2.6 Lundy Ch. 3 (1) Flashcards
presynaptic terminal
- end of the axon
- contains vesicles of NT
postsynaptic terminal
- membrane region of receiving cell
- has receptors
synaptic cleft
space between presynaptic and postsynaptic terminals
steps of synaptic transmission
- AP arrives at presynaptic terminal
- membrane depolarizes and Ca2+ channels open
- Ca2+ flows into presynaptic terminal and triggers movement of vesicles that contain NT toward a release site in the membrane
- vesicles fuse with membrane and release NT into the cleft
- NT diffuses across synaptic cleft
- NT binds to a receptor on postsynaptic membrane
- receptor changes shape
What happens when the receptor on the postsynaptic terminal changes shape?
- opens an ion channel or
- activates intracellular messengers
Synaptic transmission can happen in different locations
- axosomatic (on cell body)
- axodendritic (on dendrites)
- axoaxonic (on axon)
What influences the amount of NT released into the synaptic cleft?
number and duration of action potentials that reach the terminal
What is a neurotransmitter?
- released by presynaptic neuron
- acts either directly on postsynaptic ion channels or activates proteins inside postsynaptic neuron
What are the two types of neurotransmitters?
- ionotropic (fast acting)
- metabotropic (slow acting)
ionotropic NT
- directly affect postsynaptic membrane by activating ion channels
- short lived effects
metabotropic NT
- indirectly affect postsynaptic membrane by activating proteins inside the postsynaptic neuron
- regulate fast transmission by controlling amount of NT released from terminals
- influence actions of ionotropic NT on postsynaptic membrane
What is a neuromodulator?
- released into extracellular fluid
- adjust activity of neurons
Where do neuromodulators act?
away from the synaptic cleft
Depending on where it’s released, the same molecule may be either of these
neurotransmitter or neuromodulator
Neuromodulators often act in conjunction with ______
neurotransmitters
