Wednesday, April 29, 2009

Neurology 101


Some things here that I did not know. Cells in the brain that transmit nerve impulses are mostly white-colored, because their constituents are mainly lipids or fatty acid chains that form the insulating myelin. The parts of the brain that process information are grey-colored cells. They contain more proteins than the white cells.

From the MRI scans, my brain has an abnormally high amount of white matter present. Nobody offered to explain why -- but everyone who made an attempt to analyze the pictures made this observation.

So what? I don´t know. Still learning...

Schwannoma
Classification and external resources

A schwannoma, also known as a neurilemmoma is a benign nerve sheath tumor composed of Schwann cells, which normally produce the insulating myelin sheath covering peripheral nerves.
That is what was growing on my spinal cord.
Named after the German physiologist Theodor Schwann, Schwann cells (also referred to as neurolemnocytes) are a variety of glial cell that keep peripheral nerve fibres (both myelinated and unmyelinated) alive. In myelinated axons, Schwann cells form the myelin sheath (see below). The sheath is not continuous. Individual myelinating Schwann cells cover about 100 micrometre of an axon. The end result is a string of Schwann cells along the length of the axon, much like a string of sausages. The gaps between adjacent Schwann cells are called the nodes of Ranvier. The vertebrate nervous system relies on the myelin sheath for insulation and as a method of decreasing membrane capacitance in the axon. The action potential jumps from node to node, in a process called saltatory conduction, which can increase conduction velocity up to X10, without an increase in axonal diameter. In this sense, Schwann cells are the peripheral nervous system's analogues of the central nervous system oligodendrocytes. However, unlike oligodendrocytes, each myelinating Schwann cell provides insulation to only one axon (see image). This arrangement permits saltatory conduction of action potentials with repropagation at the Nodes of Ranvier, the gaps between myelinated segments. In this way, myelination greatly increases speed of conduction and saves energy .



Schwannomas are very homogeneous tumors, consisting only of Schwann cells. The tumor cells always stay on the outside of the nerve, but the tumor itself may either push the nerve aside and/or up against a bony structure, thereby causing damage.



8 comments:

Billy Bob Bambino Bombabious Baby the Third said...

I think that Dr. Schwann invented frozen dinners delivered to your door by yellow boxy freezer trucks...

Sorry. Couldn't resist...

:-)

Grandma Cobabe said...

Tee Hee!!!
Hey are you getting flooded out? Grandma

Billy Bob Bambino Bombabious Baby the Third said...

Nope! Not flooded! We have had over 15 inches over the last two weeks, but we weren't in the area that had 10 inches in 6 hours! That's floody... Two weeks ago we (Ammon and I) were camping with the Scouts and it rained like crazy and the lightning and thunder were amazing. Ammon slept right on through it, though!

Limasa Family said...

Jim you sound like the smartest guy on the planet from where I'm sitting!

Patricia said...

Oh boy! The physiology/neurology lessons are back!

Hopefully, this comment will get through so you know I haven't abandoned you, Jim!

Grandma Cobabe said...

Nice to hear from you Patricia.How is your family??? Mary Cobabe

Michelle said...

By the way...I like to look here, and see that you posted...sometimes I choose not to read...but I take comfort in the fact that you ARE posting...it makes me feel like you are well. Where are you? It has been a few days, you are worrying me! Are you OK?

Patricia said...

Thank you for asking, Mary. We've had illness in the house for two months, which hasn't been much fun. I think we're coming out of it now.

During the last month of that time sandstorms blasted us, picking apart the house. So we have repairs to deal with.

You probably know how it goes, sometimes.

I know you've been thinking of us and I appreciate it.

You too, Jim.