UNIT 3: Biological Rhythms

Question 1

Rhythm

Answer 1

Something that is repeated regularly.

Influenced by internal and external factors.

Question 2

Endogenous

Answer 2

Originates from within

Question 3

Endogenous pacemaker

Answer 3

A pacemaker for biological rhythms that originates from within.
Example: ‘biological clock’

Question 4

Exogenous zeitgebers

Answer 4

External factors that affect our biological rhythms.
Originate from outside the individual.
Examples include, the seasons, light, temperature and social cues- TV and radio.

Question 5

3 types of biological rhythms

Answer 5

circadian rhythms
infradian rhythms
ultradian rhythms

Question 6

circadian rhythms

Answer 6

happen daily on a 24 hr basis.

example: sleep-wake cycle, hormone secretion

Question 7

infradian rhythms

Answer 7

rhythms that repeat over a period of time greater than a day.
for example migration patterns of birds

Question 8

ultradian rhythms

Answer 8

occur over a period of less than a day

example: the sleep cycles of deep and light sleep that occur during the sleep-wake cycle.

Question 9

michael siffre

Answer 9

spent time living in caves, removing all exogenous zeitgebers.
biological clock could ‘free run’ following natural inclinations
physiological functions were monitored such as heart rate
at first his sleep-wake cycle was fairly erratic but settled down in to a 25 hour cycle

Question 10

michael siffre evaluation

Answer 10

this study is limited as it relies on findings from 1 man
his living conditions were unnatural and emotions such as loneliness may have affected his circadian rhythms
however they are strengthened by the fact that the studies took place over a long period of time

Question 11

the role of the SCN

Answer 11

part of the hypothalamus
responsible for circadian rhythms
found just above the optic chiasm (info from photoreceptor cells in retina readily available)
the rhythms created impact the SCN impact the pineal gland (which produces melatonin, which controls our bodily rhythms)
when lights levels are low more melatonin is secreted from the pineal gland, inducing a sleepy state.

Question 12

Abraham et al

Answer 12

injected sparrows with melatonin it induced sleep.
this suggests that melatonin is associated with brainstem sleep mechanisms but helping to synchronise sleep and wake patterns.

Question 13

Binkley et al

Answer 13

the reason chickens may wake at dawn break is that melatonin secretion will fall.

Question 14

Lesioned SCN

Answer 14

In rats a lesioned SCN appeared to cause complete disruption in the circadian rhythm - sleeping as well as eating

Question 15

the menstrual cycle as an example of an in infradian rhythm

Answer 15

over a period greater than a day
governed by hormones which are endogenous biological factors (external factors may also play a role)
oestrogen and progesterone (under control of pituitary gland)

‘McClintock Effect’ menstrual cycle of women who live together tend to be synchronised. ( a study found that over half the menstrual cycles of lebian couples became synchronised within two days over time )
this is called menstrual synchrony.
some scientists believe this is the result of pheremones (biochemicals relseased in to the air and affect same-species individuals)
-however rely on recall data can be unreliable. also methodology in comparing synchronisation appear to have errors.

Question 16

Advantage of menstrual synchrony

Answer 16

If females ovulate/menstruate at the same time then there will be birth synchrony meaning their care can be shared.
Also this approach suggests that when the females are menstruating men can hunt and the females will be fertile when the men return.

Question 17

human sleep rhythm as an ultradian rhythm

Answer 17

repeats in less than one day
each sleep cycle is around 90 minutes and repeats about 5-6 times a night
each state of sleep is different in terms of brain activity

Stages 1-2: light sleep
Stages 3-4: deeper sleep non-REM a.k.a slow wave sleep
After stages 1-4 the individual goes back through 3,2 and 1.
The cycle then repeats approx 5 times a night

Question 18

Sleep stages research

Answer 18

Squirrel monkeys: biological clocks seem to be the main control mechanism for the stages of sleep.
When the SCN was lesioned or destroyed their sleep cycles and stages were severely disrupted and so were their other circadian rhythms.
It seems that the SCN also has a major role in the ultradian as well as circadian rhythms sleep cycle.

Question 19

Evaluation of squirrel monkey SCN lesioning

Answer 19

Patterns of sleep may be similar in the monkeys to humans but they may react differently to the SCN lesioning.
There may be other effects on the animals of the brain surgery and this needs to be controlled for.
questionable ethics
Even if the sleep cycles and SCN functions are similar to humans it is unlikely that the monkeys’ sleep will bear much resemblance to ours.

Question 20

Exogenous factors impacting sleep

Answer 20

light levels, temperature, drugs and stress may also impact the EEG patterns and lengths of the sleep stages.
Alcohol: individuals often report that alcohol impacts sleep patterns. One study found that a single dose of alcohol had an effect on EEG patterns of sleep stages. (lacks ecological validity as it cannot be generalised to alternative patterns of alcohol use)

Question 21

Main method that physiologists and psychologists use to measure brain activity.

Answer 21

EEG machine