Circadium Rhythms- Flashcards
(9 cards)
What are biological rhythms?
Cyclical changes in biological systems’ behaviour that have evolved in response to environmental cycles like day/night and seasons.
What two factors govern biological rhythms?
1) Endogenous pacemakers (internal body clocks) and 2) Exogenous zeitgebers (external cues).
What is an endogenous pacemaker? Give an example.
An internal body clock that regulates biological rhythms; e.g., the suprachiasmatic nucleus (SCN) controls the sleep/wake cycle.
What is an exogenous zeitgeber? Give an example.
An external cue that influences or entrains biological rhythms; e.g., light influencing the sleep/wake cycle.
What is a circadian rhythm?
A biological rhythm with a cycle lasting about 24 hours, regulating bodily functions and behaviour in line with the day/night cycle.
Describe the sleep/wake cycle.
It is regulated by internal mechanisms and external light cues; strongest sleep drives occur between 2-4am and 1-3pm; homeostasis increases sleep need as awake time lengthens.
What did Siffre’s cave studies show about circadian rhythms without external cues?
His biological rhythms ‘free ran’ with a cycle around 25 hours instead of 24, showing that endogenous pacemakers operate without exogenous zeitgebers.
How does melatonin influence sleep?
Melatonin, produced by the pineal gland, promotes sleep; its production increases in darkness and decreases in light.
Describe the circadian pattern of body temperature.
Lowest around 4:30 am (~36°C), highest around 6 pm (~38°C); drops in temperature are linked to sleepiness and cognitive performance.
How does body temperature relate to cognitive performance?
Warmer internal body temperature correlates with better cognitive performance, e.g., better recall at 3 pm (Folkard et al., 1977) and higher IQ test scores at 7 pm (Gupta, 1991).
