Physiological Effects of Electricity
40 Questions
3 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What occurs when a DC current is passed through body tissues for a prolonged period?

  • Increased muscle flexibility
  • Enhanced healing process
  • Ulceration of tissues (correct)
  • Immediate muscle relaxation

    • Which current density condition is necessary for burns to occur?

  • Low current density
  • High current density (correct)
  • Moderate current density
  • No current density

    • What physiological condition may result from prolonged involuntary contraction of intercostal muscles?

  • Inability to breathe (correct)
  • Effective ventilation
  • Improved muscle tone
  • Increased lung capacity

    • What is the minimum AC current that may induce ventricular fibrillation under certain conditions?

    <p>60 mA</p> Signup and view all the answers

    What term describes the maximum current that allows a person to release their grip from an electric current source?

    <p>Let-go current</p> Signup and view all the answers

    What can prolonged tetanus of heart musculature prevent?

    <p>Normal contraction of heart</p> Signup and view all the answers

    Which of the following is a painful sensation caused by muscle contraction or overshortening?

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

    What physiological effect results from heat produced by an electric current passing through resistance?

    <p>Electrical burns</p> Signup and view all the answers

    What is the primary function of afferent neurons?

    <p>To transmit signals from tissues to the central nervous system</p> Signup and view all the answers

    Which cells are primarily involved in generating an action potential?

    <p>Excitable cells</p> Signup and view all the answers

    What causes the resting membrane potential in a neuron?

    <p>A potential difference due to unequal ion distribution</p> Signup and view all the answers

    What is the value of a typical resting membrane potential in neurons?

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

    What role do interneurons play in the nervous system?

    <p>They connect afferent and efferent neurons</p> Signup and view all the answers

    What is depolarization?

    <p>A process involving ion diffusion that reduces the potential difference to zero</p> Signup and view all the answers

    What is the purpose of using a stimulus with 100V amplitude and a duration of 100-300μs in sensory nerve field potentials?

    <p>To excite large, rapidly conducting sensory nerve fibers</p> Signup and view all the answers

    What is the M-wave response in relation to the H-reflex?

    <p>Occurs earlier, approximately 3-6 ms after stimulation</p> Signup and view all the answers

    What is the typical charge inside a neuron at rest?

    <p>Negatively charged</p> Signup and view all the answers

    Which of the following correctly describes an effector cell?

    <p>They instigate a physical effect based on received signals.</p> Signup and view all the answers

    Which statement is true about the single motor unit (SMU)?

    <p>It is the smallest unit that can be activated by a voluntary effort</p> Signup and view all the answers

    In which situation can only the high-amplitude H-wave be observed?

    <p>With low intensity stimulus</p> Signup and view all the answers

    What does the term 'junctional transmission' refer to?

    <p>Links between neurons and muscle fibers at the neuromuscular junction</p> Signup and view all the answers

    What is the primary factor affecting muscle strength?

    <p>The number of muscle fibers contracting within a muscle</p> Signup and view all the answers

    What type of current is typically used in the H-reflex test?

    <p>Square-wave current</p> Signup and view all the answers

    Which of the following best describes the role of sensory nerve field potentials?

    <p>To record nerve action potentials from sensory fibers</p> Signup and view all the answers

    What neurotransmitter is released at the neuromuscular junction?

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

    What is the time delay due to the neuromuscular junction?

    <p>0.5-1 msec</p> Signup and view all the answers

    What occurs at high stimulation rates at the neuromuscular junction?

    <p>The response fuses into a tetanus</p> Signup and view all the answers

    What property allows only neurons and muscle cells to generate an action potential?

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

    What is the typical firing rate of action potentials for nerves?

    <p>1000 action potentials per second</p> Signup and view all the answers

    How does skeletal muscle contraction occur?

    <p>Via synchronized activation of all motor unit fibers</p> Signup and view all the answers

    Which term describes the nature of action potentials, indicating they either occur fully or not at all?

    <p>All-or-none</p> Signup and view all the answers

    What is the typical duration of a motor unit's field potential?

    <p>3-15 msec</p> Signup and view all the answers

    What does myelination do to the transmission rate of action potentials?

    <p>Improves transmission rate by a factor of approximately 20</p> Signup and view all the answers

    What pattern is observed in the electromyogram (EMG) during strong muscular contractions?

    <p>Interference pattern becomes pronounced</p> Signup and view all the answers

    In which direction does an action potential travel along the axon?

    <p>In one direction only</p> Signup and view all the answers

    What characteristics can a surface electrode or needle electrode measure from a motor unit?

    <p>Both field potential and discharge rate at different locations</p> Signup and view all the answers

    What can significantly modify the shape of the SMU potential?

    <p>Partial denervation</p> Signup and view all the answers

    What does the term 'repolarized' refer to in the context of action potentials?

    <p>Process of returning to resting membrane potential</p> Signup and view all the answers

    What is the potential difference (DV) for nerves during an action potential?

