Nerve Physiology Lecture Notes
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Questions and Answers

What is the primary structural unit of the nervous system?

  • Myelin sheaths
  • Synapses
  • Neurons (correct)
  • Glial cells

    • Which type of neuron carries sensations from tissues towards the central nervous system?

  • Interneuron
  • Afferent (correct)
  • Motor neuron
  • Efferent

    • What is the term for the involuntary response to an adequate stimulus?

  • Voluntary action
  • Reflex arc
  • Stimulus reaction
  • Reflex action (correct)

    • What is the role of the effector organ in a reflex action?

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

    Which component of a reflex arc detects stimuli?

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

    What does excitability refer to in nerve physiology?

    <p>Ability to respond to stimuli (C)</p> Signup and view all the answers

    How can stimuli be classified according to their nature?

    <p>Chemical, thermal, mechanical, electrical (D)</p> Signup and view all the answers

    What is a subthreshold stimulus characterized by?

    <p>It produces no response due to inadequate intensity. (D)</p> Signup and view all the answers

    What results from a suprathreshold stimulus?

    <p>It produces a full response in a single nerve fiber. (C)</p> Signup and view all the answers

    Which statement about the threshold stimulus is true?

    <p>It produces a full response only in a single neuron. (B)</p> Signup and view all the answers

    What defines the resting membrane potential (RMP)?

    <p>Potential difference between inside and outside the cell membrane. (C)</p> Signup and view all the answers

    What is the approximate resting membrane potential in nerve cells?

    <p>-70 mV to -90 mV (C)</p> Signup and view all the answers

    How is the 'all or none' law described?

    <p>A nerve fiber must meet a threshold to respond fully or not at all. (A)</p> Signup and view all the answers

    Regarding ion distribution, what is true about Na+ and K+ concentration?

    <p>Na+ concentration is higher outside the cell while K+ is higher inside. (D)</p> Signup and view all the answers

    What ion concentrations are typically present outside a cell?

    <p>Higher Na+ and Cl- concentration compared to the inside. (D)</p> Signup and view all the answers

    What characterizes rapid repolarization during the repolarization phase?

    <p>Restoration of 70% of the resting membrane potential. (B)</p> Signup and view all the answers

    What occurs during the negative after potential phase of repolarization?

    <p>K+ efflux becomes delayed. (C)</p> Signup and view all the answers

    What leads to hyperpolarization during the positive after potential phase?

    <p>Delayed closure of K+ channels. (D)</p> Signup and view all the answers

    What happens to the Na+ and K+ distribution at resting membrane potential?

    <p>Normal distribution maintained by the Na+ - K+ pump. (B)</p> Signup and view all the answers

    During which period is there no response to any stimulus?

    <p>Absolute refractory period. (A)</p> Signup and view all the answers

    What initiates repolarization in action potential?

    <p>Delayed opening of K+ channels. (D)</p> Signup and view all the answers

    Which statement describes the state of Na+ and K+ channels during rest?

    <p>Na+ inactivation gate is open, activation gate is closed. (A)</p> Signup and view all the answers

    How does excitability change during the relative refractory period?

    <p>It decreases, requiring a stronger stimulus for a response. (A)</p> Signup and view all the answers

    What is characterized by a weak stimulus producing a response during the lower part of repolarization?

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

    Which type of neuron is primarily responsible for carrying signals from sensory receptors to the central nervous system?

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

    What is the term used for the ability of living tissue to respond to an adequate stimulus?

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

    Which of the following phases is NOT part of the action potential?

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

    What does RMP stand for and what does it represent?

    <p>Resting Membrane Potential; potential difference across the cell membrane (C)</p> Signup and view all the answers

    What is primarily responsible for the unequal distribution of ions across the cell membrane?

    <p>Na+ - K+ pump (C)</p> Signup and view all the answers

    Which channels allow for the selective permeability of the cell membrane?

    <p>Leakage channels and gated channels (A)</p> Signup and view all the answers

    How do leakage channels differ from gated channels?

    <p>Leakage channels are not gated and are always open (D)</p> Signup and view all the answers

    What occurs during the depolarization phase of an action potential?

    <p>Sodium ions influx through voltage-gated channels (A)</p> Signup and view all the answers

    What characterizes the spike potential in an action potential?

