Hormonal communication Flashcards
hormones?
secreted by endocrine glands directly into BS in response to stimulus and have effect at their target tissues
adrenal glands?
- divided into medulla and cortex
* medulla synthesises and secretes catecholamines, mainly adrenaline
Catecholamines?
are derived from the AA tyrsosine and are water soluble
adrenal glands - the cortex?
- the cortex uses cholesterol to produce steroid hormones
- Steroid hormones are derived from cholesterol and are lipid soluble
- The mineralocorticoids e.g. aldosterone - controls Na+ and K+ balance in the blood
- The glucocorticoids e.g. cortisol - a ‘stress hormone’ - regulates he metabolism of carbohydrates and proteins in the liver
where are endocrine glands situated?
• above the kidneys
what are hormones controlled by?
the endocrine system
the endocrine system?
made up of endocrine glands which secrete hormones
Hormone definition?
Chemical messengers which travel in the blood
target tissues?
the tissues hormones affect
Endocrine =
secreting inside (into blood)
Exocrine?
secrete outside (i.e. into duct) - ANYWHERE BUT THE BLOOD
hormones are small, usually
protein but some are steroid hormones - which are derived from cholesterol. E.g. testosterone, cortisol, an all of sex hormones.
Adrenaline timings?
- v. fast secretion (>1 sec)
* effects last 1 -3 minutes
Adrenaline effects?
Effects: • Relax SM in bronchioles • ⬆ HR and stroke volume • ⬆BP • Stimulate glyconeogenesis • inhibit blood flow to the gut • ⬆ BF to muscles
The effects of insulin last…
10- 15 mins
Why do hormones only last so long?
most of it gets broken down by enzymes in the blood or lost in urine (e.g. hCG)
How do hormones actually work?
- Once the hormone is at the target tissue (cells which contain a receptor for the hormone)
- The hormone binds to a receptor on the surface to trigger a response
steroid hormones - ______ soluble
- are lipid soluble so can diffuse across the PM
* they still need to bind to a receptor - they bind to a receptor inside the cell (cytoplasm)
Hormones vs Neurons?
Hormones: slow response - travel in BS to get to target, long last effects
Neurons: quick, short time (reset/ broken down quickly)
First messenger system?
- Protein hormone secreted from a cell in a endocrine organ
- Hormone circulates in body fluids (blood/ TF)
- Hormone binds to receptor in the plasma membrane of a target cell
second messenger system?
- Activation of a 2nd messenger system inside the cell - the target of the 2nd messenger system is inside the cell
hormones can b…
water or lipid soluble and can bind to membrane receptors in the cytoplasm of cells (steroid hormones)
the pancreas
- involved in the control of blood glucose
- leaf shaped organ
- both endocrine and exocrine
how is the pancreas exocrine?
- releases enzymes into the pancreatic duct and then into the duodenum (1st part of the small intestine)
- This liquid is called pancreatic juice - contains H2O, HCO3-, enzymes - lipases, carbohydrases, proteases
lipase, carbohydrase and protease are all involved in ?
- hydrolysis
- Lipase: lipids ➡FA + glycerol, ester bond broken
- Carbohydrase: carbohydrates ➡ alpha glucose (glyosidic bond is broken)
- Protease: proteins ➡ Aas - peptide bond broken
sucrose is broken down into?
alpha glucose, fructose
maltose is broken down into?
alpha glucose + alpha glucose
lactose is broken down into?
galactose and fructose
Pancreas also has?
- islands of cells called the islets of Langerhans which secrete directly into the blood (endocrine)
- they secrete insulin (β cells)
- and glucagon (α cells)
insulin and glucagon work?
against each other
way to remember which cells secrete which hormone?
glucAgon Alpha cells
insulin - Been too long Beta cells
Gall bladder?
site of bile storage
duodenum?
- top part of the small intestine
- bile gets added to food here
- pancreatic juices here
chyme?
