X-Message-Number: 28317
Date: Tue, 15 Aug 2006 19:51:22 -0700 (PDT)
From: Doug Skrecky <>
Subject: head cooling does little to cool the brain

[As long as blood still flows.]

J Appl Physiol (July 13, 2006). doi:10.1152/japplphysiol.00319.2006
How The Body Controls Brain Temperature: The Temperature Shielding Effect
of Cerebral Blood Flow
  Normal brain functioning largely depends on maintaining brain
temperature. However, the mechanisms protecting brain against a cooler
environment are poorly understood. Reported herein is the first detailed
measurement of the brain-temperature profile. It is found to be
exponential, defined by a characteristic temperature shielding length,
with cooler peripheral areas and a warmer brain core approaching body
temperature. Direct cerebral blood flow (CBF) measurements with
microspheres show that the characteristic temperature shielding length is
inversely proportional to the square root of CBF in excellent agreement
with a theoretical model. This "temperature shielding effect" quantifies
the means by which CBF prevents "extracranial cold" from penetrating deep
brain structures. The effect is crucial for research and clinical
applications - the relationship between brain, body and extracranial
temperatures can now be quantitatively predicted.

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