Electricity in the Nervous System
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Questions and Answers

Electricity plays an important role in medicine.

True (A)

What are the two aspects of electricity and magnetism in medicine?

  • Applications of electricity and magnetism to the surface of the body. (correct)
  • Applications of electricity and magnetism to the interior of the body.
  • Electrical and magnetic effects generated inside the body. (correct)
  • Electrical and magnetic effects generated outside the body.

    • What serves as the control and operation of nerves, muscles, and organs?

    Electricity generated inside the body

    What is the fundamental unit of the nervous system?

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

    What are the two parts that the nervous system can be divided into?

    <p>Central nervous system and autonomic nervous system</p> Signup and view all the answers

    What does the central nervous system consist of?

    <p>Both A and B (C)</p> Signup and view all the answers

    What are the two types of nerve fibers in the peripheral nervous system?

    <p>Efferent nerves (B), Afferent nerves (C)</p> Signup and view all the answers

    The control of the autonomic nervous system is voluntary.

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

    What are the functions of a neuron?

    <p>Reception, interpretation, and transmission of electrical signals or messages.</p> Signup and view all the answers

    Which part of the neuron receives electrical messages from other neurons?

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

    The soma of a neuron contains the nucleus.

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

    Dendrites are specialized extensions of the cell body that carry information to the cell body from other cells.

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

    What is the function of the axon?

    <p>It carries electrical messages away from the cell body.</p> Signup and view all the answers

    Axons are typically 1 meter long.

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

    Where are the signals from a neuron transmitted?

    <p>To muscles, glands, or other neurons.</p> Signup and view all the answers

    What is the basic unit of communication in the brain?

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

    A chemical neurotransmitter is released from one cell and binds to receptors on the second cell.

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

    What is the name of the potential difference created between the two environments of a cell?

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

    The bio-potential can be measured using electrodes.

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

    What are the two types of bio potential?

    <p>Resting potential (A), Action potential (D)</p> Signup and view all the answers

    The inside of a cell is typically 60 to 90 mV more positive than the outside.

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

    What is the term used to describe the large momentary change in resting potential that occurs when a neuron is stimulated?

    <p>action potential</p> Signup and view all the answers

    The action potential propagates along the axon.

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

    The action potential is the major method of transmission of signals within the body.

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

    What is the record of the potentials from muscles during movement called?

    <p>electromyogram or EMG</p> Signup and view all the answers

    A muscle is made up of many motor units.

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

    What does a motor unit consist of?

    <p>Both A and B (C)</p> Signup and view all the answers

    Muscle action is initiated by an action potential that travels along an axon and is transmitted across the motor end plates into the muscle fibers.

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

    It is easy to isolate a single muscle fiber during an EMG examination.

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

    What are the two methods of measuring electrical signals during an EMG examination?

    <p>Both A and B (C)</p> Signup and view all the answers

    Action potential appears in EMG after a latency period.

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

    EMGs of symmetrical muscles are compared to each other, or to those of normal individuals, to determine the action potential and latency periods.

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

    Nerve damage may result in a decrease in the velocity of the action potential.

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

    What is the recording of signals from the brain called?

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

    EEG signals are primarily due to the electrical activity of the neurons in the cortex of the brain.

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

    Electrodes for recording EEG signals are attached to the head at locations that are independent of what part of the brain is to be studied.

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

    The reference electrode in an EEG recording is usually attached to the ear (A1 or A2).

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

    Asymmetrical brain activity between the left and right sides is often a sign of brain disease.

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

    The amplitude of EEG signals is high (about 50 μV)

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

    Interference from external electrical signals often causes serious problems in EEG signal processing.

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

    The frequencies of the EEG signals seem to be dependent upon the physical activity of the subject.

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

    As a person becomes drowsy, the frequencies from 8 to 12 Hz (alpha wave) dominate the EEG.

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

    The amplitude of the alpha wave decreases as a person moves from light sleep to deeper sleep.

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

    Paradoxical sleep is characterized by rapid eye movement (REM) and is associated with dreaming.

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

    What is the sensorimotor rhythm (SMR)?

    <p>An oscillatory idle rhythm of synchronized electric brain activity.</p> Signup and view all the answers

    The SMR appears in recordings of EEG, MEG, and ECG over the sensorimotor cortex.

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

    Evoked responses are signals that result when the brain receives external stimuli.

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

    EEGs typically show responses to all pulses of a stimulus.

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

    What is the recording of potential changes produced by the eye when the retina is exposed to a flash of light called?

    <p>Electroretinogram (ERG)</p> Signup and view all the answers

    The ERG is more complicated than a nerve axon signal because it is the sum of many effects taking place within the eye.

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

    The B wave of the ERG is the most interesting clinically, arising in the retina.

