Action potential

• What are the main components of a neuron?

  Dendrites, axon, soma, and axon terminal

  
• What is the function of dendrites in a neuron?

  Dendrites receive signals from other neurons
• What is the role of the axon in a neuron?

  The axon transmits electrical impulses away from the soma
• What is the soma of a neuron?

  The soma is the cell body of the neuron

  
• What is the axon terminal?

  The axon terminal is the endpoint of the axon where neurotransmitters are released
• What is an action potential?

  An action potential is a rapid change in membrane potential that propagates along the axon
• What is the resting membrane potential (Em) of a neuron?

  The resting membrane potential is typically around -70 mV
• What happens during depolarization in a neuron?

  During depolarization, sodium ions enter the cell, making the inside more positive
• What is the threshold potential for action potential initiation?

  The threshold potential is around -55 mV
• What occurs during the overshoot phase of an action potential?

  During the overshoot phase, the membrane potential exceeds 0 mV
• What is hyperpolarization in the context of action potentials?

  Hyperpolarization is when the membrane potential becomes more negative than the resting potential
• What is the role of voltage-gated ion channels during an action potential?

  Voltage-gated ion channels open and close in response to changes in membrane potential, allowing ion flux

  
• What happens to sodium channels during the falling phase of an action potential?

  Sodium channels inactivate during the falling phase

  
• What is the significance of the absolute refractory period?

  During the absolute refractory period, no further action potential can be initiated
• What is the difference between absolute and relative refractory periods?

  Absolute refractory period prevents any action potential, while relative refractory period requires a stronger stimulus
• How does myelination affect action potential conduction speed?

  Myelination increases the speed of action potential conduction
• What is saltatory conduction?

  Saltatory conduction is the jumping of action potentials between nodes of Ranvier in myelinated axons
• What factors influence conduction velocity in axons?

  Conduction velocity is influenced by axon diameter and myelination
• How does cooling tissue affect action potentials?

  Cooling tissue slows down action potentials
• What is the effect of tetrodotoxin on sodium channels?

  Tetrodotoxin blocks sodium channels, preventing action potentials
• What are the symptoms of tetrodotoxin poisoning?

  Symptoms include tingling, numbness, weakness, and respiratory distress
• How do scorpion toxins affect sodium channels?

  Scorpion toxins increase the probability of sodium channel opening and inhibit inactivation
• What is the therapeutic application of sodium channel blockers?

  Sodium channel blockers can prevent pain and reduce cardiac arrhythmias
• What are the key properties of an action potential?

  • Threshold: Em where enough Na channels open
  • Rising Phase: Na ions enter, causing depolarization
  • Overshoot: Em exceeds 0 mV
  • Falling Phase: Na channels inactivate, K ions exit
  • Undershoot: Em approaches EK until K channels close
  • Returns to resting value set by leak channels
• What are the effects of chemical agents on action potentials?

  • Cooling tissue slows down action potentials
  • Lowering [Na]o reduces conduction
  • Potassium channel blockers (e.g., TEA, 4-AP) affect ion channels
  • Sodium channel blockers (e.g., lidocaine) block nerve conduction