depolarization

Examples of depolarization in the following topics:

• Stages of the Action Potential

  • Neural impulses occur when a stimulus depolarizes a cell membrane, prompting an action potential which sends an "all or nothing" signal.
  • Depolarization: A stimulus starts the depolarization of the membrane.
  • The refractory phase takes place over a short period of time after the depolarization stage.
  • During the refractory phase this particular area of the nerve cell membrane cannot be depolarized.
  • A neuron must reach a certain threshold in order to begin the depolarization step of reaching the action potential.

• Mechanics of the Action Potential

  • Depolarization.
  • A stimulus begins the depolarization of the membrane.
  • Depolarization, also referred to as the "upswing," occurs when positively charged sodium ions (Na+) suddenly rush through open sodium gates into a nerve cell.
  • During the refractory phase this particular area of the nerve cell membrane cannot be depolarized; the cell cannot be excited.
  • For example, depolarization of the presynaptic membrane will always induce a depolarization in the postsynaptic membrane, and vice versa for hyperpolarization.

• Neurotransmitters

  • Inhibitory neurotransmitters cause hyperpolarization of the postsynaptic cell (that is, decreasing the voltage gradient of the cell, thus bringing it further away from an action potential), while excitatory neurotransmitters cause depolarization (bringing it closer to an action potential).
  • The depolarizing (more likely to reach an action potential) or hyperpolarizing (less likely to reach an action potential) effect is also dependent on the receptor.
  • When acetylcholine binds to the nicotinic receptor, the postsynaptic cell is depolarized.
  • However, when acetylcholine binds to the muscarinic receptor, it might cause depolarization or hyperpolarization of the target cell.
  • Glutamate is considered an excitatory amino acid because Glu receptors in the adult cause depolarization of the postsynaptic cell.

• Olfaction: The Nasal Cavity and Smell

  • This opening allows for an influx of both Na+ and Ca2+ ions into the cell, thus depolarizing it.
  • The Ca2+ in turn activates chloride channels, causing the departure of Cl-, which results in a further depolarization of the cell.

• Gustation: Taste Buds and Taste

  • This depolarizes the cell and floods it with ions, leading to a neurotransmitter release.