why does shcwann cell doesn't form myelin sheath in non-myelinated nerve fibre?
Schwann cell is the main glial cell present in peripheral nerves. Myelin sheath is an outgrowth of schwann cell and is uasually present only around axon of a neuron for normal functioning of nervous system. Schwann cells doesn't form myelin sheath in non-myelinated nerve fibre because non-myelinated fibres contains a group of smaller axons that form cavity in single schwann cell without formin a spiral of mesoaxon. These are mainly involved in axon maintainence and survival of neuron. e.g. olfactory nerve fibres.