Circadian Rythms Flashcards
What are circadian rythms?
These are biological rythms subject to a 24-hour cycle, which regulate the number of body rpocesses such as the sleep/wake cycle and changes in core body temperature.
What are biological rhythms?
Distinct patterns of changes in body activity that conform to cyclical time periods. Biological rhythms are influenced by internal body clock (endogenous pacemakers) as well as external changes to the environment (exogenous zeitgebers).
Outline the sleep/wake cycle as an circadian rhythm.
In the Sleep wake cycle light is thought to be the primary EZ. Social cues such as when other go to sleep, or environmental cues like clocks are also thought to act as EZs.
The SCN is the EP for the sleep wake cycle. It is known as the internal body clock. It is part of the hypothalamus within the limbic system. When light is detected by the SCN it sends light to the pineal gland, stopping the production of melatonin, a hormone that results in a sleep response.
What is a Infradian Rhythm?
These are cycles which last longer than 24 hours.
Outline a Infradian rhythm.
Menstraul cycle
The Menstraul Cycle
- Occurs every 28 days
-This cycle is under hormonal control in biological females
-It consists of rising oestrogen levels to cause an egg to release from an ovary, the egg travles down the oviduct to the womb.
-If the egg is not fertillised the lining is shed.
Outline a Infradian rhythm.
Seasonal Affective Disorder
* SAD tends to hit people during the winter months when days are darker and longer.
* During these months, more meletonin is secreted which may result higher levels of depression or a generalised low mood.
* Serotonin is implicated in the Sleep wake cycle so disrupted levels of this neurotransmitter is likely to lead to an imbalance in mood.
What is a Ultradian Rhythm?
These are cycles which occur under 24-hours, best showcased in the stages of sleep.
Outline sleep stages as a Ultradian rhythm.
There are 5 recognised stages of sleep, which each cycle occurring continously throughout the night.
-Stages 1 and 2 are the stages where a person may be easily woken. In stage 1, the brain waves are high frequency and have short amplitude. These are alpha waves. In stage 2 , the alpha waves continue but there are occasional random changes in pattern called sleep spindles.
Stages 3 and 4 are known as deep sleep. The brain waves are delta waves with lower frequency and higher amplitude. It is difficult to wake someone in this stage.
Stage 5 (REM) The body is paralysed yet brain activity closely resembles that of the awake brain. During this time, the brain produces theta waves and the eyes occasionally move around, thus REM. Dreams are most often experienced during REM sleep, but may also occur in deep sleep.
Outline stage 5 of sleep.
Stage 5 (REM) The body is paralysed yet brain activity closely resembles that of the awake brain. During this time, the brain produces theta waves and the eyes occasionally move around, thus REM. Dreams are most often experienced during REM sleep, but may also occur in deep sleep.
Outline stage 1 and 2 of sleep.
-Stages 1 and 2 are the stages where a person may be easily woken. In stage 1, the brain waves are high frequency and have short amplitude. These are alpha waves. In stage 2 , the alpha waves continue but there are occasional random changes in pattern called sleep spindles.
Outline stage 3 and 4 of sleep.
Stages 3 and 4 are known as deep sleep. The brain waves are delta waves with lower frequency and higher amplitude. It is difficult to wake someone in this stage.
Outline Siffre (1975) experiment on the sleep wake cycle.
- Siffre spent 6 months in a cave with no natural light and sound, or other potential EZ such as clocks.
- Siffres body clock EP maintained a regular cycle of around 25 hours without EZ, longer than the expected 24-hour cycle.
- Suggesting the EP for the sleep wake cycle is free running but needs entertainment to keep the 24-hour day night cycle.
