F214 - Hormones Flashcards
Endocrine Gland
Definition
Releases hormone directly into the blood
Ductless
Exocrine Gland
Definition
Releases a secretion onto or at the surface of an organ via a duct
Target Tissue
Definition
Tissue made up of cells with specific complimentary receptors to the hormone molecules
First Messenger
Definition
A hormone that binds to a cell surface membrane to affect intracellular metabolic processes
Second Messenger
Definition
A molecule inside cells that acts to transmit signals from a receptor to a target
Where are the adrenal glands?
Anterior to (just above) the kidneys, one on each side of the body Each gland can be split up into a medulla region and a cortex region
Function of the Adrenal Glands
The Adrenal Medulla
Cells in the medulla manufacture the hormone adrenaline and release it in response to stress.
Function of the Adrenal Glands
The Adrenal Cortex
Uses cholesterol to produce certain steroid hormones
e.g.
Mineralocorticoids (e.g. aldosterone) help to control concentrations of sodium and potassium in the blood
Glucocorticoids (e.g. cortisol) help to control the metabolism of carbohydrates in the liver
What are the effects of adrenaline?
- relaxes smooth muscle in the bronchioles
- increases stroke volume of the heart
- increases heart rate
- causes general vasoconstriction to increase blood pressure
- stimulates conversion of glycogen to glucose
- dilates pupils
- increases mental awareness
- inhibits the action of the gut
How does adrenaline affect target muscle cells?
- adrenaline binds to a receptor protein in the cell plasma membrane
- this causes a shape change which affects a G protein on the inner membrane surface
- the G protein activates an enzyme called adenylyl cyclase
- adenylyl cyclase catalyses the production of cyclic AMP from ATP
- cyclic AMP activates an enzyme in the cytoplasm that catalyses a reaction to activate another enzyme starting a chain of enzymes
- at the end of the chain glycogen phosphorylase is activated
- glycogen phosphorylase catalyses the conversion of glycogen to glucose phosphate
What are the first and second messengers for adrenaline?
adrenaline is the first messenger
cyclic AMP is the second messenger
The Pancreas as an Exocrine Gland
- Pancreatic juices are secreted into the pancreatic duct which carries them to the duodenum
- The secretion contains digestive enzymes
- The enzymes break down large insoluble molecules to be absorbed
Glycogenolysis
Definition
The break down of glycogen to form glucose
Gluconeogenesis
Definition
The creation of glucose from non-carbohydrate substrates
Glycogenesis
Definition
Generating glycogen from glucose molecules
Alpha Cells
Definition
Cells in the pancreas which secrete glucagon
Beta Cells
Definition
Cells in the pancreas which secrete insulin
What is the role of insulin?
Reduces blood glucose levels
What is the role of glucagon?
Increases blood glucose levels
Hormone
Definition
Molecule released into the blood which acts as a messenger
What are the two types of hormone?
Protein/ peptide hormones (hormones ending in -ine) Steroid hormones (hormones ending in -ol or -one)
Peptide Hormones
Properties
Protein hormones are unable to pass through the cell plasma membrane
They do not enter cells, instead they have to bind to external receptors
Steroid Hormones
Properties
Able to pass through the cell membrane
Act upon DNA in the nucleus affecting transcription
The Pancreas as an Endocrine Gland
High Blood Sugar
Increase in blood sugar is detected in the pancreas
Alpha cells stop secreting glucagon
Beta cells start secreting insulin in to the blood
The Pancreas as an Endocrine Gland
Low Blood Sugar
Decrease in blood sugar detected in the pancreas
Beta cells stop secreting insulin
Alpha cells start secreting glucagon into the blood
How are beta cells stimulated to secrete insulin?
- the cell plasma membrane contains potassium and calcium ion channels
- potassium ion channels are normally open so potassium can flow out
- when blood glucose concentration is high glucose moves in by diffusion
- Glucose is metablised to produce ATP
- ATP closes potassium ion channels and potassium ion accumulate inside the cell
- This makes the inside of the cell less negative changing the potential difference across the membrane
- This change in p.d. opens calcium ion channels, calcium ion move in by diffusion
- Inside the cell the calcium ions cause vesicles of insulin to fuse with the plasma membrane
- Insulin is released by exocytosis
What are the effects of insulin?
- The number of glucose channels in the membranes of muscle and fat cells is increased so glucose uptake is increased
- The rate at which glucose is used up inside cells is increased especially the respiration rate in muscle cells
- Glucose is converted to glycogen or fats for storage in muscle and liver cells
What are the effects of glucagon?
- An enzyme which hydrolyses fats and glycogen to form glucose is activated (glycogenolysis)
- Liver cells convert glycogen to glucose and release glucose into the blood
- The rate at which other substances are converted to glucose is increased (faster gluconeogenesis)
- Respiration rate is reduced due to a lack of respiratory substrate
The Islets of Langerhans
small patches of the pancreas that have an endocrine fucntion
What is type 1 diabetes?
Beta cells in the pancreas which secrete insulin are targeted by the immune system
Insulin production is inhibited so blood glucose levels cant be controlled
What causes type 1 diabetes?
The exact cause is unknown
Certain genes increase the likelihood of developing type 1 diabetes
Some research suggests that environmental factors like a viral infection can trigger onset in susceptible individuals
How is type 1 diabetes treated?
Sufferers have to monitor their blood glucose levels and inject insulin into the blood stream
Injected insulin can come from animals or from genetically modified bacteria
What is type 2 diabetes?
The volume of insulin produced by beta cells is limited
The insulin that is produced is not used effectively by target cells
This means that when blood glucose levels are too high and insulin is secreted, glucose remains in the blood stream
What causes type 2 diabetes?
A number of factors increase the risk
Primarily a BMI of 30 or more, particularly abdominal fat which causes cells to produce ‘pro inflammatory chemicals’ which reduce the sensitivity of target cells to insulin
Increased age increases the risk
Certain genes can make an individual more susceptible
How is type 2 diabetes treated?
There is no cure for type 2 diabetes
Sufferers have to follow a treatment plan to manage their blood sugar levels
This involves eating a balanced diet and, getting regular exercise and checking blood sugar levels regularly
What are the advantages of using insulin from genetically engineered bacteria?
- It is an exact replica of human insulin so is faster acting and more effective
- There is less chance of the patient developing a tolerance to the insulin
- Less chance of rejection due to an immune response
- Lower risk of infection
- Cheaper to manufacture
- People are less likely to have moral objections
Stem Cells to Treat Diabetes
Research has shown that stem cells may be able to be used to treat type 1 diabetes
The most common sources of stem cells are in the bone marrow or placenta, but scientists have found precursor cells in the pancreas of adult mice
If similar cells could be found in humans they could be used to grow new beta cells
Hyperglycaemia
Definition
Very high blood glucose concentration
Hypoglycaemia
Definition
Very low blood glucose concentration
lack of respiratory substrate
What is the normal blood glucose concentration?
90mg/100cm^3
Steroids in Sport
Advantages
- can train for longer
- it is the choice of the individual
Steroids in Sport
Disadvantages
- give an unfair advantage
- dangerous / unhealthy
- distrust of outstanding performances
- athletes should be role models
