BP- Circadian Rhythms Flashcards
What are biological rhythms?
Biological rhythms are cyclical changes in physiological systems.
What are the three types of biological rhythms?
Circadian, ultradian and infradian
What are circadian rhythms?
Circadian rhythms are cycles that last 24 hours.
Give examples of cycles with circadian rhythms.
Sleep wake cycle
What are circadian rhythms driven by?
Circadian rhythms are driven by the suprachiasmatic nuclei (SCN) in the hypothalamus
Where is the suprachiasmatic nuclei found?
found in the hypothalamus
What are pacemakers?
A pacemaker controls the rate at which something occurs and must be constantly reset so that our bodies are in synchrony with the outisde world
What is photo entrainment?
When natural light provides input to the system, setting the SCN to the correct time
When is our strongest sleep drives?
- 00am-4:00am
1: 00pm-3:00pm
When is melatonin released? And where from?
Melatonin is released from the pineal gland during the hours of darkness
What does melatonin induce and how?
Melatonin induces sleep by inhibiting the neural mechanisms that promote wakefulness.
What is sleep and wakefulness also controlled by? and how?
Homeostatic control
-When we have been awake for a long time homeostasis tells us that the need for sleep is increasing because of the amount of energy used up during wakefulness.
Give advantages of circadian rhythms.
1) Practical application is chronotherapeutics.
- The time that patients take medication is very 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
- This supports the value of research into circadian rhythms as it can be applied to real life to help improve people’s health
2) Research support for light as pacemakers
- Hughes tested hormone levels in 4 participants at an Antarctic station and found that in February (summer) cortisol levels followed a pattern where their highest point was when pps were waking up and lowest when pps were about to sleep.
- After 3 months of darkness, the pattern changed as cortisol levels now peaked around noon instead.
- This supports the role of light in circadian rhythms as it demonstrates that it changes as daylight cycles changes.
- This adds validity to our understanding.
Give disadvantages of circadian rhythms.
1) There are individual differences in the length of circadian rhythms. One research study found that cycles can vary from 13 to 165 hours (Czeisler etal, 1999).
2) 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.
3) Buhr et al (2010) believes that temperature controls our body clock, not light. The SCN transforms information about light levels into neural messages that
