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OCR A-level Biology > Hormonal Communication > Flashcards

Flashcards in Hormonal Communication Deck (53)
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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
adrenal gland
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?



What does the zona fasciculata secrete?



What does the zona reticularis secrete?

Precursor molecules to sex hormones


What does the adrenal medulla secrete?



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?



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?



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



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?



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?



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?



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?

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:
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)