    <p>It includes both depolarization and repolarization phases (D)</p> Signup and view all the answers

    What effect does the Na+ - K+ pump have on intracellular protein anions?

    <p>It maintains their impermeability, leading to negative charges inside (A)</p> Signup and view all the answers

    What is the latent period in the context of action potentials?

    <p>Interval for the nerve impulse to travel from the stimulating to recording electrode (A)</p> Signup and view all the answers

    Which statement about membrane potential during the action potential is false?

    <p>Membrane potential remains consistent throughout action potential (A)</p> Signup and view all the answers

    Flashcards

    Neuron

    The basic functional unit of the nervous system. It is responsible for transmitting information throughout the body.

    Afferent Neuron

    A type of neuron that carries signals from sensory receptors towards the central nervous system (CNS).

    Efferent Neuron

    A type of neuron that carries signals from the CNS to muscles or glands.

    Interneuron

    A neuron that transmits signals between other neurons.

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    Excitability

    The ability of living tissue to respond to a stimulus.

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    Reflex Action

    An involuntary response to a stimulus.

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    Reflex Arc

    A pathway that allows a reflex action to occur, involving a receptor, sensory (afferent) neuron, interneuron, motor (efferent) neuron, and effector organ.

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    Receptor

    The structure that detects a stimulus, such as light, sound, touch, or pressure.

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    Threshold stimulus

    The minimum stimulus intensity required to elicit a response in an excitable tissue. This intensity is just adequate for a reaction.

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    Subthreshold stimulus

    A stimulus intensity below the threshold, which fails to produce any response in the excitable tissue.

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    Suprathreshold stimulus

    A stimulus intensity greater than the threshold that elicits a full response in excitable tissue.

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    Resting membrane potential (RMP)

    The difference in electrical charge between the inside and outside of a cell membrane, with the inside being relatively negative.

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    All-or-none law

    The principle that a single nerve fiber will either produce a full response or no response at all when stimulated.

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    Ion distribution across the cell membrane

    The distribution of ions across the cell membrane, with different concentrations inside and outside the cell.

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    Ion distribution: outside the cell

    Sodium (Na+), Calcium (Ca+2), Chloride (Cl-) are found in higher concentrations outside the cell, while Potassium (K+) is higher inside the cell.

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    Ion distribution: inside the cell

    Protein and bicarbonate ions (HCO3-) are found in higher concentrations inside the cell.

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    Selective Permeability of the Membrane

    This refers to the cell membrane's ability to allow certain substances to pass through while blocking others.

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    Na+/K+ Pump

    This is a protein pump that actively transports sodium (Na+) ions out of the cell and potassium (K+) ions into the cell, requiring energy. It contributes to maintaining RMP.

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    Leakage Channels

    They are passive, always open, permitting ions to move across the membrane down their concentration gradients.

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    Gated Channels

    These channels can be opened or closed in response to specific stimuli like changes in voltage or chemical binding.

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    Latent Period

    This is the period between the application of a stimulus and the actual response of the nerve. It represents the time taken for the nerve impulse to travel.

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    Spike Potential

    The rapid change in membrane potential from RMP to a higher level, followed by a return to RMP. This is a key event in nerve signal transmission.

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    Depolarization

    This is the rising phase of the spike potential where the membrane potential becomes more positive. It's caused by the influx of sodium ions (Na+) into the cell.

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    Supernormal Phase

    The period following repolarization where the cell membrane is more easily stimulated than during the resting state.

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    Subnormal Phase

    The period following repolarization where the cell membrane is less easily stimulated than during the resting state.

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    Action Potential

    A transient change in the resting membrane potential. It's a rapid sequence of events that involves a depolarization phase, repolarization phase, and an undershoot.

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    Rapid Repolarization

    The initial, fast phase of repolarization where the membrane potential quickly recovers around 70% of its resting value. This is due to inactivation of sodium channels and activation of potassium channels.

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    Positive Afterpotential (Hyperpolarization)

    A brief period following repolarization where the membrane potential becomes slightly more negative than the resting membrane potential. It's caused by the delayed closure of potassium channels, leading to a temporary increase in potassium efflux.

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    Negative Afterpotential (After Depolarization)

    A brief period following repolarization where the membrane potential becomes slightly less negative than the resting membrane potential. This is caused by a decrease in the potassium gradient, reducing the rate of potassium efflux and delaying repolarization.

