Synapses & Signal Integration Flashcards
What are boutons?
Specialized sites where neurons communicate by release of neurotransmitters
Small molecules that transmit impulses at chemical synapses
Neurotransmitters
Main excitatory neurotransmitter
Glutamate
Main inhibitor neurotransmitter
GABA
What are the three criteria for a neurotransmitter?
- Present in the nervous system in pre-synaptic terminals
- Released in response to pre-synaptic depolarization in a Ca2+ dependent manner
- Specific receptors exist for the transmitter on post-synaptic cells that generate a signal in the post-synaptic cell
What are the steps in synaptic transmission?
- Action potential in nerve terminal opens Ca2+ channels
- Ca2+ entry causes vesicle fusion and transmitter release
- Receptor-channels open, Na+ enters post-synaptic cell and vesicles recycle
T or F. Under most conditions, membrane potential changes occur only with significant change in ion concentration.
FALSE - membrane potential changes occur with LITTLE change in ion concentration under most conditions
EXCEPTION: when Ca2+ channels are active, significant concentration changes do occur for intracellular Ca2+
Electrical signaling often results in a ____ influx to transduce the electrical signal into other biochemical signals.
Ca2+
Where are Ca2+ channels position in the pre-synaptic bouton?
Directly below the active zone
What machinery in the synapses is a target of bacterial toxins?
Fusion machinery
T or F. Vesicles are destroyed after releasing neurotransmitter.
FALSE - they are recycled and reused
What is channel gating?
Conformational changes that affect channel open probability
What are 4 common gating mechanisms?
- Voltage-gated
- Ligand-gated (extracellular molecule)
- Signal-gated (intracellular molecule)
What are the main receptors found at excitatory synapses? What type of ion do they allow to pass through the channel?
Ionotrophic glutamate receptors
Cations
Opening of the glutamate receptor channel is near 0 mV so opening it drives membrane potential to _____ (depolarize/hyperpolarize)
Depolarize
_____ ensures that ionic currents will go to 0 if conductance is kept constant.
System attractor point
____ shift system attractor point toward channel’s 0 current potential if conductance is _____ or away if conductance is _____
Channel conductance changes
Increasing
Decreasing
Are glutamate receptors open or closed at rest? Why?
Closed - because opening it requires a torqued conformation which is not energetically favorable
Ligand binding to glutamate receptors only stabilizes the _____ state (activated or closed)
Activated
Where is glycine primarily used as a neurotransmitter? Is it excitatory or inhibitory
Spinal cord - inhibitory
Excitatory sites primarily use ____ channels, while inhibitory sites primarily use ____ channels
Cation
Cl-
Where in the neuron are synaptic responses generated? Where are action potentials produced?
Dendrites
Soma and hillock
For sustained current injections, the signals decay exponentially with distance with a characteristic _______
Space Constant
For passive spread of signals in neurons, _____ membrane resistance and _____ axial resistance increase the space constant
Higher
Lower
