axon hillock

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  • Info The axon hillock is a specialized part of the cell body (or soma) of a neuron that connects to the axon.
  • For many years, it had been believed that the axon hillock was the usual site of action potential initiation.
  • The axon hillock can act as a barrier for its lateral spread even though it has no transmembrane segment.
  • The net potential is then transmitted to the axon hillock, where the action potential is initiated.
  • This depolarization will travel towards the axon hillock, diminishing exponentially with time and distance.
  • If several such events occur in a short time, the axon hillock may become sufficiently depolarized for the voltage-gated sodium channels to open.
  • The loss of staining begins near the nucleus and spreads toward the axon hillock.
  • In due course it will generate a new action potential at its axon hillock to discharge neurotransmitters and pass on the information to yet an additional neighboring neuron.
  • The action potential generated at the axon hillock propagates as a wave along the axon.
  • Once this initial action potential is initiated, principally at the axon hillock, it propagates down the length of the axon.
  • If the message is to be blocked, it is best stopped by applying inhibition on the cell body, close to the axon hillock where the action potential originates.
  • Therefore, the SGC sheath of sympathetic neurons must extend even further to cover the axon hillock near the somata.
  • Summation is the adding together of these impulses at the axon hillock.
  • The axon leaves the soma at a swelling called the axon hillock, and can extend for great distances, giving rise to hundreds of branches.
  • However, some excitable cells require no such stimulus to fire: They spontaneously depolarize their axon hillock and fire action potentials at a regular rate, like an internal clock.
  • In neurons receiving axonal transection, central chromatolysis is observed in the area between the nucleus and the axon hillock following.
  • If a graded potential is strong enough, or if several graded potentials occur in a fast enough frequency, the depolarization is able to spread across the cell body to the axon hillock.
  • Some fraction of an excitatory voltage may reach the axon hillock and may (in rare cases) depolarize the membrane enough to provoke a new action potential.
  • If the sum of the stimuli reaches a certain voltage, known as the threshold potential, depolarization will continue from the axon hillock down the axon.
  • The surge of depolarization traveling from the axon hillock to the axon terminal is known as an action potential.
  • In addition, the axon hillock also has a specialized plasma membrane that contains large numbers of voltage-gated ion channels, since this is most often the site of action potential initiation.
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How axon hillock gets used