Basic rest-activity cycle The 90 minute sleep cycle is located within the 24 hour circadian cycle. This 90 minute clock is also ticking throughout the day it’s called the basic rest-activity cycle (BRAC). Friedman and Fisher (1967) found that there was a clear 90 minute cycle in eating and drinking behaviour in psychiatric patients. Evaluation of basic rest-activity cycle The basic rest-activity cycle shows that this 90 minute sleep cycle maybe a form of timing to ensure that the biological processes in the body work in unison. Infradian Rhythms (span more than one day but less than one year) Monthly Cycles The female menstrual cycle is an example of an infradian rhythm. It is driven by fluctuating hormone levels to regulate ovulation. The pituitary gland releases hormones which stimulate a follicle in one ovary to ripen an egg and release the female hormone oestrogen. Once the egg is ripened the ruptured follicle secretes progesterone which causes the lining of the womb to prepare for pregnancy. Two weeks after ovulation if there has been no pregnancy the level of progesterone falls causing the line of the womb to be shed. But what about males?! Empson (1977) found some evidence for a periodic variation of both body temperature and subjective ratings of morning alertness, with a cycle length of 20 days. Evaluation of Monthly Cycles The menstrual cycle is normally governed by endogenous (internal) cues. But it can be controlled by exogenous cues too. It has been found than women who live together and who do not take oral contraceptives tend to menstruate at the same time each month. Russell et al (1980) carried out an interesting study to investigate this, outline the procedure and findings below: We now know that PMS is a physiological problem. It is a disorder that affects many women the
Basic rest-activity cycle The 90 minute sleep cycle is located within the 24 hour circadian cycle. This 90 minute clock is also ticking throughout the day it’s called the basic rest-activity cycle (BRAC). Friedman and Fisher (1967) found that there was a clear 90 minute cycle in eating and drinking behaviour in psychiatric patients. Evaluation of basic rest-activity cycle The basic rest-activity cycle shows that this 90 minute sleep cycle maybe a form of timing to ensure that the biological processes in the body work in unison. Infradian Rhythms (span more than one day but less than one year) Monthly Cycles The female menstrual cycle is an example of an infradian rhythm. It is driven by fluctuating hormone levels to regulate ovulation. The pituitary gland releases hormones which stimulate a follicle in one ovary to ripen an egg and release the female hormone oestrogen. Once the egg is ripened the ruptured follicle secretes progesterone which causes the lining of the womb to prepare for pregnancy. Two weeks after ovulation if there has been no pregnancy the level of progesterone falls causing the line of the womb to be shed. But what about males?! Empson (1977) found some evidence for a periodic variation of both body temperature and subjective ratings of morning alertness, with a cycle length of 20 days. Evaluation of Monthly Cycles The menstrual cycle is normally governed by endogenous (internal) cues. But it can be controlled by exogenous cues too. It has been found than women who live together and who do not take oral contraceptives tend to menstruate at the same time each month. Russell et al (1980) carried out an interesting study to investigate this, outline the procedure and findings below: We now know that PMS is a physiological problem. It is a disorder that affects many women the