Action Potential Threshold Recap
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Questions and Answers

What type of ion channels are NOT present in the myelinated areas where action potential/refractory period occurs only at Nodes of Ranvier?

  • Calcium channels (correct)
  • Chloride channels
  • Sodium channels
  • Potassium channels
  • What is the function of myelination in relation to axons?

  • Increase axon diameter for faster action potential transmission
  • Allow axons to have small diameters while transmitting action potentials rapidly (correct)
  • Prevent action potential propagation
  • Promote synaptic transmission efficiency
  • What is the role of the synapse in neural communication?

  • Secreting myelin sheath
  • Initiating action potentials
  • Regulation of neurotransmitter production
  • Integration of signals between neurons (correct)
  • What determines whether inputs from another axon are excitatory or inhibitory at the synapse?

    <p>Ion channels opened at the synapse</p> Signup and view all the answers

    What occurs when a chemical messenger binds to receptors on the postsynaptic cell at a synapse?

    <p>Opening of ion channels</p> Signup and view all the answers

    What is the state of the sodium channel during the hyperpolarization phase?

    <p>m gate open, h gate closed</p> Signup and view all the answers

    Which phase sees the potassium channel activated by Na+ entering the cell and changing the membrane potential?

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

    What must happen before an action potential can be generated in terms of sodium channel inactivation?

    <p>The h gate opens</p> Signup and view all the answers

    Which channel must be open for the repolarization phase to occur?

    <p>Potassium channel - h gate</p> Signup and view all the answers

    What is the role of the inactivation (h) gate in returning to the resting potential?

    <p>Opens the h gate</p> Signup and view all the answers

    What type of channels are generally considered inhibitory in the context of neuronal signaling?

    <p>Cl channels</p> Signup and view all the answers

    What is the principle that describes the phenomenon where once the electrical impulse reaches a certain level of intensity, it fires and moves all the way down the axon without losing any intensity?

    <p>All or nothing principle</p> Signup and view all the answers

    Which ion's influx increases the membrane potential and favors the formation of an action potential?

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

    What term is used to describe when the action potential becomes more negative?

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

    What type of presynaptic neurons favor depolarization and generating a new action potential?

    <p>Excitatory Presynaptic Neurons</p> Signup and view all the answers

    In the Hodgkin and Huxley Experiment, what did they find happens when an electrical stimulation is introduced to a region of the axon?

    <p>It causes major depolarization</p> Signup and view all the answers

    Which type of presynaptic neurons make it more difficult for an impulse to cross the synapse?

    <p>Inhibitory Presynaptic Neurons</p> Signup and view all the answers

    Which of the following channels is responsible for the inactivation of sodium channels during an action potential?

    <p>Delayed-Rectifier Potassium Channel</p> Signup and view all the answers

    What is the main effect of opening Na+ or Ca+ channels at a synapse?

    <p>Stimulate depolarization</p> Signup and view all the answers

    What happens to the membrane potential after there is a massive increase due to depolarization?

    <p>It briefly drops below the resting potential</p> Signup and view all the answers

    What is the membrane potential level of a typical action potential after depolarization?

    <p>+50 mV</p> Signup and view all the answers

    What type of event are action potentials classified as?

    <p>All-or-none events</p> Signup and view all the answers

    What is the period called during which it is impossible to cause another action potential to be produced?

    <p>Refractory period</p> Signup and view all the answers

    What triggers action potentials in neurons?

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

    What type of ion channels are stimulated by excitatory presynaptic axons?

    <p>Sodium channels</p> Signup and view all the answers

    What happens to the depolarization after it occurs in an axon?

    <p>It quickly returns to its resting potential</p> Signup and view all the answers

    If sodium is removed from the system, what effect does it have on action potential?

    <p>It decreases the height of the action potential</p> Signup and view all the answers

    Which stage of action potential involves a massive spike in depolarization?

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

    What is the function of voltage-gated sodium channels?

    <p>They are gated by depolarization of the membrane</p> Signup and view all the answers

    What is the role of the Delayed-Rectifier Potassium Channel in the recovery of membrane potential?

    <p>It helps recover the membrane potential to the starting level.</p> Signup and view all the answers

    During the refractory period, what is the status of the m gate in sodium channels?

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

    What happens to the h-gate of sodium channels 5 ms after depolarization?

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

    How do One Gates m gate and h gate differ in their response to membrane potential changes?

    <p>m gate opens immediately, h gate opens with a delay</p> Signup and view all the answers

    What characterizes the refractory period of an axon in terms of sodium channel opening?

    <p>The channel remains closed regardless of membrane potential.</p> Signup and view all the answers

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