Answer:
Myelin sheath
Explanation:
Myelin sheath cover the axon of neurons and act as insulator for the faster transmission of signals.
Each axon is covered by multiple myelin sheaths and the gap between myelin sheath are known as Nodes of Ranvier.
In CNS myelin sheath is composed of glial cell called as oligodendrocytes and in PNS the myelin sheath is composed of Sachwann cells (glial cells).
I would say estuary, because that's where a fresh water river and an ocean meet, and that leads to a transition between salt to fresh water.
Answer:
by filtering it over and over again
Explanation:
