Biological Clocks and Circadian Rhythms

These flashcards cover key concepts and terms related to biological clocks and circadian rhythms, as discussed in the lecture notes.

What are the three main components of a biological clock?

Input, oscillator, and output.

What is the difference between circadian, ultradian, and infradian rhythms?

Circadian rhythms last about 24 hours, ultradian rhythms are shorter than a day, and infradian rhythms are longer than a day.

What is the term for the adjustment of an endogenous rhythm to align with an external cue?

Entrainment.

What does the Phase Response Curve (PRC) illustrate?

The relationship between the timing of a zeitgeber (like light) and the resulting phase shift in the biological clock.

How did Jean Jacques d’Ortois de Mairan contribute to understanding biological clocks?

He demonstrated that the rhythmic movements of the Mimosa plant persisted in the absence of light-dark cycles.

What is the significance of the SCN (suprachiasmatic nucleus) in mammals?

The SCN acts as the master clock by regulating circadian rhythms based on environmental light cues.

What is photoperiodism?

It is the ability of organisms to respond to the length of day and night cycles, influencing biological functions.

What is the impact of blue light on biological clocks?

Blue light can disrupt circadian rhythms by affecting the sensitivity of biological clocks.

What is the role of melatonin in circadian rhythms?

Melatonin, produced by the pineal gland, helps regulate sleep-wake cycles and is influenced by light.

How does light exposure affect the circadian clock according to the findings on hamsters?

Light can cause phase delays or advances in the circadian clock depending on the timing of exposure.