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

    The B wave is absent in the ERG of patients with inflammation of the retina.

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

    What is the recording of potential changes due to eye movements called?

    <p>Electrooculogram (EOG)</p> Signup and view all the answers

    A pair of electrodes is attached near the eye to measure the EOG.

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

    The EOG provides information on the orientation of the eye and its angular velocity.

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

    The heart's electrical system controls all the events that occur when the heart pumps blood.

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

    What is the heart's electrical system also known as?

    <p>Cardiac conduction system.</p> Signup and view all the answers

    What is the heart test called that is a graphical picture of the heart's electrical activity?

    <p>Electrocardiogram or ECG</p> Signup and view all the answers

    What are the three main parts of the heart's electrical system?

    <p>All of the above (D)</p> Signup and view all the answers

    The SA node is located in the left atrium.

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

    The AV node is located on the interatrial septum close to the tricuspid valve.

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

    The His-Purkinje system is located along the walls of the heart's atria.

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

    A heartbeat is a complex cycle of electrical conductive events.

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

    Each heartbeat has two basic parts: diastole and systole.

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

    During diastole, the heart's atria and ventricles contract.

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

    At the end of diastole, the heart's atria contract and pump blood into the ventricles.

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

    The ventricles contract first, followed by the atria, during each heartbeat.

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

    Ventricular systole involves the contraction of the ventricles, pumping blood out of the heart.

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

    The SA node and the rest of the conduction system are at rest during the heartbeat.

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

    The SA node initiates the action potential, which causes depolarization of nerves and muscles in both atria.

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

    The SA node is also known as the pacemaker of the heart.

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

    The delay of approximately 100 ms after the electrical signal reaches the AV node allows the atria to complete pumping blood before the impulse is transmitted to the atrioventricular bundle.

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

    The impulse travels through the atrioventricular bundle, bundle branches, and Purkinje fibers, reaching the contractile fibers of the ventricle.

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

    Ventricular contraction forces blood into the two systems, then ventricles are repolarized, completing the heartbeat cycle.

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

    The normal heart rate at rest ranges between 60 and 100 beats per minute on average.

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

    The SA node is responsible for adjusting the heart rate to meet the body's needs.

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

    During periods of exercise, the heart rate decreases to conserve energy for physical exertion.

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

    During periods of rest or sleep, the heart rate increases to meet the reduced oxygen demands of the body.

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

    Changes in heart rate are a normal part of the heart's effort to meet the needs of the body.

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

    In a normal ECG waveform, the P wave represents ventricular depolarization

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

    The QRS complex represents ventricular depolarization.

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

    The T wave represents atrial repolarization.

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

    The P-R interval is measured from the start of the P wave to the start of the QRS complex.

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

    The Q-T interval is measured from the start of the QRS complex to the end of the T wave.

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

    The S-T segment is measured from the end of the QRS complex to the start of the T wave and represents the period when all cells are normally depolarized during that phase.

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

    The P-R interval is typically between 0.12-0.2 seconds (3-5 small squares) on a standard ECG paper.

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

    The QRS complex duration is typically less than or equal to 0.1 seconds (2.5 small squares) on a standard ECG paper.

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

    The Q-T interval corrected for heart rate (QTc) is typically less than or equal to 0.44 seconds.

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

    The location of the electrodes used for ECG recording does not significantly affect the measurements obtained.

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

    The most common electrode placement for ECG recording is in the left arm (LA), right arm (RA), and left leg (LL).

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

    A standard ECG graphing typically includes 6 sections, all of which are in the frontal plane.

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

    The potential difference between any two electrodes provides information about the relative amplitude and direction of the electric dipole vector in the frontal plane.

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

    What does lead I measure in an ECG?

    <p>The potential difference between the right arm and left arm electrodes. (C)</p> Signup and view all the answers

    The aVR augmented lead measures the potential difference between the right arm and the center of the resistance between the left leg and left arm.

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

    The aVL augmented lead measures the potential difference between the left arm and the center of the resistance between the left leg and right arm.

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

    The aVF augmented lead measures the potential difference between the left leg and the center of the resistance between the right arm and left arm.

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

    The chest electrodes are typically placed in the 4th intercostal space.

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

    V1 is placed in the 4th intercostal space, right of the sternum.

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

    V3 is placed between V1 and V3.

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

    V4 is placed in the fifth intercostal space in the nipple line.

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

    V6 is placed in the mid axillary line on the same height as V4, but not necessarily in the 5th intercostal space.

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

    The ECG can be used to diagnose problems with the heart, including arrhythmias.

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

    Arrhythmias are an irregular pumping pattern which is quite common in young people and often exacerbated by exercise.

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

    An ECG can reveal blockages in the blood supply to the heart, which can lead to myocardial infarction (heart attack).

