5.1.4 Hormonal Communication Flashcards
What are endocrine glands?
groups of cells that are specialised to secrete hormones into the blood
What are hormones?
they are chemical messengers, many are proteins + peptides (insulin) or steroids (progesterone)
How can glands be stimulated?
change in conc of other substances or electrical impulses
How do hormones work?
They are diffused into blood and taken round body. They diffuse out of blood all over the body but each hormone will only bind to specific receptors( found on membranes of some cells, called target cells) for that hormone - tissue containing target cells is called target tissue + hormones trigger a response in target cell (effector)
Why are hormones called the first messenger?
It carries the chemical message from the endocrine gland to the receptor on target cells
What does the secondary messenger do?
An enzyme catalyses the production of a molecule inside the cell called a signalling molecule (secondary messenger) which signals to other parts of cell - carries message from the receptor to other parts of the target cell - activates a chain of reactions called a cascade
Which gland is adrenaline excreted from and to what stimuli?
- secreted from medulla of the adrenal glands
- is secreted in response to ↓ blood glucose levels, when one is stressed and when one is exercising
What is the function of adrenaline?
It prepares the body for action by making more glucose available for muscles to respire , e.g. by activating glycogenolysis
What is the function of adrenaline?
It prepares the body for action by making more glucose available for muscles to respire , e.g. by activating glycogenolysis
Increases energy available in short term by ↑ heart rate + breathing rate + constricting some blood vessels so that blood is diverted to brain and muscles
How does adrenaline induce a response?
It binds to specific receptors in CSM of many cells e.g. hepatocytes and when bound it activates an enzyme in the membrane called ADENYLYL CYCLASE, where adenylyl cyclase catalyses the production of SM called cAMP from ATP
cAMP then activates a cascade e.g. the cascade of enzyme reactions makes more glucose available to the cell by catalysing breakdown of glycogen into glucose
Name for part of pancreas that contains endocrine tissue?
Islets of Langerhans which are clusters of cells
What types of cell do the IoL contain and what are their functions?
ALPHA CELLS - secrete glucagon
BETA CELLS - secretes insulin
3 way to differentiate alpha and beta cells under a microscope?
- Alpha cells a larger
- Alpha cells are more abundant
- differential staining e.g. chrome haematoxylin + phloxine
How do IoL appear under a microscope?
they are paler patches in amongst other cells
Role of insulin
Decreases glucose levels in blood when too high
Promotes enzyme action of GLYCOGENESIS - formation of glycogen(stored in liver + muscle cell cytoplasm) from glucose
Binds to specific receptors on CSM of hepatocytes + muscle cells to ↑ the permeability of cell membranes to glucose so cells take up more glucose
also ↑ roRe of glucose in muscle cells
Role of glucagon
Increases glucose levels in blood when too low
Binds to specific receptors on CSM of hepatocytes which activates enzymes for GLYCOGENOLYSIS - break down of glycogen into glucose
Also promotes GLUCONEOGENESIS - formation of glucose from glycerol + aa (non-carbs)
Also ↓ roRe of glucose in cells
Where does insulin act?
Hepatocytes and muscle cells
Where does glucagon act?
only hepatocytes
Define Hypoglycaemia
condition where BGC is abnormally ↓
Define Hyperglycaemia
condition where BGC is abnormally ↑
What kind of glands are adrenal glands and where are they situated?
Endocrine glands and are found just above the kidneys
What is the adrenal cortex?
Outer part of kidney
What is the adrenal medulla?
Inner part of kidney
What is the function of the adrenal cortex?
secretes steroid hormones
CACA (aldosterone, cortisol and androgens)
What is the function of the adrenal medulla?
secretes catecholamine hormones (modified aa)
MAN (adrenaline and noradrenaline)
Function of androgens
male and female sex hormones
Function of aldosterone
Helps control blood pressure by maintaining the balance between salt and water concentration in blood + bodily fluids
Function of cortisol
regulates metabolism by controlling how body converts fats, proteins and carbohydrates to energy + also helps regulate blood pressure and cardiovascular function in response to stress
Function of Adrenaline
Increases heart rate by sending blood to brain + muscles
Also rapidly increases glucose conc in blood by converting glycogen into glucose in the kidney (glycogenolysis)
Function of Noradrenaline
works with adrenaline in response to stress to increase heart rate, widen pupils, widen air passage in lungs and narrow blood vessels in non essential organs
How is the pancreas an endocrine and exocrine gland?
