Hormonal Communication Flashcards
What is the endocrine system?
A communication system
Consisting of hormone secreting glands
What are the 2 types of hormone?
Protein based (adrenaline, insulin, glucagon)
Steroid (oestrogen, testosterone)
Where do protein hormones bind?
On the cell surface membrane
don’t enter the cell as they aren’t soluble in phospholipid membrane
Where steroid hormones act/ bind?
Can enter the cell as they are soluble in the membrane
enter the nucleus and have a direct impact on the DNA
Name glands in the endocrine system
Pituitary gland thyroid gland thymus adrenal gland pancreas ovaries (females) testes (males)
What are Target cells?
The cell that the hormone is intended to effect
What must a target cell have in order for a non-steroid hormone to act?
A specific receptor on the cell membrane that is complementary to the shape of the hormone
What is the first messenger?
Something that binds to the cell surface causing a change inside the cell
e.g non-steroid hormones
What is the second messenger?
A molecule released inside the cell as a result of the first messenger
stimulates a change in activity of the cell
What is activated when a hormone binds to the receptor on the cell surface membrane?
G protien
What does the G protein do once it is activated?
Activates an effector molecule
This is normally an enzyme that activates a second messenger
What is the most common effector molecule and what second messenger does it form?
Adenyl cyclase
converts ATP to cAMP
Where are the adrenal glands found?
Just above the kidneys
What are the 2 sections of the adrenal gland?
adrenal cortex
adrenal medulla
What are the 3 layers of the adrenal cortex?
Zona glomerulosa - outermost layer, secretes mineralocorticoids
Zona fasciculata - middle layer, secretes glucocorticoids
Zona reticularis - inner layer, secretes precursor to sex hormones
What does the zona glomerulosa secrete?
mineralocorticoids
What does the zona fasciculata secrete?
glucocorticoids
What does the zona reticularis secrete?
Precursor molecules to sex hormones
What does the adrenal medulla secrete?
Adrenaline
What type of hormones are made by the adrenal cortex? (steroid or non-steroid)
Steroid Hormones
How do steroid hormones work?
Pass through cell membrane
Bind with a receptor in the cytoplasm
Hormone-receptor complex passes into the nucleus
binds to receptor on the DNA
Drives production of mRNA which makes a specific protein
What is the function of mineralocorticoids?
Control Na+ and K+ concentrations in blood
as a result control blood pressure
What is the function of glucocorticoids?
control the metabolism of carbohydrates, fats andf proteins
e.g Cortisol can stimulate the production of glucose from stores
What kind of hormone is adrenaline?
non-steroid
What are the effects of adrenaline?
Relaxes smooth muscle in the bronchioles Increased SV of heart Increased HR Vasoconstriction (increases blood pressure) Stimulates glycogen to glucose conversion Dilating pupils Increases mental awareness Inhibits action of the gut Causing body hair to stand up
What is an exocrine gland?
A gland that releases hormones through a duct
In what way is the pancreas different to most other hormone-secreting organs?
It has both Endocrine and Exocrine functions
What is the exocrine function of the pancreas?
Secreting digestive enzymes into the small intestine through the pancreatic duct
Where in the pancreas are the digestive enzymes produced?
Acini
What is the structure of an Acinus?
exocrine cells that surround a tiny tubule
these tubules converge to form intralobular ducts that then converge to form the pancreatic duct
What are the three main enzymes in the pancreatic fluid?
Pancreatic amylase
Trypsinogen - inactive form of the protease Trypsin
Lipase
What is the name of the endocrine cells of the pancreas?
Islets of Langerhans
Which cells produce insulin?
Beta cells
Which cells produce Glucagon?
Alpha Cells
How is insulin released from the Beta cells? (long answer)
K+ channels are normally open so K+ can flow out
When glucose concentration is too high glucose move into Beta cell
It is metabolised into ATP
ATP closes K+ channels
accumulation of K+ alters the potential difference across membrane
This causes Ca2+ channels to open and Ca2+ to rush in
Ca2+ causes vesicles containing insulin to bind with cell membrane and are released by exocytosis
What is the name given to someone who’s blood sugar falls too low?
Hypoglycaemia
What is the name given to someone who’s blood sugar gets too high?
Hyperglycaemia or Diabetes if it is consistently too high
If blood glucose gets too high what will the body do to correct it?
Beta cells in the islets of Langerhans will secrete insulin to convert glucose to glycogen
What is the name given to the process where glucose is converted to glycogen?
Glycogenesis
Describe the hormone action of insulin on the cells?
Insulin is a non-steroid hormone so binds to surface receptor on the hepatocytes
Activates the enzyme tyrosine kinase which phosphorylates inactive enzymes within the cell
Cascade of reactions causes glucose transporter proteins to be released allowing more glucose into the cell to be converted to glycogen and fats
If blood glucose gets too low, what will the body do to correct it?
Alpha cells in the islets of Langerhans will secrete glucagon to convert glycogen to glucose
What is the name given to the process where glycogen is converted to glucose?
glycogenolysis
How does Glucagon work?
Glucagon is a non-steroid hormone so binds to surface receptor on the hepatocytes
Activates G-protein which activates adenyl cyclase
adenyl cyclase converts ATP to cAMP
cAMP activates enzyme catalysed reactions causing glycogenolysis
Why is blood glucose concentration control an example of negative feedback?
A change is brought about in order to oppose the change in blood glucose
If it is too high, insulin will reduce it
If it is too low, glucagon will increase it
What is Diabetes mellitus?
A condition where the body is unable to control blood glucose concentrations
Causes hyperglycaemia after a meal rich in carbohydrates or lipids
Causes hypoglycaemia after exercise or fasting
What causes Type 1 diabetes?
Autoimmune response in which the immune system attacks and destroys beta cells in the islets of Langerhans
Can be post viral
How can Type 1 diabetes lead to hypoglycaemia?
Because they cannot produce sufficient insulin they are unable to create glycogen stores when blood glucose is high (e.g after a meal)
This means when blood glucose is low there are no stores of glycogen to be hydrolysed and so they become hypoglycaemic
What causes Type 2 diabetes?
Where the person is able to produce insulin however this insulin is unable to have an effect on the hepatocytes
Blood glucose is almost always too high in Type 2 diabetes
What factors can bring an earlier onset of Type 2 diabetes?
Obesity Lack of exercise high sugar diet Family history Ethnicity (Asian or Afro-Caribbean)
What are the treatments for Type 1 diabetes?
Insulin injections (most common)
Insulin pump therapy - a small device pumps insulin into the bloodstream at a controlled rate
Islet cell transplant - Healthy beta cells transplanted into host
Pancreas transplant
What are the treatments for type 2 diabetes?
Lifestyle changes e.g:
Diet
More regular exercise
weight loss
in severe cases may use insulin injections
How has insulin become more available in recent years
Used to be extracted from pigs and cows
Produced by a GM bacteria
this allows mass production and made insulin a lot cheaper
What are the advantages of using insulin from GM bacteria?
Makes Human insulin (as opposed to pig or cow insulin)
Less chance of developing a tolerance to insulin
Less chance of rejection
Lower risk of infection
Cheaper to manufacture
People are less likely to have moral objections to the way it is produced (religious, vegan)
