biological rhythms

• biological rhythms: regular variations in the biological activity of living organisms, such as sleep, body temp, alertness, neurotransmitter levels
• ultradian - more than once a day

  circadian - approx every 24 hours

  Infradian - over a period longer than 24 hours
• What is an infradian rhythm?

  A biological rhythm lasting longer than 24 hours
• What regulates the female menstrual cycle?

  Hormones that promote ovulation and fertilization
• When does ovulation occur in the menstrual cycle?

  Roughly halfway through the cycle
• What happens to progesterone levels after ovulation?

  They increase in preparation for implantation
• What is the average length of a menstrual cycle?

  Around 28 days
• What variation can occur in menstrual cycles?

  Some women have cycles of 23 to 36 days
• What is seasonal affective disorder (SAD)?

  A mood disorder related to seasonal changes
• What hormone is linked to SAD?

  Melatonin secreted by the pineal gland
• How does light affect melatonin secretion in winter?

  Less light leads to longer melatonin secretion
• What did Reinberg's study in a cave suggest about menstrual cycles?

  Lack of light affects menstrual cycle length
• What did Russell et al.'s study find about menstrual cycles?

  They can synchronize through odour exposure
• What are pheromones believed to affect?

  Menstrual cycle synchronization among women
• What do evolutionary psychologists claim about synchronized menstrual cycles?

  They provide an evolutionary advantage for childcare
• What did Penton-Volk et al. (1999) find about women's preferences?

  Preferences for faces change with fertility stages
• What did Terman (1988) find about SAD rates in different regions?

  SAD is more common in northern countries
• What percentage of people in New Hampshire are affected by SAD?

  About 10%
• What is the link between light and SAD according to Terman's findings?

  Light affects melatonin levels and SAD rates
• Endogenous pacemakers: Biological 'clocks' in the brain controlling biological rhythms. most likely the suprachiasmatic nucleus in the hypothalamus
• exogenous zietgebers (timegivers): external stimuli that help tpwards regulating biological rythms to the outside world
• biological rhythms are controlled by endogenous and exogenous factors:

  endogenous - eg biological clock, hormones

  exogenous - light, exercise, meals
• endogenous pacemakers and exogenous zeitgebers interact with each other - the endogenous body clock is reset with the help of exogenous factors eg sublight.
• the main endogenous pacemaker in mammals is the suprachiasmatic nucleus (SN), it is located just above where the optic nerves cross over. it receives light
• sleep cycle:

  A) eye

  B) suprachiasmatic nucleus

  C) pineal

  D) melatonin

  E) increase