Neuron Structure and Function
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Questions and Answers

What is the purpose of the six precordial, unipolar chest leads?

  • To record ECGs in the transverse plane (correct)
  • To measure electrical signals from the brain
  • To obtain ECGs in the frontal plane
  • To measure atrial repolarization

    • What is the aVR lead connected to?

  • LL and the center of two resistors connected to LA and RA
  • LA and LL
  • RA and the center of two resistors connected to LL and LA (correct)
  • RA and LL

    • What event produces the QRS complex?

  • Ventricular depolarization (correct)
  • Atrial depolarization
  • Ventricular repolarization
  • Atrial repolarization

    • What type of signals are obtained when measuring electrical activity from the brain?

    <p>Weak complex electrical signals</p> Signup and view all the answers

    What is the name of the recording of the signals from the brain?

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

    What is the purpose of the reference electrode in EEG?

    <p>To provide a reference point for the signals</p> Signup and view all the answers

    What type of electrodes are often used for recording EEG signals?

    <p>Small discs of chlorided silver</p> Signup and view all the answers

    What is the location of the reference electrode in EEG?

    <p>On the ear (A1 or A2)</p> Signup and view all the answers

    What is the insulating layer that covers the axons of myelinated nerves?

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

    Which type of nerve fiber conducts action potentials faster?

    <p>Myelinated nerves</p> Signup and view all the answers

    What is the approximate spacing between the nodes of Ranvier in a myelinated nerve fiber?

    <p>280a</p> Signup and view all the answers

    Which of the following factors affects the propagation speed of an action potential?

    <p>Both a and b</p> Signup and view all the answers

    How does the diameter of an axon affect the propagation speed of an action potential?

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

    What is the approximate conduction speed (in m/s) of an unmyelinated nerve fiber with a radius of 0.2 μm?

    <p>3.6</p> Signup and view all the answers

    What is the electromyogram (EMG)?

    <p>A record of the potentials from muscles during movement</p> Signup and view all the answers

    What is the relationship between capacitance and propagation speed of an action potential?

    <p>Inversely proportional</p> Signup and view all the answers

    What frequency range is associated with alpha waves?

    <p>8 to 13 Hz</p> Signup and view all the answers

    What physiological activity can interfere with EEG signal processing?

    <p>Muscle activity</p> Signup and view all the answers

    What is the function of electrodes in an electroretinogram (ERG)?

    <p>To record changes in potential from the retina</p> Signup and view all the answers

    Which wave is clinically significant due to its absence in retinal inflammation?

    <p>B wave</p> Signup and view all the answers

    What type of signal is recorded by an electrooculogram (EOG)?

    <p>Potential changes due to eye movement</p> Signup and view all the answers

    What does a higher frequency EEG signal indicate about a person's mental state?

    <p>The person is alert and focused</p> Signup and view all the answers

    Which of the following is not a type of brain wave recorded in EEG?

    <p>Gallop waves</p> Signup and view all the answers

    What initiates the electrical signal that controls the rhythmical action of the heart?

    <p>Sinoatrial node</p> Signup and view all the answers

    What is typically caused by external electrical signals in EEG processing?

    <p>Artifacts in the recordings</p> Signup and view all the answers

    How many times does the sinoatrial node typically fire in a minute?

    <p>72 times</p> Signup and view all the answers

    Which part of the heart does the electrical signal travel to after the atria contract?

    <p>Atrioventricular node</p> Signup and view all the answers

    What do the electrodes used for an electrocardiogram primarily measure?

    <p>Electrical potentials generated by the heart</p> Signup and view all the answers

    Where are the standard limb leads primarily located for obtaining an ECG?

    <p>Left arm, right arm, and left leg</p> Signup and view all the answers

    What is the measurement of the potential between the right arm and left arm called?

    <p>Lead I</p> Signup and view all the answers

    What happens to the atria after they contract and pump blood into the ventricles?

    <p>They undergo repolarization</p> Signup and view all the answers

    What is the main function of the electrocardiogram (ECG)?

    <p>To record heart electrical activity</p> Signup and view all the answers

    What is the typical voltage difference between the inside and outside of a neuron at rest?

