Endocrine Communication Flashcards
What is the endocrine system
Used for communication around the body
How does the endocrine system transport its signals
Uses blood circulatory system
What are signals released by the endocrine system called
Hormones
How many types of hormones are there in
2
What are the two types of hormones
1) Protein and pepetide hormones
2) Steroid hormones
What are examples of protein/peptide hormones
Adrenaline
Insulin
Glucagon
What are examples of steroid hormones
Oestrogen
Testosterone
Describe the characteristics of protein hormones
-not soluble in the phospholipid membrane
-do not enter the cell
-need to bind to the cell surface membrane and release a second messenger inside the cell
Describe the characteristics of steroid hormones
-can pass through the membrane
-enter the cell and the nucleus
-have a direct effect on the DNA in the nucleus
What are hormones released by
Endocrine glands
Describe endocrine glands
- ductless-> consist of groups of cells that release the hormone directly into the blood
- release hormones
Name the 7 main endocrine glands in the body
1) pituitary gland
2) thyroid gland
3) thymus
4) adrenal glands
5) pancreas
6) ovaries (females)
7) testes (males)
What are hormones
chemical messengers that travel through the blood to target organs or tissues, where they trigger specific responses.
Why can steroid hormones enter cells directly but peptide hormones can’t?
-Steroid hormones are lipid-soluble so they can dissolve in the fatty cell membrane and pass through it.
-Peptide hormones are water-soluble and can’t pass through the fatty cell membrane so they bind to receptors on the cell surface instead.
What does the target cell have to have for non-steroid hormones
-must possess a specific receptor on their plasma membrane that is complementary to the shape of the hormone
Why can hormones be carried in the blood without affecting every cell
Because the hormone will only bind to the cells with the correct specific receptor which will initiate a change in the cell
What are non-steroid hormones known as
First messengers
What are first messengers
Signalling molecules outside the cell that bind to the cell surface membrane and initiate an effect inside the cell
What do first messengers usually cause
The release of another signalling molecule in the cell (second messenger)
What does the second messenger do
Stimulate a change in the activity of the cell
Describe the first and second messenger mechanism
1) the hormone (first messenger) binds to a complementary receptor on the cell surface membrane of the target cell
2) this causes the G protein to be activated
3) the G protein then activates adenyl cyclase
4) the activated adenyl cyclase then converts ATP to cAMP (cyclic AMP) which is the second messenger
5) this second messenger may act directly on another protein or initiate a cascade of enzyme-controlled reactions
Where are the adrenal glands found
Just above the kidneys, one on each side of the body
How is each adrenal gland divided
-the adrenal coretx (the outer)
-the adrenal medulla (the inner)
Name and describe the regions of the adrenal cortex
1) zona glomerulosa= outermost later, secretes aldosterone
2) zone fasciculata= middle layer, secretes cortisol
3) zona reticularis= innermost layer, secretes precursors molecules that are uses to make sex hormones
Where is the adrenal medulla found
In the centre of the adrenal gland
What does the adrenal gland secrete
Adrenaline
Noradrenaline
What does the adrenal cortex use to produce a range of hormones
Cholesterol
What type of hormones are produced by the adrenal cortex
Steroid hormones
Describe the action of steroid hormones
1) steroid hormone passes through the cell membrane of the target cell
2) steroid hormone binds with a specific receptor (with a complementary shape) in the cytoplasm
3) the receptor-steroid hormone complex enters the nucleus of the target cell and binds to another specific receptor on the chromosomal material
4) binding stimulates the production of messenger RNA (mRNA) molecules, which code for the production of proteins
What is the role of aldosterone
Maintains blood pressure
By helping to control the concentrations of sodium and potassium in the blood
What is the role of cortisol when released by the zona fasciculata
Help to control the metabolism of carbohydrates, fats and protein in the liver
When is cortisol released
In response to stress or as a result of low blood glucose concentration
Is adrenaline polar or non-polar
Polar
Can adrenaline enter cells through the plasma membrane? Why?
