Hormonal communication. Flashcards
What is the endocrine system?
A communication system that uses hormones as signalling molecules
What are the two types of hormone and give examples.
- Protein and peptide hormones (adrenaline, insulin and glucagon)
- Steroid hormones (oestrogen and testosterone)
What is the difference between how steroid hormones and peptide hormones in how they pass over the membrane?
- Peptide hormones (proteins) are not soluble in the phospholipid membrane so they cannot enter the cell, instead they bind to the cell surface membrane and release a secondary messenger inside.
- Steroid hormones can pass through the membrane and enter the cell and nucleus
Endocrine glands are ductless, true or false ?
True
List the main endocrine glands in the body
- Pituitary gland
- Thyroid gland
- Adrenal glands
- Pancreas
- Ovaries
- Testes
What are the two types of glands in the body?
- Endocrine glands (release hormones)
- Exocrine glands (releases non-hormones into ducts)
How are signals detected from hormones
- NON-STEROID hormones move to target cells and will bind to specific receptors on the cell surface membrane complementary to the shape of the signalling molecule.
This binding initiates changes in the cell.
What are non-steroid hormones also known as?
First / primary messengers
Why are non-steroid hormones known as ‘first messengers’
- They are signalling molecules that bind to the outside of the cell surface membrane and initiates an effect from inside the cell
They usually cause the release of another signalling molecule in the cell, which is the ** second messenger** - this stimulates a change in the activity of the cell.
How do non-steroid hormones interact with G proteins
- Non-steroid hormones can act via a G protein in the membrane.
The G protein is activated when the hormone binds to a receptor.
The G protein will then activate an effector molecule (can be an enzyme that converts an inactive molecule into an active secondary messenger). - An example is adenyl cyclase, converting ATP to cAMP (cyclic AMP) which is a second messenger
What can a second messenger do?
Act directly on another protein (such as an ion channel) or initiate a cascade of enzyme controlled reactions that alter the activity of the cell
What are the two main sections of the adrenal gland?
- The adrenal cortex (outer layer)
- The adrenal medulla (inner layer)
What layers of cells are found in the adrenal cortex? (hard)
- Zona glomerulosa (outer layer)
- Zona fasciculata (middle layer)
- Zona reticularis (inner most layer)
What does each layer of the adrenal cortex secrete
- Zona glomerulosa: mineralcorticoids (such as aldosterone)
- Zona fasciculata: glucocorticoids (such as cortisol)
- Zona reticularis: precursor molecules to androgens
What does the adrenal medulla secrete?
- Adrenaline
- Noradrenaline
What effect does adrenaline have?
Stimulates the body to prepare for the fight or flight response
What do mineralcorticoids (secreted by the zona glomerulosa) do and what is an example?
Help to control concentrations of sodium and potassium in the blood.
This then contributes to maintaining blood pressure
Aldosterone acts on cells in the distal tubules and collecting ducts - increasing absorption of sodium ions, decreasing absorption of potassium ions so it INCREASES water retention, INCREASING blood pressure.
What do glucocorticoids (secreted by the Zona fasciculata) do and what is an example?
- Glucocorticoids help to control metabolism of carbohydrates, fats and proteins in the liver.
- Cortisol is released in response to stress or when there is low blood glucose concentration, stimulating gluconeogenesis in the liver
What does the Zona reticularis do and give an example.
- The Zona reticularis can secrete cortisol, if enzymes are not present for the release of cortisol then it releases precursor androgens - these are taken up by ovaries/testes and converted to sex hormones.
- Sex hormones help development of secondary sexual characteristics and regulate the production of gametes
List the effects of adrenaline
- Relaxes smooth muscle in the bronchioles
- Increasing stroke volume of the heart
- Increases heart rate
- Vasoconstriction to raise blood pressure
- Stimulates conversion of glycogen to glucose
- Dilates pupils
- Inhibits digestion
- Erects hair
What amino acid is adrenaline derived from?
Tyrosine
What are the main two functions of the pancreas
- Exocrine: secrete pancreatic juices into the digestive system
- Endocrine: secrete hormones from ioL into the blood for glucose control
What do exocrine glands do?
Secrete substances into a duct
What is the exocrine function of the pancreas?
Synthesising and secreting pancreatic juices containing digestive enzymes into the small intestine (from group of cells called acinus)
What enzymes does pancreatic juice consist of?
- Pancreatic amylase: digests amylose to maltose
- Trypsinogen: inactive protease activated to trypsin in the duodenum
- Lipase: digests lipid molecules
- Sodium hydrogencarbonate to make it alkaline and neutralise
What are the pancreatic lobules called?
Acini
What cells make up the islet of Langerhans?
- Alpha cells
- Beta cells
- Delta cells
What do alpha cells secrete?
Glucagon
What do beta cells secrete?
Insulin
What cells in the islets of Langerhans react to low blood sugar (hypoglycaemia) and how?
Alpha cells, they secrete glucagon
What cells in the islets of Langerhans respond to high blood sugar (hypoglycaemia) and how?
Alpha cells - they secrete insulin
What % of the islets of Langerhans is Alpha cells and what % is beta cells?
- Alpha cells: 20%
- Beta cells: 70%
Outline the mechanism of responding to high blood sugar
- Glucose diffuses down high concentration gradient into the beta cells.
- In the beta cells glucose is metabolised to produce ATP
-Due to an increase in ATP, potassium channels close, lowering the negativity inside the cell which changes the potential over the membrane. - Potential change opens calcium ion channels which releases vesicles containing insulin to undergo exocytosis. Insulin then moves to liver and muscle cells
- Insulin binds to receptors on the muscle and liver cells membranes.
- These cells insert more glucose channel proteins into the membrane which causes rate of glucose uptake AND respiration in muscle cells to increase
- In liver cells, it stimulates the conversion of glucose to glycogen in glycogenesis
Outline the mechanism of responding to low blood sugar
- Alpha cells detect a fall in blood sugar
- Alpha
