3. Sea vegetables. Sea vegetables are rich in iodine. Iodine attaches to tyrosine (an amino acid) to form thyroxine. If you have insufficient levels of iodine, it becomes a rate-limiting step in the production of thyroid hormones and you'll inhibit your thyroid function.
Confidence votes 48. Special glia called Schwann cells form the myelin sheath which cover axons in the peripheral nervous system. The myelin sheath is actually two layers. The first layer surrounding the axon is called the myelin sheath and it is made up of the plasma membrane of the Schwann cells. The Schwann cells cytoplasm creates the second layer and is called the neurolemma. A neuron in the peripheral nervous system with a myelin sheath is called a myelinated neuron.
17 Contributions.   Surrounding the myelin sheath, there is a thin membrane called neurilemmal sheath. This is also called neurilemma or sheath of Schwann. This contains Schwann cells, whicâ¦h have flattened and elongated nuclei. The cytoplasm is thin and modified to form the thin sheath of neurilemma enclosing the myelin sheath.   One nucleus is present in each internode of the axon.