circadian rhythms

Question 1

biological rhythms

Answer 1

• cyclical changes in physiological systems
• evolved cus the environments in which organisms live have cyclical changes e.g. day/ night, summer/ winter etc..
• ultradian
• circadian
• infradian

Question 2

circadian rhythms

Answer 2

• any cycle that lasts 24 hours
• optimise an organisms’ physiology + behaviour to best meet the varying demands of the day/ night cycle
• driven by the suprachiasmatic nuclei (SCN) in the hypothalamus = pacemaker
• photoentrainment = natural light inputs into the system, setting SCN to correct time
• the SCN then uses this info to coordinate activity of circadian rhythms
• promps us to sleep as it becomes dark
• sleep-wake cycle
• melatonin
• homeostasis

Question 3

the sleep-wake cycle

Answer 3

• external signals = light + darkness
  –> determine when we feel the need to sleep + wake up
• strongest sleep drives: 2-4am, 1-3pm
• melatonin
• homeostatic control

Question 4

melatonin - sleep-wake cycle

Answer 4

• release of MELATONIN from the pineal gland
  = induces sleep
  = by inhibiting the neural mechanisms that promote wakefulness
• light suppresses the production of melatonin

Question 5

homeostasis - sleep-wake cycle

Answer 5

• homeostatic control
• when we have been awake for too long, homeostasis tells us that the need for sleep is increasing due to amount of energy used up
• reaches max in late evening

Question 6

chronotherapeutics - ad

Answer 6

• practical application = chronotherapeutics
• the time that patients take medication is very important for treatment success
• essential that the right concentration of drug is released in target area of body at the right time
• e.g. risk of heart attack is greatest during early morning hours after waking
  = medicines developed that are taken before person goes to sleep
• BUT not released until vulnerable time of 6 am

Question 7

disads

Answer 7

• natural vs artificial
• ID: length
• ID: morning vs evening
• Arctic regions

Question 8

natural vs artifical - disads

Answer 8

• research on circadian rhythms has not isolated ppl from artificial light
• believed only natural light affected circadian rhythms
• HOWEVER more recent research suggests that this might not be true
• psych altered parts’ circadian rhythms down to 22 hrs + up to 28 hrs
  = using artificial light alone

Question 9

ID: length - disads

Answer 9

• there are individual differences in the length of circadian rhythms
• one research study found that cycles can vary from 13-165 hrs

Question 10

ID: morning vs evening - disads

Answer 10

• there are individual differences when circadian rhythms reach their peak
• ‘morning people’ prefer to rise early + go to bed early
• whereas ‘evening people’ prefer to rise later

Question 11

Arctic regions - disads

Answer 11

• studies of individuals who live in the Arctic regions
  = sun doesn’t set in the summer months
  = show normal sleeping patterns
• despite prolonged exposure to light
  = suggests that there are occasions where the exogenous zeitgeber of light
  = has very little bearing on our internal biological rhythms