Circadian Rhythmns, Exogenous Zeitgeibers And Endogeous Pacemakers Flashcards
(19 cards)
What are biological rhythms?
Internal processes that impact our behaviour that are sometimes affected by external factors due to the cyclical nature of environment
- they are our bodies natural body clocks
How are biological rhythms important in routine (AO3)?
Important in telling people when to take their drugs as biological rhythms give the knowledge that your highest/lowest levels of blood pressure are at different times of the day
What are circadian rhythms and give an example?
Cycle of bodily rhythms that occur approximately once a day e.g sleep wake cycle
Why are circadian rhythms important?
To balance behaviour and body states to environmental changes to maintain an internal state of homeostasis despite changes in environment
What are endogenous pacemakers and what is an example?
Internal body clocks that regulate biological rhythms e.g Suprachiasmatic nucleus
What is the SCN and what is it needed for?
Structure within the brain that can detect light even when your eyes are closed
- regulates circadian rhythms of sleep wake cycle
What are exogenous zeitgebers?
External factors which help reset our biological clocks
What are the endogenous pacemakers and exogenous zeitgebers for the sleep wake cycle?
EP: SCN
EZ: light and dark
What are the main areas of research for infradian rhythms?
. Menstrual cycle
. seasonal affective disorder (SAD)
What is the main ultradian rhythm?
Sleep-wake cycle
How does the SCN regulate the sleep-wake cycle?
. Light/dark is detected by receptors on the eye which then send messages to the SCN via the optic nerve
. SCN sends signal to pineal gland to increase melatonin to reduce brain activity and make us sleepy/ inhibit melatonin production if light
What are two main animal studies to support the role of the SCN?
. De Coursey et al
. Martin Ralph et al
What was the procedure of DeCoursey et al?
. 30 chipmunks had their SCN connections destroyed
. Returned to their natural habitat and observed for 80 days
What were the findings of DeCoursey et al?
. Chipmunks’ sleep/wake cycles disappeared
. By the end of the study a significant proportion of them had been killed by predators
How does the menstrual cycle (ultradian rhythm) work?
. Monthly changes in hormone levels regulate ovulation
. Cycle takes around 28 days
. Rising levels of oestrogen causes ovary to develop and release egg
. Progesterone then helps womb lining thicken to ready body for pregnancy
. If not pregnant, womb lining sheds (menstrual flow)
What research is there to suggest that endogenous systems such as the menstrual cycle may be influenced by exogenous factors?
Stern and McClintock (period Bluetooth study)
- demonstrated how menstrual cycles may synchronise as a result of the influence of female pheromones (smells)
What was the procedure of the McClintock study?
29 women with a history of irregular periods. 9 of them had their pheromones sampled on different stages of menstrual cycle via a cotton pad in their armpit
- pads worn for at least 8 hours to ensure pheromones picked up
- pads treated with alcohol and frozen to be rubbed on the lip of other participants
. Day one, pads from start of cycle applied to 20 women, day two given pads from second day of cycle etc
What were the findings of the McClintock study?
68% of women experienced changes to their cycle which brought them closer to the cycle of their ‘odour donor’
How does SAD come about?
As melatonin is secreted by the pineal gland at night and there are longer nights in the winter months, this increase in melatonin secretion is linked to increases in depressive symptoms
