Integrative Brain Function - Sleep 1 (round 1)

What are all the body clocks synchronised by?

suprachiasmatic nucleus (SCN)

Where is the SCN located and what genes does it contain?

hypothalamus, clock genes

How are circadian rhythms generated?

endogenously

When is the desire for sleep the strongest?

2-4am, 1-3pm

How does the circadian period vary?

25%: <24 hrs, 75%: >24 hrs, average: 24.2 hrs

What are ultradian rhythms?

recurrent cycle repeated throughout 24-hr day (periods shorter than circadian rhythm)

What are infradian rhythms?

rhythms with periods longer than circadian rhythms

How is the SCN divided functionally?

dorsomedial SCN (constant darkness)

ventrolateral SCN (direct retinal input)

What are zeitgebers?

external factors that entrain the circadian rhythm

How does light entrain SCN?

through ipRGCs that contain melanopsin

What are ipRGCs?

intrinsically-photosensitive RGCs that send their axons directly to SCN via retino-hypothalamic tract

What is the SCN’s inherent cycle?

24 hours ±11 mins

What does the pineal gland produce?

melatonin

What is the function of melatonin?

to mediate info about the dark

How does SCN control melatonin levels?

inhibition of pineal gland