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Graded Potentials quiz #1

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  • What are graded potentials, where do they occur in a neuron, and how do they influence the likelihood of an action potential being generated?
    Graded potentials are changes in membrane potential that occur in the soma and dendrites of neurons, primarily at chemical synapses. They can be excitatory (EPSPs), which depolarize the membrane and increase the likelihood of an action potential, or inhibitory (IPSPs), which hyperpolarize the membrane and decrease the likelihood of an action potential.
  • How does a depolarizing graded potential (EPSP) occur at the postsynaptic membrane, and why does its strength decrease as it spreads?
    A depolarizing graded potential (EPSP) occurs when neurotransmitters open gated sodium channels, allowing sodium ions to enter the postsynaptic cell and depolarize the membrane. As the depolarization spreads, its strength decreases due to sodium loss through leak channels in the membrane.
  • What is summation in the context of graded potentials, and what are the differences between temporal and spatial summation?
    Summation is the process by which multiple graded potentials combine at the initial segment of a neuron to influence whether the threshold for an action potential is reached. Temporal summation involves multiple signals from a single synapse overlapping in time, while spatial summation involves graded potentials from multiple synapses located close together on the membrane, which can include both EPSPs and IPSPs.
  • Where in a neuron do graded potentials occur and what type of synapse are they most commonly associated with?
    Graded potentials occur in the soma and dendrites of neurons, primarily at chemical synapses, which are the most common type in the human body.
  • What are the two main types of postsynaptic graded potentials and how do they affect the neuron's membrane potential?
    The two main types are excitatory postsynaptic potentials (EPSPs), which depolarize the membrane and make it more likely to fire an action potential, and inhibitory postsynaptic potentials (IPSPs), which hyperpolarize the membrane and make it less likely to fire.
  • How does a depolarizing graded potential (EPSP) occur at the postsynaptic membrane?
    A depolarizing graded potential occurs when neurotransmitters open gated sodium channels, allowing sodium ions to enter the cell and depolarize the membrane.
  • Why does the strength of a graded potential decrease as it spreads from the site of stimulation?
    The strength decreases because sodium ions are lost through leak channels in the membrane as the depolarization spreads.
  • What is summation in the context of graded potentials?
    Summation is the process by which multiple graded potentials combine at the initial segment of a neuron to determine if the threshold for an action potential is reached.
  • What is temporal summation and how does it contribute to reaching action potential threshold?
    Temporal summation occurs when multiple signals from a single synapse overlap in time, allowing their effects to add up and potentially reach the threshold for an action potential.
  • How does spatial summation differ from temporal summation in neurons?
    Spatial summation involves the additive effect of graded potentials from multiple synapses located close together on the membrane, which can include both EPSPs and IPSPs, while temporal summation involves repeated signals from one synapse over time.