Neuronal Physiology Quiz

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Questions and Answers

What type of potential is generated at the dendrites of a neuron?

  • Action potential
  • Resting potential
  • Synaptic potential
  • Graded potential (correct)

Which of the following is NOT a characteristic of action potentials?

  • They are initiated at the axon hillock
  • They are all-or-nothing events
  • They can be summed (correct)
  • They travel along the axon without decrement

What is the role of the myelin sheath in neuronal communication?

  • It helps to generate action potentials
  • It prevents the leakage of ions from the axon
  • It acts as a neurotransmitter receptor
  • It increases the speed of action potential conduction (correct)

Which of the following is responsible for the repolarization phase of an action potential?

<p>Potassium ion efflux (A)</p> Signup and view all the answers

What is the primary method of communication between neurons?

<p>Chemical synapses (C)</p> Signup and view all the answers

How does the inactivation gate of voltage-gated sodium channels (VGSCs) contribute to the refractory period?

<p>The inactivation gate closes, preventing further sodium influx and contributing to the repolarization phase. (B)</p> Signup and view all the answers

What is the primary role of the sodium-potassium pump (Na+-K+-ATPase) in action potential propagation?

<p>To maintain the resting membrane potential by actively transporting sodium ions out of the cell and potassium ions into the cell. (A)</p> Signup and view all the answers

Which of the following statements accurately describes the relationship between action potential frequency and stimulus strength?

<p>A stronger stimulus causes a higher frequency of action potentials, but the amplitude remains constant. (D)</p> Signup and view all the answers

How does myelination contribute to the speed of action potential propagation?

<p>Myelination reduces the resistance of the axonal membrane, speeding up the speed of conduction. (D)</p> Signup and view all the answers

How does the diameter of a nerve fiber influence the speed of action potential propagation?

<p>A larger diameter nerve fiber has a lower resistance, speeding up the speed of conduction. (A)</p> Signup and view all the answers

Why is the 'all-or-none' principle important for action potential transmission?

<p>It guarantees that each action potential is propagated with the same strength and speed, regardless of the strength of the stimulus. (D)</p> Signup and view all the answers

What is the primary difference between graded potentials and action potentials?

<p>Graded potentials can be summed, while action potentials are 'all-or-none' events. (A)</p> Signup and view all the answers

Which of the following best describes the role of voltage-gated potassium channels (VGPCs) in action potential propagation?

<p>They open during repolarization, allowing potassium efflux and contributing to the falling phase of the action potential. (C)</p> Signup and view all the answers

Which of these statements about graded potentials is NOT true?

<p>Graded potentials can travel long distances without decrement, making them ideal for long-distance signal transmission. (B)</p> Signup and view all the answers

What is the primary function of the axon hillock?

<p>To generate and propagate action potentials. (B)</p> Signup and view all the answers

Which of the following is NOT a characteristic of a graded potential?

<p>They propagate in a unidirectional manner along the neuron. (C)</p> Signup and view all the answers

Which type of potential is responsible for initiating an action potential at the axon hillock?

<p>Postsynaptic potential (C)</p> Signup and view all the answers

What is the primary function of dendrites?

<p>To receive and integrate incoming signals from other neurons. (D)</p> Signup and view all the answers

A drug that blocks the reuptake of a neurotransmitter would likely have what effect on synaptic transmission?

<p>Increase the intensity of the signal transmitted across the synapse. (C)</p> Signup and view all the answers

Which of these statements about action potentials is true?

<p>Action potentials are all-or-none, meaning they either occur with full amplitude or not at all. (C)</p> Signup and view all the answers

How do myelin sheaths affect the propagation of action potentials?

<p>Myelin sheaths increase the speed of action potential propagation. (B)</p> Signup and view all the answers

Which of the following is an example of a graded potential?

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

Which of the following statements about the neuron's trigger zone is true?

<p>It is the region where action potentials are initiated. (D)</p> Signup and view all the answers

Flashcards

Neuron Structure

Neurons consist of cell bodies, dendrites, and axons.

Graded Potentials

Localized changes in membrane potential that vary in magnitude.

Action Potentials

Rapid, all-or-nothing electrical signals that travel along axons.

Neuron Communication

Neurons transfer electrical signals via synapses and neurotransmitters.

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Neuronal Linkage

Neurons are linked together through synaptic connections.

