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Neurophysiology: Resting Membrane Potential, Action Potential, and Synaptic Potentials

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Terms in this set (23)

  • What is the resting membrane potential (RMP)?
    The resting membrane potential is the electrical potential difference across the cell membrane when the neuron is not transmitting a signal, typically around -80 mV.
  • Which ion primarily sets the resting membrane potential?
    Potassium ions (K+) set the resting membrane potential by moving out of the cell through leaky K+ channels, making the inside of the cell more negative.
  • How are ion concentration differences across the cell membrane generated?
    Ion concentration differences are generated by the low permeability of the membrane, selective ion channels, and the sodium-potassium pump.
  • What is the role of the sodium-potassium pump?
    The sodium-potassium pump uses ATP to transport 3 Na+ ions out and 2 K+ ions into the cell, maintaining ion gradients essential for neuronal activity.
  • What happens during depolarisation of the membrane potential?
    During depolarisation, the membrane potential becomes less negative (more positive), moving closer to the threshold for an action potential.
  • What is hyperpolarisation?
    Hyperpolarisation is when the membrane potential becomes more negative than the resting potential, making the neuron less likely to fire an action potential.
  • What are voltage-gated ion channels?
    Voltage-gated ion channels open or close in response to changes in membrane potential and are critical for generating action potentials.
  • Describe the phases of an action potential.
    Phases include: resting membrane potential, threshold, depolarisation (Na+ influx), repolarisation (K+ efflux), hyperpolarisation, and return to resting potential.
  • What causes the rising phase of the action potential?
    The rising phase is caused by the opening of voltage-gated Na+ channels, allowing Na+ to enter the cell and depolarise the membrane.
  • What causes the falling phase of the action potential?
    The falling phase is caused by the opening of voltage-gated K+ channels, allowing K+ to leave the cell and repolarise the membrane.
  • What is the absolute refractory period?
    The absolute refractory period is when Na+ channels are inactivated and no new action potential can be generated.
  • What is the relative refractory period?
    The relative refractory period follows the absolute period; Na+ channels reset but K+ channels remain open, requiring a stronger stimulus to generate an action potential.
  • What is the function of ligand-gated ion channels at synapses?
    Ligand-gated ion channels open in response to neurotransmitter binding, allowing ions to flow and generate postsynaptic potentials.
  • What is an excitatory postsynaptic potential (EPSP)?
    An EPSP is a depolarisation caused by Na+ influx through ligand-gated channels, increasing the likelihood of an action potential.
  • What is an inhibitory postsynaptic potential (IPSP)?
    An IPSP is a hyperpolarisation caused by Cl- influx or K+ efflux, decreasing the likelihood of an action potential.
  • How do neurons integrate synaptic inputs?
    Neurons integrate inputs by summing EPSPs and IPSPs spatially (different locations) and temporally (over time) to determine if threshold is reached.
  • What is the difference between continuous and saltatory conduction?
    Continuous conduction occurs in unmyelinated axons with sequential channel opening; saltatory conduction occurs in myelinated axons with action potentials jumping between nodes of Ranvier.
  • Why is the sodium-potassium pump important despite not generating the RMP directly?
    It maintains the Na+ and K+ concentration gradients that are essential for generating the resting membrane potential and action potentials.
  • What happens to neuronal excitability if extracellular K+ increases?
    Increased extracellular K+ depolarises the neuron, making it more excitable and closer to firing an action potential.
  • Name a clinical condition related to failure of the sodium-potassium pump.
    Ischemia, such as stroke, causes pump failure due to lack of oxygen, leading to loss of ion gradients and neuronal activity.
  • What is a channelopathy?
    A channelopathy is a disorder caused by dysfunction of ion channels, affecting neuronal excitability and leading to diseases like epilepsy.
  • How do local anaesthetics affect action potentials?
    Local anaesthetics like lidocaine block voltage-gated Na+ channels, preventing action potentials and thus blocking nerve signals.
  • What is the role of calcium channels in neurons?
    Voltage-gated Ca2+ channels open at the axon terminal to trigger neurotransmitter release into the synaptic cleft.