Circadian rhythms Flashcards
(28 cards)
How long is circadian cycle?
20-28 h
How long is ultradian cycle?
Less than 20 hours
How long is circamensual cycle?
30 days
How long is infradian cycle?
Less than 38 hours
How long is human period?
25 hours
Where is SCN?
Anterior hypothalamus
RHT
- Signal from light-dark cycle through retinal hypothalamic tract which is glutamatergic
- Glutamate into SEN - activates neurons
- SEN ontop of optic chiasm
- Circadian rhythms are endogenous - not driven by light-dark cycle
When does real time start?
0
What is ZT 0?
Lights on
What is ZT 12?
Lights off
What is CT 0?
Subjective lights on
What is CT 12?
Subjective lights off
What is the phase of a clock?
How delayed a cycle is compared to lights on
What is phase advance?
How delayed a cycle is compared to lights on
How do clocks work?
BMAL1 and CLOCK activate PER-CRY
PER-CRY inhibit BMAL1 and CLOCK
When is SCN more hyper polarised and depolarised?
Night and day
Do SCN cells contain GABA?
Yes
Why are glial cells good?
Support electrical conductivity
How does the retina communicate with the SCN?
RHT and glutamate PACAP
How does the intergenticulate leaflet communicate with the SCN?
Geniculohypothalamic tract
How does Median Raphe communicate with the SCN?
Serotonin
Processes regulated by SCN
- Vasoactive intestinal polypeptide
- Vasopressin
- Prokineticin
- Neuromedin
- Enkephalin
- Help circadian rhythm in other areas of body
- Physiology and behaviours: memory/reward/sleep/temperature/metabolism etc
- Helps with cell cycle progression, DNA repair, cell detoxification
- Master clock organises clocks in all tissues
Where is melatonin released?
Pineal gland
How do the PVN and SCN communicate?
HPA axis
