202 T1 L14: Physiology of Neurons
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Questions and Answers

Which type of synapse is faster and coupled via gap junctions?

  • Electrical synapse (correct)
  • Inhibitory synapse
  • Excitatory synapse
  • Chemical synapse

    • What is the size of the gap in electrical synapses?

  • 3.5 nm (correct)
  • 5 nm
  • 1 nm
  • 2 nm

    • Which of the following is true about electrical synapses?

  • They weaken the signal as it is transmitted (correct)
  • They exhibit plasticity
  • They can inhibit the post-synaptic cell
  • They have amplification

    • What determines whether a neuron fires based on the 'add together' of all the tiny signals it receives from several other neurons?

    <p>Spatial summation</p> Signup and view all the answers

    Which ion channel is most likely inhibited by this mechanism?

    <p>Ca2+</p> Signup and view all the answers

    What is the equilibrium potential of K+?

    <p>-90 mV</p> Signup and view all the answers

    What is the role of the electrical force in determining the equilibrium potential?

    <p>It is the force that exactly counter-balances the chemical force.</p> Signup and view all the answers

    If the cell membrane was 1000X more permeable to K+ than to any other ion, what would be the membrane potential?

    <p>-90 mV</p> Signup and view all the answers

    What would be the membrane potential if both K+ channels and Na+ channels were open and if the cell was exactly equally permeable to Na+ and K+?

    <p>-15 mV</p> Signup and view all the answers

    What is the reversal potential of K+ (EK)?

    <p>-90 mV</p> Signup and view all the answers

    Which of the following represents the main way that neurons code the intensity of their synaptic input?

    <p>Firing frequency represents the intensity of activity</p> Signup and view all the answers

    What is the relationship between threshold voltage and firing frequency?

    <p>Increasing threshold voltage decreases firing frequency</p> Signup and view all the answers

    What is the difference between inactivated and closed channels?

    <p>Inactivated channels are non-conducting, while closed channels are conducting</p> Signup and view all the answers

    What happens to the membrane voltage when Na+ channels open?

    <p>The membrane becomes positive inside</p> Signup and view all the answers

    What happens to the membrane voltage when K+ channels open?

    <p>The membrane becomes negative inside</p> Signup and view all the answers

    Which of the following drugs raises the threshold and lowers excitability of neurons?

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

    According to the mnemonic for equilibrium potentials, which of the following statements is true?

    <p>The voltages for positive events are positive, while the voltages for negative events are negative.</p> Signup and view all the answers

    Which equation represents the Nernst Equation for deriving equilibrium potentials?

    <p>$E = 2.3 \log \left( \frac{[ion]_o},{[ion]_i} \right)$</p> Signup and view all the answers

    Which of the following is true about action potentials?

    <p>They are always the same - &quot;All or none&quot;.</p> Signup and view all the answers

    What is the basis of saltatory conduction?

    <p>Action potentials</p> Signup and view all the answers

    Which of the following statements about electrotonic conduction is true?

    <p>It transmits electric field instantly.</p> Signup and view all the answers

    What is the typical conduction velocity for alpha motor fibers?

    <p>100 m/s</p> Signup and view all the answers

    Which of the following best describes temporal summation in neuronal signaling?

    <p>When the input neuron is firing fast enough so that the receiving neuron can 'add together' the many tiny signals</p> Signup and view all the answers

    During an action potential, what happens when the voltage reaches the threshold?

    <p>Na+ conductance shoots up, Na+ current goes into the cell, and the membrane potential depolarizes</p> Signup and view all the answers

    What causes the initial depolarization in an action potential?

    <p>Synaptic transmission where a neurotransmitter opens a ligand-gated channel</p> Signup and view all the answers

    What happens during the positive feedback loop of depolarization in an action potential?

    <p>Na+ channels open and K+ channels open, leading to depolarization</p> Signup and view all the answers

    What causes repolarization in an action potential?

    <p>Na+ channel inactivation and delayed rectifier K+ channels opening</p> Signup and view all the answers

    What happens during the after-hyperpolarization phase of an action potential?

    <p>The voltage inside the cell temporarily goes slightly more negative than at rest</p> Signup and view all the answers

    Which of the following best describes the resting membrane potential (RMP)?

    <p>The voltage across the cell membrane when it is at rest</p> Signup and view all the answers

    What is the equilibrium potential of Na+ (ENa)?

    <p>+30 mV</p> Signup and view all the answers

    Which ion channel is responsible for the initial depolarization in an action potential?

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

    What is the typical conduction velocity for C fibers?

    <p>10-20 meters per second</p> Signup and view all the answers

    What is the difference between inactivated and closed channels?

    <p>Inactivated channels cannot open, while closed channels can open</p> Signup and view all the answers

    What happens to the membrane voltage when K+ channels open?

    <p>The membrane voltage becomes more negative</p> Signup and view all the answers

    What happens to the membrane voltage when Na+ channels open?

    <p>The membrane voltage becomes more positive</p> Signup and view all the answers

    What happens during the after-hyperpolarization phase of an action potential?

    <p>The membrane potential becomes more negative</p> Signup and view all the answers

    What happens during the positive feedback loop of depolarization in an action potential?

    <p>The membrane potential becomes more positive</p> Signup and view all the answers

    During which phase of the action potential does the membrane voltage reach its peak?

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

    What is the approximate duration of an action potential?

    <p>2-4 ms</p> Signup and view all the answers

    What is the resting membrane potential (RMP) range?

    <p>-85 mV to -55 mV</p> Signup and view all the answers

    What is the primary determinant of the resting membrane potential (RMP)?

