The circadian rhythm refers to our internal biological clock that regulates the timing of periods of sleepiness and wakefulness throughout a twenty four hour period. The circadian rhythm dips and rises at different times of the day. It is natural for there to be dips in energy throughout the day, but if we achieve sufficient sleep the dips may be less intense.
One sleep cycle is divided into four stages, each associated with different types of mental and physical activity. One full cycle typically lasts from 90 to 110 minutes and is a vital part of getting quality sleep.
|Stage 1 (N1)||This stage consists of very light sleep of which we can drift in and out. During this stage you are somewhat alert and can be easily awoken. Many people experience sudden muscle contractions called hypnotic jerks, often preceded by the sensation that they are falling or about to fall. This stage of sleep is brief, lasting up to about 7 minutes.|
|Stage 2 (N2)||This stage is also fairly light but our eye movements stop and our brain waves become slower with occasional bursts of rapid waves, or sleep spindles. The heart rate slows and body temperature decreases. We spend about 45-55% of the night in stage 2 sleep.|
|Stage 3 and 4 (N3)||This is the deepest stage of sleep or “slow wave sleep” where the brain produces the slowest brain waves or delta waves. During this stage it is harder to be awakened because your body becomes less responsive to external stimuli and you do not experience any eye movement or muscle activity. If you are awakened during this stage, it is common to feel groggy or disoriented for several minutes. Slow wave sleep seems to be associated with bodily restoration of muscles and tissues, boosted immune function, certain types of learning and central nervous system changes.|
|Rapid Eye Movement (REM)||During this final phase of sleep, your brain becomes more active and brain waves are similar to those in the waking state. Breathing becomes more rapid, irregular and shallow, eyes move rapidly and limbs become temporarily paralyzed. Heart rate increases and blood pressure rises. This stage is when most dreams occur. REM sleep is thought to play an important role in learning and memory consolidation, the synthesis and organization of cognition and mood regulation. We spend about 20-25% of the night in REM sleep.|
|Lowers Brain Function||Research shows that after just 24 hours of sleep deprivation, there is an overall reduction of 6% in glucose reaching the brain. Glucose is one of the main energy sources for your brain to function well .|
|Slowed Reaction time||According to research, individuals that were sleep deprived took 14% longer to complete a task compared to individuals that were well rested .|
|Increased Likelihood of Errors||The same research mentioned above further showed that individuals who were sleep deprived made 20% more errors compared to individuals that were well rested .|
|Short-term memory loss||Sleep helps the brain form connections and link events, facts, and sensory data together. Without sleep, the brain struggles with forming these connections. This makes it difficult to learn new things at a fast pace.|
|Suppression of immune system||Without sleep, your body will direct energy sources elsewhere, often at the expense of your immune system. This will make you more susceptible to illnesses, such as a cold or the flu, which can lead to missed classes and late assignments.|
 Heffernan, Margaret. “Too Little Sleep: The New Performance Killer.” CBS News, 2011.
 Taffinder, NJ, McManus, IC, Gul, Y, Russel, RCG, Darzi, A. “Effect of sleep deprivation on surgeons’ dexterity on laparoscopy simulator.” The Lancet.
*This list is not exhaustive