13. Biological Rhythms: Circadian Rhythms AO1

Question 1

What are biological rhythms?

Answer 1

Periodic activity

Question 2

What are biological rhythms governed by?

Answer 2

1. Internal biological ‘clocks’

2. External changes in the environment

Question 3

What are internal biological ‘clocks’ called?

Answer 3

Endogenous pacemakers

Question 4

What are external changes in the environment called?

Answer 4

Exogenous zeitgebers

Question 5

When do rhythms occur?

Answer 5

Ultradian rhythms - many times a day
Infradian rhythms - take less than a day to complete
Circannual rhythms - much longer

Question 6

How many important types of circadian rhythms are there

Answer 6

Several such as sleep/wake cycle

Question 7

Explain exogenous zeitgebers

Answer 7

The fact we feels drowsy when it’s night-time and alert during day-time shows the effect of daylight

Question 8

Explain endogenous pacemakers

Answer 8

A biological ‘clock’ left to its own devices without the influence of external stimuli (e.g. Light) is called free-running

Question 9

Explain the idea of there being a basic rhythm

Answer 9

It’s governed by the suprachiasmatic nucleus (SCN), which lies just above optic chaise and receive information about light.

Question 10

What can exogenous zeitgebers do to the SCN

Answer 10

Reset it

Question 11

What did Siffre do?

Answer 11

Spent long periods in dark caves to examine the extent of free running biological rhythms

Question 12

Where did Siffre stay?

Answer 12

• Two months in caves in the Southern Alps

- Six months in a Texan cave

Question 13

What did Siffre demonstrate?

Answer 13

Free-running circadian rhythms of about 25 hours

Question 14

What is important to remember about Siffre?

Answer 14

He did have a regular sleep/wake cycle

Question 15

Who found a similar circadian rhythm?

Answer 15

Aschoff and Wever

Question 16

What did Aschoff and Wever do?

Answer 16

A group of participants spent four weeks in a World War II bunker deprived of natural light

Question 17

What did Aschoff and Wever find?

Answer 17

All but one display a circadian rhythm between 24 and 25 hours

Question 18

What did the research suggest

Answer 18

Siffre and Aschoff’s research suggested the ‘natural’ sleep/wake cycle may be slightly longer than 24 hours but is entrained by exogenous zeitgebers associated with out 24- hour day

Question 19

What may endogenous pacemakers have?

Answer 19

Stronger influence than exogenous zeitgebers

Question 20

Who did Folkard et al study and what was the procedure?

Answer 20

A group of 12 people who lived in a dark cave for three weeks, going to bed 1 o’clock said 11:45 PM and waking when it said 7:45 AM

Question 21

What did Folkard et al change?

Answer 21

Research is gradually speeded up the clock so an apparent 24 hour day eventually lasted only 22 hours

Question 22

What did Folkard et al find?

Answer 22

Only one participant comfortably adjusted to

Question 23

What does Folkard et al’s study suggest?

Answer 23

A strong free running circadian rhythm cannot easily be over written by changes in external environment