Week 6. Chronobiology

Question 1

Why do we have endogenous clocks?

Answer 1

To anticipate daily change in external environment.

Question 2

What is chronopharmacokinetics?

Answer 2

Absorption, metabolism and clearance of drugs varies over circadian cycle.
Chronotherapy halves the chances of side effects compared to constant infusion.

Question 3

How is the circadian rhythm generated?

Answer 3

SCN –> hypothalamus –> pituitary –> adrenal glands

Question 4

Name four tissues that use circadian rhythm with an example for each.

Answer 4

Skeletal muscle –> glucose uptake and metabolism
Pancreatic clock –> insulin secretion
Liver –> fasting glycaemic control, glucose clearance
Adipose tissue –> lipid storage/metabolism

Question 5

Which area of the brain generates the circadian rhythm?

Answer 5

Superchiasmatic nucleus (SCN)

Question 6

What is melatonin?

Answer 6

A hormone that determines the biological clock. In humans, pharmacological levels help sleep. In sheep, allows them to recognise breeding season.

Question 7

Name one example of the pathological effects of disturbed circadian rhythm?

Answer 7

Shift work is associated with increased risk in obesity, type 2 diabetes and CHD.

• disturbed and fragmented sleep
• eating at suboptimal times.

Question 8

Describe the following terms:

1. Circatidal
2. Circadian
3. Circalunar
4. Circannual

Answer 8

1. According to the tide
2. Daily
3. New moon
4. Annually