Flashcards in Endocrine Communication Deck (21):
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?
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?
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 is a G-protein?
A second messenger that many non-steroid hormones rely upon.
What does the G-protein do once it is activated by the non-steroid hormone?
The G-protein in turn activates an effector molecule - usually an enzyme that converts an inactive molecule into the active second messenger.
What is the effector molecule in many cells?
The enzyme adenyl cyclase.
What does adenyl cyclase do?
Converts ATP to cyclic AMP (cAMP).