Synapses Flashcards
What do chemical synapses involve?
neurotransmitters (NT) that are released from the presynaptic cell and bind receptors to excite, inhibit, or modify post-synaptic cell
How many neurotransmitters have been identified?
More than 100
How many ways can NTs be conducted?
One way
What determines the function of the NT?
The receptor itself
What is the order of presynaptic events?
- AP arrival at the synaptic terminal causes membrane depolarization
- Voltage Gated Ca2+ channels open
- Ca2+ enters the synaptic terminal
- Exocytosis of vesicles filled with NT
What does the amount of calcium determine?
The amount of NT released
What is the synaptic delay?
at least 0.5ms between the pre-synaptic depolarization and post-synaptic response
What causes the synaptic delay?
time for calcium entry for exocytosis, presynaptic neurotransmitter release, diffusion in the synaptic cleft, and postsynaptic receptor activation
What does the synaptic delay allow one to gauge?
the complexity of a reflex pathway (number of synapses) by looking at the speed of the reflex
What are the two groups of neurotransmitters?
Small molecules and neuropeptides
What are small molecule neurotransmitters?
Rapidly-acting; elicit acute responses
What are neuropeptides?
Larger molecules, slower; Effects are slower, more potent, & more prolonged.
Fewer neuropeptides produced and released
What terminates NT action?
A. Re-uptake of the NT by the pre-synaptic membrane,
B. Inactivation of the NT by enzymes in the synapse (ex. Acetylcholinesterase).
C. Diffusion of the NT away from the synapse (and receptors)
What are ionotropic receptors?
directly affect ion channels
Binding of the ligand and the opening or closing the channel for ionotropic receptors can:
- Change a cell’s membrane potential
- Stimulate muscle contraction and/or relaxation
- Stimulate secretion
- Act as a second messenger to alter cellular activity
