CIRCADIAN RHYTHMS

Question 1

Circadian rhythms are a characteristic of _____

Answer 1

virtually all organisms

Question 2

Persist in constsnt conditions, where the ________ is typically either just under or just over 24hrs, controlled by an endogenous _____

Answer 2

free-running period; circadian clock

Question 3

In nature the circadian rhythm is ______ by daylight, reset each day, so the observed rhythm is exactly 24hrs

Answer 3

entrained

Question 4

Animals are either

Answer 4

nocturnal (active at night e.g. bats)
Diurnal (active during day e.g. humans)

Question 5

Circadian rhythms of

Answer 5

sleep, temperature, urine production, some hormones

Question 6

Location and functioning of circadian clock

Answer 6

Isolated cells display circadian rhythms (including cells from adrenal glands, pineal
gland, lung);

Question 7

This implies:

Answer 7

• Clock at cellular level; many clocks in body
• Master clock located in brain

Question 8

How the mammalian “clock”
works:

Answer 8

Light is perceived by the retina
(rods and cones are not necessary)

Question 9

Information about light is
transmitted directly from the retina to the

Answer 9

master clock or pacemaker
in the suprachiasmatic nuclei
(SCN) of the hypothalamus; the
information passes along the
retino-hypothalamic tract