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 (C)</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 (A)</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 (B)</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 (A)</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 (D)</p> Signup and view all the answers

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

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

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

<p>Cl channels (D)</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 (B)</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+ (B)</p> Signup and view all the answers

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

<p>Hyperpolarization (D)</p> Signup and view all the answers

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

<p>Excitatory Presynaptic Neurons (B)</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 (D)</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 (C)</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 (B)</p> Signup and view all the answers

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

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

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

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

What type of event are action potentials classified as?

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

What triggers action potentials in neurons?

<p>Depolarization (B)</p> Signup and view all the answers

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

<p>Sodium channels (B)</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 (A)</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 (D)</p> Signup and view all the answers

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

<p>Depolarization (A)</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 (C)</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. (A)</p> Signup and view all the answers

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

<p>Closed (D)</p> Signup and view all the answers

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

<p>Closes (D)</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 (D)</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. (C)</p> Signup and view all the answers

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