Lesson 10: Circadian Rhythms Flashcards
What are biological rhythms?
they are CYCLICAL changes in PHYSIOLOGICAL systems
that have EVOLVED as the ENVIRONMENTS in which organisms live in have cyclical changes e.g day/night summer/winter
What are the three types of biological rhythms?
(Can’t Use Internet)
Circadian
Ultradian
Infradian
What are circadian rhythms
any cycle that lasts 24 HOURS
What do Circadian rhythms optimise?
1) an organisms’ PHYSIOLOGY
2) BEHAVIOUR to best meet the varying demands of the DAY/NIGHT cycle
What are Circadian rhythms driven by?
Suprachaismatic nuclei (SCN) in the HYPOTHALAMUS
What does the Suprachaismatic nuclei (SCN) act as
a PACEMAKER (controlling the rate at which something occurs)
Why must the SCN be constantly reset?
so our bodies are in SYNCHRONY with the outside world
What does NATURAL light do in order to co-ordinate the activity of circadian rhythms in the body
1) Natural light SETS the SCN to the correct time in a process called PHOTOENTRAINMENT
2) SCN then uses this information to co-ordinate activity of circadian rhythms throughout the body
According to the sleep-wake cycle, what do lightness and darkness act as?
EXTERNAL signs that determine when we feel the need to SLEEP and WAKE up
When does our strongest drive to sleep occur?
between 2:00am- 4:00am
AND
1:00pm-3:00pm
What gland releases MELATONIN
PINEAL gland
When is the release of melatonin from the pineal gland at its PEAK?
during hours of DARKNESS
How does Melatonin induce sleep?
it INHIBITS the NEURAL MECHANISMS that promote WAKEFULNESS
Fill in the blank:
The production of _______ supresses the production of melatonin
Light
What type of control is sleep and wakefulness under?
Homeostatic control
What is homeostasis?
The maintenance of internal body conditions at a set limit
Why is sleep and wakefulness under homeostatic control?
When we have been awake from long periods of time-> HOMEOSTATIC PROCESSES work in a way that reminds us that the NEED FOR SLEEP is INCREASING because of the amount of ENERGY used in WAKEFULNESS
Fill in the blanks:
This homeostatic drive for sleep 1)_________ gradually throughout the day, reaching its 2)__________ in the late evening.
1) Increases
2) Maximum
What will the internal circadian rhythm maintain?
a cycle of 24-25 hours, even without natural light
State a POSITIVE evaluation of Circadian rhytms
(Hint: Chronotherapeutics)
+ One PRATICAL application of circadian rhythms is CHRONOTHERAPEUTICS.
The time that patients take medication= important for treatment success.
It is ESSENTIAL that the right concentration of drug is released in the target area of the body at the time the drug is most needed.
For example, the risk of HEART ATTACK is greatest during the early morning hours after waking. Medications have been DEVELOPED that are taken before the person goes to sleep but are not released until the vulnerable time of 6:00 am.
State a NEGATIVE evaluation of Circadian rhythms
(Hint: natural vs artificial light)
- Research on circadian rhythms has not ISOLATED people from ARTIFICIAL light, because it was believed only NATURAL light affected circadian rhythms.
HOWEVER, more recent research suggests this might NOT be true.
Cziesler et al. (1999) altered participant’s circadian rhythms down to 22 hours and up to 28 hours by using artificial light alone.
State a NEGATIVE evaluation of Circadian rhythms
(Hint: Individual differences: 13-> 165 hours)
- There are INDIVIDUAL differences in the length of circadian rhythms. One research study found that cycles can VARY from 13 to 165 hours (Czeisler et al, 1999).
State a NEGATIVE evaluation of Circadian rhythms
(Hint: morning person vs evening person)
- Another individual difference in circadian rhythms is when they reach their PEAK.
Morning people’ prefer to rise early and go to bed early whereas ‘evening people’ prefer to rise late.
State a NEGATIVE evaluation of Circadian rhythms
(Hint: Artic regions)
- Studies of individuals who live in ARTIC regions, where the sun does not set in the summer months->normal sleeping patterns despite the prolonged exposure to light.
This suggests that there are occasions where the EXOGENOUS ZEITGEBERS of light may have very little bearing on our internal biological rhythms
