Lecture 58-Mechanism Of Hormone Action And Second Messengers Flashcards
The final outcome of interaction of hormone and target cells depends on …. (5 things)
- Hormone concentration
- Receptor number
- Affinity of hormone for receptor
- Duration of exposure to hormone
- Intracellular factors—enzymes, cofactors
What is hormone responsiveness expressed as?
Dose-response relationship
As concentration of hormone increases, response ______ and then _______.
Increases
Levels off
More receptors on a target tissue, ______ maximal response.
Increases
What is the maximum response in hormone action?
A further increase in hormone will elicit no more response
What is a decrease in responsiveness caused by?
-decrease in number target cells or total receptors/cells
-decrease concentration of enzymes activated by hormone
What are two ways that sensitivity can be changed in a hormone?
Changing number of receptors
Changing affinity of receptors
If more hormone is required to get _____ response, then the sensitivity goes _____.
50%
Down
Decreasing sensitivity = _____-_____ of receptors
Down-regulation
What will happen to the number or affinity of receptors, even when hormone concentration is high?
Decrease
Increasing sensitivity = ___-____ of receptors
Up-regulation
When either number or affinity of receptors increases, what happens to synthesis and degradation?
Increase synthesis of new receptors
decrease degradation of existing
Activate receptors!
What is the general mechanism of hormone action?
- Hormone is recognized and binds to membrane receptor -> hormone receptor complex
- Hormone-receptor complex EITHER coupled to a signal-generating mechanism OR must act as one
- Generated signal (second messenger) affects intracellular process by altering activity OR concentration of functional or structural proteins
Where are hormone receptor systems located? Which has a faster response?
Cell membrane (Faster response)
Within the cell, cytoplasm or nucleus (slower response)
How does the classic cell membrane receptor system work?
-classified according to membrane receptor structure OR second messenger system
-usually a rapid response (minutes)
How does the catalytic cell membrane receptor system work?
-doesnt use second messenger system, but rather an enzyme system such as kinases
-usually a rapid response (minutes)