Circadian Rhythms

Question 1

What is the definition for Circadian rhythms ?

Answer 1

• A pattern of behaviour that occurs or recurs approximately every 24hrs and which is set and reset by environmental light levels.

Question 2

What is the sleep wake cycle?

Answer 2

• Refers to alternating states of sleep and waking that are dependent on the 24hrs circadian rhythms.

Question 3

What are the two other types of Circadian rhythms?

Answer 3

• core temperature

- hormone production

Question 4

what is the core temperature ?

Answer 4

• temperature is the best indicators for Circardian rhythms.
• lowest at 4:30am (about 36 degrees) highest at 6pm (about 38 degrees)
• sleep occurs when core temperature drops and body temp start to rise in the last hrs of sleep

Question 5

when does a small drop in body temperature occur in most people ?

Answer 5

At 2pm to 4pm - explains why many feel sleepy in the early afternoon

Question 6

What is hormone production ?

Answer 6

• Hormone release circadian rhythms
  e. g. the production and release of melatonin from the pineal gland in the brain follows a circadian rhythm, with peak levels occurring during the hours of darkness.

By activating chemical receptors in the brain, melatonin encourages feeling of sleep.

When dark more melatonin is produced

Question 7

Case Study

Answer 7

• Evidence conducted by Michel Siffre
• subjected himself to long periods of time living underground in order to study his own circadian rhythm.
• underground he had no external cues to guide his rhythm - no daylight, no clocks
• he just woke , ate and slept when he felt it was appropriate to do so. - only influence from internal clock
• stayed 61 days in the southern alps in 1962 - resurfaced on 17th September thinking it was 20th august

He found that his body clock ticked more slowly compared to when he was a younger man - sometimes stretching his circadian rhythms to 48hrs.

Question 8

Evaluation points

Answer 8

• Buhr et al (2010)
• Czeisler et al (19099)
• Evans and Marain (1996) - Chronotherapeutic
• Hughes
• research mythology artificial lights

Question 9

What does the evaluation of

Hughes state ? :)

Answer 9

• Supports the importance of light
• tested the circadian hormone release in four participants stationed at the British Antarctic Station.
• February - the end of the Antarctic summer - cortisol levels followed the familiar pattern reach their highest points as the participants awoke and their lowest point as the participants retired to bed.

Question 10

What does the evaluation of Buhr et al (2010) suggest ? :(

Answer 10

• Temperature may be more important than light in setting circadian rhythms
• temperature controls our body clock
• SCN transforms information about light levels into neural messages that set the body temperature.
• Small changes in body temp can send a powerful signal to our body clock
• Set the timing of cells in the body and causes tissues and organs to become active or inactive.

Question 11

What does the evaluation of Czeisler et al suggest ? :(

Answer 11

• Individual differences
• Cycle length - can vary from 13 to 65 hrs
• cycle onset - individuals appear to be innately different in terms of when their circadian rhythms reach their peak.

Question 12

the sleep wake cycle - more info

Answer 12

• Dictates when we should be sleeping and when we should be awake
• Light and darkness are external signals that determine when we feel the need to either wake or sleep.
• Circadian rhythm - dips and rises at different times of the day
• strongest sleep drive - two dips - one between 2 am - 4am and one between 1 - 3pm
• sleep and wakeness are not determined only on the circadian rhythm but also under homeostatic control
• the internal clock is described as ‘free running’

Question 13

What is homeostatic control ?

Answer 13

• Maintained by the body’s response to adverse stimuli

examples of Homeostatic is blood glucose regulation , calcium and potassium homeostatic

• regulating a normal level of something

Question 14

What does the evaluation on the methodology state ?

Answer 14

• Early research studies of circadian rhythms suffered from an important flaw when estimating the ‘free running’ cycle of the human circadian rhythm.
• initial belief was that only natural light entrained our circadian rhythm but it was found when all variables where avoided one that wasn’t was dim artificial light.
• Research suggests confounding variable need to include the avoiding of artificial light as without any clocks ,radio etc circadian rhythms where affect by this light.