ENDOCRINE - secretes hormones into blood
EXOCRINE - secretes enzymes via a duct into the duodenum
Histology of a pancreas
Islets of Langerhans for endocrine function (alpha + beta cells)
Acinar cells for exocrine function (enzymes such as amylase which breaks down carbohydrates) - help with digestion
What stain can be used to differentiate between alpha and beta cells?
Chrome Haematoxylin and Phloxine
How do beta cells control insulin secretion?
- High BGC detected as more glucose enters beta cells by FACILITATED DIFFUSION (channel and carrier proteins)
- The increased glucose conc causes a rise in RoRe thus making more ATP
- Rise in ATP triggers K+ ion channels in plasma mem to close - means K+ions cannot get through membrane so build up inside of cell, making inside of cell less negative, PLASMA MEMBRANE IS DEPOLARISED (-30mV)
- Depolarisation triggers VG Ca2+ ion channels in mem to open so Ca2+ ions diffuse INTO beta cells
- The diffusion of Ca2+ ions into beta cells cause vesicles to move + fuse with beta cell membrane
- Insulin is released via exocytosis
What are beta cells at ‘resting potential’?
BGC is normal (or lower)
K+ ion channels are open thus K+ ions diffuse out
Ca 2+ ion channels are closed
Thus inside of beta cells is more negatively charged (-70mV) than outside as there are more positive ions outside than inside
MEMBRANE IS POLARISED
What is diabetes mellitus?
Condition where BGC cannot be controlled properly
What is Type 1 diabetes?
An autoimmune disease where body attacks beta cells in the IoL
Don’t produce insulin
Occurs in children or young adults usually with ↑ risk with family history
What is type 2 diabetes?
When beta cells don’t produce enough insulin or when body’s cells don’t respond properly to insulin - the insulin receptors on membranes don’t function properly so cells don’t take up enough glucose - BGC is ↑ than normal
Usually acquired later in life than Type 1 + is often linked to obesity - also risk ↑ with ethnicity (african or asian) or family history
How to treat Type 1 diabetes?
INSULIN THERAPY - regular insulin injections throughout day
- insulin pump is a machine that continuously delivers insulin into body via a tube inserted beneath the skin
- islet cell transplantation means that one receives healthy islet cells from donor so their pancreas can produce some insulin
- need to think about BGC, diet and exercise activity
How to treat Type 2 diabetes?
Managed through lifestyle changes - eating a healthy, balanced diet + getting regular exercise + losing weight if necessary - can prevent the onset of Type 2 diabetes + control effects
If BGL cannot be controlled through lifestyle changes then medicine may be prescribed
What 3 medicines are prescribed for Type 2 diabetes?
- Metformin - acts on liver cells to reduce amount of glucose that they release into blood - also acts to ↑ sensitivity of cells to insulin so more glucose can be taken with same amount of insulin
- Sulfonylureas - stimulate pancreas to produce more insulin
- Thiazolidinediones - make body cells more sensitive to insulin
INSULIN therapy may also be used if medication does not work
How is human insulin created?
With genetically modified bacteria
Benefits of creating human insulin with GM bacteria?
- Cheaper than extracting insulin from animal pancreas
- Larger quantities of insulin can be produced using GM bacteria
- human insulin is more effective than using pig or cattle insulin + is less likely to be rejected (trigger an allergic response to be rejected by immune system)
- prefer insulin from GM BAC due to ethical reasons or religious e.g. vegetarians using animals or issues extracting insulin from pigs
How can stem cells potentially cure diabetes?
As they are undifferentiated, they could be grown into beta cells which would be implanted into pancreas of person with type 1 diabetes - thus would be able to make insulin as normal - cures type 1 diabetes as no need for insulin therapy
