HBF 102: Action Potential Quiz
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Questions and Answers

Which of the following statements accurately describes the function of action potentials in neurons?

  • Action potentials are essential for the mediated transmission of signals from neurons to target tissues. (correct)
  • Action potentials allow for the passive diffusion of neurotransmitters.
  • Action potentials decrease the excitability of neurons.
  • Action potentials are responsible for the synthesis of neurotransmitters.

What is a key characteristic of monophasic action potentials?

  • They are exclusive to muscle fibers and absent in neurons.
  • They exhibit multiple phases of depolarization and repolarization.
  • They require continuous stimulation to sustain.
  • They consist of only one phase of change in membrane potential. (correct)

Which of the following is NOT a prerequisite for understanding action potentials?

  • Mechanism of resting membrane potential.
  • Types of transport across the cell membrane.
  • Types of channels in the plasma membrane.
  • Types of neurotransmitter synthesis. (correct)

Which phase of the monophasic action potential is characterized by the influx of sodium ions?

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

What is the primary significance of action potentials in excitable tissues?

<p>They facilitate rapid communication through transient changes in membrane potential. (B)</p> Signup and view all the answers

What changes in excitability coincide with the occurrence of a monophasic action potential?

<p>Sudden decrease in excitability during the repolarization phase. (A)</p> Signup and view all the answers

Which term describes the state where there is no potential difference between the inner and outer surfaces of excitable tissue?

<p>Loss of polarity (B)</p> Signup and view all the answers

What is the maximum voltage reached during a reverse of polarity in excitable tissues?

<p>+35 (B)</p> Signup and view all the answers

What does repolarization achieve in excitable tissues?

<p>Return membrane potential to normal state (A)</p> Signup and view all the answers

Which of the following values indicates hyperpolarization?

<p>-80 or more (D)</p> Signup and view all the answers

What are local electrical changes in excitable tissue in response to subthreshold stimuli called?

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

Which of the following statements about action potentials is true?

<p>They are brief, self-propagating electrical changes. (D)</p> Signup and view all the answers

What does a decrease in negativity inside the cell during depolarization lead to?

<p>An increase in membrane potential towards a positive value (C)</p> Signup and view all the answers

Which ion is responsible for the rapid depolarization of a neuron during action potential generation?

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

What effect does the opening of sodium channels have on the membrane potential of a neuron?

<p>It results in a rapid increase in membrane potential. (D)</p> Signup and view all the answers

What is the role of the inactivation gate of the voltage-gated sodium channel?

<p>To prevent excessive sodium influx after depolarization. (A)</p> Signup and view all the answers

During which phase does the sodium-potassium pump primarily contribute to restoring the resting membrane potential?

<p>Repolarization (A)</p> Signup and view all the answers

What triggers the opening of voltage-gated sodium channels in neurons?

<p>A change in membrane potential reaching a certain threshold. (B)</p> Signup and view all the answers

What is the primary role of action potentials in excitable tissues?

<p>They allow for communication between neurons and other cells. (D)</p> Signup and view all the answers

Which of the following processes is NOT associated with action potentials?

<p>Cellular respiration enhancement. (B)</p> Signup and view all the answers

In the context of medical diagnostics, which of the following techniques utilizes the concept of action potentials?

<p>EEG (Electroencephalography). (B)</p> Signup and view all the answers

Which of the following best characterizes the action potential's importance in neuroscience research?

<p>It provides insights into neural communication mechanisms. (B)</p> Signup and view all the answers

Which phase of the monophasic action potential is characterized by rapid depolarization?

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

Action potentials can be classified into different types. Which type is characterized by a gradual increase in membrane potential?

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

Which of the following statements regarding action potentials is incorrect?

<p>They can change in magnitude based on stimulus strength. (A)</p> Signup and view all the answers

What is the key role of action potentials in excitation-contraction coupling?

<p>They initiate contraction of muscle fibers. (B)</p> Signup and view all the answers

Which of the following accurately describes a characteristic of action potentials?

<p>They exhibit a threshold voltage that must be reached. (D)</p> Signup and view all the answers

Which of the following is NOT a function of action potentials in excitable cells?

<p>Transmission of genetic information. (B)</p> Signup and view all the answers

Which type of action potential is characterized by a single phase?

<p>Monophasic Action Potential (B)</p> Signup and view all the answers

What type of action potential is associated with nodal cardiac muscle?

