Biopsychology - Biological Rhythms Flashcards
What are the 3 bodily rhythms?
- Circadian rhythms: follow a 24-hour cycle: e.g. the sleep-waking cycle
- Ultradian rhythms: occur more than once a day: e.g. the cycles of REM and NREM sleep in a single night’s sleep
- Infradian rhythms: occur less than once a day: e.g. menstruation (monthly) or hibernation (yearly)
What are endogenous pacemakers?
Internal biological structures that control and regulate the rhythm.
What are exogenous zeitgebers?
External environmental factors that influence the rhythm.
How does the sleep/wake cycle work?
The sleep-wake cycle is an example of a circadian rhythm, which dictates when humans and animals should be asleep and awake. Light provides the primary input to this system, acting as the external cue for sleeping or waking. Light is first detected by the eye, which then sends messages concerning the level of brightness to the SCN. The SCN then uses this information to coordinate the activity of the entire circadian system. Sleeping and wakefulness are not determined by the circadian rhythm alone, but also by homoeostasis. When an individual has been awake for a long time, homeostasis tells the body that there is a need for sleep because of energy consumption. This homeostatic drive for sleep increases throughout the day, reaching its maximum in the late evening, when most people fall asleep.
Which endogenous pacemaker regulates the sleep-wake cycle?
The endogenous pacemaker that regulates the sleep-wake cycle is the SCN which signals the pineal gland to produce or inhibit melatonin (a hormone of the sleep-wake cycle) depending on if there is daylight or not.
How is body temperature an example of a circadian rhythm?
Body temperature is another circadian rhythm. Human body temperature is at its lowest in the early hours of the morning (36oC at 4:30 am) and at its highest in the early evening (38oC at 6 pm). Sleep typically occurs when the core temperature starts to drop, and the body temperature starts to rise towards the end of a sleep cycle promoting feelings of alertness first thing in the morning.
Evaluate circadian rhythms - Siffre
Research has been conducted to investigate circadian rhythms and the effect of external cues like light on this system.
Siffre (1975) found that the absence of external cues significantly altered his circadian rhythm. He spent 6 months underground in an environment completely cut off from all EZ’s. Although he organised his time in regular patterns of sleeping and waking his body seemed to have a preference for a 25 hour rather than a 24-hour cycle.
This implies that circadian rhythms are mainly controlled by EP’s rather than EZ’s.
Evaluate circadian rhythms - Duffy
it is important to note the differences between individuals when it comes to circadian cycles.
Duffy et al. (2001) found that ‘morning people’ prefer to rise and go to bed early (about 6 am and 10 pm) whereas ‘evening people’ prefer to wake and go to bed later (about 10 am and 1 am).
This demonstrates that there may be innate individual differences in circadian rhythms, which suggests that researchers should focus on these differences during investigations.
Evaluate circadian rhythms - temperature
It has been suggested that temperature may be more important than light in determining circadian rhythms.
Buhr et al. (2010) found that fluctuations in temperature set the timing of cells in the body and caused tissues and organs to become active or inactive. Buhr claimed that information about light levels is transformed into neural messages that set the body’s temperature. Body temperature fluctuates on a 24-hour circadian rhythm and even small changes in it can send a powerful signal to our body clocks.
This shows that circadian rhythms are controlled and affected by several different factors, and suggests that a more holistic approach to research might be preferable.
Describe jet lag
Disruption of the circadian sleep-waking cycle (e.g. jet lag and shift work) has been shown to cause negative physical and psychological effects.
Jet Lag occurs when we cross several world time zones quickly. Circadian rhythms will be disrupted as although our endogenous pacemakers stay the same, the exogenous zeitgebers (patterns of light and dark in the new environment) have changed.
Symptoms of Jet lag/shift work include:
Tiredness during the new daytime and insomnia at night
Decreased mental performance and lack of concentration
Decreased physical performance
Loss of appetite, indigestion and nausea
Irritability, headaches and mental confusion
