Harding Flashcards
(10 cards)
What are two different ways to classify extracellular signals?
How far the molecule has to travel
Molecule’s physiological properties
What are the classifications of extracellular signals by travel distance?
Endocrine Paracrine (and autocrine) Neurotransmitters
Endocrine signal properties
Enter circulation Travel long distances Biologically stable Broken down only by the liver Slow to influence cell Slow to turn off reaction Some act as NTs in the CNS because the CNS has the mechanisms to remove them quickly, unlike the circulation.
Paracrine signal properties
Affect a small group of cells
Less biologically stable
Shorter duration of effect
Faster response of cell
Autocrine signals
Signals that affect the cell that produced them.
Example: platelets
Neurotransmitter properties
Shortest distance - synapse Interact with only one other cell Highly biologically unstable Very fast response Short duration of effect Some endocrine molecules can act as neurotransmitters in the brain.
Extra-cellular matrix
Mass of proteins between each cell - up to 11,000 known protein types
Immovable signals that interact with cell membranes
Hugely dynamic, with local rather than global changes.
Anoikis
Specialized type of programmed cell death that happens when a cell is removed from the signals of the ECM.
Ionotropic receptors
Rapid response channels that change the cell membrane’s permeability to a specific ion.
Easy to turn both on and off.
Metabotropic receptors
Slow response channels like G-proteins that require a scaffold formation between the receptor and the cell response. Also hard to turn off - once the stimulus is removed the scaffold remains.