    <p>Leak and inward rectifier currents</p> Signup and view all the answers

    Which of the following accurately describes the effect of an increase in extracellular Na+ on the resting membrane potential (RMP)?

    <p>The RMP would become slightly less negative</p> Signup and view all the answers

    What would happen to the resting membrane potential if extracellular K+ suddenly increased?

    <p>The RMP would become less negative</p> Signup and view all the answers

    Why do graded potentials diminish over distance?

    <p>Voltage approaches zero as it travels along a resistor</p> Signup and view all the answers

    Why do axons need action potentials to propagate signals long distances?

    <p>Action potentials restore and re-amplify signals</p> Signup and view all the answers

    Which of the following is true about conduction velocity in neurons?

    <p>Alpha motor neurons have a higher conduction velocity than C fibers</p> Signup and view all the answers

    Which of the following structural features increases conduction velocity in neurons?

    <p>Larger diameter</p> Signup and view all the answers

    What is the effect of myelination on conduction velocity in neurons?

    <p>Increases conduction velocity</p> Signup and view all the answers

    What is the purpose of Nodes of Ranvier in myelinated axons?

    <p>Increase conduction velocity</p> Signup and view all the answers

    Which of the following is NOT a source of K+ permeability that causes K+ to flow out of the cell during the afterhyperpolarisation?

    <p>Outward rectifiers</p> Signup and view all the answers

    Which of the following is true about a graded potential?

    <p>It can occur at synapses</p> Signup and view all the answers

    What is the main transmembrane force on an ion at its equilibrium potential?

    <p>Chemical (diffusional) force</p> Signup and view all the answers

    Which of the following drug classes does NOT block sodium channels as part of their mechanism of action?

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

    Which of the following is true about the velocity of blood in the aorta?

    <p>It is approximately 1 meter/second</p> Signup and view all the answers

    Which of the following best describes the effect of selective serotonin reuptake inhibitors (SSRIs)?

    <p>They block the reuptake of serotonin from the synaptic cleft</p> Signup and view all the answers

    What would happen if the membrane suddenly became 100X more permeable to Cl¯ ions than to any other ion?

    <p>The membrane potential would become clamped to ECl (e.g. -65 mV)</p> Signup and view all the answers

    What is the definition of Na+ channel inactivation and how does it affect sodium channel activity during different phases of the action potential?

    <p>Na+ channel inactivation is the process whereby depolarization of the membrane leads to reduced (or eliminated) channel conductance. It reduces Na+ conduction during repolarization and after-hyperpolarization phases of the action potential.</p> Signup and view all the answers

    Which of the following is true about the resting membrane potential (RMP) under the influence of this drug?

    <p>The RMP will move up toward ECl, possibly going as high as -65 mV.</p> Signup and view all the answers

    What effect will the drug have on the repolarization of the action potential (AP)?

    <p>The repolarization of the AP will be delayed.</p> Signup and view all the answers

    What effect will the drug have on the duration of the action potential (AP)?

    <p>The duration of the AP will be longer.</p> Signup and view all the answers

    What effect will doubling the Na/K pump activity have on the resting membrane potential (RMP)?

    <p>The RMP will be hyperpolarized by 3 mV.</p> Signup and view all the answers

    What effect will half-blocking the K+ current have on the resting membrane potential (RMP)?

    <p>The RMP will be depolarized, possibly by as much as half.</p> Signup and view all the answers

    What effect will doubling the Na/K pump activity have on the electrogenic effects of the drug?

    <p>The electrogenic effects will be double.</p> Signup and view all the answers

    According to the text, what would happen if the delayed rectifier K+ channels opened immediately upon depolarization?

    <p>The action potential would repolarize faster and smaller</p> Signup and view all the answers

    According to the text, what are 5 ways to initiate a subthreshold stimulus in a neuron that might lead to an action potential?

    <p>EPSP from a synapse, an electrical signal from a nearby part of the same neuron, a signal via an electrical synapse, a receptor stimulus, a change in extracellular ion concentration</p> Signup and view all the answers

    According to the text, why does Vm become more negative than the RMP during the after-hyperpolarization?

    <p>Increased K+ current due to the delayed rectifier, decreased Na+ current, equivalent amount of inward rectifier K+ current</p> Signup and view all the answers

    According to the text, what would be the equilibrium potential of the nicotinic acetylcholine receptor if it is equally permeable to Na+ and K+?

    <p>-17.5 mV</p> Signup and view all the answers

    Which of the following channels is responsible for the initial depolarization in an action potential?

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

    What is the main transmembrane force on an ion at its equilibrium potential?

    <p>Chemical force</p> Signup and view all the answers

    Which of the following drugs raises the threshold and lowers excitability of neurons?

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

    What is the effect of myelination on conduction velocity in neurons?

    <p>Increases conduction velocity</p> Signup and view all the answers

    Which of the following best describes the effect of selective serotonin reuptake inhibitors (SSRIs)?

    <p>Inhibits serotonin reuptake</p> Signup and view all the answers

    What is the typical conduction velocity for alpha motor fibers?

    <p>50-75 m/s</p> Signup and view all the answers

    Which of the following is NOT a source of K+ permeability that causes K+ to flow out of the cell during the afterhyperpolarisation?

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

    What would be the membrane potential if both K+ channels and Na+ channels were open and if the cell was exactly equally permeable to Na+ and K+?

    <p>Resting membrane potential (RMP)</p> Signup and view all the answers

    What happens during the positive feedback loop of depolarization in an action potential?

    <p>Membrane voltage increases exponentially</p> Signup and view all the answers

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