circadian rhythms [BIOLOGICAL RHYTHMS]

Question 1

What is a circadian rhythm?

Answer 1

A type of biological rhythm that occurs in a 24 hour period

Question 2

What is an example of a circadian rhythm?

Answer 2

The sleep/wake cycle

Question 3

What are biological rhythms influenced by?

Answer 3

Endogenous pacemakers (internal body clocks)
Exogenous zeitgebers (external environmental factors)

Question 4

How is the sleep/wake cycle influenced by exogenous zeitgebers? (2)

Answer 4

DAYLIGHT - we feel drowsy when it is night time because light can reset the SCN
SOCIAL CUES - newborn babies begin with a random cycle, but it settles down in 6 weeks due to schedules

Question 5

What have many studies investigated the impact of on circadian rhythms?

Answer 5

Absence of exogenous zeitgebers/extent of endogenous pacemakers

Question 6

What was the method of Siffres cave study?

Answer 6

He spent 2 months isolated in a cave, documenting his sleeping, waking and eating to an outside team.

Question 7

What were the results of Siffres cave study?

Answer 7

He fell into a roughly 25-hour sleep/wake cycle

Question 8

What does Siffres cave study show about circadian rhythms?

Answer 8

Endogenous pacemakers can maintain regular rhythms with little external influence
[and the natural rhythm may be longer than 24 hours]

Question 9

What was the method of Aschoff and Wever’s bunker study?

Answer 9

Ppts spent 4 weeks in a WW2 bunker with no natural light, their sleep/wake cycle was recorded

Question 10

What did Aschoff and Wever find in their bunker study?

Answer 10

All but one ppt fell into a rhythm of 24-25 hours, one fell into a 29-hour cycle

Question 11

What does Aschoff and Wevers study show about circadian rhythms?

Answer 11

Endogenous pacemakers maintain regular rhythms with little external influences
[and the natural rhythm may be longer than 24 hours]

Question 12

What was the method of Folkards cave study?

Answer 12

12 ppts lived in a dark cave for 3 weeks, their day was changed from 24 hours to 22 hours without them knowing

Question 13

What were the results of Folkards cave study?

Answer 13

Only 1 ppt adjusted to the new schedule

Question 14

What does Folkards study show about circadian rhythms?

Answer 14

They cannot be overridden by exogenous zeitgebers

Question 15

How has research into circadian rhythms helped practical application in shift work?

Answer 15

SHIFT WORK
Research found that workers experience reduced concentration at 6am (circadian trough) & that there was a relationship between shift work and heart disease
= identifying the damage resulted in adjustments to shift work; which is better for worker health and has economic implications of improved productivity

Question 16

How has research into circadian rhythms helped practical application in pharmacokinetics?

Answer 16

Circadian rhythms also coordinate digestion and hormones in the body, research has revealed the most effective times to take drugs
= dosage guidelines make treatment more efficient; cost-effective for NHS

Question 17

Which study contradicts the findings on circadian rhythms and how?

Answer 17

CZEISLER was able to adjust the sleep/wake cycle by shining light on the backs of ppts knees, which shows the influence that exogenous zeitgebers have on circadian rhythms

Question 18

Why does the methodology of the circadian rhythms studies decrease their internal validity?

Answer 18

They all used artificial lighting (proven to have an effect) therefore the endogenous pacemakers were being influenced by stimuli, and the studies weren’t testing the isolated internal mechanisms

Question 19

What is the problem with generalising the circadian rhythms studies?
(2)

Answer 19

Small groups failed to consider individual differences, which were seen in the fact that not all ppts had the same results
Siffre repeated his experiment when he was 69 and found different results, indicating that age is a confounding variable, and others could exist