Neuroscience: Action Potentials Overview
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Questions and Answers

What is the resting membrane potential of a typical neuron?

  • -70 mV (correct)
  • +70 mV
  • -40 mV
  • 0 mV

    • Action potentials can vary in strength depending on the stimulus.

    False

    Which two ions are most important in generating and maintaining the resting potential in neurons?

    potassium (K+) and sodium (Na+)

    The movement of __________ ions is primarily responsible for the cell's resting membrane potential.

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

    Match the following terms with their descriptions.

    <p>Action Potential = An all-or-nothing electrical impulse Resting Potential = The net electric potential difference at rest Potassium Leak Channels = Facilitate the outward movement of potassium Equilibrium = No net movement of ions due to balanced forces</p> Signup and view all the answers

    What happens to potassium ions as negative charge builds up inside the neuron?

    <p>Potassium ions are drawn back into the cell</p> Signup and view all the answers

    The outside of a resting neuron is slightly positively charged compared to the inside.

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

    What is the process called when the nerve signal 'hops' from node to node?

    <p>Saltatory conduction</p> Signup and view all the answers

    All action potentials within the same type of neuron have different potential differences during depolarization.

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

    What are the two types of neurons based on the effect of neurotransmitters?

    <p>Excitatory and inhibitory</p> Signup and view all the answers

    The small space between neurons is called the ______.

    <p>synaptic cleft</p> Signup and view all the answers

    Match the following neurotransmitter mechanisms with their descriptions:

    <p>Enzymatic breakdown = Neurotransmitter is destroyed by enzymes Reuptake = Neurotransmitter is returned to the presynaptic neuron Diffusion = Neurotransmitter moves out of the synaptic cleft</p> Signup and view all the answers

    Which neurotransmitter is broken down by acetylcholinesterase?

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

    Neurotransmitters can only be removed from the synaptic cleft by enzymatic reactions.

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

    What triggers the release of neurotransmitters from synaptic vesicles?

    <p>Increase in intracellular calcium</p> Signup and view all the answers

    Neurons communicating with glands or muscles are called ______ cells.

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

    What triggers the opening of voltage-gated sodium channels?

    <p>Change in membrane potential (depolarization)</p> Signup and view all the answers

    During depolarization, the inside of the cell becomes more negative.

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

    What are the three states of sodium channels?

    <p>Closed, Open, Inactive</p> Signup and view all the answers

    The ______ pump helps restore the resting potential after an action potential.

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

    What happens during the absolute refractory period?

    <p>The neuron cannot fire another action potential regardless of stimuli.</p> Signup and view all the answers

    Match the terms with their definitions:

    <p>Depolarization = The process of the membrane potential becoming more positive Repolarization = The process of returning to a more negative potential Hyperpolarization = The membrane potential becoming more negative than resting potential Refractory period = A time when a neuron cannot fire again easily</p> Signup and view all the answers

    Potassium ions efflux contributes to depolarization of the neuron.

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

    What effect does tetrodotoxin have on neuronal transmission?

    <p>It blocks voltage-gated sodium channels.</p> Signup and view all the answers

    Which factor more significantly affects the speed of action potential propagation?

    <p>Cross-sectional area of the axon</p> Signup and view all the answers

    Local anesthetics enhance pain perception by blocking sodium channels.

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

    What causes hyperpolarization of the neuron?

    <p>Efflux of potassium ions</p> Signup and view all the answers

    Match the effects to their causes:

    <p>Opening of sodium channels = Depolarization Opening of potassium channels = Repolarization and hyperpolarization Blockage of sodium channels = Decreased neuronal transmission Increased cross-sectional area = Faster action potential propagation</p> Signup and view all the answers

    What is the resting potential of a neuron?

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

    What is the equilibrium potential of potassium?

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

    What effect does sodium have on the resting membrane potential?

    <p>Pulls it toward +60 mV</p> Signup and view all the answers

    Potassium's equilibrium potential is positive.

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

    What is the typical resting membrane potential of an average nerve cell?

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

    The process of Na+/K+ ATPase pumps sodium ______ the cell and potassium ______ the cell.

    Signup and view all the answers

    What is the equilibrium potential of potassium?

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

    The equilibrium potential of sodium is negative.

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

    What is the term for the additive effect of multiple signals received by a postsynaptic neuron?

