Biological Rhythms

Question 1

What are biological rhythms?

Answer 1

Distinct patterns of changes in body activity that conform to cyclical time periods

Question 2

What are the 3 types of biological rhythms?

Answer 2

Circadian rhythms
Infradian rhythms
Ultradian rhythms

Question 3

What are circadian rhythms?

Answer 3

• A type of biological rhythm where cycles are 24 hours in length
• e.g the sleep wake cycle, body temperature

Question 4

What are infradian rhythms?

Answer 4

• A type of biological rhythm with a frequency of less than one cycle in 24 hours
• e.g menstrual cycle, seasonal affective disorder

Question 5

What are ultradian rhythms?

Answer 5

• A type of biological rhythm with a frequency of more than one cycle in 24 hours
• e.g sleep cycles, BRAC (basic activity rest cycle)

Question 6

What is an endogenous pacemaker?

Answer 6

Internal body clocks

Question 7

What are exogenous zeitgebers?

Answer 7

External changes in our environment

Question 8

Why is light an exogenous zeitgeber?

Answer 8

• Acts as an external cue for sleeping and waking
• Detected by photoreceptors in the eye, which sends messages about brightness levels to the suprachiasmatic nuclei
• The nuclei is an exogenous pacemaker and coordinates activity of circadian system using this info

Question 9

How does melatonin follow a circadian rhythm?

Answer 9

• Melatonin peaks during the hours of darkness
• This activates chemical receptors in the brain which encourages feelings of sleep
• Drop in melatonin leads to wakefulness
• Sleeping also determined by homeostasis

Question 10

How is body temperature a circadian rhythm?

Answer 10

• Human body temp lowest in the early hours of the morning (36 degrees at 4:30am)
• Human body temp highest in the early evening (38 degrees at 6pm)
• Sleep generally occurs when core temperature begins to drop
• Body temp rises in early morning, promoting feelings of alertness

Question 11

Circadian rhythms - research support (AO3)

Answer 11

• Siffre (a French geologist) was studied by Dement (1975) whilst he spent 61 days underground
• Found that the absence of external cues significantly altered his circadian rhythm
• He believed the date to be a month earlier than it actually was
• This suggests his circadian rhythm was lengthened by a lack of external cues, making him think that one day was longer than it was
• Ashcoff and Weaver (1976) studied participants living in a WWII bunker for 4 weeks
• All participants showed a lengthened circadian rhythm between 24-25 hours

Question 12

Circadian rhythms - participant variables (AO3)

Answer 12

• Duffy et al. (2001) found that ‘morning people’ prefer to rise and go to bed earlier, whereas ‘evening people’ rise and go to bed later
• Genetic screening suggested that there’s a genetic base to these differences
• Adolescents are set to wake later and sleep earlier than in adulthood
• This shows that researchers should focus on this during studies, as there may be individual differences with circadian rhythms

Question 13

Circadian rhythms - real life applications (AO3)

Answer 13

• Knowledge of circadian rhythms have given researchers a better understanding of consequences that can occur as result of disruption
• Night shift workers experience a reduced shift of concentration at about 6 in the morning (a circadian trough)
• Research has also suggested as relationship between shift work and poor health: shift workers are 3 times more likely to develop heart disease
• Due to stress of adjusting the sleep wake cycle
• Research into sleep wake cycle may have economic implications in terms of how to manage worker productivity and good health and safety in the workplace

Question 14

What does the cycle of human sleep alternate between?

Answer 14

REM (rapid eye movement)
NREM (non-rapid eye movement)

Question 15

Explain the stages of the sleep cycle.

Answer 15

Stage 1 & 2: light sleep, brainwave patterns become slower and more rhythmic starting with alpha waves and progressing to theta weaves
Stage 3 & 4: deep sleep, characterised by slower deltas waves
Stage 5: REM sleep, the person dreams but the body is paralysed to prevent them acting out the dream
Brain activity resembles an awake person

Question 16

What is the basic-rest activity cycle (BRAC)?

Answer 16

Characterised by periods of alertness followed by a spell of psychological fatigue
This 90 min cycle repeats across the day

Question 17

What evidence is there for BRAC?

Answer 17

Anecdotal evidence: its frequently observed that students find it difficult to concentrate for periods longer than 90 minute at a time. Most also require a coffee break to break up the morning and afternoon
Research evidence: Ericsson et al. (1993) found that the best violinists tended to practise for 3 sessions during the course of the day, each lasted no more than 90 minutes. There was a break in between sessions in order to ‘recharge’.

Question 18

Research support for distinct stages of sleep - AO3

Answer 18

• Dement and Kleitman (1957) used EEG’s to monitor the sleep patterns of 9 adults in a sleep lab
• The environment was standardised and effects of caffeine and alcohol were controlled
• REM activity during sleep was relative to the experience of dreaming with brain activity, varying according to how vivid the dreams were
• Participants woken during REM showed clear recall of dreams and correlated with eye movements
• Replications have been conducted and shown similar results, but the small sample size of the original study was criticised

Question 19

Biologically determined sleep patterns - AO3

Answer 19

• Tucker et al. (2007) studied participants over 11 consecutive days and nights in a controlled lab environment
• Sleep duration, time to fall asleep and amount of time spent in each sleep stage were assessed
• Large differences were recorded in each of these categories and these differences showed up consistently across each night
• For stages 3 and 4 (deep sleep) individual differences were significant
• This shows that differences were at least partly biologically determined

Question 20

What hormones are released during the menstrual cycle?

Answer 20

• Ovaries releases oestrogen and progesterone in response to LH (luteinising hormone) which causes the egg to mature and FSH (follicle stimulating hormone) to release the egg
• Released from pituitary gland

Question 21

How does the menstrual cycle follow an infradian rhythm?

Answer 21

• Ovulation occurs on around day 14 of the cycle when oestrogen levels are highest, and usually lasts for 16-32 hours
• After ovulation, progesterone levels rise in preparation for possible implantation of an embryo in the uterus
• The usual menstrual cycle is 28 days, but this may vary, ranging from 23-36 days

Question 22

What is Seasonal Affective Disorder (SAD)?

Answer 22

• SAD is a depressive disorder which has a seasonal pattern of onset
• Symptoms are persistent low mood, as with other forms of depression (usually described as winter blues)

Question 23

How is Seasonal Affective Disorder (SAD) follow an infradian rhythm?

Answer 23

• Particular type of rhythm called a circannual rhythm as it’s subject to a yearly cycle
• Psychologists have hypothesised that melatonin is implicated in the cause of SAD
• During the night, the pineal gland secretes melatonin until dawn when there’s an increase in light
• The lack of light in winter means that secretion of melatonin continues for longer
• This is thought to have a knock-on effect on the production of serotonin - linked to onset of depressive symptoms