A 10-degree decrease in temperature causes decreases in cerebral metabolic rate by :
**Core Concept**
A 10-degree decrease in temperature causes a significant reduction in cerebral metabolic rate, which is a critical adaptation to conserve energy and maintain cellular homeostasis in the brain. This phenomenon is often observed in hypothermic patients, where the brain's metabolic rate decreases in an attempt to compensate for the reduced oxygen delivery.
**Why the Correct Answer is Right**
The decrease in cerebral metabolic rate is largely due to the reduction in oxygen demand, which is mediated by the decrease in neuronal activity and the subsequent decrease in the release of excitatory neurotransmitters such as glutamate. Additionally, the decrease in temperature also affects the activity of enzymes and ion channels in the brain, leading to a reduction in the production of ATP. This reduction in ATP production is a critical factor in the decrease in cerebral metabolic rate.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the mechanism by which a decrease in temperature affects the cerebral metabolic rate. While the brain does have a high metabolic rate, the decrease in temperature is not primarily due to a decrease in the brain's metabolic rate per se.
**Option B:** This option is incorrect because it does not accurately describe the relationship between temperature and cerebral metabolic rate. While the brain does have a high metabolic rate, the decrease in temperature is not primarily due to a decrease in the brain's metabolic rate per se.
**Option C:** This option is incorrect because it does not accurately describe the mechanism by which a decrease in temperature affects the cerebral metabolic rate. While the brain does have a high metabolic rate, the decrease in temperature is not primarily due to a decrease in the brain's metabolic rate per se.
**Clinical Pearl / High-Yield Fact**
A 10-degree decrease in temperature can reduce the cerebral metabolic rate by up to 50%, making it a critical adaptation to conserve energy and maintain cellular homeostasis in the brain.
**Correct Answer:** C. Reduction in oxygen demand.