axon hillock
The specialized region of a neuron where the cell body transitions to the axon and action potentials are initiated.
Full Definition
The axon hillock is a specialized area of the neuronal cell body (soma) that tapers to form the initial segment of the axon. This region contains the highest concentration of voltage-gated sodium channels in the neuron, making it the site where action potentials are typically initiated when the membrane potential reaches threshold. The axon hillock functions as the neuron's decision-making center, integrating all incoming synaptic inputs and determining whether the combined signal is strong enough to generate an action potential. This region is crucial for understanding neuronal excitability and signal propagation in neural circuits.
Usage
Usage note: Sometimes called the initial segment; distinct from axon terminals at the other end of the axon.
In Context
- "Patch-clamp recordings confirmed that action potentials originate at the axon hillock in these cortical neurons." — Electrophysiology study
- "Immunostaining revealed dense clustering of sodium channels at the axon hillock region." — Histological analysis