Archive for August, 2010

Blood supply of the spinal cord

August 12, 2010 1 comment

Arterial supply : Supplied by 3 small arteries + feeder arteries

Segmental spinal arteries

ASA and PSA arteries are reinforced by segmental arteries, which enter the vertebral canal through the inter vertebral foramina. These arteries are branches of arteries outside the vertebral column (deep cervical, intercostal and lumbar arteries). Segmental arteries give rise to anterior and posterior radicular arteries.

Feeder arteries

Enter the vertebral arteries and anastomose with the ASA & PSA. The most important feeder artery is the Great anterior medullar artery (GAM) of Adamkiewicz. It arises from the aorta at lower thoracic or upper lumbar vertebral levels. This artery is unilateral. It lies in the left side of most people. It represents the major source of blood to the lower 2/3 of the spinal cord.

Veins of the spinal cord

Drain mainly into the veins of the brain and the venous sinuses via 6 tortuous longitudinal channels. Finally, they drain into the internal vertebral venous plexus.

Structure of the spinal cord (Grey matter & White matter)

August 12, 2010 1 comment

Transverse section of the spinal cord:

Gray matter

White matter

An Old Illusion

The Monkey Business Illusion

“Imagine you are asked to watch a short video (above) in which six people-three in white shirts and three in black shirts-pass basketballs around. While you watch, you must keep a silent count of the number of passes made by the people in white shirts. At some point, a gorilla strolls into the middle of the action, faces the camera and thumps its chest, and then leaves, spending nine seconds on screen. Would you see the gorilla?

Almost everyone has the intuition that the answer is “yes, of course I would.” How could something so obvious go completely unnoticed? But when we did this experiment at Harvard University several years ago, we found that half of the people who watched the video and counted the passes missed the gorilla. It was as though the gorilla was invisible.

This experiment reveals two things: that we are missing a lot of what goes on around us, and that we have no idea that we are missing so much. To our surprise, it has become one of the best-known experiments in psychology. It is described in most introductory textbooks and is featured in more than a dozen science museums. It has been used by everyone from preachers and teachers to corporate trainers and terrorist hunters, not to mention characters on the TV show C.S.I., to help explain what we see and what we don’t see. And it got us thinking that many other intuitive beliefs that we have about our own minds might be just as wrong. We wrote The Invisible Gorilla to explore the limits of human intuition and what they mean for ourselves and our world. We hope you read it, and if you do, we would love to hear what you think.”

-Christopher Chabris and Daniel Simons