    <p>-60 to -90 mV</p> Signup and view all the answers

    What happens to the membrane of an axon when it is stimulated?

    <p>It becomes permeable to both Na+ and K+ ions.</p> Signup and view all the answers

    What is the term for the process of restoring the resting potential after an action potential?

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

    What is the function of the myelin sheath?

    <p>To insulate the axon and speed up the transmission of nerve impulses.</p> Signup and view all the answers

    What is the term for the regions of the axon that are not covered by the myelin sheath?

    <p>Nodes of Ranvier</p> Signup and view all the answers

    What is the role of the action potential in nerve signal transmission?

    <p>It allows for communication between neurons.</p> Signup and view all the answers

    What is the typical voltage inside an axon during depolarization?

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

    What is the main factor that contributes to the resting potential of a neuron?

    <p>The presence of more negative ions inside the cell than outside.</p> Signup and view all the answers

    Study Notes

    Electrical Potentials of Nerves

    • Neurons are usually insulated by a myelin sheath, except at Nodes of Synapse where signal transparency allows one-directional flow.
    • The resting potential of a neuron is a voltage difference across the membrane, ranging from -60 to -90 mV, indicating polarization with more negative ions inside.

    Action Potential

    • When a neuron is stimulated, resting potential changes, and action potential propagates along the axon.
    • Depolarization occurs due to Na+ ions entering the neuron, causing the inside to briefly reach +50 mV.
    • Repolarization follows as K+ ions exit, restoring the resting potential.

    Types of Nerve Fibers

    • Myelinated Nerves:
      • Covered with myelin sheath and Nodes of Ranvier are present.
      • Conduct action potentials faster due to low electrical capacitance.
      • Conduction speed formula: u ≈ 12(a + b), where (a) is the axon's radius and (b) is myelin thickness.
    • Unmyelinated Nerves:
      • Make up about 2/3 of axon fibers in the body.
      • Radii range from 0.05 to 0.6 μm; speed of conduction is slower, approximated by u ≈ 1.8 √a.

    Factors Affecting Action Potential Propagation Speed

    • Speed is influenced by resistance within the axon core and capacitance across the membrane.
    • Larger axon diameters decrease internal resistance, increasing velocity.
    • Greater stored charge (capacitance) slows down depolarization and action potential speed.

    Electrical Signals from Muscles

    • Electromyogram (EMG) records electrical activity in muscles during movement for diagnostic purposes.

    Electrical Signals from the Heart

    • The sinoatrial (SA) node acts as the heart's pacemaker, firing approximately 72 times per minute to initiate the cardiac cycle.
    • Depolarization spreads from the SA node to the atria, followed by repolarization.
    • Atrioventricular (AV) node further propagates the electrical signal to the ventricles.

    Electrocardiogram (ECG)

    • ECG measures heart potentials through surface electrodes, typically placed on the left arm, right arm, and left leg.
    • Standard limb leads include Lead I (RA to LA), Lead II (RA to LL), and Lead III (LA to LL).
    • Augmented leads (aVR, aVL, aVF) measure potential in different configurations.
    • Six additional precordial leads (V1-V6) are positioned across the chest wall for comprehensive cardiac monitoring.

    Heart Cycle Electrical Events

    • P wave: Atrial depolarization.
    • QRS complex: Ventricular depolarization.
    • T wave: Ventricular repolarization.

    Electrical Signals from the Brain

    • Electroencephalogram (EEG) records weak electrical activity from the brain's cortex.
    • Electrodes are typically attached to the scalp, with a reference electrode placed on the ear.
    • EEG frequency bands include alpha (8-13 Hz), beta (above 13 Hz), delta (0.5-3.5 Hz), and theta (4-7 Hz), correlating with mental states.

    Electrical Signals from the Eye

    • Electroretinogram (ERG) measures electrical potential changes in response to light, using electrodes placed on the cornea and another on the ear or forehead.
    • B wave is significant clinically; its absence indicates retinal inflammation.
    • Electrooculogram (EOG) records eye movement potential changes, providing insight into eye orientation and motion dynamics.

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    Description

    Quiz about the structure and function of neurons, including the myelin sheath, nodes of synapse, and electrical potentials.

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