Axon hillock

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Learn about the morphology and histology of neurons, the basic building blocks of the nervous system.

The axon hillock refers to the triangular, cone-shaped region of a neuron cell body which serves as the origin from which the axon extends. The axon hillock helps to differentiate the axon from a dendrite of a neuron on microscopy.

This anatomically and functionally specialized area is devoid of large cytoplasmic organelles such as chromatophillic substance (Nissl bodies) and Golgi apparatus however contains microtubules, neurofilaments, mitochondria and vesicles, as well as a high concentration of ion channels.

The axon hillock plays an important role in neural communication. It serves as a neuron's primary integrative zone, receiving various excitatory and inhibitory stimuli. It determines whether or not the sum of all incoming signals warrants the propagation of an action potential and transmission of a signal.

The region of the neuron axon which lies between the apex of the axon hillock and the starting point of the myelin sheath is called the initial segment. The initial segment of the axon is the actual site where the action potential is then generated, although more recent research states that both the axon hillock and initial segment are capable of generating action potentials. Once generated in the initial segment, the action potential then propagates along the axon.