Lecture 6 (week 3)

Question 1

What is chronobiology?

Answer 1

The study of timescales and cycles in biology

Question 2

What are the 3 biological rhythms?

Answer 2

1. Ultradian
2. Circadian
3. Infradian

Question 3

What is the Ultradian rhythm?

Answer 3

-Less than 24 hour cycle
-Ex. appetite (ghrelin), cortisol (pulse)

Question 4

What is the circadian rhythm?

Answer 4

-24 hour cycle
-ex. Cortisol (lowest at night, highest after awakening)

Question 5

What is the infradian rhythm?

Answer 5

-Greater than 24 hour cycle
-Ex. menstrual cycle

Question 6

What controls circadian rhythm?

Answer 6

Controlled by peripheral clocks that are governed by a master clock

Question 7

What do the peripheral and master clocks control?

Answer 7

Controls gene expression, regulation of enzymatic activities, neural function, hormone secretion, etc.

Question 8

What does your circadian rhythm coordinate?

Answer 8

Coordinate sleep, nutrient supply, & activity
patterns with metabolic patterns required at different stages of the day

Question 9

What does disruption of circadian rhythms in experimental animals lead to?

Answer 9

Wide spectrum of health problems and premature aging
-Elevated inflammatory cytokines
* Gastrointestinal function (ulcer, irritable bowel)
* Obesity
* Metabolic syndrome

Question 10

When is neural function best and worst?

Answer 10

best late morning, worst at night

Question 11

What is the master or central clock of the brain called and what does it do?

Answer 11

Called the suprachiasmatic nucleus, and keeps time based on light signals from the retina.

Question 12

Does Nearly every cell in the body have a subsidiary (peripheral) clock that coordinates its metabolism with the rest of the body?

Answer 12

Yes!

Question 13

What is melatonin? How is it’s release inhibited?

Answer 13

A hormone produced by the pinela gland of the brain.

Blue light from screens and monitors inhibit melatonin release

Question 14

How does a blind persons molecular clock function if they cant see ?

Answer 14

They still live by light/dark cycles and their retinas are still able to detect light.

Question 15

What are some examples of disruption of circadian rhythms and what are the consequences?

Answer 15

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

Question 16

What is a specific health related example of circadian rhythm disruption?

Answer 16

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.

Question 17

Because of our daily 2cm height variation, how can we accurately measure heigh progression?

Answer 17

Measure height at same time everyday

Question 18

When is the highest effect of compression?

Answer 18

Within th eifrst hour of getting out of bed

Question 19

What do osteoblasts do?

Answer 19

Build bone matrix

Question 20

What do osteoclasts do?

Answer 20

Break down bone matrix

Question 21

What is a DEXA scan?

Answer 21

A dual energy X-ray absorptiometry to determine bone mineral density. It is more definitive and generally safe.

Question 22

What does the DEXA scan measure and why?

Answer 22

DEXA estimates the amount of hydroxyapatite because it’s dense and able to absorb the rays.

Question 23

What is hydroxyapatite?

Answer 23

The mineral structure of bone is composed of hydroxyapatite, which is an insoluble deposit of calcium and phosphate within an extracellular (collagen) matrix.

Question 24

How does bone mineral density T-score work?

Answer 24

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

Question 25

What do bones serve as?

Answer 25

Bones serve as a functional calcium store in the body.

Question 26

Plasma calcium must be maintained over a ______________

Answer 26

very narrow range (ex. limited variation between fed & fasted states)

Question 27

Where are main sites of fracture?

Answer 27

Neck of femur and intravertebral disks

Question 28

How can we maximize bone density, as 90+% of maximal bone density is achieved by age 20?

Answer 28

1. Consume food with calcium in adolescence and early childhood
2. Get adequate vitamin D (sun exposure, diet, supplements)
3. Participate in weight bearing physical activity/excercise most days of the week
4. Maintain stable body mass
5. Get sleep

Question 29

What factors hinder maximal bone density?

Answer 29

-Smoking, alcohol, caffeine
-High phosphate
-Drugs (ex. corticosteroids)