<p>Monophasic Action Potential (C)</p> Signup and view all the answers

Which of the following is NOT a type of action potential mentioned?

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

Monophasic action potentials can be observed in which of the following tissues?

<p>Skeletal muscle and large sized nerves (C)</p> Signup and view all the answers

What action potential type is typically associated with cardiac muscle tissue that does not exhibit nodes?

<p>Monophasic Action Potential (B)</p> Signup and view all the answers

How many types of action potentials are explicitly listed in the provided content?

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

In the context of electrical activities, which phase characteristic is associated with monophasic action potentials?

<p>Single depolarization phase (C)</p> Signup and view all the answers

Which statement accurately describes a biphasic action potential?

<p>It consists of both depolarization and repolarization phases. (B)</p> Signup and view all the answers

What objective will students NOT achieve by the end of the lecture?

<p>Determine voltage thresholds for action potentials (A)</p> Signup and view all the answers

Which of the following describe the mechanism of action potentials?

<p>Involves sodium influx followed by potassium efflux (D)</p> Signup and view all the answers

Flashcards

Action Potential Definition

The electrical signal that transmits information from neurons to their target tissues.

Action Potential Importance

Crucial for communication between nerves and target tissues.

Monophasic Action Potential

A single electrical waveform in action potential.

Phases of Action Potential

Different stages in a single action potential waveform.

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Excitability Changes

Changes in a cell's responsiveness to stimuli during an action potential.

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Electrophysiology

The study of electrical phenomena in biological systems.

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Electrical activity

Change of voltage between two points in the nervous system.

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Resting Membrane Potential

The potential difference between the outer and inner surfaces of excitable tissue at rest.

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Depolarization

Increasing membrane potential toward a positive value, decreasing the negativity inside the cell.

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Loss of Polarity

No potential difference between the outer and inner surfaces of excitable tissue.

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Reverse of Polarity

The inner surface of the membrane is positive compared to the outer surface.

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Repolarization

Return of the membrane potential to the normal resting state.

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Hyperpolarization

The inner surface of the membrane becomes more negative than the resting state.

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Action Potential

A series of brief, self-propagating electrical changes in excitable tissue due to adequate stimulation.

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Electrotonus

Local electrical changes in excitable tissue from a subthreshold stimulus.

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Electrical Activities of Excitable Tissue

A group of processes involving changes in electrical potential across the cell membrane, crucial for the cell's function.

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Nerve Impulse Transmission

Communication between neurons and other cells using action potentials.

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Excitation-Contraction Coupling

How electrical signals (action potentials) trigger muscle contraction.

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Excitation-Secretion Coupling

How electrical signals trigger release of neurotransmitters or hormones.

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Types of Action Potentials

Different forms based on the specific excitable tissue and stimuli.

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ECG

Electrocardiogram; a medical diagnostic tool for measuring electrical activity of the heart.

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EEG

Electroencephalogram; a medical diagnostic tool for measuring electrical activity of the brain.

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Medical Diagnosis

Using action potentials to assess conditions; an example is the electrocardiogram (ECG).

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Neuroscience and AI

Research area focusing on how action potentials relate to brain function and computation.

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What causes rapid depolarization?

The rapid influx of sodium ions through open voltage-gated sodium channels causes the membrane potential to rise quickly, leading to a steep depolarization of the cell.

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What is the role of the inactivation gate?

The inactivation gate closes shortly after the activation gate opens, limiting the influx of sodium ions and preventing excessive depolarization.

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What happens to the membrane potential during depolarization?

The membrane potential becomes more positive as sodium ions enter the cell, moving it closer to the threshold for triggering an action potential.

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What is the resting membrane potential (RMP)?

The RMP is the stable, negative charge of a neuron when it is at rest, maintained by the Na+/K+ pump and selective ion permeability of the membrane.

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What is the role of the sodium-potassium pump?

The Na+/K+ pump actively transports sodium ions out of the cell and potassium ions into the cell, contributing to maintaining the RMP and restoring the ion concentration gradients after an action potential.

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Biphasic Action Potential

A type of electrical signal in excitable tissues characterized by two distinct waveforms.

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Compound Action Potential

A type of electrical signal resulting from the combined action potentials of multiple excitable cells.

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Medium Sized Nerve Action Potential

Monophasic action potential of a nerve with intermediate size.

