Question

Human circadian (24-hour) rhythms

A. Are triggered totally by external (exogenous) factors.

B. Depend more on the integrity of the cerebral cortex than of the hypothalamus.

C. Adapt within 48 hours on changing from day to night shift work.

D. For melatonin secretion produce high night-time and low day-time levels of the hormone.

E. For the eosinophil count produce peak values around midday.

Answer 1

A. False External triggers modulate an endogenous clock.

B. False The hypothalamus is thought to be the location of the endogenous clock.

C. False Adaptation takes about a week or longer.

D. True Melatonin given at bedtime has been used to allay the circadian rhythm disturbances of sleep with jet-lag.

E. False The peak is at night when cortisol level is minimal.