6. BIOPSYCHOLOGY (THE EFFECT OF ENDOGENOUS PACEMAKERS AND EXOGENEOUS ZEITGEBERS ON THE SLEEP/WAKE CYCLE) Flashcards
What are endogenous pacemakers?
Endogenous pacemakers are internal body clocks that regulate biological rhythms, such as the sleep/wake cycle, and include structures like the suprachiasmatic nucleus (SCN) and the pineal gland.
What are exogenous zeitgebers?
Exogenous zeitgebers are external environmental cues, such as light, that reset our biological clocks through a process called entrainment, influencing rhythms like the sleep/wake cycle.
What is the role of the SCN in the sleep/wake cycle?
The SCN is a key endogenous pacemaker located in the hypothalamus. It receives information about light through nerve fibres connected to the eyes and adjusts the body’s biological clock to align with changes in daylight, helping maintain the sleep/wake cycle.
How does the SCN influence the sleep/wake cycle?
The SCN receives light information and helps reset the biological clock. For example, if the biological clock is out of sync (e.g., the sun rises earlier), light exposure helps realign the rhythm with the environment.
What did DeCoursey et al. (2000) find in their animal study?
DeCoursey et al. destroyed the SCN in chipmunks and found that their sleep/wake cycle disappeared. Additionally, the chipmunks were more vulnerable to predators, suggesting the SCN’s role in maintaining the rhythm is vital for survival.
What was the conclusion of Morgan et al.’s (1995) research on SCN?
Morgan et al. showed that transplanting SCN neurons from hamsters with a 20-hour circadian rhythm to normal hamsters caused the recipient hamsters to adopt the 20-hour rhythm, demonstrating the SCN’s influence on circadian rhythms.
What is the role of the pineal gland in the sleep/wake cycle?
The pineal gland produces melatonin, a hormone that induces sleep. Its production is influenced by light signals received from the SCN, with higher melatonin production occurring at night.
Why is it difficult to study the role of endogenous pacemakers in isolation?
Endogenous pacemakers are hard to study in isolation because they interact with exogenous zeitgebers, such as light and social cues, making it difficult to determine the exact influence of internal biological rhythms alone.
What is the role of light as an exogenous zeitgeber?
Light is a powerful exogenous zeitgeber that can reset the body’s main endogenous pacemaker, the SCN. It also influences bodily processes like hormone secretion and blood circulation, playing a crucial role in the sleep/wake cycle.
How do social cues affect the sleep/wake cycle in infants?
Social cues like mealtimes and bedtimes help entrain circadian rhythms in infants. By around 16 weeks, babies’ sleep/wake cycles begin to align with these external schedules, indicating the influence of social cues.
What did research on jet lag show about social cues?
Research on jet lag suggests that adopting local times for eating and sleeping (social cues) immediately upon arrival helps entrain circadian rhythms and alleviate jet lag, emphasizing the role of social cues in regulating the sleep/wake cycle.
What was the finding of the Inuits case study regarding light as an exogenous zeitgeber?
The Inuits, living in near total darkness for six months, maintained a consistent sleep/wake cycle, suggesting that endogenous pacemakers may be more important than light as an exogenous zeitgeber in regulating the sleep/wake cycle.
What did Miles et al. (1977) find regarding social cues and circadian rhythms?
Miles et al. found that a blind man with a circadian rhythm of 24.9 hours, despite exposure to regular social cues like mealtimes, could not adjust his sleep/wake cycle, highlighting that social cues alone are insufficient to regulate the sleep/wake cycle.
Why is research into endogenous pacemakers and exogenous zeitgebers criticized for biological reductionism?
It is criticized for being biologically reductionist because it focuses primarily on biological mechanisms, ignoring the influence of social and environmental factors, such as social norms, on the sleep/wake cycle.
How did Siffre’s (1975) research demonstrate the importance of exogenous zeitgebers?
Siffre spent time in a cave without clocks or natural light and believed his sleep/wake cycle was longer than 24 hours, suggesting that the lack of external cues (exogenous zeitgebers) extended his cycle, highlighting their impact on circadian rhythms.
What does the interaction between endogenous pacemakers and exogenous zeitgebers suggest about the sleep/wake cycle?
The interaction suggests that the sleep/wake cycle is regulated by both internal biological clocks (endogenous pacemakers) and external environmental cues (exogenous zeitgebers), with both factors playing a significant role in maintaining the rhythm.