Lecture 6

Question 1

Chronobiology

Answer 1

• The study of timescales and cycles in biology
• Branch of biology concerned with natural physiological rhythms

Question 2

Biological rhythms

Answer 2

Ultradian - less then 24 hours (appetite)

Circadian - 24 hours (Cortisol…sleep)

Infradian - more then 24 hours (menstrual cycles)

Question 3

What are circadian rhythms?

Answer 3

Involved in essentially all physiological processes

• Controlled by peripheral “clocks” that are governed by a “master or central clock”
• Circadian rhythms coordinate sleep, nutrient supply and activity patterns with metabolic patterns differ by time of days

Question 4

Disruption of circadian rhythms can lead to:

Answer 4

A wide spectrum of health problems and premature aging including:

• Elevated inflammatory cytokines
• Gastrointestinal function (ulcer, irritable bowel)
• Obesity
  -Metabolic syndrome

Question 5

Circadian rhythms

Answer 5

The master or central “clock” is a brain region called the “superchiasmatic nucleus” which keeps time based on light signals from the retina

• located in the hypothalamus
• pace maker of the body
  -SCN is the central clock that relies on light

Question 6

What controls the molecular clock

Answer 6

Not very well understood:
- Entrained by light/dark circles
- Still intact in most blind individuals (retina still detects light )

-Chemical signals involved are not clear
- Melatonin is hormone produces by pineal gland of the brain

-Blue spectrum light (screens/monitors) inhibit melatonin release

Question 7

Bone and plasma Ca 2+ homeostasis

Answer 7

• Bone serves as a functional calcium store in the body
  -Acts as a “buffer” for plasma calcium labels

Question 8

Why is it so easy to lose bone density?

Answer 8

Plasma calcium must be maintained over a very narrow range

When you have a meal high in calcium it will deposit some in your bones (Calcitonin)

If your diet is low in calcium it will prevent your calcium from getting to low (takes from bones) (PTH)

Question 9

What is osteoporosis

Answer 9

A bone disease that develops when bone mineral density and bone mass decreases, or when the structure and strength of bone changes.

This can lead to a decrease in bone strength that can increase the risk of fractures (broken bones).

(-2.5 is T= osteoporosis)

Question 10

What can you do to maximize bone density (20-30)

Answer 10

1. Consume sufficient calcium (food, supplementation) in adolescence and early adulthood
2. Get adequate vitamin D (sun exposure, diet and supplements)
3. Participate in weight bearing physical activity/exercise most days of the week
4. Maintain a stable body mass with a BMI that is not too low (BMI >???)
5. Get plenty of sleep