Endogenous Pacemakers and Exogenous Zeitgebers on the Sleep/Wake Cycle

Flashcards on Endogenous Pacemakers and Exogenous Zeitgebers

What are endogenous pacemakers?

Internal body clocks that regulate biological rhythms.

What are exogenous zeitgebers?

External changes in our environment that may affect biological rhythms.

What is the suprachiasmatic nucleus (SCN)?

The master clock, a primary endogenous pacemaker in mammals, located in the hypothalamus, maintaining circadian rhythms like the sleep/wake cycle.

How does the SCN respond to light?

It detects changes in light intensity via the optic chiasm, signaling the pineal gland to convert serotonin into melatonin at night and stopping melatonin production in the morning.

What is the role of melatonin?

It induces sleep by causing drowsiness, decreasing body temperature, and suppressing neurotransmitters like cortisol.

Describe DeCoursey et al.'s (2000) study on chipmunks.

Destroyed SCN connections in chipmunks; their sleep/wake cycle disappeared, and many were killed by predators, showing the SCN's role in maintaining the sleep/wake cycle.

Describe Ralph et al.'s (1990) study on hamsters.

Transplanted fetal SCN cells from mutant hamsters with a 20-hour cycle into normal hamsters, defaulting the normal hamsters' cycle to 20 hours.

What is entrainment?

The process by which exogenous zeitgebers reset biological rhythms.

Why is light considered the most important zeitgeber?

It can reset the body’s main endogenous pacemaker (SCN) every morning and influences hormone secretion.

Describe Campbell & Murphy's (1998) study.

Shining a light pad on the back of participants' knees changed their sleep/wake cycle by up to 3 hours, suggesting light can be detected by skin receptors.

How do social cues act as exogenous zeitgebers?

Adapting to local times for eating and sleeping can entrain circadian rhythms when traveling.

Describe Klein & Wegmann's (1974) study on jet lag and how does it provide jet lag as practical application for exogenous zeitgebers?

Air travelers adjusted to new time zones more quickly if they went outside more, exposing them to social cues. Adapting to local times for eating and sleeping rather than doing so when feeling tired/fatigued can be effective for entraining circadian rhythms.