Hormonal Communication Flashcards
What is an endocrine gland?
Group of cells specialised to secrete hormones directly into the bloodstream.
Why are hormones considered as chemical messengers?
They carry information from one part of the body to another.
How do hormones work when they are secreted into the bloodstream?
They diffuse out of blood and bind to specific receptors for that hormone (target cells). Once bound, they stimulate the target cell to produce a response.
What are steroid hormones?
- Lipid soluble
- Pass through cell membrane
- Bind to steroid hormone receptors to form a hormone-receptor complex.
- The complex formed acts as a transcription factor which facilitates or inhibits the transcription of a specific gene.
What are non-steroid hormones?
- Hydrophilic
- Bind to specific receptors of the cell surface membrane of target cells.
- Triggers reactions mediated by chemicals called second messengers.
What is an example of a steroid hormone?
Oestrogen
What is an example of a non-steroid hormone?
Adrenaline
How is hormonal communication different from neuronal communication?
Hormonal is... - Slower - Less specific - Longer lasting - Widespread - Irreversible Communication by hormones
What two parts make up the adrenal glands?
1) Adrenal cortex
2) Adrenal medulla
What are the 3 main types of hormones produced by the adrenal cortex?
- Glucocorticoids
- Mineralocorticoids
- Androgens
What the 2 hormone secreted by the adrenal medulla?
- Adrenaline
- Noradrenaline
Adrenaline
Increases heart rate and raises blood glucose concentration
Noradrenaline
Works with adrenaline
Causes increased heart rate, widening of pupils and widening of air passages in the lungs
Androgens
Small amounts of female and male sex hormones are released.
Mineralocorticoids
Main one is aldosterone.
Helps to control blood pressure by maintaining the balance between salt and water concentrations in the blood.
Glucocorticoids
Include cortisol which regulates metalbolism by controlling how the body converts fats, proteins and carbohydrates to energy.
Also corticosterone which regulates the immune system.
What is the exocrine gland?
Produces enzymes and releases them via a duct into the duodenum.
Name 2 Islets of Lanferhans
Alpha and beta cells
What do alpha cells secrete and produce?
Glucagon
What do beta cells secrete and produce?
Insulin
What are the roles of the exocrine gland?
Responsible for producing digestive enzymes and pancreatic juice.
The enzymes and juice are secreted into ducts which leafs to the pancreatic duct.
From here they are released into the duodenum.
What is pancreas made up of mostly?
Exocrine glandular tissue
What is the duodenum?
Top part of the small intestine
The pancreas produces 3 digestive enzymes…
Amylases
Proteases
Lipases
Amylases
Starch to simple sugars
Proteases
Proteins to amino acids
Lipases
Lipids to fatty acids and glycerol
Roles of endocrine gland
Endocrine tissue is called islets of Langerhans
Name 3 ways in which the blood glucose concentration can be increased
Diet- Eat carbohydrate rich foods
Glycogenolysis
Gluconeogenesis
Glycogenolysis
Glycogen is broken down into glucose
Gluconeogensis
Production of glucose from non-carbohydrate sources such as glycerol and amino acids
Name 2 ways in which blood glucose concentration can be decreased
Respiration
Glycogenesis
Glucogenesis
Production of glycogen from glucose
What is the role of insulin?
If the blood glucose concentration is too high, beta cells detect this and secrete insulin into the bloodstream.
How does insulin lower the blood glucose concentration?
- Increases rate of absorption of glucose by cells
- Increases respiratory rate of cells so cells require more glucose
- Increase rate of glucose to fat conversion
What is the role of glucagon?
If the blood glucose concentration is too low, alpha cells secrete glucagon into the bloodstream.
How does glucagon raise the blood glucose concentration?
- Glycogenolysis
- Gluconeogenesis
- Reducing the amount of glucose absorbed by the liver cells
What is the control of insulin secretion?
1) At normal blood glucose concentrations, K channels in the plasma membrane of beta cells are open and K+ ions diffuse out of the cell. Cell potential is -70mV.
2) When blood glucose concentration rises, glucose enters the cell by a glucose transporter.
3) The glucose is metabolised inside the mitochondria, resulting in the production of ATP.
4) ATP binds to K channels and causes them to close.
5) As K+ ions can no longer diffuse out of the cell and depolariation occurs so the p.d. reduces to -30mV.
6) Depolarisation occurs the voltage gated calcium channels to open.
7) Ca2+ iions ener the cell and cause secretory vesicles to release the insulin they contain by exocytosis.
What are the symptoms of diabetes?
- High blood glucose concentration
- Glucose in urine
- Excessive need to urinate
- Excessive thirst
- Weight loss
What is type 1 diabetes?
Unable to produce insulin, arises due to an autoimmune response where the body’s own immune system attacks the beta cells.
What is the type 2 diabetes?
Beta cells do not respond to insulin.
What is the treatment for type 1 diabetes?
Regular injections of insulin
What is the treatment for type 2 diabetes?
Matching carbohydrate intake to exercise levels.
What is the advantages of making insulin from genetically modified bacteria?
- Cheaper production costs
- Does not use animals
- Pure form so less likely to cause allergic reaction
- Produced in much higher quantities
What are the advantages of stem cells in diabetes treatment?
- Don’t have to inject yourself
- Reduced likelihood of rejection
- Donor availability will not be an issue
What are the disadvantages of stem cells in diabetes treatment?
Our ability to control growth and differentiation in stem cells is limited
What is the second messenger model of hormone action?
1) Adrenaline binds to its receptor and adenylyl cyclase is activated.
2) This triggers the conservation of ATP to cyclic AMP on the inner surface of the cell membrane.
3) cAMP activates protein kinase enzymes which activates other enzymes.
What is the first and second messenger in the second messenger model?
1st- Adrenaline
2nd- cAMP
Where are the baroreceptors present?
Aorta and carotid artery wall
What are baroreceptors?
Pressure receptors.
Detect changes in the blood pressure.
What happens when the blood pressure is too high?
1) Baroreceptors detect the changes in blood pressure.
2) Impulses are sent to the medulla oblongata centre which decreases the heart rate.
3) Medulla oblongata sends impulses along the parasympathetic neurones to the SAN which decreases the rate at which the heart beats.
4) This reduced blood pressure back to normal.
What are the 2 centres within the medulla oblongata?
One centre increases the heart rate by sending impulses through the sympathetic nervous system. These impulses are transmitted by the accelerator nerve.
The other centre decreases the heart rate by sending impulses through the parasympathetic nervous system. These impulses are transmitted by the vagus nerve.
What are chemoreceptors?
Sensitive to changes in blood pH level.
What happens when the carbon dioxide level in the blood increases?
pH decreases because carbonic acid is formed. Chemoreceptors detect this and cause the heart rate to be increased. So blood flow increases and carbon dioxide can be exhaled.
What happens when the carbon dioxide level in the blood decreases?
pH rises
Detected by chemoreceptors
Reduction in frequency of nerve impulses sent to the medulla oblongata
Reduction in the frequency of impulses being sent to the SAN via the sympathetic nervous system
Heart rate decreases and level returns to normal
