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The axon hillock is the last site in the soma where membrane potentials propagated from synaptic inputs are summated before being transmitted to the axon. [2] For many years, it was believed that the axon hillock was the usual site of initiation of action potentials—the trigger zone.
The axon hillock is the area formed from the cell body of the neuron as it extends to become the axon. It precedes the initial segment. It precedes the initial segment. The received action potentials that are summed in the neuron are transmitted to the axon hillock for the generation of an action potential from the initial segment.
At the axon hillock of a typical neuron, the resting potential is around –70 millivolts (mV) and the threshold potential is around –55 mV. Synaptic inputs to a neuron cause the membrane to depolarize or hyperpolarize ; that is, they cause the membrane potential to rise or fall.
Therefore, the postsynaptic potential attenuates by the time it reaches the neuron cell body. The neuron cell body acts as a computer by integrating (adding or summing up) the incoming potentials. The net potential is then transmitted to the axon hillock, where the action potential is initiated. Another factor that should be considered is the ...
The action potential, which typically starts at the axon hillock, propagates down the length of the axon to the axon terminals where it triggers the release of neurotransmitters, but also backwards into the dendrite (retrograde propagation), providing an important signal for spike-timing-dependent plasticity (STDP). [4]
In biology, a motor unit is made up of a motor neuron and all of the skeletal muscle fibers innervated by the neuron's axon terminals, including the neuromuscular junctions between the neuron and the fibres. [1] Groups of motor units often work together as a motor pool to coordinate the contractions of a single muscle.
The axon hillock is a specialized domain of the neuronal cell body from which the axon originates. A high amount of protein synthesis occurs in this region, as it contains many Nissl granules (which are ribosomes wrapped in RER) and polyribosomes. Within the axon hillock, materials are sorted as either items that will enter the axon (like the ...
This difference across the membrane is what the neuron uses to actually do the work of sending messages from the axon hillock of the neuron all the way down to the presynaptic terminal and then on to the postsynaptic terminal because of the release of neurotransmitter into the synaptic cleft. [3]