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

    The resting membrane potential of a typical nerve cell is around __________ mV.

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

    Match the following ions with their equilibrium potentials:

    <p>Potassium = -90 mV Sodium = +60 mV</p> Signup and view all the answers

    Which of the following is a reason why potassium has a stronger influence on the resting potential?

    <p>The cell membrane is more permeable to potassium</p> Signup and view all the answers

    Both sodium and potassium ions are continuously leaking across the cell membrane.

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

    What process do neurons use to maintain ion concentration gradients against their natural tendency?

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

    In spatial summation, the additive effects depend on the __________ and location of incoming signals.

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

    What role does the axon hillock play in action potential generation?

    <p>It integrates excitatory and inhibitory inputs</p> Signup and view all the answers

    The influx of sodium ions tends to hyperpolarize the neuron.

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

    What is the typical concentration of sodium inside the cell in mM?

    <p>12 mM</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Temporal summation = Integration of signals over a short period Hyperpolarization = Decrease in membrane potential Depolarization = Increase in membrane potential</p> Signup and view all the answers

    The electric potential due to a small amount of potassium exiting is called the __________ potential.

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

    What is the primary function of Na+/K+ ATPase beyond maintaining resting potential?

    <p>Pumping ions against their gradients</p> Signup and view all the answers

    Study Notes

    Action Potentials

    • Action potentials are all-or-nothing electrical messages used by neurons to relay impulses down the axon.
    • Trigger the release of neurotransmitters into the synaptic cleft.

    Resting Potential

    • Resting membrane potential averages around -70 mV, with the inside of the neuron being negative compared to the outside.
    • Key ions: potassium (K+) is about 140 mM inside the cell and 4 mM outside; sodium (Na+) is about 12 mM inside and 145 mM outside.
    • Potassium's equilibrium potential is around -90 mV; sodium's equilibrium potential is around +60 mV.
    • The resting potential results from the opposing movements of sodium and potassium, maintaining a balance around -70 mV.

    Mechanisms Maintaining Resting Potential

    • Na+/K+ ATPase continuously pumps Na+ out of the cell and K+ into the cell, consuming more ATP than any other cellular activity.
    • Ion leakage is facilitated by specific ion channels for both sodium and potassium.

    Axon Hillock

    • The axon hillock integrates excitatory and inhibitory inputs, determining whether an action potential is fired.
    • Action potentials are triggered if the membrane potential reaches a threshold of about -55 to -40 mV due to excitatory input.
    • Summation of signals occurs through temporal (timing) and spatial (location and number) summation.

    Ion Channels and Action Potential Phases

    • Upon reaching threshold, voltage-gated sodium channels open, allowing Na+ to flood into the cell (depolarization).
    • Sodium channels become inactive at +35 mV; potassium channels then open, allowing K+ to exit (repolarization), leading to a temporary hyperpolarization.
    • Absolute refractory period: no action potential can occur; relative refractory period: requires stronger stimulation for action potential.

    Impulse Propagation

    • Action potentials propagate along the axon via depolarization of adjacent sections, allowing only unidirectional signal flow due to refractory periods.
    • Myelin insulation allows for faster conduction through saltatory conduction, as action potentials jump between nodes of Ranvier.

    Synaptic Transmission

    • The synapse is the gap between neurons where neurotransmitters are released from the presynaptic neuron to affect the postsynaptic neuron.
    • Neurotransmitters are stored in vesicles and released upon action potential-induced calcium influx, leading to exocytosis.

    Regulation of Neurotransmission

    • Neurotransmission is terminated through enzymatic breakdown, reuptake by presynaptic neurons, or diffusion away from the synaptic cleft.
    • Acetylcholine (ACh) is broken down by acetylcholinesterase; serotonin (5-HT) is reabsorbed via reuptake carriers.

    Key Concepts

    • The distinction between electrical (within the neuron) and chemical (between neurons) transmission of signals is crucial for understanding neurobiology.
    • Increased stimulus intensity results in a greater frequency of action potentials rather than higher voltage of individual action potentials.

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    Description

    Explore the fundamental concepts of action potentials and resting potentials in neurons. This quiz delves into how electrical impulses are generated and transmitted, as well as the implications for neurotransmitter release. Understand the key mechanisms that underlie neuronal communication.

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