Endogenous Pacemakers and Exogenous Zeitgebers

Question 1

Endogenous Pacemaker

Answer 1

Internal body clocks that regulates many of our biological rhythms such as the influence of the SCN on the sleep/wake cycle.

Question 2

Suprachiasmatic Nucleus (SCN)

Answer 2

Tiny bundle of nerve cells located in the hypothalamus, influential in maintaining circadian rhythms such as sleep/wake cycle.
SCN lies just above optic chiasm, it receives light info directly from this structure.
This continues when eyes are closed to adjust sleep patterns based on daylight.

Question 3

Animal Studies and SCN

Answer 3

DeCoursey et al. (2000): Destroyed SCN in chipmunks, disrupted sleep cycles. Many became prey due to irregular sleep, showing the SCN’s role in survival.
Ralph et al. (1990): Transplanted SCN cells from mutant hamsters (20-hour cycle) to normal hamsters, altering their sleep/wake cycle to match the donor, which reinforced the SCN’s role in rhythm regulation.

Question 4

Pineal Gland and Melatonin

Answer 4

The SCN sends signals to the pineal gland, influencing melatonin production based on light levels.
Melatonin release increases in darkness, promoting sleep. Inadequate melatonin regulation has been linked to Seasonal Affective Disorder (SAD).

Question 5

Exogenous Zeitgebers

Answer 5

External cues that may affect our biological rhythms, such as the influence of light on the sleep/wake cycle.

Question 6

How is Light as a Zeitgeber important for humans?

Answer 6

Light is a crucial zeitgeber for humans, influencing the SCN and the regulation of the sleep/wake cycle.
Light impacts physiological processes, such as hormone secretion and blood circulation, which help regulate biological rhythms.

Question 7

Research by Campbell and Murphy (1998)

Answer 7

Exposing participants’ skin to light on the backs of their knees altered their sleep/wake cycle by up to three hours, indicating that light affects circadian rhythms even when not perceived directly by the eyes.

Question 8

How do Social Cues as Zeitgebers Play a role in synchronizing sleep/wake cycles?

Answer 8

Especially in infants and young children.
Infants typically develop circadian rhythms around 6-16 weeks, influenced by feeding schedules and parental routines.
Social cues can also aid in adapting to new time zones.