Characteristics of the Sleep Wake Cycle

The sleep-wake cycle is part of the body's circadian rhythms and helps us to function properly. Disturbances in this cycle significantly affect the quality of life. Continue reading to find out more!
Characteristics of the Sleep Wake Cycle

Last update: 30 September, 2021

The sleep-wake cycle refers to that moment just before we fall asleep. The waking part of the cycle happens when we’re not asleep, and vice versa.

The nervous system is in charge of regulating the wake-sleep cycle. There are specialized neurons to coordinate the function and neural tissues, the biological clock.

Chronobiology studies the chronometer we living beings have inside. The one that stipulates every vital function has a rhythm.

Humans have three types of them:

  • Circadian are those your body completes in 24 hours, approximately, such as the wake-sleep cycle.
  • Infradian are those that last more than one day, such as the female menstrual cycle.
  • Ultradian are those that complete in less than a day.

How does wakefulness differ from sleep?

The wake-sleep cycle combines two moments of your life: waking and sleeping. Both stages are vital even though they greatly differ from one another.

Wakefulness implies a state of consciousness. That is we’re aware of what’s happening and we use our senses to communicate with the environment around us. Thus, we can think, plan, and act accordingly.

Being awake is a task of the nervous system, more precisely of the ascending reticular system, which is a set of specialized neurons. Furthermore, this tissue communicates with the thalamus and the cerebral cortex.

One of the neurotransmitters most used in wakefulness is noradrenaline, unlike in sleep which uses melatonin. This substance regulates the attention we pay and our impulse to perform activities.

Serotonin and noradrenaline are important. It has important functions in the cerebral cortex, especially in the area of the neurons that regulate vision.

An illustration of a sleeping man.
Hormones and part of the neural tissue regulate the wake-sleep cycle.

Melatonin in the wake-sleep cycle

As we said above, melatonin is a key hormone in the wake-sleep cycle as it counteracts noradrenaline to induce sleep. It cyclically replenishes throughout the circadian rhythm.

Melatonin generates in the pineal gland when it detects darkness. On the contrary, sunlight or artificial light sends orders to the gland to stop its production.

During a relatively normal night in which a person rests for 8 hours, the maximum production of melatonin will happen at the fourth hour of sleep to sustain rest.

Then, exposure to light stops the effect of melatonin, and it’s common for any activities done under bright light before bedtime to alter the wake-sleep cycle. The use of cell phones, for example, is one of the most characteristic habits that delays melatonin production.

One can also take an artificial capsule form of this substance:

  • The medium effect can sustain sleep for no more than 4 hours.
  • Prolonged-release can simulate the natural effect and help complete 8 hours of sleep.

Disorders of the sleep-wake cycle

The wake-sleep cycle is easy to disturb. In fact, the disorders resulting from a problem in the biological clock are diseases of the circadian rhythm. Medicine has cataloged some of them:

  • Phase delay happens in people who go to sleep late, in the early morning, and then don’t wake up early in the morning. It can happen to anyone but becomes a disorder when it lasts for more than a month.
  • Phase advance is the opposite of the previous one. Here, the individual gets sleepy early on and so they fall asleep. However, they wake up in the middle of the night and can no longer fall asleep.
  • It’s hard to determine the irregular rhythm because the biological clock follows no parameters to mark the stages. There may be a phase delay one day and a phase advance the next. It qualifies as a disorder when it lasts for 3 months.

Disorders of the sleep-wake cycle

The disorders of the wake-sleep cycle vary and alter the quality of life.

  • Jet lag is a traveler’s disease, as it happens to people who cross different time zones in just a few hours, usually via airplanes.
  • Shift work is the usual disorder of those who work at night such as guards and nurses.
  • Hypernychthemeral is a disorder in which the circadian sleep-wake rhythm lasts longer than 24 hours and gets progressively longer (the person usually sleeps longer every day until they sleep almost a full day).

Getting a good night’s rest to remain awake

The wake-sleep cycle is for our body to function properly. Thus, good rest is key to a healthy waking period. Conversely, being awake without feeling tired leads to a pleasant night’s sleep.

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