Mental health III - Circadian cycles and sleep Flashcards
What are the 2 interacting processes that are said to function together to regulate physiological rhythms, and what are they?
Sleep homeostatic drive - how much pressure neurons feel before sleep is triggered
Circadian clock - the 24 hour physiological rhythms generated by internal molecular clocks
What have organisms evolved to anticipate and how have they done this?
Organisms have evolved to anticipate regular 24 hour environmental changes, so that they can establish 24 hour rhythms to deal with these changes and give appropriate outputs at the right time of day
What is the circadian clock and what does it set out to do?
The circadian clock coordinates the internal time with the external world, allowing normal physiological functioning
Why do people feel most ill at the start and end of the day when they are unwell?
This is due to the circadian clock controlling hormone levels in the body throughout the day
Clock genes also specifically regulate the inflammatory system which is most active in the morning and at night time making you feel more unwell
AWAKE VS ASLEEP? What are the bodies’ internal processes at these times
When awake: high temperature, quick reactions, on high alert, no melatonin secretion, high B.P, cortisol being released
When asleep: low temperature, melatonin secretion, low B.P, no alertness or reactions
The molecular clock - what is it maintained by and where is this found?
Maintained by the master clock which is named the SUPRACHIASMATIC NUCLEI found in the hypothalamus.
The molecular clock - what does it refer to, what does it impact and what % of tissue transcriptome?
The molecular clock refers to thousands of clock controlled genes which control oscillations of tissue-specific metabolic and physiological functions.
The molecular clock impacts practically all cells of the body - 2-30% of each tissue’s transcriptome displays circadian rhythm
Why do we only grow at night time?
- Growth hormone is released by hypothalamic neurons which are ‘wrapped’ with TANYCYTES
- these open up at night and release growth hormone
Feedback loops - how do they work and what influences them?
Feedback loops are cell autonomous transcription-translation feedback loops of protein transcription factors which are also entrained by external factors.
They take 24 hours.
Give an example of a transcription factor feedback loop and say how it works?
CLOCK and BMAL1 genes drive expression of the genes Period and Cryptochrome, which in turn negatively feedback the transcription of CLOCK and BMAL1.
Example of how environmental inputs can entrain the molecular clock (light)
Light activates the CRY gene protein product promoting its binding to TIM
What disorders are linked to disruption of circadian rhythm and sleep?
What is the problem when considering the link?
-Schizophrenia
-Bipolar
-Depression
NOT SURE IF IT IS CAUSE OR CONSEQUENCE
INTRINSIC CLOCK AND MENTAL HEALTH - what was shown in fibroblasts isolated from schizophrenic patients?
- Loss of rhythmicity in CRY/PER1 expression
- Peripheral blood leukocytes showed disrupted expression of CLOCK/PER/CRY1/NPA2 genes
GWAS/SNP analyses - what have these shown re C.Rs and mental disorders?
Genes encoding core compounds of the molecular clock are disrupted in schiz, bipolar and depression
Lack of sleep is linked to poor mental health – what does this suggest about C.R?
Lack of sleep is associated with poor mental health – poor mental health is linked with disruption to the C.R – is lack of sleep therefore causal to poor mental health or does it contribute towards some mental health disorders?
