Circadian rhythms Flashcards
Describe how the circadian rhythm works in humans.
- 24h rhythm that persists in constant darkness, but not constant light
- it varries from person to person, but is app. 24h
What brain region are responsible for controlling daily rhythms in physiology?
Suprachiasmatic nucleus (SCN)
What is a standardized way of displaying 24h rhythms?
By an actogram
How was the SCN identified as the circadian clock?
By lesion experiments
Describe the human molecular clockwork.
All cells have a circadian clock as clock genes are transcriped until it inhibits itself by a negative feed-back loop, following a daily rhythm independent of darkness
What is the phenotype of a CRY-1 mutant?
Having a hard time falling asleep
Which cells in the eyes are responsible for controlling the circadian rhythm?
The melonoopsin containing retinal ganglion cells
What happens if you shine light on the retina?
The circadian rhythm resets
Describe the signaling pathway of the circadian photoneuroendocrine system in the human brain.
Retinal ganglion cells –> SCN in hypothalamus –> intermediolateral cell column in the spinal cord –> superior cervical ganglion –> pineal gland
What are melatonin, and how is it synthesized?
The hormonal output of the photoneuroendocrine system
Serotonin –> –> melatonin
What enzymes are involved in the melatonine synthesis?
AANAT: enzyme generating the melatonin rhythm
ASMT: also important for the transversion of serotonin –> melatonin, but no rhythm
How does the knockout of one clock (Bmal1) gene in the neocortex affect rodents (also seen in humans)?
No clock genes work, but same physiology
BUT: express symptoms of despression, and reduced monoamine signaling
What hormone induces clock gene rhythms in the hippocampus, and where is it released from?
Corticosterone, released from the adrenal gland