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    Sodium-Potassium Pump

    The active process that restores normal ion distribution across the membrane after an action potential. The sodium-potassium pump moves sodium ions out of the cell and potassium ions into the cell, maintaining the resting membrane potential.

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    Absolute Refractory Period

    The period during which the membrane is unable to generate another action potential, no matter how strong the stimulus.

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    Relative Refractory Period

    The period during which the membrane can generate an action potential, but only with a stronger-than-usual stimulus.

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    Study Notes

    Nerve Physiology Lecture Notes

    • The lecture is about nerve physiology
    • The presenter is Dr. Nanees El-Malkey, an assistant professor at Sinai University
    • Topics covered include:
      • General organization of the nervous system
      • Types of neurons
      • Action potential
      • Structure of a neuron
    • The neuron is the anatomical unit of the nervous system
    • The reflex action is the functional unit of the nervous system
    • A neuron can be myelinated or non-myelinated, depending on the presence of a myelin sheath
    • Neurons can be classified by function as afferent (sensory), efferent (motor), or interneurons
    • Afferent neurons carry signals from tissues to the central nervous system (CNS)
    • Efferent neurons carry signals from the CNS to tissues
    • Interneurons transmit impulses between other neurons
    • Reflex arc:
      • Receptor detects a stimulus
      • Afferent neuron carries the signal to the spinal cord
      • Interneuron relays the signal within the spinal cord
      • Efferent neuron carries the signal to the effector organ (muscle)
      • Effector organ responds to the stimulus, e.g., a muscle contracts
    • Excitability:
      • The ability of living tissues to respond to stimuli
      • The stimulus is a change in the environment of the living tissue
      • Types of stimuli: electrical, chemical, mechanical, thermal
        • According to intensity
          • Threshold stimulus: Minimal stimulus to produce a response in excitable tissues
          • Subthreshold stimulus: Insufficient to elicit a response
          • Suprathreshold stimulus: Greater than the threshold stimulus
    • All-or-none law:
      • A single nerve fiber will either fire fully or not at all
    • Resting membrane potential (RMP):
      • The potential difference between the inside and outside of the cell membrane
      • Inside is more negative than the outside
      • RMP in nerve cells is roughly 70mV
      • RMP values vary across cell types
    • Causes of RMP:
      • Unequal distribution of ions across the cell membrane
      • Selective permeability of the cell membrane (leakage and gated channels)
      • Sodium-potassium pump
        • Moves sodium out of the cell and potassium into the cell, against concentration gradients
      • Impermeability of the membrane to intracellular protein anions
    • Action potential phases
      • Latent period: time taken for nerve impulse to reach recording electrode
      • Depolarization: rapid increase in membrane potential (Na+ ions enter the cell)
      • Repolarization: rapid decrease in membrane potential (K+ ions exit the cell)
    • Steps of repolarization
      • Rapid increase in K+ permeability, leading to rapid decrease in membrane potential
      • Negative after potential: further decrease in membrane potential that slow to return to RMP
      • Positive after potential: further rapid return to RMP
    • Action potential characteristics (nerve vs. skeletal vs. cardiac muscle)
      • RMP variation, firing level variation, amplitude variation, duration of spike variation, chronaxie variation
      • Excitability changes (refractory periods) during action potentials
        • Absolute refractory period: no response to a stimulus
        • Relative refractory period: response only to a stronger stimulus than normal
        • Supernormal phase: high excitability
        • Subnormal phase: low excitability
    • Wrap up
      • Nervous system has CNS and PNS
      • The CNS is made up of the brain and spinal cord
      • The PNS consists of spinal and cranial nerves
      • Neurons can be myelinated or non-myelinated
      • Neurons can be afferent, efferent or interneurons
      • Reflex arc: receptor → afferent → center → efferent→ effector organ
      • Excitability is the ability of living tissue to respond to a stimulus

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    Nerve Physiology Lecture Notes PDF

    Description

    Explore the fundamentals of nerve physiology with Dr. Nanees El-Malkey. This lecture delves into the organization of the nervous system, types of neurons, and the process of action potentials. Understand the critical roles of afferent, efferent, and interneurons in reflex actions.

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