No, because it is a polar molecule and so it is a protein/ peptide hormone
How is adrenaline detected
By specialised receptors on the plasma membrane of target cells
Why are the effects of adrenaline widespread
Because many cells and tissues have adrenaline receptors
What is the role of adrenaline
Prepare the body for activity
What effects does adrenaline have when preparing the body for activity
-relaxing smooth muscles in the bronchioles
-increasing stroke volume of the heart
-increasing heart rate
-dilating pupils
-inhibiting gut action
-causing body hair to stand erect
-stimulating conversion of glycogen to glucose
-causing vasoconstriction to raise blood pressure
What in the pancreas
A small dual-function gland
Where is the pancreas located
Below the stomach
Why is the pancreas described as dual-functioning
Because it has both endocrine and exocrine functions
What is an exocrine function
- when glands secrete digestive enzymes into a duct
What is an endocrine function
-when hormones are released into the bloodstream
What are the two main secretions of the pancreas
1) pancreatic juices containing enzymes which are secretes into the small intestine
2) hormones which are secreted from the islets of Langerhans into the blood
What is the exocrine function of the pancreas
-synthesising and releasing digestive enzymes
What is an endocrine function of the pancreas
-the secretion of glucagon and insulin
What is each group of cells in the pancreas called
Acinus
What 3 enzymes does the fluid from the pancreatic duct contain
1) pancreatic amylase- a carbohydrate which digest amylose to maltose
2) trypsinogen- an inactive protease which will be converted to the active trypsin when it enters the duodenum
3) lipase- which digests lipid molecules
Where is the fluid containing the enzymes taken to once it is in the pancreatic ducts
The first part of the small intestine (duodenum)
Where are the alpha and beta cells found in the pancreas
In the Islet of Langerhan
What hormone does the alpha cell secrete
Glucagon
What hormone does the beta cell secrete
Insulin
Name the 6 main parts of a pancreatic cell
1) blood capillary
2) islet of Langerhans
3) beta cells
4) alpha cells
5) Acinus
6) tubules in the centre of acinus
What effect does the release of insulin have on the body
-reduces the blood glucose concentration
When does insulin secretion stop
-when the blood glucose concentration drops too low
Describe the release of insulin from beta cells
1) the cell membrane has potassium and calcium channels
2) the potassium ion channels are normally open- so potassium ions flow out
3) when blood glucose concentration is high the glucose moves into the cell
4) glucose is metabolised to produce ATP
5) the ATP closes the potassium ion channels
6) the accumulation of potassium ions alters the potential difference across the cell membrane- the inside becomes less negative
7) the change in the potential difference opens the calcium ion channels
8) calcium ions cause the vesicles of insulin to fuse with the cell membrane, realising insulin by exocytosis
What is the normal blood concentration of glucose
- Betweeen 4 and 6 mmoldm^-3
Define hypoglycaemia
- When a persons blood glucose concentration is below 4 mmoldm^-3 (low) and remains low for long periods of time
What is the main problem caused by hypoglycaemia
- inadequate delivery of glucose to the body tissues and to the brain
What are some symptoms of mild hypoglycaemia
- tiredness
- irritability
What are symptoms of severe hypoglycaemia
- impairment of brain function and infusion which may lead on to seizures, unconsciousness and even death
Define hyperglycaemia
- when the blood glucose concentration rises too high for long periods
What can permanent high blood glucose concentrations lead to
- significant organ damage
What is a blood glucose concentration that is consistently higher than 7 mmoldm^-3 used to diagnose
- diabetes mellitus
What monitors the blood concentration of glucose in the blood
- the cells in the islet of langerhans
If their is an increase in glucose how does the cells in the islets of Langerhans respond
- the alpha and beta cells in the islets of Langerhans detect the change and insulin will be released by the beta cell
If their is a decrease in glucose how does the cells in the islets of Langerhans respond
- the alpha answer beta cells detect the change and glucagon is release and by the alpha cell
Where do insulin and glucagon act
- cells in the liver (hepatocytes)
Why do insulin and glucagon act on liver cells
- because they store glucose in the form of glycogen
Fill in the blank:
1) When there is _______ glucose in the blood it is converted to glycogen
2) If glucose is needed to ______ the blood concentration then _____ is converted back to glucose
1) excess
2) raise
3) glycogen
Is insulin a steroid or protein (non-steroid) hormone
-Protein hormone
Describe how insulin acts on the liver cells when high blood glucose concentration is detected
1) insulin bind to the specific membrane bound receptor of the target cell (liver cells)
2) this activates the enzyme tyrosine kinase
3) tyrosine kinase causes phosphorylation of inactive enzymes in the cell
4) this activates the enzymes leading to a cascade of enzyme-controlled reactions inside the cell
What are the 5 effects of insulin on the cell
1) more transporter proteins specific to glucose are placed into the cell surface membrane
2) more glucose enters the cell
3) glucose in the cell is converted to glycogen for storage (glycogenesis)
4) more glucose is converted to fats
5) more glucose is used in respiration
What is homeostasis
- the maintenance of a constant internal environment
Is glucagon a steroid or protein (non-steroid) hormone
- protein homrone
Describe how glucagon acts on the liver cells when blood glucose concentration is low
- it is detected by the alpha cells
1) alpha cells then secrete the hormone glucagon into the blood
2) glucagon binds to the specific membrane bound receptors on the liver cell
3) this stimulates a G protein inside the membrane
4) which activates the adenyl cyclase inside each cell
5) adenyl cyclase converts ATP to cAMP
6) this activates a series of enzyme controlled reactions in the cell
What are the 3 effects of glucagon on the liver cells
1) glycogen is converted to glucose (glycogenolysis) by phosphorylase A, one of the enzymes activated in the cascade
2) more fatty acids are used in respiration
3) amino acids and fats are converted into additional glucose, by gluconeogenesis
Define glucose
- a 6 carbon sugar (Hexose sugar), monosaccharide
Define glucagon
- hormone
Define glycogen
- a polysaccharide made of glucose with 1–4, 1–6 glycosidic bonds
Define glycogenesis
- glucose to be converted to gylcogen
Define gluconeogenesis
- production of glucose by conversion of amino acids and fats
Define glycogenolysis
- glycogen to be converted to glucose
What is glycogen synthase
- an enzyme in glycogenesis
What is glucokinase
- an enzyme that phosphorylates glucose to glucose- 6 - phosphate in the liver & pancreas
Define a glycosidic bond
- a bond that is formed between two monosaccharides by a condensation reaction
What is GLUT4
- an insulin-regulated glucose transporter found in fat tissues and any skeletal muscle
What type of mechanism controls the concentration of blood glucose
- negative feedback mechanism
What is the relationship between the hormones insulin and glucagon called and why?