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

    Fibrillation is a condition where there is no coordinated pumping activity, which can lead to death if left untreated.

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

    Study Notes

    Electricity Within The Body

    • Electricity and magnetism have been observed since ancient times, playing a crucial role in medicine
    • Two aspects of electricity and magnetism in medicine:
      • Electrical and magnetic effects generated inside the body
      • Applications of electricity and magnetism to the surface of the body
    • Electricity generated inside the body controls and operates nerves, muscles, and organs
    • The nervous system is fundamental to nearly every body function, acting as a central computer processing internal and external signals
    • The nervous system is divided into two parts:
      • Central nervous system (brain, spinal cord, peripheral nerves)
      • Autonomic nervous system (controls internal organs)

    The Neuron

    • Neuron: the basic structural unit of the nervous system; specialized for receiving, interpreting, and transmitting electrical signals
    • Structure:
      • Dendrites: short, branched, unmyelinated parts that receive signals from other neurons
      • Soma (cell body): contains the nucleus and associated intracellular structures; receives signals from dendrites
      • Axon (nerve fiber): carries electrical signals away from the cell body to axon terminals; typically about 1 meter long
      • Axon terminals: transmit signals to other neurons or muscle/glands
      • Synapses: the basic unit of communication in the brain; chemical neurotransmitters relay signals between neurons

    Electrical Potentials of Nerves

    • A cell membrane separates the intracellular and extracellular environments, each with different concentrations of ions (chemicals)
    • This difference in ion concentration leads to a potential difference (biopotential, measured through electrodes and amplifiers); necessary for studying heart, brain, muscles, etc.
    • Two types of biopotentials:
      • Resting potential: a stable voltage difference across the neuron membrane
      • Action potential: a temporary, significant change in membrane voltage that rapidly propagates along the axon

    Electrical Signals From Muscles (EMG)

    • EMG: the recording of potentials from muscles during movement
    • Muscles are made of motor units, each comprising a neuron and many muscle fibers
    • Muscle contraction is initiated by action potentials that travel along the neuron to motor end plates, causing muscles to contract
    • EMG electrodes measure electrical activity from several fibers to study muscle function. There are surface and concentric needle types.

    Electrical Signals From The Brain (EEG)

    • EEG: measures electrical activity from neurons in the brain's cortex, resulting in complex electrical signals.
    • Electrodes are used on the scalp to collect the electrical signals for analysis.
    • EEG can be used to detect brain diseases or abnormalities (e.g., asymmetrical activity)
    • External electrical interference can be a problem during EEG signal processing.

    Electrical Signals From The Eye (ERG)

    • ERG: measures the electrical signals produced when the retina in the eye is exposed to light.
    • Two electrodes are used (one in a contact lens and the other external), to measure the electrical potential change.
    • ERG waves are important for retinal health analysis.
    • Clinical uses help detect inflammatory diseases such a inflammation of the retina

    Electrical Signals From The Eye (EOG)

    • EOG: measures electrical signals produced due to eye movement.
    • Two electrodes placed around the eyes; used to measure eye movement related activity.
    • EOG used in clinical diagnosis of eye related conditions.

    Electrical Signals From The Heart (ECG)

    • ECG: provides a graphical record of the heart's electrical activity, showing the cardiac conduction system activity.
    • The heart has three main parts to its electrical system: Sinoatrial (SA) node, atrioventricular (AV) node and His-Purkinje system
    • The different waves in an ECG represent different phases of the heart's electrical activity (e.g., P wave for atrial depolarization, QRS complex for ventricular depolarization, T wave for ventricular repolarization)
    • Heart rate can adjust according to body's needs/physical activity

    Heartbeat Conduction Cycle

    • A heartbeat is a complete cycle of electrical events, involving the heart's chambers relaxation and contraction to pump blood
    • This cycle includes diastole (relaxation) for filling of chambers and systole (contraction) for pumping

    ECG Normal Values

    • Specific time frames for different components of the ECG are characteristic of a healthy heart
    • Certain measurement values of ECG waves should follow certain norms, otherwise medical interventions are necessary

    Surface Electrodes

    • ECG electrodes measure the potential differences between different parts of the body to create a graphical representation of the heart's electrical activity
    • Several electrode positions (frontal plane and chest electrodes)
    • The amplitude/direction of the electric dipole vector between different electrodes provides important signal information; the ECG measurement is not only an absolute value, but also relative between electrodes.

    Other Diagnostic Notes

    • ECG can be used to detect medical conditions such as arrhythmia, heart attack and fibrillation.

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    Electricity Within the Body PDF

    Description

    Explore the role of electricity and magnetism in the human body, focusing on how they affect the nervous system. Understand the structure and function of neurons, and learn about the central and autonomic nervous systems. This quiz covers essential concepts in medical physics and neuroscience.

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