Sleep is defined as the state when your body is reduced in consciousness and your body is less responsive to the external world. We go through 5 different stages throughout the night. The first is a light sleep as you are drifting off and it lasts 5-10 minutes. The second includes a deeper sleep as your brain waves slow and sleep spindles show up on an EEG (used to check your brains activity). The bodys temperature and heart rate reduce. Stage 3 occurs after 25 minutes and delta waves occur, gradually increasing. Stage 4 is an even more profound sleep and if woken you would become groggy and disorientated. The final stage is different from the rest – REM sleep. This occurs 90 minutes into sleep and is the point in your sleep when you are found to dream. The body is a lot more active during this stage, at the point of wakefulness. The body is also relaxed and steady. REM stands for rapid eye movement meaning your eyes show
bursts of movements under your eyelids during this stage. The main differences between non-REM and REM, is the type of sleep you are in and what regulates these stages. Sleep is also needed for concentration. Sleep deprivation has found to be linked to a reduction in memories. People who are sleep deprived have worse immune systems, meaning they are prone to catch illnesses. Caffeine and amphetamine are stimulants which make people more alert and less tired. After consuming these people may struggle to sleep. This is due to a naturally occurring hormone in our brain called adenosine which block the receptors in our brain, causing drowsiness. We need less sleep the older we get. Infants need 18 hours of sleep per day and spend half of this time in REM sleep. The developing brain requires a great deal of protein synthesis. This replenishes and renews brain processes for cell manufacture and growth, REM sleep helps achieve this.