Neurons and the Nervous System 2
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Questions and Answers

What triggers depolarization in a neuron?

  • Closing of voltage-gated Na+ channels
  • Opening of voltage-gated K+ channels
  • Movement of organic anions into the cell
  • Opening of voltage-gated Na+ channels (correct)

    • What happens during repolarization in neurons?

  • Na+ channels remain open while K+ channels open
  • Na+ channels open and K+ channels close
  • K+ channels open and remain open indefinitely
  • K+ channels open and Na+ channels close (correct)

    • What is the role of the Na+/K+-ATPase pump in neurons?

  • To establish the resting potential by re-establishing ion gradients (correct)
  • To facilitate the opening of K+ channels during action potential
  • To promote depolarization by increasing Na+ concentration inside the cell
  • To close voltage-gated Na+ channels

    • What occurs during transient hyperpolarization?

    <p>Rapid efflux of K+ ions</p> Signup and view all the answers

    What primarily causes the depolarization effect on the neuronal membrane?

    <p>Movement of Na+ ions into the cell</p> Signup and view all the answers

    What is the resting potential of a neuron?

    <p>-70mV</p> Signup and view all the answers

    What occurs immediately after depolarization in an action potential?

    <p>Repolarization</p> Signup and view all the answers

    What must occur for an action potential to be generated?

    <p>Threshold potential must be exceeded</p> Signup and view all the answers

    Which ion has a higher concentration inside the neuron at resting potential?

    <p>K+</p> Signup and view all the answers

    What happens during hyperpolarization?

    <p>Membrane potential decreases below resting potential</p> Signup and view all the answers

    Where do incoming signals summate in a neuron?

    <p>Axon hillock</p> Signup and view all the answers

    What defines the action potential graph at one node of Ranvier?

    <p>Threshold potential passing</p> Signup and view all the answers

    What characterizes the transient phases of the action potential?

    <p>Three distinct phases of voltage change</p> Signup and view all the answers

    What happens if the stimulus does not exceed the threshold potential?

    <p>There is no action potential.</p> Signup and view all the answers

    What is the primary role of the Na+/K+-ATPase in neurons?

    <p>To maintain the resting potential by regulating ion concentrations.</p> Signup and view all the answers

    Which statement correctly describes voltage-gated ion channels in neurons?

    <p>They open in response to changes in membrane voltage.</p> Signup and view all the answers

    During the process of depolarization, which ion primarily enters the neuron?

    <p>Sodium (Na+)</p> Signup and view all the answers

    What contributes significantly to the resting membrane potential in neurons?

    <p>The Na+/K+-ATPase activity.</p> Signup and view all the answers

    What causes the sequential opening and closing of voltage-gated ion channels in neurons?

    <p>A change in membrane voltage.</p> Signup and view all the answers

    Which of the following ions does the voltage-gated K+ channel primarily allow to diffuse?

    <p>Potassium (K+)</p> Signup and view all the answers

    What role do the voltage-gated Na+ channels play during an action potential?

    <p>They help facilitate the rapid depolarization phase.</p> Signup and view all the answers

    What is the primary role of the refractory period in neuronal signaling?

    <p>To prevent upstream depolarizations from triggering action potentials</p> Signup and view all the answers

    Which transport protein is NOT involved in generating an action potential?

    <p>Calcium channel</p> Signup and view all the answers

    What does the process of salutatory conduction entail?

    <p>The action potential 'jumps' between nodes of Ranvier</p> Signup and view all the answers

    What happens when the stimulus generated by the axon hillock exceeds the threshold potential?

    <p>Voltage-gated Na+ channels open, leading to depolarization.</p> Signup and view all the answers

    During the repolarization phase of an action potential, which ion rapidly diffuses out of the cell?

    <p>K+</p> Signup and view all the answers

    What initiates an action potential in a post-synaptic neuron?

    <p>The binding of neurotransmitters to receptors</p> Signup and view all the answers

    Where is an action potential typically generated in a neuron?

    <p>At the axon hillock</p> Signup and view all the answers

    What is the result when K+ channels open during an action potential?

    <p>The cell experiences hyperpolarization.</p> Signup and view all the answers

    What happens to Na+ channels after a sufficient stimulus is applied?

    <p>They close after a rapid influx of Na+.</p> Signup and view all the answers

    How do Na+ ions affect the neuronal action potential?

    <p>Their influx causes rapid depolarization</p> Signup and view all the answers

    If the stimulus generated by the axon hillock is small, what is the outcome?

    <p>There is a complete failure to initiate an action potential.</p> Signup and view all the answers

    What is a synapse?

    <p>The junction where two neurons communicate</p> Signup and view all the answers

    What physiological process occurs after the opening of voltage-gated K+ channels?

    <p>Repolarization followed by hyperpolarization.</p> Signup and view all the answers

    What is the function of voltage-gated K+ channels during an action potential?

    <p>They help in restoring the resting membrane potential</p> Signup and view all the answers

    Which ion is primarily responsible for the rapid depolarization of the axon during an action potential?

    <p>Na+</p> Signup and view all the answers

    What is the role of the Na+/K+-ATPase in neuronal function?

