Confused About C.O.W.S

[adagio]

I Have a question regarding the cold/warm water test ( to check for the integrity of the vestibulo-ocular reflex ) :
The textbooks says that we administer cold water into the right external ear ( for example ) ; the cold water exerts an inhibitory effect on the flow of the endolymph in this side, which, in turn, inhibits the Right Hair Cells (Vestibular Nerve Receptors), and in consequence, the Right Vestibular Nucleus, thus, the Left Vestibular Nucleus, now that is liberated from the (Inhibitory effect) of the Right VN, acts as if it is stimulated (And this stimulation implies that the head is turning to the Left ) and causes the eyes to move slowly (Slow phase of the Nystagmus) to the right, HOWEVER ( AND HERE IS WHY I AM CONFUSED ) the textbooks dictates that a Rapid CORRECTIVE movement of the eyes occurs to the LEFT ( because the head is not moving, and we only administered water ), which produces the Left Nystagmus (A nystagmus is named after the direction of its RAPID phase)
My question is the following :
If the first stimulator of this whole cascade (which is the INHIBITION the right hair cells, and thus the assumption that the right side is DAMAGED), how come a corrective action is taking place with no consideration to the previously mentioned assumption ?

I hope that you would help me figure this out guys, because I am really confused …

Thank you so much for your patience and help.

Kind regards,

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[AlternateSome1]

I think the problem is the assumption that inhibition = damage. This is not true. You can think of the two vestibular systems as yolked together with each side having a base level of stimulation keeping your vision centered. When you turn your head and need to look to the opposite direction to maintain focus, you COULD do this by only increasing stimulation on one side, but it is more efficient to simultaneously inhibit the opposing drive. The nystagmus seen toward the direction of experienced motion then recenters toward the direction of perceived travel and is not ignoring damage. The same effect of slow smooth pursuit followed by countered nystagmus can be experienced if you spin your chair around and try to focus on objects in the room. If you spin to your left, you will focus and follow the object to the right, then rapidly correct to the left once it leaves your field of vision.

Other examples of inhibition are found within the endocrine system. Often, high levels of a hormone will inhibit the production of either the hormone or the signal to produce the hormone or both. This is not damage when this occurs, just a decrease in drive.


Edited - http://books.google.com/books?id=E5...ts=-1egtQBOmY&sig=_5M7KIsTUdIKfoFW-8kVsQYynlo
This page discusses the actual effect of the temperatures on the endolymph and the semicircular canal system. This might help to explain why inhibitory and stimulatory signals are produced when cold vs hot water is placed into the external auditory canal.

 

[adagio]

I think the problem is the assumption that inhibition = damage. This is not true. You can think of the two vestibular systems as yolked together with each side having a base level of stimulation keeping your vision centered. When you turn your head and need to look to the opposite direction to maintain focus, you COULD do this by only increasing stimulation on one side, but it is more efficient to simultaneously inhibit the opposing drive. The nystagmus seen toward the direction of experienced motion then recenters toward the direction of perceived travel and is not ignoring damage. The same effect of slow smooth pursuit followed by countered nystagmus can be experienced if you spin your chair around and try to focus on objects in the room. If you spin to your left, you will focus and follow the object to the right, then rapidly correct to the left once it leaves your field of vision.

Other examples of inhibition are found within the endocrine system. Often, high levels of a hormone will inhibit the production of either the hormone or the signal to produce the hormone or both. This is not damage when this occurs, just a decrease in drive.


Edited - http://books.google.com/books?id=E5...ts=-1egtQBOmY&sig=_5M7KIsTUdIKfoFW-8kVsQYynlo
This page discusses the actual effect of the temperatures on the endolymph and the semicircular canal system. This might help to explain why inhibitory and stimulatory signals are produced when cold vs hot water is placed into the external auditory canal.

Dear Alternatesome1, thank you so much for your adequate reply, and i really appreciate the link that you have provided. Your point was clearly illustrated. Thanks again.

Kind regards,