English subtitles for clip: File:Melatoninausschüttung und Körper-Rhythmus.webm
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1 00:00:02,000 --> 00:00:07,000 In brightness, the receptors on our retina pick up light 2 00:00:07,000 --> 00:00:11,000 and the production of the hormone melatonin is suppressed. 3 00:00:11,000 --> 00:00:17,000 A complex control organ in our brain is responsible for this. 4 00:00:17,000 --> 00:00:22,000 The pineal gland regulates the day-night rhythm of the body 5 00:00:22,000 --> 00:00:25,000 (circadian rhythm) by releasing melatonin. 6 00:00:25,000 --> 00:00:28,000 So when it gets dark and hardly any light 7 00:00:28,000 --> 00:00:30,000 hits the eyes, it secretes melatonin. 8 00:00:30,000 --> 00:00:38,000 The increased melatonin level makes us tired, lowers appetite, body temperature and blood pressure. 9 00:00:38,000 --> 00:00:44,000 This is not unique to humans, but works similarly in almost all vertebrates. 10 00:00:44,000 --> 00:00:47,000 Fish are particularly well studied in this regard. 11 00:00:47,000 --> 00:00:51,000 Even small amounts of light lower their melatonin levels. 12 00:00:51,000 --> 00:00:57,000 And that, in turn, affects their growth, immune defenses, and reproduction. 13 00:00:57,000 --> 00:01:03,000 So they are particularly affected by artificial light at night.