- antagonistic
- because they have opposite effects on blood glucose concentration (one of their effects inhibits the effects of the opposing hormone)
In summary, describe the neagtive feedback if there was a rise in blood glucose concentration
1) detected by the beta cells in the islet of langerhans
2) beta cells secrete insulin into the blood
3) insulin detected by receptors on liver and muscle cells
4) liver and muscle cells remove glucose from blood and convert glucose to gylcogen
5) glucose concentration falls
In summary, describe the neagtive feedback if there was a fall in blood glucose concentration
1) detected by alpha cells in the islet of langerhans
2) alpha cells secrete glucagon into the blood
3) glucagon detected by receptors on liver cells
4) liver cells converted glycogen to glucose and release glucose into the blood
5) glucose concentration rises
What is diabetes mellitus
- a condition in which the body is no longer able to produce sufficient insulin to control its blood glucose concentration
What can diabetes mellitus lead to
- prolonged very high concentrations of glucose (hyperglycaemia) after a meal rich in sugars and other carbohydrates
- can lead to the concentration dropping too low (hypoglycaemia) after exercise or after fasting
What is type 1 diabetes also known as
- insulin-dependent diabetes
When does type 1 diabetes usually start
- in childhood
What is type 1 diabetes thought to be a result of
- an autoimmune response in which the body’s immune system attacks and destroys the beta cells
Fill in the blank:
A person with Type 1 diabetes is no longer able to ______ _______ _____ and cannot store excess ______ as ______
1) synthesis
2) sufficient
3) insulin
4) glucose
5) glycogen
Because of diabetes excess glucose in the blood is not removed quickly causing what?
- a prolonged period of high concentration
However in type 1 diabetes there is no stored glycogen, what problem does this cause
- when glucose falls there is no glycogen that can be used to release glucose
- therefore blood glucose concentration falls too low
What is the treatment for Type 1 diabetes
- usually insulin injections
What are alternative treatments to insulin injections for treating type 1 diabetes
1) insulin pump therapy (needle permanently inserted under skin)
2) islet cell transplantation
3) a complete pancreas transplant
4) stem cells (grow new islet of Langerhans in the pancreas)
What is type 2 diabetes also known as
- non-insulin-dependent diabetes
What can a person with type 2 diabetes not produce enough of
- insulin
What causes type 2 diabetes? Why?
- their responsiveness to insulin declines as they age
- because the specific receptors on the surface of the liver and muscle cells become less responsive and the cells lose their ability to respond to the insulin in the blood
At what age does type 2 diabetes usually develop
- as an adult
Fill in the blank:
In Type 2 diabetes the blood glucose concentration is almost _______ _____, which can damage major _____ and _____
1) permanently
2) raised
3) organs
4) circulation
What are the 5 risk factors that bring an earlier onset of type 2 diabetes
1) obesity
2) lack of regular exercise
3) high in sugar diet
4) being of Asian or Afro- Caribbean origin
5) family history
What are the treatments for type 2 diabetes
- change in lifestyle:
-> lose weight
-> exercise regularly
-> monitor diet
In severe cases of type 2 diabetes what are the treatments
- insulin injections
- use of drugs that slow down the absorption of glucose from the digestive system
Where did insulin used to be extracted form
The pancreas of animals (usually pigs)
How has insulin been more recently produced
- by Escherichia coli bacteria which undergoes genetic modification to manufacture human insulin
What are the 7 advantages of using genetically modified insulin bacteria
1) an exact copy of human insulin, so it is faster acting and more effective
2) less chance of developing tolerance to the insulin
3) less chance of rejection
4) lower risk of infection
5) cheaper to manufacture the insulin than to extract it from animals
6) manufacturing process is more adaptable to demand
7) people are less likely to have moral objections to using the insulin produced from bacteria than to using that extracted from animals
