Glial cells called help maintain the blood-brain barrier, whereas create the myelin that envelopes axons. astrocytes; microglia Schwann cells; astrocytes microglia; Schwann cells astrocytes; Schwann cells

Glial cells called ASTROCYTES help maintain the blood-brain barrier, whereas SCHWANN CELLS create the myelin that envelopes axons

Explanation: Glial cells are specialized cell that are found in both central and peripheral nervous systems, that surrounds the neurones, providing them with support and insulation. There are different types of Glial cells these includes:

- Astrocytes: they maintain the blood brain barrier.

- Schwann cells: create the myelin that envelopes axons of the peripheral nervous system neurones.

- satellite cells: These cells help regulate the external chemical environment of neurones.

- Microglia: they clean up cellular debris through phagocytosis.

- Oligodendrocytes: create the myelin that envelopes axons of the central nervous system

answer is a

explanation:

when the displaced particles are perpendicular to the direction the wave travels, is called a transverse wave, whereas in longitudinal wave the displace practices are parallel to the direction of the wave.

in the given image:

first image shows - longitudinal wave

second image shows - transverse wave

third image shows - longitudinal wave

fourth image shows - longitudinal wave