Biological Rhythms

Topics: Circadian rhythm, Sleep, Menstrual cycle Pages: 2 (546 words) Published: October 17, 2010
Mini - assignments for biological rhythms

1. Outline what we mean by an endogenous pacemaker (3)

Endogenous rhythms are rhythms that aren’t imposed by the environment but generated from within the organism. Since many of our biological cycles follow an approximation 24-hour rhythm, even in the absence of external stimuli, it follows that there must be some kind of internal biological clock.

2. What is the name given to external events that play a role in rhythmic activities? Give an example (2)

The name given this is the exogenous zietgebers, an example of this would be the light-dark cycle. Thus, the rhythms become aligned to the new cues.

3. Name four types of biological rhythm, describe each one briefly, and give an example of each (12)

A circadian rhythm is a roughly 24-hour cycle in the biochemical, physiological, or behavioural processes of living entities, Although circadian rhythms are endogenous ("built-in", self-sustained), they are adjusted (entrained) to the environment by external cues called zeitgebers, the primary one of which is daylight. Infradian Rhythms the timing of which is governed by endogenous (internal) biological cycles and possibly also by exogenous cues (zeitgebers). One exogenous cue may be female pheromone production, which may bring women's menstrual cycles into synchronization with those of other women with whom they are in close proximity for an extended period of time. This is known as the dormitory effect or the McClintock effect. Ultradian rhythms are recurrent periods or cycles repeated throughout a 24-hour circadian day. In contrast, infradian rhythms, such as the human menstrual cycle, have periods longer than a day.The descriptive term ultradian is used in sleep research in reference to the 90–120 minute cycling of the sleep stages during human sleep Some of the other ultradian cyclings of the body are hormonal release, heart rate, thermoregulation Diurnal rhythms are an extension of circadian...
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