    <p>$120 mV$</p> Signup and view all the answers

    What role does the myelin sheath play in inhibiting electrical losses?

    <p>It reduces leakage currents</p> Signup and view all the answers

    Study Notes

    Physiological Effects of Electricity

    • Electrolysis Using an electric current to separate a chemical compound can cause ulceration.
    • Burns Heat is generated when electrical current flows through a substance with electrical resistance. This can cause burns depending on the current density.
    • Muscle Cramps Electrical stimulation can cause muscle contractions. Prolonged contractions can lead to muscle fatigue.
    • Respiratory Arrest Prolonged muscle contraction of the intercostal muscles involved in breathing can prevent breathing.
    • Ventricular Fibrillation Tetanus of the heart muscles can prevent pumping. AC currents through the chest can cause ventricular fibrillation at currents as low as 60 mA. DC currents require a higher threshold, 300 to 500 mA.

    Let-Go Current

    • When a high enough current flows, muscle spasm occurs, preventing a person from releasing the source of the current.
    • The maximum current that permits a person to release their hand from the current source is called the let-go current.

    Excitable Cells and Biopotentials

    • Excitable cells, such as neurons, muscle cells, and neuroendocrine cells, generate action potentials. These potentials are the source of biopotentials in the body.
    • Afferent neurons transmit signals from tissues and organs to the central nervous system.
    • Efferent neurons transmit signals from the central nervous system to effector cells.
    • Effector cells include muscle cells and neuroendocrine cells and trigger physical effects based on received signals.
    • Interneurons exist entirely within the central nervous system and connect afferent neurons to efferent neurons.

    Membrane Potential

    • Living cells maintain electrical neutrality with an equal number of positive and negative charges.
    • Despite neutrality, there is a difference in the concentration of charges on the inner and outer cell membranes. This difference creates a potential difference across the membrane, known as the membrane potential.
    • Depolarization involves reducing this potential difference by allowing ions to diffuse through the membrane.

    The Resting State

    • A neuron at rest has a negative charge. The inside of the cell is around 70 millivolts more negative than the outside (-70mV). This voltage is called the resting membrane potential and is due to ion concentration differences across the cell membrane.

    Action Potential

    • A stimulus that depolarizes a cell beyond its threshold potential triggers an action potential.
    • Action potentials are sudden, fast, transient, and propagate changes in the resting membrane potential.
    • Only neurons and muscle cells can generate action potentials. This property is called excitability.
    • Action potentials travel in one direction.
    • Myelination reduces leakage currents and improves transmission rate by about 20 times.

    Sensory Nerve Field Potentials

    • These potentials are obtained by stimulating sensory fibers and recording the nerve action potential further along the nerve.
    • A typical stimulus uses 100V amplitude and 100-300µs duration. This effectively excites large, rapidly conducting sensory nerve fibers without eliciting pain fibers.
    • Sensory nerve field potentials are used to diagnose peripheral nerve disorders.

    H-Reflex

    • This reflex is a response to stimulation of sensory fibers in their innervating nerves.
    • The test involves electrical stimulation of a nerve and recording the muscle response.
    • The intensity of the stimulus affects the amplitude of the H-wave and M-wave.

    Electromyogram (EMG)

    • Skeletal muscle functions through the contraction of a motor unit.
    • A motor unit is the smallest unit that can be activated voluntarily. All fibers in the unit contract synchronously.
    • Muscle fibers of a single motor unit create a distributed, unit bioelectric source within the muscle.

    Muscle Fiber (Cell)

    • Muscle fibers are elongated, multinucleated cells responsible for muscle contraction.

    Junctional Transmission

    • Synapses serve as intercommunicating links between neurons.

    • Neuromuscular junctions are links between neurons and muscle fibers, specifically at the end-plate region.

    • At the neuromuscular junction, acetylcholine (Ach) is released as a neurotransmitter.

    • There is a time delay (0.5 to 1 msec) due to the junction.

    • High stimulation rates can cause the mechanical response to fuse into a continuous contraction - known as a tetanus.

    Innervated-Denervated Muscles

    • This refers to muscle response in healthy vs. denervated conditions. Denervation significantly hinders muscle contraction.

    Electromyogram (EMG)

    • EMG records the field potential of active motor units, specifically:
      • Triphasic form.
      • Duration of 3-15 msec.
      • Discharge rate of 6 to 30 per second.
      • Amplitude range from 20 to 2000 µV.
    • Surface electrodes help record these potentials in surface muscles.
    • Needle electrodes can be used to record these potentials in specific locations.

    Factors Influencing Muscle Strength

    • The number of muscle fibers contracting within a muscle.
    • The tension developed by each contracting muscle fiber.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    2nd Lecture 2024 Biopotentials PDF

    Description

    Explore the various physiological effects of electricity, including electrolysis, burns, muscle cramps, and more. This quiz delves into how electrical current impacts the human body and the potential dangers it poses. Test your knowledge on electric shocks and their consequences.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser