2.1.7 Regulation of sensitivity Flashcards
(21 cards)
What is signal transduction?
The process by which a hormone binds to a receptor on or in a cell, causing a change in cellular activity.
What is down-regulation?
The process that results in fewer receptors on the surface of the target cell.
What is up-regulation?
The process that causes an increase in the number of receptors for a particular hormone.
How does a cell’s sensitivity to a hormone depend on receptor quantity?
More receptors = greater sensitivity; less receptors = less sensitivity.
What range of receptor numbers can a cell display for a hormone?
500 to 100,000 receptors.
What occurs during hormonal upregulation?
An increase in the number of receptors increases the cell’s sensitivity to that hormone.
What can cause upregulation?
- A weak signal (reduced hormone amount) * Response to toxins * Specific hormones * Nerve damage reducing neurotransmitter levels.
What happens during downregulation?
Receptors are pinched inwards to form a vesicle that fuses with a lysosome to destroy excess receptors.
What can cause receptor downregulation?
Overexposure to drugs, hormones, and neurotransmitters.
How does downregulation relate to Type 2 Diabetes?
Overweight individuals with high blood glucose downregulate insulin receptors on liver cells.
What initiates a signal transduction pathway?
When a hormone binds to the receptor on or in a cell.
What occurs to the receptor molecule when a hormone binds?
The receptor undergoes a change in shape.
What types of cellular responses can hormones control?
- Activating/inactivating hormones * Exocytosis of molecules * Switching on or off genes * Opening or closing of protein channels.
What is the significance of signal amplification?
A single hormone molecule can activate many effector proteins, eliciting a strong cellular response.
Fill in the blank: The effects of signaling molecules are triggered only by the specific receptor that it can bind to. Only cells that express this specific _______ will be affected.
receptor.
What is a benefit of a cell permanently expressing a large number of receptors for a hormone?
Every cell will be acutely sensitive to the required hormones.
What is a downside to a cell maintaining a large number of receptors?
Resource-intensive for the cell and increases the risk of incorrect binding.
Why might an organism need both an endocrine system and a nervous system?
The nervous system provides fast responses for movements, while the endocrine system regulates long-term processes like growth.
True or False: Upregulation of a receptor is the starting point for degrading it.
False.
In general, fat-soluble hormones bind to which type of receptors?
Intracellular receptors.
Which of the following is not a phase of hormonal signal transduction? * Hormone binds to a receptor * Neurotransmitters cross the synapse * Second messengers amplify signal * Receptor activates second messengers
Neurotransmitters cross the synapse.
