Hormonal Communication

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What is the endocrine system?
A communication system using hormones as signalling molecules- in the blood stream
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What are hormones?
Chemical messengers released by endocrine glands into the blood. They carry a signal to target cells/tissues from endocrine glands.
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What are endocrine glands?
Ductless glands that manufacture and secrete hormones directly into the blood stream
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What are exocrine glands?
Glands that produce substances (other than hormones) which are secreted into ducts (e.g. pancreatic juice, saliva)
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What are target cells?
Cells that have specific receptors on their membrane that are complementary to the shape of the (amino acid derived) hormone molecule
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What are the types of hormones?
Amino acid derived (protein, peptide) + Steriod
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Examples of amino acid derived hormones?
Adrenaline, insulin + glycagon
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Examples of steriod hormones?
Oestrogen + testosterone
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Are protein hormones soluble in the phospholipid bilayer?
No, they are polar so they can't diffuse across into target cells
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Are steroid hormones soluble in the phospholipid bilayer?
Yes, they are small and polar so they cant diffuse into the cell and have a direct effect on the DNA in the nucleus
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How do protein hormones have an effect on a target cell?
They bind to complementary receptors on the cell membrane of a target cell + use first and secondary messengers
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What is the first messenger?
The amino acid derived hormone (signalling molecule)
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What does the first messenger cause when it binds to a cell membrane receptor?
The activation of a G protein molecule within the cell
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What does the G protein activate?
Adenyl cyclase - an enzyme used to convert ATP into cyclic AMP
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What is the second messenger?
cAMP- another signalling molecule inside the cell
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Why is cAMP a secondary messenger?
Because it brings about a response in the cell e.g. opening a channel protein, causing protein synthesis or activating an enzyme
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What are the adrenal glands?
A pair of endocrine glands that lie above the kidneys, that release adrenaline and other hormones
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What are the adrenal glands made up of?
The (inner) adrenal medulla and (outer) adrenal cortex
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What are the 3 distinct layers of cells of the adrenal cortex?
Zone glomerulosa, Zona fasciculata + Zona Reticularis
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What does the zona glomerulosa secrete?
mineralocorticoids e.g. aldosterone
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What does the zona fasciculata secrete?
glucocorticoids e.g. cortisol
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What does the zona reticularis secrete?
The innermost layer; that secretes precursor molecules used to make sex hormones
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What does the adrenal cortex use to make a range or hormones?
Cholesterol
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Are these hormones amino acid derived or steroid?
Steroid- so they have a direct effect on DNA inside the cells, causing protein synthesis
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Where is adrenaline manufactured and released from?
The adrenal medulla
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What type of hormone is adrenaline?
An amino acid derived- so uses first and second messengers to bring about a response in a cell
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What effect does adrenaline?
Widespread effects that prepares the body for activity e.g. the fight or flight response
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What do the effects of adrenaline include?
Pupil dilation, increased heart rate and breathing rate, reduced digestion rate + vasoconstrication: to increase blood pressure
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What is the pancreas?
A small organ below the stomach
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What functions does the pancreas have?
Exocrine + endocrine functions
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What is the exocrine function?
To secrete digestive juices (containing enzymes) into the small intestine via. the pancreatic duct
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Describe th histology of the exocrine tissues?
Exocrine cells are grouped into acini. Acini are grouped to form small lobules, separated by connective tissue
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What is in the centre of the acini?
Tiny tubules
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Where are the digestive enzymes produced by acinus secreted?
Into the tiny tubules
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What do the tiny tubules join to form?
Intralobular ducts that eventually make up the pancreatic duct
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Where do the pancreatic ducts do?
Carry the digestive juices into the small intestine
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What does the digestive juice contain?
Amylase, trypsinogen, lipase + sodium hydrogencarbonate (neutralises contents)
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What is typsinogen?
An inactive protease, that is converted into trypsin (active form) in the small intestone
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What does the islet of Langerhans contain?
Alpha and beta cells
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What endocrine function do alpha cells have?
Secrete glycagon (raises blood glucose conc)
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What endocrine function fo beta cells have?
Secrete insulin (lowers blood glucose conc)
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When is insulin released from beta cells?
When the concentration of glucose is high
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Describe the process by which insulin is secreted from beta cells?
Check notes for answers :)
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What is normal blood glucose concentration levels?
4-6 mol dm-3
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What is hypoglycaemia?
When blood glucose levels are low for long periods of time (below 4moldm-3). So there's inadequate delivery of glucose to body tissues; especially the brain
