Sleeping Versus Waking

Why do treatments for the symptoms of the common cold make us drowsy How does coffee work This chapter touches briefly on neurotransmitters whose actions in the brain affect our sleep—wake cycle and on a few well-known 

HISTAMINE AND OREXIN One such neurotransmitter is histamine, whose neurons influence our level of arousal throughout the day. Lying next to these neurons is another group of neurons that release orexin, which is a neurotransmitter that influences both our level of arousal and craving for food. Take a moment to appreciate how the anatomical organization of this system optimizes your daily 

This neurotransmitter has diverse functions throughout the brain that are also related to our sleep—wake cycles. We know a lot about it because of the ready availability of a very safe, highly effective adenosine receptor antagonist that is served hot or cold, with or without cream, throughout the world—caffeinated coffee Caffeine is also commonly found with theophylline (a molecule that is very similar to caffeine) in tea. Indeed, although caffeine is found in at least 63 plant species, 54% of the world s 

Coffee drinking (or consuming caffeine from non-coffee sources) has been associated with a significantly lowered risk of developing Parkinson s disease. The neuroprotective effect 

Many people drink coffee to reduce drowsiness. How does caffeine achieve this effect in the brain The answer begins with a consideration of the function of the acetylcholine neurons that control your ability to pay attention. Adenosine negatively controls the activity of these neurons, meaning that when adenosine binds to its receptor on acetylcholine neurons, their activity slows. The production and release of adenosine in your brain is linked to metabolic activity while you are awake. Therefore, the concentration of adenosine in the neighborhood of acetylcholine neurons increases constantly while your brain is active during the day. As the levels of adenosine increase, they steadily inhibit your acetylcholine neurons, your brain s activity gradually slows, and you begin to feel drowsy and ultimately fall asleep. Caffeine comes to the rescue because it, like theophylline 

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Mezzanotte WS, Tangel DJ, White DP (1992) Waking genioglossal electromyogram in sleep apnea patients versus normal controls (a neuromuscular compensatory mechanism). J Clin Invest 89 1571-1579... 

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