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Large Sized Nerve Action Potential

Monophasic action potential of a large nerve.

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Skeletal Muscle Action Potential

Monophasic action potential of skeletal muscle tissue.

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Non-nodal Ventricular Cardiac Muscle Action Potential

Monophasic action potential unique to non-nodal cardiac muscle cells.

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Nodal Cardiac Muscle Action Potential

Monophasic action potential of specialized cardiac muscle cells in the conduction system.

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Action Potential Phases

Different stages within the electrical event; like rising, peaking, and falling phases.

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Study Notes

Course Information

  • Academic Year: 2024-2025
  • Year: 1
  • Semester: 1
  • Module: Human Body Function (HBF) 102
  • Faculty: Medicine
  • University: Helwan National University

Action Potential

  • Topic: Action Potential
  • Presented by: Ashraf Algendy, Professor
  • Department: Medical Physiology

Prerequisites

  • Understanding different channels in the plasma membrane
  • Defining and understanding the mechanism of resting membrane potential
  • Knowing different types of transport across the cell membrane

Objectives

  • Understanding essential terminology related to different electrical activities of excitable tissues
  • Defining different electrical activities of excitable tissues
  • Clarifying the importance of action potential
  • Listing and discriminating different types of action potential
  • Drawing and labeling different phases of monophasic action potential
  • Explaining the mechanism of different phases of monophasic action potential
  • Recognizing excitability changes that coincide with monophasic action potential

Introduction

  • Communication between nerves and target tissues was previously unknown to physiologists.
  • The discovery of electrical activity in neurons, with the development of electrophysiology, demonstrated that action potentials mediate signal transmission.

Polarization

  • Polarization is the potential difference between the inner and outer surface of an excitable tissue during rest.
  • A medium-sized nerve has a value of -70 mV.

Depolarization

  • Depolarization is raising the membrane potential towards a positive value, reducing negativity inside the cell.
  • The value ranges from -69 to -1 mV.

Loss of Polarity

  • When there is no potential difference between the outer and inner surface of the excitable tissue, this is called loss of polarity.
  • The value is zero.

Reverse of Polarity

  • If the inner membrane is more positive in relation to the outer membrane, it is called reverse of polarity.
  • The value ranges from +0 to +35 mV.

Repolarization

  • Repolarization is the return of the membrane potential to its normal state.
  • The value is -70 mV.

Hyperpolarization

  • The inner surface of the membrane becomes more negative than its' resting state.
  • The value is -80 mV or greater.

Action Potential Types

  • Types of action potentials include: Monophasic, Biphasic, and Compound.

Electrical Activities of Excitable Tissues

  • The electrical activities of excitable tissue include resting membrane potential, electrotonus, and action potential.

Monophasic Action Potential of a Medium-sized Nerve

  • Describes an action potential
  • Medium sized nerve.

Monophasic Action Potential of a Large Nerve/Skeletal Muscle

  • Describes action potential of larger nerves and skeletal muscle.

Monophasic Action Potential of Non-nodal Ventricular Cardiac Muscle

  • Describes action potential of non-nodal ventricular, hearts muscle.

Monophasic Action Potential of Nodal Cardiac Muscle

  • Describes nodal cardiac muscle action potential.

Excitability Changes

  • Absolute refractory period (ARP): Excitability is zero, no response regardless of stimulus strength.
  • Relative refractory period (RRP): Excitability is greater than zero but less than normal, only suprathreshold stimuli cause a response.
  • Supernormal period (SNP): Excitability is higher than normal, subthreshold stimuli can produce a response.
  • Subnormal period (SubNP): Excitability is greater than zero but less than normal, only suprathreshold stimuli cause a response.

Clinical Significance of Action Potential

  • Nerve impulse transmission: Action potentials are the basis for nerve impulse transmission, allowing for communication between neurons and other cells.
  • Excitation-contraction coupling: Crucial for muscle contractions.
  • Excitation-secretion coupling: Essential for neurotransmitter release.
  • Medical diagnosis: Used in ECG, EEG, and EM for medical diagnosis.
  • Neuroscience and AI research: Essential for research in these fields.

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Description

Test your understanding of action potential in excitable tissues with this quiz designed for Human Body Function (HBF) 102. You'll encounter questions on essential terminology, mechanisms, and phases of monophasic action potential. Make sure you're well-versed in the prerequisites for a successful attempt!

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