Structure and Function of Schwann Cells

Structure and Function

• Schwann cells are glial cells in the peripheral nervous system (PNS).
• They myelinate axons, increasing nerve impulse speed.
• Myelin is a fatty substance forming an insulating sheath around the axon.
• The myelin sheath is segmented by Schwann cell membranes.
• Gaps between segments are Nodes of Ranvier.
• Saltatory conduction occurs at the nodes, where action potentials jump between nodes, speeding transmission.
• Schwann cells support and nourish myelinated axons.

Myelination Process

• Schwann cells wrap around the axon in a spiral.
• Cytoplasm and nucleus of the Schwann cell are pushed to the periphery during wrapping.
• Tight packing of the cell membrane forms the myelin sheath.

Types of Schwann Cells:

• Myelinating Schwann cells form myelin sheaths around large-diameter axons; the most common type.
• Non-myelinating Schwann cells support and surround small, unmyelinated axons, also known as supporting cells (or satellite cells). They lack the tight layering of myelinating Schwann cells.

PNS vs. CNS

• Schwann cells myelinate axons in the peripheral nervous system (PNS).
• Oligodendrocytes myelinate axons in the central nervous system (CNS).
• Oligodendrocytes can myelinate multiple axons, while Schwann cells myelinate only one.

Regeneration

• Schwann cells are crucial for peripheral nerve regeneration after injury.
• They form a regeneration tube guiding growing axons to their target.
• Schwann cells are essential for successful regeneration in the PNS.

Functions Beyond Myelination

• Schwann cells have support roles beyond myelination.
• They influence synaptic transmission rates by regulating neurotransmitter release and uptake.
• They maintain the chemical balance of the extracellular environment around neurons.
• They are involved in PNS development and maintenance.

Diseases Affecting Schwann Cells

• Guillain-Barré syndrome targets Schwann cells; an autoimmune disease.
• Demyelination of peripheral nerves in Guillain-Barré leads to muscle weakness and paralysis.
• Hereditary neuropathies can also affect Schwann cell function.

Other Key Details

• Schwann cells maintain the structural integrity of peripheral nerves.
• Their function is critical for signal transmission throughout the body.
• Their role in nerve regeneration highlights their importance for recovery after nerve damage.