Membrane and Action Potential

Cards (108)

  • Steps in muscle contraction:
    • Initiated by a depolarizing stimulus opening voltage-gated Na+ channels
    • Na+ influx depolarizes the membrane further, causing more Na+ channels to open
    • Positive feedback loop leads to rapid depolarization, the action potential
    • Terminated by inactivation of Na+ channels and opening of voltage-gated K+ channels
    • K+ efflux repolarizes the membrane, restoring the resting potential
  • Image of a skeletal muscle fiber, the basic unit of skeletal muscle, with multiple nuclei beneath the sarcolemma
  • Image of a skeletal muscle fiber seen with an electron microscope
  • permit passage of certain ions
    Integral proteins
  • An example of voltage-gated channel

    Activation and Inactivation gate of Sodium channel
  • It balances the tendency for diffusion caused by
    concentration difference
    Equilibrium potential
  • generated across a membrane because of a concentration difference of an ion
    potential difference
  • No net diffusion occurs in Nernst Potential

    True
  • Value of Normal nerve RMP
    -70mV
  • exhibited by all cells
    RMP
  • Causes of occurrence of RMP
    Nernst potential of Na and K
    K leak channels
    Na K ATPase pump
  • Nerve membrane is more permeable to K+ than Na+
    True
  • Why is nerve membrane more permeable to K+ than Na+?
    High resting conductance to K
  • Exhibited only by excitable cells

    AP
  • Characteristics of true Ap
    Stereotypical size and shape
    Propagating
    All or none
  • Each normal AP for a given cell type looks identical,
    depolarizes to the same potential and repolarizes to the same RMP

    True
  • AP at one cell causes depolarization of adjacent cells in a nondecremental
    manner
    Propagating
  • If a threshold is reached, a full-sized AP will be produced, otherwise, none at all
    All or none principle
  • Positive charges flow into the cell causing depolarization
    Inward current
  • Positive charges flow out of the cell causing hyperpolarization
    Outward current
  • Make the MP more positive
    Depolarization
  • Make the MP more negative
    Hyperpolarization
  • Occurs during an AP when MP>0mV
    Overshoot
  • Occurs during an AP when MP<RMP
    Undershoot
  • Non-propagated local potential due to local change in ionic conductance
    Electrotonic potential
  • the larger the nerve fiber, the smaller the internal resistance, and
    the faster the conduction velocity

    True
  • Where is conduction velocity is most dependent?
    Nerve diameter
  • Where is AP is regenerated, which contains the highest concentration of Na+ channels per square micrometer of cell membrane?
    Nodes of Ranvier
  • The basic working unit of CNS and PNS, and exhibits the characteristic of being electrically excitable
    Neurons
  • Contains the nucleus, which is the neuron's metabolic center

    Soma
  • bring signal away from the body (presynaptic terminal)
    Axon
  • Brings and transmits signal towards the cell body
    Dendrite
  • A protein-lipid complex that is wrapped around the axon
    Myelin sheath
  • It is where action potentials cause the release of synaptic
    transmitters
    nerve endings
  • It transmits propagated impulses to the nerve endings
    Axonal process
  • minimal intensity of stimulating current needed to produce an action potential
    Threshold intesnsity
  • weak stimulus needs a long duration.
    True
  • A strong stimulus is sufficient at a short duration

    True
  • No action potential occurs if the stimulus is subthreshold in magnitude, and the
    action potential has a constant amplitude and form at any stimulus strength above
    the threshold
    True
  • Associated with the immune system; scavenger cells that resemble tissue macrophages
    Microglia