    <p>To maintain resting membrane potential.</p> Signup and view all the answers

    What triggers the opening of voltage-gated Ca2+ channels in the synaptic terminal?

    <p>Action potential arrival</p> Signup and view all the answers

    What is the primary function of the Ca2+-ATPase in the axon terminal?

    <p>To remove Ca2+ from the cytosol</p> Signup and view all the answers

    What occurs immediately after Ca2+ enters the synaptic terminal?

    <p>Exocytosis of synaptic vesicles commences</p> Signup and view all the answers

    What is a consequence of neurotransmitter binding to a ligand-gated ion channel on the post-synaptic neuron?

    <p>Generation of an electrical signal</p> Signup and view all the answers

    How is the neurotransmitter signal removed from the synaptic cleft after signaling?

    <p>By enzymatic degradation or reuptake</p> Signup and view all the answers

    What effect does tetrodotoxin have on the nervous system?

    <p>Inhibition of voltage-gated Na+ channels</p> Signup and view all the answers

    What characterizes the action of anatoxin-a in the nervous system?

    <p>It binds to the nicotinic acetylcholine receptor and cannot be degraded.</p> Signup and view all the answers

    What is the physiological consequence of increased intracellular Ca2+ concentration during neurotransmitter release?

    <p>Promotion of synaptic vesicle exocytosis</p> Signup and view all the answers

    Study Notes

    Neurons and the Nervous System 2

    • The resting potential of a neuron is -70mV.
    • A nervous signal is a transient depolarization, also known as an action potential, followed by repolarization and transient hyperpolarization.
    • The action potential is a decrease in voltage.
    • The electrical signal travels down the axon.
    • The action potential is a depolarization (decrease in voltage) followed by repolarization and then hyperpolarization, returning finally to the resting potential.
    • The stimulus (depolarization) must exceed a threshold potential for an action potential to be generated.
    • Incoming signals are summed at the axon hillock.
    • If the summed signals are large enough (larger than the threshold potential), an action potential is generated.
    • The axon hillock integrates impulses from upstream neurons.
    • Action potentials travel down the axon, from one node of Ranvier to the next in myelinated neurons, a process called saltatory conduction.
    • The myelin sheath acts as an insulator, allowing for faster signal transmission.
    • The refractory period is a brief period after an action potential where a node of Ranvier cannot generate another action potential.
    • The refractory period is initiated by the temporary inactivation of voltage-gated Na+ channels.
    • In a chemical synapse, the electrical signal of the presynaptic neuron becomes a chemical signal in the synaptic cleft. This chemical signal triggers an electrical signal in the postsynaptic neuron.
    • Neurotransmitters diffuse across the synaptic cleft and bind to ligand-gated ion channels in the postsynaptic membrane.
    • The binding of neurotransmitters to ligand-gated ion channels causes channels to open, leading to an influx of ions and a localized depolarization. This creates an action potential in the post-synaptic neuron.
    • After an action potential, either 1) the ligand is enzymatically degraded, 2) diffuses away, 3) is re-uptaken by the pre-synaptic neuron.
    • Ca2+ entry causes neurotransmitters containing synaptic vesicles to release their contents by exocytosis into the synaptic cleft.
    • Two Ca2+ transport proteins are associated with the axon terminal during a chemical synapse: 1) voltage-gated Ca2+ channel and 2) Ca2+-ATPase.
    • Ca2+ enters the synaptic terminal and triggers neurotransmitter release into the synaptic cleft by triggering the movement of synaptic vesicles to the membrane, fusing them, and releasing the neurotransmitters.

    Ion Channels

    • Voltage-gated Na⁺ and K⁺ channels are in the neuron plasma membrane
    • Voltage-gated channels are closed when there is no action potential, but open when the voltage changes across the membrane.
    • Na⁺ channels allow the diffusion of Na+ down the concentration gradient (∆[Na+])
    • K⁺ channels allow the diffusion of K⁺ down the concentration gradient (∆[K+])
    • Opening and closing of these channels leads to depolarization, then repolarization.

    Action Potential Summary

    • Action potentials are rapid depolarizations/repolarizations across the axon plasma membrane.
    • Three types of transport proteins are involved in action potentials: voltage-gated Na+ channels, voltage-gated K+ channels, and Na+/K+ pump (or Na+/K+-ATPase).
    • The action potential is generated at the axon hillock.
    • The action potential jumps down the axon (salutatory conduction) until the axon terminal.
    • The refractory period prevents upstream-moving depolarizations from triggering a new action potential

    Diseases and Toxins of the Nervous System

    • Multiple Sclerosis (MS) is due to demyelination of axons.
    • Dysautonomia is dysfunction of the autonomic nervous system.
    • Tetrodotoxin inhibits voltage-gated Na+ channels.
    • Anatoxin-a mimics the neurotransmitter acetylcholine.

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    Description

    Explore the intricate workings of neurons and the nervous system in this quiz. Learn about the action potential, resting potential, and the role of the axon hillock in integrating signals. Test your understanding of how electrical signals propagate through neurons.

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