biological rhythms Flashcards
what are all biological rhythms controlled by?
endogenous pacemakers - the body’s internal clock
what are all biological rhythms influence by?
exogenous zeitgebers - external changes in the environment
describe the interaction of endogenous pacemakers and exogenous zeitgebers in maintaining a consistent circadian rhythm (sleep wake cycle)
- sleep wake cycle is controlled by master endogenous pacemaker - suprachiasmatic nucleus (SCN)
- eyes notice a change in light when it becomes dark, retina receives less light
- sends info to the SCN stimulating the pineal gland to release melatonin and promote sleep
- when eyes detect light again the SCN resets stimulating the pineal gland inhibiting the release of melatonin promoting wakefulness
- sleep wake cycle is controlled by endogenous pacemakers
circadian rhythm AO3
:) - rts DeCoursey
destroyed scn connections in 30 chipmunks
let them free and observed for 80 days
all died/were killed by predators
supports importance of endogenous pacemakers - exogenous zeitgebers not able to keep alive
increasing validity
:( - animal bias
humans have more complex interaction, greater number of zeitgebers that influence rhythms
issues with extrapolating findings to humans
limits to extent findings support EP’s
Infradian rhythms (menstrual cycle)
Start of cycle - first day of period, womb lining is shed - pituitary gland releases FSH activating the release of oestrogen from ovaries, egg matures
Middle of cycle - increase of oestrogen increases LH levels, promotes release of egg - oestrogen develops womb lining and progesterone helps it grow thicker, reads womb for pregnancy
End of cycle - egg absorbed into body if no pregnancy, womb lining comes away and cycle begins again.
What endogenous pacemakers and exogenous zeitgebers affect the menstrual cycle?
Endogenous - regulated by pituitary gland and oestrogen and progesterone
Exogenous - affected by light, stress and pheromones
Lead to inconsistent/dysregulated infradian rhythm
Infradian rhythm AO3
:) - rtc - Russell
Women cotton pads under arms, control group rub on upper lip (5 months)
4 out of 5 control group synced cycles within one day
Infradian rhythms can be influenced by exogenous factors
Reduces validity
:( - low control over EV’s
what have ultradian rhythms found?
- there are 5 distinct stages to sleep.
- characterised by differences in the brain, muscle and eye activity during NERM and REM sleep stages.
- argued that ultradian rhythms are under endogenous control
5 sleep stages
- Stages 1 + 2 = light sleep, easily awoken, alpha brain waves, EEG’s pick up on sleep spindles
- Stages 3 + 4 = deep sleep, difficult to wake, delta brain waves, body repairs muscles and brain replenishes neurotransmitter levels (stage 4)
- Stage 5 = body paralysed, brain activity closely resembles awake brain, dreams often experienced
what is the role of exogenous zeitgebers in ultradian rhythms
- exercise = more exercise means more time in stage 4 for recovery (replenish NT and repair muscles)
- mental health conditions = enter stage 5 earlier, shows increased REM sleep (NT remain unbalanced)
ultradian rhythms AO3
:) - prac apps in age related changes in sleep
- growth hormone associated with sleep deficit in old age
- less stage 4 sleep
- medication and relaxation techniques (meditation/mindfulness) developed to increase stage 4 sleep
- important part of applied psychology
:( - low ecological validity
- conducted in artificial environment
- not reflect genuine sleep patterns due to unfamiliar surroundings
- alters length of rhythm making it difficult to generalise findings
- lowers internal validity