•ball of food and enzymes
ileum?
reabsorb food here
acinar cells?
- secrete pancreatic juice
* contains, enzymes, ions, HCO3- which neutralises stomach acid
alpha and beta cells are found in?
islets of Langerhans
alpha cells?
secrete glucagon in response to low BG
Beta cells?
secrete insulin in response to high BG
which causes glucose ➡ glycogen
Effects of glucagon?
- Binds to receptors on the PM of target cells
- This triggers a 2nd messenger system
- This activates a number of enzymes that causes storage molecules to convert glycogen into glucose
- glucose then leaves the cell by facilitated diffusion
Effects of insulin?
- When blood glucose is high, insulin is secreted by beta cells and binds to insulin receptors in the cell surface membrane of liver/ adipose cells
- This binding triggers a 2nd messenger system
- that increases the permeability of the cell to glucose, by inserting glucose channels into the cell surface membrane
- and activates a number of enzymes that cause the conversion of glucose into storage molecules.
insulin?
- 51 AA long peptide hormone
- causes glucose to move from he blood to muscle, liver and adipose cells, and to be converted into storage molecules - glycogen manly but also fats and protein
glucagon causes?
causes storage molecules to be broken down inside muscle, liver and adipose cells, and for glucose to move from these cells into the blood
Type 1 diabetes?
- a.k.a juvenile onset
- no insulin produced
- risk factors not really known but possible genetic link in some cases
- autoimmune disorder - kills off own Beta cells
type 2 diabetes?
- late onset
- insulin produced and secreted
- target cells don’t respond
- risk factors: link to obesity - BMI >27, genetic link. apple shaped body
In both types of diabetes: thirst?
- High BG conc after a meal, stays high (hyperglycaemia)
- May be glucose in urine if v high (can’t be reabsorbed in PCT quick enough)
- water follows so always thirsty and hungry
In both types of diabetes: ketoacidosis?
- In both cases, glucose entering the cell is slow and thfr cells respond metabolising fats and proteins
- This causes a build up of keto acids which lowers the pH causing ketoacidosis which can lead to coma
- 10% of ppl w ketoacidosis die in hospital
In both types of diabetes: hypoglycaemia?
- between meals, BG conc ⬇ (hypoglycaemia) so no glycogen stores to
- coma bc of lack of glucose for respiration
Diagnosis of diabetes?
- Test blood for glucose conc but this is not definitive
- Test urine for GC but not definitive
• Together though, they are suggestive and patient is offered a glucose tolerance test (GTT)
GTT?
- Patient to rest overnight
- given a glucose drink
- changes in [G] in blood & insulin measured
- diabetic has much higher glucose levels
treatments for diabetes?
- no cure
* in the future, stem cells
type 1 diabetes treatment?
- after a meal, take insulin intravenously
- control diet
- need to monitor BG conc several times a day
- genetically engineered insulin is much better than insulin from pigs
genetically engineered insulin?
- has a rapid response for a shorter duration
- less chance of an immune response
- effective to those who develop tolerance
- ethical?
type 2 diabetes treatment?
- diet controlled - small, regular meals
- polysaccharides much better than monosaccharides – poly take longer to break down and be absorbed
- tablets e.g. metformin
What is diabetes?
condition where BG levels become really high
why do BG levels get so high?
- glucose stays in the blood when it would normally move into cells to be used as a respiratory substrate, or stored as e.g. glycogen
- insulin is the hormone normally responsible for this movement
why does glucose stay in the blood?
2 reasons explaning the 2 main types of db:
- beta cells in the pancreases have been destroyed so no insulin can be produced - type 1 db
- the insulin produced by beta cells has become ineffective. Cells have become ‘insulin resistant’ - type 2 db.
the range that blood glucose needs to stay in?
narrow range of 80-1-00 mg100cm-3
what is hypoglycaemia?
- blood glucose drops too low - leads to confusion- brain can only respire glucose, affects osmotic balance.
