Circadian Rhythm

• Heliotropism


  Light-seeking movements in plants
• Chronobiologusts


  Scientists that study the relationship between organisms and their day-night dependancies
• Circadian rhythm


  Behaviors or psychological measures that intrinsically rely on a 24-hour cycle
• Zeitgebers


  Social or environmental cues that entrain your circadian rhythm to match the place you're in
• Timeless


  Gene that encodes for the circadian rhythm. Proteins TIM and PER form dimers that inhibit protein transcription, but TIM is degraded by light, so during the day there are less dimers, so more protein transcription
• Glutamate and norepinepherine spike when you're awake and keeps you alert. GABA makes you sleepy and drugs that act as positive allosteric modulators of it are sleep aids
• Adenosine


  As the body uses up energy, it builds up, so after a long time of being awake, too much of it makes you sleepy. Things like caffeine block it
• Caffeine


  Antagonist for adenosine, which staves off sleepiness and makes you more alert. Most commonly used psychostimulant
• Melatonin


  Produced by the pineal gland, which converts tryptophan into this. Helps regulate the sleep-awake cycle, and is regulated by the presence of light
• Retinohypothalamic tract(RHT)

  Where light-sensing cells send their signals to outside of the optic nerve, which directs them to the hypothalamus
• Suprachiasmatic nucleus (SCN)


  Clump of cells in the hypothalamus that synapse onto the pineal gland, which inhibits melatonin production in light conditions
• Half life


  Term used by pharmacologists and biologists to describe the amount of time it takes for half of a substance to leave your system. After 5, it has been functionally eliminated.
• Blue light is much more effective at activating the RHT which is why it makes it so hard to sleep after looking at a screen
• Histamine


  Used in the immune system to create inflammation or allergies, but in the brain is also used to communicate pro-wakefulness. Their antagonists used to cause mad drowsiness as a side effect
• Encephalitis lethargica


  Disease that damaged the anterior hypothalamus (causing fatal insomnia) or the posterior hypothalamus (causing fatal sleepiness)
• Tuberomammillary nucleus


  Major hypothalamic site of histamine production
• Orexin


  Pro-wakefulness signaling molecule absent in people with narcolepsy that is produced in the lateral hypothalamus
• Reticular formation


  Neurons in the brainstem whose activity relates to awakefulness and sleepiness. In has upwards and downwards pathways. The upward one, called ARAS, receives sensory inputs before sending them all throughout the cortex (the downward one is just muscle stuff)