Synapse Flashcards
What electrical signal happens at a synapse?
Small graded potential
Excitatory Synapse
membrane potential of a postsynaptic neuron is brought closer to threshold
Inhibitory Synapse
membrane potential of a postsynaptic neuron is driven further from threshold or stablized at its resting membrane potential
Electrical Synapse characteristics
-direct cell to cell contact
-contains gap junctions which allow ion and other small solutes to pass through
-conducts electrical signals very quickly
Chemical Synapse characteristics
-synaptic vesicles in presynaptic neuro
-slower than electrical synapse
Steps of NT release
- AP goes down the axon to the terminal
- Volate gated calcium channels open
- calcium enters the axon terminals
- calcium induces the exocyptosos of NTs and they are released and diffuse into the cleft
- NTs bind to postsynaptic receptors
- NTs removed from cleft
Excitatory NT steps
- NT binds to the receptor
- Ligand gated ionotropic receptor channel opens
- Net cation iflux of mainly sodium or calcium into postsynaptic cell
- The net effect is depolarization
Inhibitory NT steps
- NT binds to the receptor
- Ligand gated ionotropic channels open
- either potassium flows out, chloride flows in or no net flux of cl-
- Net effect is either hyperpolarization or prevents depolarization
What happens to NTs in the cleft?
- NTs can diffuse away unbounded
- Can be destroyed by enzymes and turn inactive
- NTs are taken back into the presynaptic terminals or transported into nearby glial cells
Synaptotgamin
senses incoming calcium and induces wrapping of the protein. The protein twists together and draws vesicle to the membrane. Exocytosis of NTs occur when vesicle binds to the membrane
NTs can bind to two different kinds of receptors?
Ionotropic and meatbotropic
Ionotropic Receptors
Ligand gated/chemical
Contain and ion chennal
Membrane potential changes immediatly
Metabotropic Receptors
Do not contain ion channels and many are coupled to G protein transducters
-g protein transduction activate second messenger signaling cascades which may open or close ion channels
Temporal summation
one input is repeadtly releasing and adding together
Spatial summation
2 different inputs fired close in time can sumate in space