- as a result, capillaries can collapse, results in coma and death
what is hyperglycaemia?
- blood glucose rises too high - water moves into blood
- cases increased vol of blood which increases BP
- can cause damage to veins and arteries, capillaries to collapse, which leads to death
- glucose in urine
what happens in response to a rise in the BG level?
- detected by alpha and beta cells
* alpha cells secrete less glucagon and beta cells secret more insulin
what happens in response to a fall in BG level?
- detected by alpha and beta cells
* alpha cells secrete more glucagon and beta cells secrete less insulin
it not either/ or
with insulin and glucagon, we just produce more/ or less depending on BG level
which cells can store glucose?
- Certain cells can store glucose as different storage molecules - glycogen, triglycerides, and protein (which can’t be stored)
- these cells are liver, muscle, and adipose cells (which store triglycerides)
role of insulin?
stimulates cells to take in glucose when BG levels are high and convert it into storage molecules
fats and glycogen have no ?
solute potential
role of glucagon?
stimulates the release of glucose from the storage molecules and its movement into the blood when BG is low
what is the ‘normal’ storage molecule?
- Glycogen
- Found in liver and muscle cells
- if glycogen runs out, fats and proteins can be used as a respiratory substrate
- if no more glucose can b stored it can be converted to fats and proteins
order in which the other storage molecules are broken down?
carbs ➡ fats ➡ proteins
gluco=
glucose
glycogen- =
to do w glycogen
-genesis =?
the beginning of
-olysis =
the splitting of
-neo- =
new
The action of insulin and glycogen is an e.g. of?
negative feedback
glucose definition?
A monosaccharide used as a respiratory substrate
glycogen definition?
glucose is stored as this
glycogenesis definition?
the formation of glycogen from glucose
glycogenolysis definition?
the hydrolysis of glycogen into glucose
gluconeogenesis definition?
conversion of other molecules into glucose (triglycerides, FAs, proteins, AAs)
glucagon definition?
hormone released by alpha cells that stimulates the release of glucose from the storage molecules and its movement into blood when BG level is low.
glycolysis definition?
the first stage of resp. The conversion of glucose to pyruvate.
Cause of T1 DB
- Although the exact cause of type 1 diabetes is unknown, usually the person’s immune system destroys the Beta cells in the islet of langerhans.
- Exposure to viruses and other environmental factors and genetics may also cause type 1 diabetes
T1 DB risk factors
- Risk factors for this type of diabetes include:
- family history - a person who has a family member with diabetes has an increased chance of developing it
- genetics - certain genes have been identified to indicate an increased risk of developing type of 1 diabetes
- location - there seems to be an increase in the occurrence of type 1 diabetes further from the equator.
- age - type 1 diabetes can develop at any age, but there are 2 peaks at which it noticeably occurs: in children aged 4-7 years old and 10-14
T2 DB causes
Type 2 diabetes occurs when the body becomes insulin resistant or when the β cells of the islet of langerhans cannot produce sufficient insulin. The exact cause of this is unknown although ‘genetics and environmental factors, such as being overweight and inactive, seem to be contributing factors.
T2 diabetes risk factors
- Being overweight is the main risk factor for this type of diabetes
- however there are several others as such fat being stored mainly in the abdomen - in men there is a greater risk if the waist size is exceeds 40 inches and in women if the waist size exceeds 35 inches.
- Low activity levels, family history, age, ethnicity, prediabetes, polycystic ovarian syndrome
Diabetes symptoms?
- appearance of glucose in urine
- thirst and dry mouth (polydipsia)
- tiredness
- hunger - polyphagia
- blurred vision
- ketoacidosis
- diabetic coma
- peripheral artery disease
- diabetic retinopathy
Diabetes symptoms: why does glucose appear in urine
+ what causes polydipsia?
- insulin would usually cause glucose to be taken into cells and converted into glycogen or other storage molecules,
- this lowers the glucose level in the blood but due to the lack of insulin/ lack of effect of the insulin, the blood glucose levels remain high in the blood.
