
Mineralcorticoids like aldosterone
Glucocorticoids like cortisol
- precursor androgen molecules, which are used to make sex hormones like testosterone & oestrogen
What does aldosterone regulate
Levels of sodium & potassium & water balance in blood, which impacts blood volume & pressure by targeting the collecting duct
What does cortisol, the primary stress hormone regulate
Released in response to stress & low B.G.C
-> regulates metabolism of glucose, fats & proteins -> releasing usable energy
-> stimulates production of glucose from stored compounds: glycogen, fats & proteins in the lvier
What do sex hormones do
Help development of secondary sexual characteristics & regulate production of gametes
What does the adrenal medulla secrete
- adrenaline & noradrenaline
Effects of adrenaline
Increases breathing rate not heart rate
Effects of noradrenaline
- works with adrenaline in response to stress
Increases heart rate
Widens pupils
Widens air passages in lungs
Narrow blood vessels in non-essential organs (so higher blood pressure)
When is adrenaline produced & how does it work
Produced @ times of stress of excitement: prepares the body for activity & to respond to emergency situations (fight/flight)
-> binds to specialised adrenaline receptors on cell-surface membrane of target cells (many cells & tissues have adrenaline receptors)
