Ion channels, receptors and signalling Flashcards
What is a receptor?
Sensing element in the complex system of chemical communication within the body
What are receptors the target of?
Neurotransmitters
Hormones
Mediators such as growth factors, chemokines, cytokines
Therapeutic agents such as agonists, antagonists
What is a autocrine response?
When the signalling molecule targets the signalling cell it was made in
What is a paracrine response?
When the signalling molecule targets a neighboring cell called a target cell
What is an endocrine response?
When the signalling molecule enters the circulation targeting cells all over the body
What are the 4 types of receptor?
Ligand-gated ion channels
G-protein-coupled receptors
Kinase-linked
Nuclear
Where are ligand gated ion channels located?
Plasma membrane and are therefore targets of hydrophilic signalling molecules e.g. neurotransmitters
Where are G-protein-coupled receptors located?
Plasma membrane and therefore targeted by hydrophilic signalling molecules
Where are kinase-linked receptors found?
Plasma membrane and so are targets of hydrophilic protein mediators such as insulin
Where are nuclear receptors found?
In the nucleus and so are targeted mostly by hydrophobic signalling molecules such as steroid and thyroid hormones
What are ion channels made from?
Transmembrane pores that are formed by glycoproteins that span the membrane to form an ion conducting pathway
How are ion channels regulated?
By signals that cause the channel to cycle reversibly between a closed state and an open state known as gating
How do open channels conduct ions?
The ions are passed passively down their electrochemical gradient at rapid rates
What are examples of gates on ion channels?
Chemical signals e.g. ligand gated
Transmembrane voltage e.g. voltage gated
Physical stimuli e.g. thermal and mechanical energy
What are the three types of ligand gated ion channels?
Trimeric
Tetrameric
Pentameric