Biological Rhythms

Question 1

Where is the ‘biological clock’ of the body found?

Answer 1

In the brain in a small group of neurones in the suprachiasmatic nucleus in the hypothalamus

Question 2

Give an example of a hormone that varies in levels depending on the time of day

Answer 2

1. Cortisol in blood:

Peak at 7am to dip at 7pm

*because of this change in levels, the time should always be noted when taking a sample of blood for cortisol measurement and repeated measurements should be taken at the same time of day.

Question 3

Give an example something within the body that is set by biological rhythms

Answer 3

Menstrual cycle:

Women’s core body temp varies during the cycles. A sudden increase in body temp can be used as a marker of ovulation.

Question 4

What hormone released from the pineal gland is involved in setting the biological clock?

Answer 4

Melatonin