- This means that in selective reabsorption not all glucose can be reabsorbed in the PCT (renal threshold is reached),
- therefore glucose appears in the urine.
- This can lead to polyuria as the high concentration of glucose in the collecting duct lowers the water potential in the CD which means that water moves into the CD by osmosis,
- increasing the volume of urine produced.
- This can cause polydipsia - thirst and dry mouth as more water is lost in the urine than would be the case in a non-diabetic person
Diabetes symptoms: why might a diabetic feel very tired?
- glucose is not moving into cells, so it cannot be used in respiration to produce ATP.
- Glucose not moving into cells can also cause polyphagia - hunger
diabetic symptoms: why might a diabetic suffer from blurred vision?
high blood glucose can cause fluid to be pulled from the lenses of the eyes, resulting in swelling, leading to temporarily blurred vision
diabetes symptoms: why is ketoacidosis caused?
When fat is broken down for energy instead of glucose, ketones are produced. Ketones are weak acids so they cause blood pH to decrease, the result is the metabolic state of diabetic ketoacidosis
diabetes symptoms: diabetic coma?
• Diabetic coma is another symptom - it is caused by hyperglycaemia or hypoglycaemia.
• The ‘the three most common causes of coma in people with diabetes are: severe hypoglycaemia
diabetic ketoacidosis, hyperglycaemic hyperosmolar state
diabetes symptoms: peripheral artery disease?
- Diabetes can lead to peripheral artery disease, which causes narrowed blood vessels.
- This leads to reduced blood flow to the limbs.
- Peripheral neuropathy (nerve damage) may also occur.
- Reduced blood flow slows wound repair which can cause tissue damage, which may be irreparable and so an amputation may be necessary.
diabetes symptoms: diabetic retinopathy?
- It is caused by high blood sugar levels damaging the retina.
- It can cause blindness if left undiagnosed and untreated. It usually takes years for the person to go blind however
diagnosis of diabetes?
- The glucose tolerance test is used to diagnose diabetes.
- The oral glucose tolerance test (OGTT) is the most common glucose tolerance test used.
- A blood sample is taken from the patient, the patient is then asked to drink a liquid containing 75g of glucose, and blood samples are then taken again every 30-60 minutes.
- The test is used to check how the body moves sugar from the blood into tissue and could take up to 3 hours
diabetes type 1 treatment
- There is no cure for diabetes although type 1 can be controlled using insulin injections.
- Patients with type 1 diabetes regularly test their blood glucose level which allows the insulin dose to be worked out.
- The insulin injected causes more glucose to be absorbed by cells and glycogenesis to occur, resulting in a reduction of blood glucose concentration.
Type 2 diabetes treatment?`
- Type 2 diabetes is treated differently.
- Firstly, the patient’s diet and exercise are regulated, this often involves encouraging overweight individuals to lose weight.
- Sometimes, controlling diet and increasing exercise is not enough and so drugs are used.
- Drugs can be used to stimulate insulin production, slow the rate at which the body absorbs glucose from the intestine
- insulin injections can also be used
genetically engineered insulin and diabetes
- Traditionally, insulin was taken from cows and pigs, but this process was expensive and could cause adverse reactions in humans.
- Since the structure of insulin was identified in 1955, it can now be made using bacteria.
- There are several advantages to this: human insulin is produced so the insulin is less likely to cause allergic reactions, insulin can be produced in larger quantities, cheaper cost, less ethical issues as no animals are being used.
- However, there is a risk of side effects, and many people disagree with genetic engineering in general due to religious reasons.
diabetes and stem cells
- Pluripotent stem cells can be caused to differentiate into insulin producing β cells, this could be a possible cure for type 1 diabetes.
- Although they can also be used to treat type 2 diabetes who do not produce enough insulin, type 2 diabetes with insulin resistance would not benefit from it.
