A mid ocean ridge is made by a divergent boundary. The mid-ocean ridges of the world are connected and form a single global mid-oceanic ridge system that is part of every ocean. The mid-oceanic ridge system is the longest mountain range in the world. The continuous mountain range is 65,000 km (40,400 mi) long.
Circadian rhythms are important in determining human sleep patterns. The body's master clock, or SCN, controls the production of melatonin, a hormone that makes you sleepy. Since it is located just above the optic nerves, which relay information from the eyes to the brain, the SCN receives information about incoming light.
The Characteristics of Sleep. At a Glance. Sleep is a state that is characterized by changes in brain wave activity, breathing, heart rate, body temperature, and other physiological functions. Depending on the sleep stage, different physiological functions may be more active and variable (for example, during REM sleep), or less active and more stable (for example, during NREM sleep).