biological rhythms

Question 1

Ralph et al

Answer 1

removed SCN of mutant hamsters who had 21 hour sleep wake cycle and transplanted them into normal hamsters. They changed their cycle to 21 hours showing SCN has a role as an endogenous pacemaker.

Question 2

Siffre

Answer 2

isolated himself in a dark cave with artificial light for 6 months. Sleep wake cycle settled at 25 hours but could range up to 48. Absence of natural daylight allowed biological clock to run normal. Shows external cues are not needed.

Question 3

Folkard et al

Answer 3

12 participants in isolation for 3 weeks in a cave with no external light and a single clock controlled by researchers. Increases speed of clock to make a day pass in 22 hours. 11 struggled to synchronise sleep wake cycles to clock page. Shows circadian rhythms cannot change.

Question 4

Czeisler et al

Answer 4

individual cycles can vary from 13 to 65 hours. Shows individual differences in circadian rhythms.

Question 5

McClintock

Answer 5

studies women with irregular periods. Pheromones collected from sweat of women at different stages in their menstrual cycles. Pheromones rubbed on upper lip of other women. 68% experienced changes in their cycle. Shows menstrual cycle can be affected by exogenous factors.

Question 6

Terman

Answer 6

SAD is more common in northern countries where winter nights are longer. Affected by light.

Question 7

Ericsson et al

Answer 7

violin practice lasted for 90 minutes before concentration decreased. Basic Rest Activity Cycle (BRAC). Sleep cycle is 90 minutes so other ultradian cycles should be the same.