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What moderate symptoms occur as result?
Tiredness and irritability
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What symptoms may occur as a more severe result?
Impairment of brain function, confusion, seizures, unconsciousness and even death
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What is hyperglycaemia?
When blood glucose are too high for long periods of time (above 6moldm-3)
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What can hyperglycaemia lead to?
Organ damage (also a diagnosis for diabetes mellitus)
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What detects changes in the concentration of glucose in the blood?
Beta and alpha cells in the islet of Langerhans
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What happens if they detect that the blood glucose levels are too low?
Alpha cells release glycagon
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What happens if they detect that blood glucose levels are too high?
Beta cells release insulin
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What are the target cells for insulin?
The liver, muscles and cells
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Why doesn't insulin have a direct effect on the DNA of their target cells?
Because it is an amino acid derived hormone
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Summarise the actions of insulin...
Binds to complementary receptors, activates tryosin kinase which phosphorylates inactive enzymes to active ones.Vesicles containing glucose transporter proteins fuse with the cell membrane so more glucose enters the cell
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What 3 things occur, as a result of glucose entering the cells?
Glucose is converted into glycogen (glycogenosis), glucose is converted into fats & glucose is used in repsiration
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What are the target cells for glucagon?
Liver cells (hepatocytes)
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Can glucagon have direct effects on the DNA in target cells?
No- because it is amino acid derived thus insoluble in the phospholipid bilayer
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Summarise the actions of glucagon?
Binds to complementary receptors, this activates a G protein, which activates adenyl cyclase that converts ATP into cAMP. cAMP activates a series of enzyme-catalysed reaction within the cell
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What are the enzyme catalysed-reactions?
Glycogen is converted/hydrolysed into glucose, amino acids and fats are converted into more glucose & fatty acids used in respiration
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What is the conversion of glycogen to glucose called?
Glycogenolysis
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What is the conversion of amino acids and fats into additional glucose called?
Gluconeogenesis
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What is diabetes mellitus?
A condition where the body is unable to produce enough insulin to control blood glucose levels
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What can result?
Hyperglycaemia (after a meal rich in carbohydrates + sugars) & Hypoglycaemia after exercise or fasting
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What is the cause of type 1 diabetes?
From childhood. Autoimmune response where the immune system attacks and destroys beta cells
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What does this mean?
Enough insulin isn't produced, so excess blood glucose can't be converted into glycogen (glycogenesis). This leads to prolonged high conc of glucose.
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Why might hypoglycaemia result?
There is no store of glycogen to be converted into glucose (glycogenolysis), when blood glucose conc lowers
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Ways of treating type 1 diabetes?
Insulin injections, pancreas transplant, islet cell transplant + insulin pump therapy
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What is the cause of type 2 diabetes?
Not enough insulin is produced + as people age their insulin receptors on liver, muscle + brain cells become less responsive to insulin. So a response isn't produced in the cell to lower blood glucose levels.
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What is the problem associated with type 2 diabetes?
The blood glucose concentration is almost permanently high which cause damage to major organs + circulation
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What factors can bring on type 2 diabetes?
Obesity, lack of regular exercise, diet high in sugars/especially refined sugars, family history + being of asian/afro-carribean descent
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How is type 2 diabetes treated?
By lifestyle changes; regular exercise, lose weight, monitored diet (with less sugars + carbs)
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What might supplement these lifestyle changes?
Medication that reduces the amount of glucose in the bloodstream or boosts the amount of insulin released from beta cells
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In severe cases what happens?
Insulin injections are administered or drugs that slow the absorption of glucose in the digestive system
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Where did insulin used to sourced from?
Extracted from animals- especially pigs as their insulin is similar to human insulin
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How is insulin sourced now?
Human insulin produced from genetically modified E.coli bacteria
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Name some benefits of how human insulin is produced?
(check notes for answers...)
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Why can't insulin be taken in tablet form?
Because it may be digested into amino acids
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What has recent research suggested as a treatment for diabetes?
Stem cells
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How does this work?
They can differentiate into new beta cells that can produce insulin
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Where have scientists found precursor cells?
In the pancreas of adult mice, that may be true stem cells
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What happens if stem cells are found in the human pancreas?
They can produce beta cells in patients with type 1 diabetes- so patients don't have to take daily injections
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Other cards in this set

Card 2

Front

What are hormones?

Back

Chemical messengers released by endocrine glands into the blood. They carry a signal to target cells/tissues from endocrine glands.

Card 3

Front

What are endocrine glands?

Back

Preview of the front of card 3

Card 4

Front

What are exocrine glands?

Back

Preview of the front of card 4

Card 5

Front

What are target cells?

Back

Preview of the front of card 5
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