Endocrine Communication + Adrenal Glands Flashcards
What is the endocrine system?
A communication system using hormones as signalling molecules.
What are hormones?
Molecules (proteins or steroids) that are released by endocrine glands directly into the blood. They act as messengers, carrying a signal from the endocrine gland to a specific target organ or tissue.
What are target cells?
For non-steroid hormones, cells that process a specific receptor on their plasma (cell surface) membrane. The shape of the receptor is complementary to the shape of the hormone molecule. Many similar cells together form a target tissue.
What does the endocrine system use to transmit its signals?
The blood circulatory system.
What are the signals released by the endocrine system called?
Hormones
What are the two types of hormone?
Protein/peptide and steroid.
Protein hormones are not soluble in the phospholipid bilayer so therefore what do they do?
Protein hormones need to bind to the cell surface membrane and release a second messenger inside the cell.
From what are hormones released?
Endocrine glands.
Describe the endocrine glands.
The endocrine glands are ductless glands - they consist of groups of cells that manufacture and release the hormone directly into the blood in the capillaries running through the gland.
How come steroid hormones are able to have a direct effect on the DNA in the nucleus?
They are able to pass through the membrane.
What is the benefit to having a receptor that is specific to one type of protein hormone?
It means that the hormone is not able to affect other cells that don’t have the receptor as it passes through the system.
What are the two types of adrenergic receptor?
Alpha and Beta
What do alpha receptors cause?
They are excitatory in smooth muscles and gland cells, but cause relaxation of intestinal smooth muscles.
What are first-messengers?
Non-steroid hormones. They are signalling molecules outside of the cell that bind to the cell surface membrane and initiate an effect inside of the cell.
What is the second messenger?
The second signalling molecule found inside the cell that is released when the first messenger binds to the cell surface membrane.
What does the second messenger do?
Stimulates a change in the activity of the cell.
What does the G-protein do once it is activated by the non-steroid hormone?
G protein activation leads to activation of various second messenger systems and intracellular responses, leading to physiological responses of tissues and organisms.
What does adenyl cyclase do?
adenylate cyclase is activated and converts ATP to cAMP
What does cAMP do?
cAMP activates protein kinase
What is the adrenal cortex?
The outer layer of the adrenal gland.
What is the adrenal gland?
One of a pair of glands lying anterior to the kidneys, which release adrenaline and a number of other hormones known as corticoids (or corticosteroids) such as aldosterone.
What is adrenaline?
A hormone released from the adrenal glands, which stimulates the body to prepare fro fight or flight.
What is the adrenal medulla?
The inner layer of the adrenal gland.
What are the three layers of the adrenal cortex starting from outside in?
Outermost layer - Zona glomerulosa
Middle layer - Zona fasciculata
Innermost layer - Zona reticularis
What does the zona glomerulosa do?
Secretes mineralocorticoids such as aldosterone.
What does the zona fasciculata secrete?
Glucocorticoids such as cortisol.
What does the zona reticularis secrete?
Thought to secrete precursor molecules that are used to make sex hormones.
What does the adrenal medulla secrete?
Adrenaline and noradrenaline.
Peptide
What does the adrenal cortex used to produce a range of hormones?
Cholesterol
Are the hormones from the adrenal cortex steroid or non-steroid?
Steroid based.
Give the steps of the action of a steroid hormone.
- Hormone passes through membrane of target cell.
- Hormone binds with a specific receptor in the cytoplasm.
- Receptor-steroid hormone complex enters nucleus of target cell and binds to another specific receptor on the chromosomal material.
- Binding stimulates the production of mRNA molecules, which code for the production of proteins.
What do mineralocorticoids do?
Help to control the concentrations of sodium and potassium in the blood. As a result the also contribute to maintaining blood pressure.
What does aldosterone do?
Acts on the cells of the distal tubules and collecting ducts in the kidney. It increases absorption of sodium ions, decreases absorption of potassium ions, and increases water retention so increasing blood pressure.
What do glucocorticoids do?
Helps to control the metabolism of fats, carbohydrates and proteins in the liver.
When is cortisol released and what does it do?
Cortisol is released in response to stress or as a result of low blood glucose concentration.
It stimulates the production of glucose from stored compounds (especially glycogen, fats, and proteins) in the liver.
What do the precursor molecules that are secreted from the zona reticularis do?
Helps produce sex hormones
What do sex hormones do?
Sex hormones are responsible for driving sexual development (puberty).
What are the immediate effects of adrenaline being released?
Key actions of adrenaline include increasing the heart rate, increasing blood pressure, expanding the air passages of the lungs, enlarging the pupil in the eye, redistributing blood to the muscles and altering the body’s metabolism, so as to maximise blood glucose levels (primarily for the brain).
What are exocrine glands?
Glands that secrete chemicals through ducts into organs or to the surface of the body.
What is the glycocalyx?
An area of carbohydrate chains outside the cell surface membrane
Glycolipid function?
Involved in cell to cell signalling and binding to make tissues
Glycoprotein function?
Receptors for chemical signals
Why can proteins and peptide hormones be carried in the blood plasma?
They are hydrophilic so water soluble
How are steroid hormones carried in the blood? Why?
Bound to specific carrier proteins as they are hydrophobic
Describe the second messenger system.
- water soluble hormone leaves capillary via fenestrations. as it is membrane insoluble it cannot enter the cell but instead binds to a glycoprotein receptor on the cell surface membrane. Hormone = primary messenger
- The binding of hormone activates a G protein that is intrinsically positioned on the inside of the cell surface membrane
- The activated G protein activates adenyl cylase
- This catalyses the conversion of ATP to cyclic AMP (cAMP). It is the cAMP that acts as the secondary messenger.
- cAMP activates other proteins and triggers a cascade of events in the cell by activating protein kinase
- Protein kinase activates other proteins by phosphorylating them.
Where are the adrenal glands located
above kidneys