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Dendrites

Input zones of neurons that receive signals and contain neurotransmitter receptors.

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Axon Terminals

Output zones of neurons that release neurotransmitters to communicate with other neurons.

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Axon Hillock

Trigger zone where action potentials are initiated, containing many voltage-gated sodium channels.

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Characteristics of Graded Potentials

Magnitude and duration are proportional to the stimulus strength and die out over short distances.

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Summation of Graded Potentials

Multiple graded potentials can add together to potentially initiate an action potential.

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Neurotransmitters

Chemical messengers released from axon terminals to communicate between neurons.

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Neuropeptides

Small protein-like molecules used by neurons to communicate with each other, often having modulatory effects.

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Influences on Synaptic Activity

Drugs and diseases can affect how well neurotransmitters function at synapses, altering neural communication.

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Magnitude & Duration of Action Potentials

Action potentials have a consistent magnitude and duration of 1 millisecond.

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Long-Distance Signals

Action potentials do not die out and can travel long distances.

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Voltage-Gated Channels Action

Action potentials arise from changes in permeability due to voltage-gated sodium and potassium channels.

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Contiguous Conduction

Action potentials are conducted in a contiguous manner in unmyelinated neurons.

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One Direction Propagation

Action potentials propagate in only one direction along the axon.

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Refractory Period

During the refractory period, voltage-gated sodium channels cannot be reopened.

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Stimulus Strength and Frequency

The frequency of action potentials increases with the strength of the stimulus.

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All-or-None Principle

Action potentials occur in an all-or-nothing fashion; either they happen fully or not at all.

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Study Notes

Neuronal Physiology

  • This study guide covers neuronal physiology, focusing on neurons, electrical signals, synapses, and the effects of drugs/diseases on synaptic activity.

Lecture Objectives

  • Understand the structure of neurons and how they connect.
  • Learn about graded potentials and action potentials as neuronal electrical signals.
  • Explore how neurons transmit electrical signals across synapses.
  • Examine the role of neurotransmitters and neuropeptides in synaptic transmission.
  • Investigate how drugs and diseases affect synaptic activity.

Structure of the Neuron

  • Dendrites: Input zone, increasing surface area for receiving signals, containing receptors for neurotransmitters. Initial graded potentials.
  • Axon Hillock: Trigger zone, initiating action potentials; abundant voltage-gated sodium channels.
  • Axon/Nerve Fiber: Single elongated tubular structure, often myelinated, carrying signals away from cell body.
  • Cell Body (Soma): Nucleus, organelles, basic cell functions.

Neuronal Linkage

  • Converging input: One neuron receives input from thousands of others.
  • Diverging output: One neuron influences thousands of other neurons.

Graded Potentials

  • Local changes in membrane potential (RMP) strength proportional to stimulus.
  • Varying grades, not all-or-none
  • examples include receptor potentials, postsynaptic potentials, pacemaker potentials, and slow-wave potentials.
  • Spread passively as local currents.
  • Die out over short distances.

Action Potentials

  • Brief, rapid, large changes in membrane potential, where the inside of the cell becomes more positive.
  • Differ from graded potentials by being all-or-none and propagating without diminishing strength.
  • Generated at trigger zone.
  • Serve as long-distance signals.

Action Potential Characteristics

  • Conduction along an axon: Adjacent inactive areas are brought to threshold by local current flow, leading to action potential propagation.
  • Propagation in one direction: Current flow is unidirectional.
  • Refractory period: Absolute refractory period prevents backward propagation and limits the rate of action potential generation.

Action Potential Mechanisms and Channels

  • Voltage-Gated Sodium Channels:
    • Rapid opening at threshold, followed by inactivation.
  • Voltage-Gated Potassium Channels:
    • Delayed opening, repolarizing the cell.

Refractory Period

  • Absolute Refractory Period: Impossible to generate another action potential due to sodium channels being inactivated.
  • Relative Refractory Period: More difficult to generate an action potential due to potassium channels being open.
  • Essential for unidirectional signal transmission.

Frequency of Action Potentials

  • The frequency (how often) depends on stimulus strength.
  • Stronger stimulus generates higher frequency than weak stimulus.

Speed of Action Potentials, Diameter and Myelin

  • Speed increases with larger axon diameter.
  • Myelination increases the speed of action potential propagation by saltatory conduction, jumping between nodes of Ranvier.

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