Lecture 6 (week 3) Flashcards
What is chronobiology?
The study of timescales and cycles in biology
What are the 3 biological rhythms?
- Ultradian
- Circadian
- Infradian
What is the Ultradian rhythm?
-Less than 24 hour cycle
-Ex. appetite (ghrelin), cortisol (pulse)
What is the circadian rhythm?
-24 hour cycle
-ex. Cortisol (lowest at night, highest after awakening)
What is the infradian rhythm?
-Greater than 24 hour cycle
-Ex. menstrual cycle
What controls circadian rhythm?
Controlled by peripheral clocks that are governed by a master clock
What do the peripheral and master clocks control?
Controls gene expression, regulation of enzymatic activities, neural function, hormone secretion, etc.
What does your circadian rhythm coordinate?
Coordinate sleep, nutrient supply, & activity
patterns with metabolic patterns required at different stages of the day
What does disruption of circadian rhythms in experimental animals lead to?
Wide spectrum of health problems and premature aging
-Elevated inflammatory cytokines
* Gastrointestinal function (ulcer, irritable bowel)
* Obesity
* Metabolic syndrome
When is neural function best and worst?
best late morning, worst at night
What is the master or central clock of the brain called and what does it do?
Called the suprachiasmatic nucleus, and keeps time based on light signals from the retina.
Does Nearly every cell in the body have a subsidiary (peripheral) clock that coordinates its metabolism with the rest of the body?
Yes!
What is melatonin? How is it’s release inhibited?
A hormone produced by the pinela gland of the brain.
Blue light from screens and monitors inhibit melatonin release
How does a blind persons molecular clock function if they cant see ?
They still live by light/dark cycles and their retinas are still able to detect light.
What are some examples of disruption of circadian rhythms and what are the consequences?
Shift workers
* Heart attacks
* Obesity, diabetes, cardiovascular complications
* Cancer
* Alzheimer’s Disease
Late chronotypes (“night owls”)
* More likely to suffer from mental stress
* More likely to smoke
What is a specific health related example of circadian rhythm disruption?
Risk of sudden heart attack is greatest mid-morning
* No clear answer yet
* May be due to a protein called Kruppel-like factor 15 (Klf15), which
affects K+ efflux in the heart
* Combination of factors: caffeine, stress, high fat diet, etc.
Because of our daily 2cm height variation, how can we accurately measure heigh progression?
Measure height at same time everyday
When is the highest effect of compression?
Within th eifrst hour of getting out of bed
What do osteoblasts do?
Build bone matrix
What do osteoclasts do?
Break down bone matrix
What is a DEXA scan?
A dual energy X-ray absorptiometry to determine bone mineral density. It is more definitive and generally safe.
What does the DEXA scan measure and why?
DEXA estimates the amount of hydroxyapatite because it’s dense and able to absorb the rays.
What is hydroxyapatite?
The mineral structure of bone is composed of hydroxyapatite, which is an insoluble deposit of calcium and phosphate within an extracellular (collagen) matrix.
How does bone mineral density T-score work?
A higher number is a lower risk of bone mineral density, and a lower number is a higher risk.
ex. -4 is a high risk
ex. 1 is a low risk
