AO1 - Infradian Rhythms

• Infradian rhythms last longer than 24 hours. One example of an infradian rhythm is the female menstrual cycle which is a 28 day cycle
• 1. Begins on the first day of the period, where the womb lining is shed (3-7 days)
• 2. The pituitary gland in the brain releases FSH, which activates the release of oestrogen from the ovaries - this increase in oestrogen causes an egg to mature
• 3. LH is released from the pituitary gland, which promotes the release of the egg
• 4. Oestrogen develops the lining of the womb, and progesterone makes the womb lining thicker, ready for pregnancy
• 5. If pregnancy does not occur, the egg is absorbed into the body, the womb lining is shed again - this repeats the cycle
• Exogenous factors that might affect the menstrual cycle is stress and pheromones