What is Sleep?

What is sleep?

Sleep is a natural, regularly recurring condition of rest for the body and mind. It is observed in humans and many animals. It is different from quiet wakefulness because it has a decreased ability to react to stimuli in the environment. It is more reversible than hibernation or coma. And it is important for survival in many ways.

The purpose and mechanisms of sleep are partially understood. It is a current subject of intense research for safety and well being.

Why do we sleep?

In humans, sleep cycles last 90 to 110 minutes. Each cycle has a distinct set of functions that affect the normal activities of the body and its parts.

Adverse effects of poor sleep or lack of sleep (sleep deprivation)

Things that impact sleep in a negative way include alcohol, sleeping pills, other drugs, trauma, hormonal disorders, diet and many other things. They can impair or stop certain stages of sleep. The result is a person who may sleep less than is needed or sleep enough hours  but have trouble with certain body functions or parts.

Total or selective sleep deprivation for both humans and animals results in disturbances in the central nervous system (CNS) – brain, brain stem and spinal cord. They show up as:


  • irritability
  • nervousness
  • depression and anxiety
  • loss of memory and concentration
  • mental, physical and emotional fatigue

After sleep deprivation, a person will recuperate by increasing the proportion of deep sleep (stage 4 or N3) for physical body repair and rapid eye movement (REM) sleep/dreaming for CNS healing. Physiological (normal body and body part) functions affected by poor sleep result in:

  • Poor wound healing
  • Weakened immune system
  • Reduced hormone secretion for body growth
  • Poor brain development for babies
  • Loss of memory for facts or learned skills
  • and more …

Body Restoration Through Sleep

The body needs to restore itself through sleep.  Think about when you last were sick – perhaps the flu or a trauma such as surgery. The most common thing you did was sleep. This allowed your body to recharge itself.

Sleep is a state of growth for the body. It produces substances called anabolic hormones. These hormones, like growth hormone, promote repair and growth of new tissue in the body. This can affect the muscles, immunity, nerves and skeleton. A rat study (Gumustekin et al. 2004) demonstrated that sleep deprived rats healed more slowly than those with regular sleep. Various studies on loss of sleep and immune function indicate that the body may produce higher white blood cell counts when we have normal sleep. This would be more protective for the body against bacteria and viruses.

Wakefulness on the other hand, is more catabolic. It consumes energy from the food and beverages we drink and the air that we breathe. It uses up our resources like sugar in the blood.

Brain development in children is impacted by sleep. Newborns need hours of sleep for brain development. If they do not get the sleep they need, it can result in behavior problems, disruption in sleep and decreased brain mass (Mirmiran et al. 1983).

Healthy sleep allows our bodies to grow and protect itself. Abnormal sleep disrupts these functions. Disease and dysfunction are effects of poor sleep.

Pat Casello-Maddox
Health Right Copy



Gumestein K, Seven B, Karabulut, N, et al. Effects of sleep deprivation, nicotine, and selenium on wound healing in rats. Neurosci 2004; 114 (11) 1431-1442.

Mirmarian, M, Scholtens J, Van de Poll NE, Uyulings HBM, Van der Gugten, J., Boer,GJ. Effects of experimental suppression of active (REM) sleep during early development upon adult brain and behavior in the rat. Dev Brain Res 1983; 7:277-286.