Axon Initial Segment (also known as Axon Initial Segments, Axon Hillock): First segment of axon that connects distal axon segments to the neuronal CELL BODY at the axon hillock region. The axon initial segment is not protected by the MYELIN SHEATH and has properties critical for axonal growth. The axon initial segment

NIH MeSH · D000071040Anatomy

Axon Initial Segment

Also known asAxon Initial Segments · Axon Hillock · Axon Hillocks · Axonal Trigger Zone · Axonal Trigger Zones · Trigger Zone, Axonal

Definition

First segment of axon that connects distal axon segments to the neuronal CELL BODY at the axon hillock region. The axon initial segment is not protected by the MYELIN SHEATH and has properties critical for axonal growth. The axon initial segment and the axon hillock form an axonal trigger zone.

MeSH classification

  • A08.675.542.145.250
  • A11.284.180.075.125
  • A11.671.501.145.250

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Related concepts

Axons

Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.

Common questions about Axon Initial Segment

What does Axon Initial Segment mean in medicine?
First segment of axon that connects distal axon segments to the neuronal CELL BODY at the axon hillock region. The axon initial segment is not protected by the MYELIN SHEATH and has properties critical for axonal growth. The axon initial segment and the axon hillock form an axonal trigger zone. This definition is taken from the National Library of Medicine's MeSH (Medical Subject Headings) 2026 release, which is the standard vocabulary used to index PubMed and most medical literature.
Is Axon Initial Segment known by any other names?
Yes. Axon Initial Segment is also referred to as Axon Initial Segments, Axon Hillock, Axon Hillocks, Axonal Trigger Zone in different clinical, research and patient-facing contexts. The MeSH descriptor groups all of these synonyms under a single canonical concept so research and records stay consistent.
Where does Axon Initial Segment sit in the medical classification?
Axon Initial Segment falls under the broader medical category "Anatomy" in the MeSH hierarchy (tree numbers: A08.675.542.145.250, A11.284.180.075.125, A11.671.501.145.250). Browsing the related concepts on this page takes you to neighbouring topics in the same branch of medicine.
Where can I get a plain-language explanation of Axon Initial Segment?
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Source: NIH MeSH 2026 (D000071040) — National Library of Medicine, public domain. View official MeSH record ↗