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21 Cards in this Set
- Front
- Back
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What are the two types of synaptic transmission?
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electrical and chemical
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What are electrical synapses composed of?
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low resistance gap junctions
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What are three characteristics of electrical synaptic transmission?
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1)Little delay at the synapse, 2)bidirectional transmission, 3)influenced by previous activity but over a longer time scale 4)temporal and spatial summation
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Where are electrical synapses frequently observed?
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Between dendrites
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How are electrical synapses modulated?
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By opening and closing of gap junctions
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What are some factors that regulate connexon opening and closing?
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Changes in pH, Ca++ levels
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Differences between neuromuscular transmission and neuron-neuron synaptic transmission
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1) NMT = always excitatory, NN = excitatory or inhibitory 2) NMT = 1 neuron, NN= multiply inputs 3) NMT = Ach exclusive NN= many transmitters 4)NMT = EPP gives rise to AP, NN =single excitatory potential generally doesn't produce AP
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The reversal potential of a EPSP is near 0mv meaning what?
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The channles are monovalent cation channels permeable to both Na+ and K+
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Explain why some EPSPs decrease membrane permeability?
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Decreased permeability to K+ increases the excitability of the neuron
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What ions are affected by IPSPs?
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K+ and Cl- channel permeability are both increased resulting in hyperpolarization away from the threshold potential
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What is the best studied inhibitory neurotransmitter?
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GABA
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What does GABA do?
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It activates a receptor that directly opens a gated Cl- channel
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What other amino acid peptide works similarly to GABA and what does it do?
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Glycine activates a Cl- channel
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What is the goal of presynaptic inhibition?
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Reduce the amount of transmitter released from the synaptic bouton by reducing the duration of the axonal AP
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How is presynaptic inhibition accomplished?
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1) inactivation of Na+ channels leading to a shorter AP 2) inactivation of voltage gated Ca++ channles leading to less vesicle fusion with the membrane
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What is meant by presynaptic facilitation?
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When presynaptic events lead to an increased influx of Ca2+ into the terminal and hence an increase in the transmitter release
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Why won't a single EPSP or IPSP greatly influence the membrane potential of the cell body or axon hillock?
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The EPSP or IPSP decays before reaching these points because it is propagated electrotonically
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What is spatial summation?
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Simultaneous post synaptic potentials from two or more inputs combine on the membrane
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What is temporal summation?
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Occurs when a single input fires rapidly enough that a second EPSP occurs before the first is over
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What is meant by synaptic divergence?
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When one source provides output to many different targets
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What is meant by synaptic convergence?
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multiply sources arrive onto one neuron
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