1) Membrane 2) Tissue layer 
The axolemma is the cell membrane surrounding an axon. It is responsible for maintaining the membrane potential of the neuron, and it contains ion channels through which ions can flow. When this occurs, the voltage inside the axon changes, and depolarization or hyperpolarization of the membrane can occur. Adequate depolarization can lead to an act...
<cell biology> Plasma membrane of an axon. ... (12 Mar 1998) ... 
(ak-so-lem´ә) the surface membrane of an axon.
Plasma membrane of an axon.
Type: Term Pronunciation: ak′sō-lem′ă Definitions: 1. The plasma membrane of the axon. Synonyms: Mauthner sheath
[n] - outer membrane covering an axon
noun outer membrane covering an axon