Our sleep rhythms are tied to an exact 24-hour day because
A)the time of peak activity is invariant from person to person.
B)they are tied to external time markers like light and dark.
C)there is a gravitational pull on the body from the sun and moon.
D)everyone needs at least eight hours of sleep every night.

Question

Quizplus · Accepted Answer

Our sleep rhythms, also known as circadian rhythms, are tied to external time markers like light and dark. The suprachiasmatic nucleus (SCN) in our brain receives signals from the eyes about the amount of light in our environment, which helps regulate our sleep-wake cycle to an approximately 24-hour day. This is why we tend to feel sleepy at night and awake during the day. While everyone's need for sleep may vary, it is not the reason why our sleep rhythms are tied to a 24-hour day.

Our Sleep Rhythms Are Tied to an Exact 24-Hour Day