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Human Phys
Circadian rhythm
| Question | Answer |
|---|---|
| Our circadian clock | - human physiology organised around sleep and activity - almost all life on earth has a internalised biological clock (light/dark cycles) - all activities need internal synchronisation - adapted to rotation around the sun |
| Active phase | energy higher, food/water consumed, organs active and prepare for intake/processing of nutrients |
| Sleep phase | energy/digestive processes decrease but cell repair, toxin clearance, memory consolidation and info processing increases |
| What is the circadian rhythm? | - allows humans to adapt to changes in our environment and anticipate changes in radiation, food availability and temperature - disruption of this can cause physical, mental and cognitive health |
| Entrainment | - rhythms don'd run for 24 hrs a day, but for longer - light the leading entrainment clue - zeitgeber: time giver - photoentrainment: process of daily resetting |
| What makes a rhythm circadian? | - free running period lasting at least 24hrs - entrainable: resets in response to external stimuli (light/heat) - temperature compensation: maintain this rhythm over a range of temperatures |
| Biological clocks in plants | Sunflowers follow the sun throughout the day, starting east, moving to west then back to east - helped by growth hormones - east stem side grows faster in day, west at night - effects photosynthesis, pollen production and heat protection mechanisms |
| An example: Drosophila | - gene identified that controls biological rhythm - saw gene encode a protein that accumulates in cells during the day and is degraded at night - Drosophilla displays circadian rhythms in its physiological processes ie. lays in the morning |
| Pathways of biolological clocks in humans | Input pathway: environmental cues to sensory receptors to brain Output pathway: physiological affect (activity, hormone release, feeding) - molecular clock controls physiological output |
| Master synchroniser: Suprachiasmatic nuclei (SCN) | - photopigment OPSIN4 in the retina - SCN has two nuclei that affect nervous and hormone signals - synchronises physiology through the day |
| Day and night | - daylight rich in blue light - OPSIN4 triggered by this wavelengh and suppresses melatonin, promoting awareness |
| Melatonin | Light-> Eyes-> SCN-> Cervical ganglion-> Pineal gland - main regulator of the circadian rhythm - amino acid hormone derived from trytophan |
| Cortisol | - steroid hormone - release linked to activity patterns - hypothalamus (CRH) to anterior pituitary (ACTH) to secretion from adrenal glands |
| SCN coordinates biological clock in peripheral | - other tissues in rats: skeletal muscle, liver, and lung make rhythms - gene and protein expression patterns that regulate function of tissue - control by synchronizing "slave oscillators - exhibit near-24-hour rhythms and control circadian tissue |
| More than sleep | 1.light/dark 2.food 3.exercise 4.temperature - if zeitgebers are out of time, things get mixed - eat at night, no choice for organs but to process - evening exercise can affect when you feel sleepy - cool temperature can help sleep |
| Circadian at molecular levels | - Circadian ‘cell-autonomous’ transcriptional–translational feedback loop - Circadian rhythms are controlled by "clock genes" that code for clock proteins - The levels of these proteins rise and fall in rhythmic patterns over 24 hours |
| Core circadian genes | Day: BMAL1/CLOCK Night: PER/CRY |
| When the circadian rhythm goes wrong | - Development of chronic diseases and conditions such as cancer, cardiovascular diseases - Altered core clock gene expression in a range of diseases |
| Sleep wake cycle disorders | ie. jetlag problems such as sleepiness, decreased mental and cognitive function |
| How this affects health | - increased risk of obesity, cardiovascular disease, neurodegenerative and gastrointestinal diseases - aging naturally dampens circadian rhythm |
| How can circadian rhythms affect medication | - enzymes metabolise drugs present through the day - drugs most effective when the target is actively happening - certain disease are amplified at different times of the day ie. osteoperosis pain generally hits at night |
Created by:
reub8n
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