Substrate Notes — human biochemistry in plain languagePlain-language deep dives into hormones, sleep, stress, mitochondria, and the molecular machinery of everyday life.https://simple-blog-en.pages.dev/The afternoon dip is a pacing problem, not a moral onehttps://simple-blog-en.pages.dev/afternoon-dip-mitochondria/https://simple-blog-en.pages.dev/afternoon-dip-mitochondria/The mid-afternoon slump is circadian and post-meal, with mitochondria supplying ATP at the pace the cell allows.Cold hits the nerves first and the thyroid laterhttps://simple-blog-en.pages.dev/cold-and-thyroid/https://simple-blog-en.pages.dev/cold-and-thyroid/The first response to cold is sympathetic. Thyroid hormone turnover changes on a slower clock than shivering.Daylight, brain serotonin, and the gut's separate poolhttps://simple-blog-en.pages.dev/daylight-serotonin-gut/https://simple-blog-en.pages.dev/daylight-serotonin-gut/Morning light reaches brain serotonin through the eye. The gut's serotonin does not commute upstairs to become a mood.Growth hormone waits for deep sleep, not for an early bedtimehttps://simple-blog-en.pages.dev/deep-sleep-growth-hormone/https://simple-blog-en.pages.dev/deep-sleep-growth-hormone/The big growth-hormone pulse rides slow-wave sleep. Going to bed early does nothing if that deep sleep never arrives.What dopamine does in the last minutes of hard efforthttps://simple-blog-en.pages.dev/dopamine-in-the-last-minutes/https://simple-blog-en.pages.dev/dopamine-in-the-last-minutes/Dopamine in hard effort is a keep-going signal, not a pleasure spray that arrives when the work is over.What the day-after ache is actually signalinghttps://simple-blog-en.pages.dev/inflammation-the-day-after/https://simple-blog-en.pages.dev/inflammation-the-day-after/The soreness after a long effort is not the same signal as chronic inflammation, and muscle IL-6 is not a fire alarm.Lactate is a fuel, not the thing that burnshttps://simple-blog-en.pages.dev/lactate-as-fuel/https://simple-blog-en.pages.dev/lactate-as-fuel/Working muscle ships lactate as a fuel other tissues can oxidize. The burn is not lactate acting as a toxin.A late meal and the next morning's insulinhttps://simple-blog-en.pages.dev/late-meal-insulin/https://simple-blog-en.pages.dev/late-meal-insulin/Eating late lands the meal when insulin sensitivity is already lower, and the next morning still shows it.Light affection and the oxytocin pulsehttps://simple-blog-en.pages.dev/light-affection-oxytocin/https://simple-blog-en.pages.dev/light-affection-oxytocin/A hand on an arm can raise oxytocin when the touch is wanted. The pulse is a context signal, not a switch.What an orgasm changes in the next hourhttps://simple-blog-en.pages.dev/orgasm-prolactin-next-hour/https://simple-blog-en.pages.dev/orgasm-prolactin-next-hour/After orgasm, prolactin often rises and oxytocin can rise with it. The next hour is a hormone shift, not a cure.How a short night changes the next morning's glucosehttps://simple-blog-en.pages.dev/overnight-glucose-after-short-sleep/https://simple-blog-en.pages.dev/overnight-glucose-after-short-sleep/A short night raises the morning cortisol signal and makes the same breakfast harder for insulin to clear.Why nerves misfire when you only drink waterhttps://simple-blog-en.pages.dev/sodium-and-nerve-firing/https://simple-blog-en.pages.dev/sodium-and-nerve-firing/A nerve fires on a sodium gradient. Drinking only water during long effort can wash that gradient down.