Biopsychology- biological rhythms

What are biological rhythms?

Biological rhythms are [blank_start]regulated[blank_end] by Endogenous [blank_start]pacemakers[blank_end] (internal [blank_start]biological[blank_end] clock) and exogenous [blank_start]zeitgebers[blank_end] (external [blank_start]factors[blank_end]).

Endogenous pacemakers are internal [blank_start]mechanisms[blank_end] that [blank_start]govern[blank_end] our biological rhythms, e.g. our [blank_start]circadian[blank_end] sleep/wake cycle. The most important EP is the [blank_start]suprachiasmatic nucleus[blank_end] in the [blank_start]hypothalamus[blank_end]. It receives information about [blank_start]light levels[blank_end] from the [blank_start]optic nerve[blank_end] in our eye and instructs the [blank_start]pineal[blank_end] gland to release [blank_start]melatonin[blank_end] when light levels are [blank_start]low[blank_end] - at night. This ensures our biological rhythms are [blank_start]synchronised[blank_end] with the [blank_start]outside world[blank_end].

Exogenous zeitgebers are environmental [blank_start]events[blank_end] which [blank_start]entrain[blank_end] our biological rhythms. Including [blank_start]social cues[blank_end] such as meal times, but most important zeitgeber is [blank_start]light[blank_end]. This is responsible for [blank_start]regulating[blank_end] a 24 hour [blank_start]circadian[blank_end] rhythm by [blank_start]resetting[blank_end] our [blank_start]biological clock[blank_end] each day.

Circadian rhythms are a type of biological rhythm that occurs across a [blank_start]24[blank_end] hour cycle, e.g. the [blank_start]sleep/wake[blank_end] cycle or core body temperature. (which [blank_start]decreases[blank_end] at night, then [blank_start]increases[blank_end] at the end of [blank_start]sleep[blank_end] cycle to make body feel [blank_start]alert[blank_end]).

Who did research that supports the importance of endogenous pacemakers?

Research to support the importance of EPs - [blank_start]Morgan[blank_end]: bred hamsters with a circadian rhythm of [blank_start]20[blank_end] hours rather than 24. They implanted their SCN's into normal hamsters, which then developed the same [blank_start]20[blank_end] hour [blank_start]circadian[blank_end] rhythm. BUT - its hard to [blank_start]generalise[blank_end] due to the use of hamsters... humans would respond differently to their biological rhythms being manipulated and disrupted- we are not only biologically different, but we have very different [blank_start]environmental[blank_end] contexts. SO - while it does highlight the importance of [blank_start]endogenous pacemakers[blank_end] and the SCN on our [blank_start]sleep/wake cycle[blank_end], and how the lack of them can disrupt it, we are unable to explain this in [blank_start]humans[blank_end].

What are infradian rhythms?