Questions and Answers
What causes the depolarization in a postsynaptic neuron during EPSP?
Which neurotransmitter is the most common excitatory neurotransmitter in the central nervous system?
What is the outcome of spatial summation in synaptic transmission?
What describes the timing of temporal summation in synaptic transmission?
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How does IPSP affect the postsynaptic neuron?
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What happens to a neurotransmitter during its inactivation?
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What is the primary effect of cation channels when neurotransmitters bind to them?
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Which neurotransmitter is commonly associated with the activation of anion channels?
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In the context of EPSP, what occurs after depolarization begins in response to an afferent impulse?
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What role do second messengers play in synaptic transmission?
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What determines whether the postsynaptic membrane undergoes depolarization or hyperpolarization?
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How is the activity of neurotransmitters in the synaptic cleft typically terminated?
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Which process contributes to hyperpolarization during an IPSP?
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What is the result of the temporal summation of IPSPs?
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Which neurotransmitter is primarily associated with generating IPSPs?
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What occurs during the mechanism resulting in slow IPSPs?
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Which of the following methods is NOT involved in the inactivation of neurotransmitters from the synaptic cleft?
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What determines the membrane potential of the postsynaptic neuron?
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Which factor increases Cl- influx during an IPSP?
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In the context of synaptic transmission, what does spatial summation primarily involve?
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Study Notes
Inhibitory Post Synaptic Potential (IPSP)
- IPSP decreases neuron excitability to stimuli.
- Produced by inhibitory neurotransmitters (NTs) such as GABA and glycine.
- Ionic mechanisms involved:
- Opening of Cl- channels increases Cl- influx.
- Opening of K+ channels increases K+ efflux.
- Closing of Na+ channels decreases Na+ influx.
- Closing of Ca2+ channels decreases Ca2+ influx.
- Results in hyperpolarization, making the neuron more negative.
- Increased concentration of anions in the postsynaptic neuron leads to hyperpolarization.
Summation of IPSP
- Spatial Summation: Multiple active synaptic knobs enhance each other’s effects.
- Temporal Summation: Repeated activity of one knob in quick succession creates a new IPSP before the previous one decays.
Slow EPSP & IPSP
- Occur in autonomic ganglia, cardiac muscle, smooth muscle, and cortical neurons.
- Latency ranges from 100 to 500 ms and can last several seconds.
- Slow EPSP is induced by decreased K+ conductance.
- Slow IPSP is induced by increased K+ conductance.
Inactivation of Neurotransmitters
- Released neurotransmitters in the synaptic cleft are quickly inactivated by:
- Diffusion out of the cleft.
- Enzymatic degradation.
- Reuptake into the presynaptic terminal.
Generation of Action Potential in Postsynaptic Neuron
- Membrane potential fluctuates due to the balance of excitatory and inhibitory inputs.
- The overall effect of excitatory post synaptic potentials (EPSPs) and IPSPs determines neuron excitability.
- Glutamate is the primary excitatory neurotransmitter in the CNS.
Ionic Basis of EPSP
- Opening of Na+ channels increases Na+ influx.
- Opening of Ca2+ channels increases Ca2+ influx.
- Closing of Cl- channels decreases Cl- influx.
- Closing of K+ channels decreases K+ efflux.
- Results in depolarization, making the neuron more positive (excited).
EPSP and IPSP Summation
- Spatial Summation: Concurrent activation of multiple synaptic knobs leads to reaching the threshold for action potential (AP).
- Temporal Summation: Rapid succession of stimulation from one knob generates sufficient EPSPs to reach the threshold.
Definition of EPSP and IPSP
- EPSP refers to potential change toward depolarization.
- Hyperpolarization in the postsynaptic neuron is indicative of IPSP.
- Hyperpolarization peaks at 1.5 - 2 ms after impulse and subsequently declines.
Mechanism of Neurotransmitter Action
- Neurotransmitters bind to ligand-gated ion channels:
- Cation channels (e.g., glutamate) lead to Na+ influx and depolarization (EPSP).
- Anion channels (e.g., glycine, GABA) lead to Cl- influx and hyperpolarization (IPSP).
- Neurotransmitters activate G protein-linked receptors, initiating processes that alter ionic permeability, causing prolonged excitatory or inhibitory effects.
Synaptic Potential
- Synaptic potentials (EPSP and IPSP) determine the membrane potential of the postsynaptic neuron.
- Depending on ionic flow, the potential may shift towards depolarization or hyperpolarization, creating signals essential for neuron communications.
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Description
Explore the intricate processes that occur in postsynaptic cells when neurotransmitters (NT) bind to receptors. This quiz covers the mechanisms of excitatory (EPSP) and inhibitory (IPSP) synaptic transmissions through ligand-gated ion channels and second messengers. Test your understanding of neural communication dynamics.
