Supportive Cells (Neuroglia)

Neurons are outnumbered by as much as 10 to 1 by cells called ______, or glial cells.

neuroglia

What is one of the main roles of neuroglia cells in regards to neurons?

They bind neurons together

There are six types of neuroglia, each of which has a unique function; four types occur only in the CNS.

oligodendrocytes, ependymal cells, microglia, and astrocytes

What do Oligodendrocytes resemble?

They resemble small, dark branches with few branches

What is myelin sheath and what does it do?

The myelin sheath is spiral layers of insulation around an axon. It provides electrical insulation and gives faster signal speed

What do Ependymal cells resemble? What do they produce?

They resemble a simple cuboidal. They secrete and circulate CSF

What are Microglia, and what do they do? Where would they become concentrated?

They are macrophages that engulf debris and provide defense against pathogens. They are found through the entire CNS.

What do Astrocytes look like? What are some of their functions?

They look like stars. Their functions are providing a framework for nervous tissue, extensions of contact capillaries and stimulate formation of blood-brain barrier.

Where are Schwann cells found (which division of the nervous system) and what do they do?

Schwann cells are found in PNS. They form myelin sheath and assist in regeneration of damaged cells

Where are Satellite cells found and what do they do?

Found in PNS and they provide insulation around cell body and regulate chemical environment

What is the composition of myelin?

40% water and 60% dry mass

Production of the myelin sheath is called what? When does it begin and when is it complete?

It is called myelination. It begins during fetal development, proceeds rapidly during infancy, complete by late adolescence.

In the PNS, a Schwann cell spirals repeatedly around a single nerve fiber, laying down up to 100 compact layers of its own membrane with almost no

cytoplasm

What is the neurilemma, and what does it contain?

The neurilemma is the thick, outermost coil. It contains Schwann cell nucleus and most of its cytoplasm.

What are the nodes of Ranvier?

They are the gaps on the axon terminals

What are internodes?

They allow the electrical signal to conduct passively

Signal conduction occurs where?

Along the surface of a nerve fiber

Large fibers have more surface area and conduct more ___ than small fibers.

signals

Slow unmyelinated fibers are sufficient for many processes. Fast myelinated fibers occur where speed is vital, such as in motor commands to

skeletal muscles

Nerve fibers of the PNS are vulnerable to trauma, but may regenerate if its ____ is intact and at least some neurilemma remains.

soma