Circadian rhythm - AO1

Question 1

What are biological rhythms?

Answer 1

Distinct patterns of changes in body activity that occur in cyclical time periods
They are influenced by endogenous pacemakers and exogenous zeitgebers

Question 2

What are endogenous pacemakers and exogenous zeitgebers?

Answer 2

• Internal body clocks
• Environmental change

Question 3

What are the three types of rhythms and how long do they last?

Answer 3

• Circadian rhythm - takes 24 hours
• Infradian rhythms - taes longer than 24 hours
• Ultradian rhythms - takes less than 24 hours

Question 4

What are the two examples of circadian rhythms?

Answer 4

Main example: Sleep wake cycle
Back up: Body temperature

Question 5

What are exogenous zeitgebers in sleep wake cycle?

Answer 5

Light is first detected by the eye which then sends messages concerning the level of brightness to the SCN

Question 6

What are endogenous pacemakers in sleep wake cycle?

Answer 6

Suprachiasmatic nuclei (SCN) a bundle of nerve cells located in the hypothalamus then messages to the pineal gland, moderating melatonin levels

Question 7

What is the Sieffre cave study?

Answer 7

Two months in caves in Southern alps
Had access to food and drink but no lighter and sound/clocks
Resurfaced in mid-sept 1962 but believed it to be mid-august

1972:
6 months in a cave

• In each case his free running biological rhythm settled down to one that was just beyond the usal 24 hours (25 hours)
• Light entrains cycle to 24 hours

Question 8

What is rhe Aschoff and Wever study?

Answer 8

• 1976: PPs spent four weeks in a disused WW2 bunker, no natural light
• All but on PP (cycle extended to 29 hours) had rhythm between 24-23 hours
• Free running cycle is entrained by exogenous zeitgebers