Printer Friendly

Brain neurons blamed for dizzy spells.

Brain neurons blamed for dizzy spells

In a bygone era, fainting or dizzy spells signified a response to great passion or trauma. Modern science has since taken the romance out of these episodes, ascribing many of them to the mundane activity of standing up too quickly.

When a person stands up, a complex system called the baroreflex kicks into action: Nerve endings in key blood vessels detect the resulting drop in pressure and send a message to brain neurons, which respond by boosting blood pressure. Scientists know that the baroreflex often begins to fail with age, leading to dizziness, fainting spells and even stroke. But the exact nature of this failure has remained elusive.

George Hajduczok, a physiologist at the University of Iowa in Iowa City, now reports evidence suggesting that the blame lies with malfunctioning neurons. He and his colleagues studied 11 elderly purebred beagles and five young beagles. They increased blood pressure within the dogs' carotid arteries, which contain pressure-sensing nerve endings. Young dogs quickly sensed that change and lowered the activity of the sympathetic nervous system -- which boosts blood pressure -- by 70 percent, whereas elderly beagles damped such activity by only 20 percent, the researchers found.

A separate experiment showed that elderly dogs can lower sympathetic nervous system activity as much as young dogs, but only for a few seconds -- a finding that suggests the problem lies with the brain neurons rather than the nerve endings.

Such studies may help explain why some elderly people experience dangerous swings in blood pressure. A faulty baroreflex, says Hajduczok, can cause fainting when pressure dips too low, or a stroke when pressure soars too high.
COPYRIGHT 1991 Science Service, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1991, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:fainting
Publication:Science News
Date:Jan 26, 1991
Previous Article:Proteins guide early heart development.
Next Article:Ribbons of chaos: researchers develop a lab technique for snatching order out of chaos.

Related Articles
Million cell memories; surprisingly large portions of the brain may participate in a simple memory, thus challenging the notion that memory 'traces'...
Human brain neurons grown in culture.
AIDS dementia: neurons nixed by virus?
Data transfer via noisy neurons.
Tracing earliest neutrons' migration.
Neurons at work.
Brain cells work together to pay attention.
How the immune system eliminates mosquito-borne viruses--new insights. (EH Update).
Brain cells for alertness fire without cues. (No Rest for the Waking).
Autism's cell off: neural losses appear in boys, men with disorder.

Terms of use | Copyright © 2016 Farlex, Inc. | Feedback | For webmasters