There is nothing like a messed up sleep schedule to negate all the rest and restoration we may have brought back from a vacation or holiday travel. Whether it’s a missed nap, a delayed bedtime, travel-induced jet-lag or some other sleep issue, lack of quality sleep can amount to an over-abundance of cranky.

To help ease the stress of fatigue and frustration, it may help to know that there is a lot of biology behind successful sleep.

Knowing a little about sleep may help us be more objective about what is going on in the moment, and a little easier on ourselves and our kids because of it. By understanding what happens during quality, healthy sleep, we can strengthen our resolve to put systems and routines in place that prioritize sleep and respect it for the critical role it plays in our own lives and our children’s growth and development.

So, when are we supposed to sleep?

Circadian rhythms

The body’s natural circadian (daily) rhythms are regulated by the brain’s “executive network,” and certain brain chemicals that produce the states of sleeping and waking.

Early in a newborn’s life, this internal clock begins to establish and control the daily rhythm of biological systems, including body temperature, blood pressure, and the release of hormones.

This is why is takes awhile for new babies to settle on any predictable eat-sleep-wake cycle. During the first few months of life though, the irregularity of these rhythms gives way to more stability as the brain continues to develop and mature.

Melatonin, the “feel sleepy” hormone, is produced naturally by the body in the evenings, helping us wind down and prepare for sleep. Melatonin levels in the body are almost non-existent during the day and to begin climb after dark and ebb after dawn. Additionally, the activity of our brain’s posterior hypothalamus diminishes naturally during sleep when it releases less histamine, a molecule that it uses as a neurotransmitter, helping us stay asleep. (Antihistamines taken for allergy symptoms cause sleepiness in the same way.)

Nothing throws off a sleep cycle like jet-lag

Our circadian system is normally synchronized with the solar day, ensuring that alertness and performance peak during daytime hours and consolidated sleep occurs during the night. Jet-lag can be explained by exposure to light at the wrong time that results in a shift of sleep and wakefulness to undesired times.

Just like for us, being out of sync with circadian rhythms can make it more difficult for kids to fall asleep or stay asleep, resulting in an overtired and stressed kiddo. Ultimately, adjusting the schedule to be in sync with their’s can lessen the disruption.

Experts recommend building in at least one “recovery day” when going on or returning from a vacation.

Whether it is one state over or across many time zones—we should stay awake as long as possible. So when it’s nighttime in our new time zone, we need to keep the lights low inside, and when it’s daytime in our new locale, we need to be exposed to bright light—ideally, natural outdoor light.

When it comes to retraining our children’s internal clock, exposure to light at the appropriate time helps keep the circadian clock on the correct time schedule. Appropriately-timed exposure to bright light—Bright Light Therapy—can reset the timing of sleep and wake to the desired times, and improve sleep quality and daytime alertness.

However, recovery from a trip through many times zones is quite different than the three hours difference between San Francisco and New Jersey. “Apparently the brain may confuse dawn with dusk,” says Naturopath Hillary Roland.

To counteract that effect, Roland says the current expert suggestion is to “actually stay indoors after long eastward flights for a few hours after dawn, and for a few hours before dusk after a long westward flight.” This advice is supported by studies on jet-lag that have determined that the efficacy of bright light therapy is dependent on the time-of-day of the circadian cycle that the light is administered.

So, what’s going on when we sleep?

Types and stages of sleep

We progress through a series of distinct physiological stages during sleep that serve an important purpose in keeping our brain and body healthy. During the night, Quiet/Non-REM (NREM) sleep alternates with periods of Dreaming/REM (rapid eye movement) sleep in which our most vivid dreams occur.

We cycle through five separate stages of sleep every 90-110 minutes, experiencing between three and five dream periods each night.

Quiet/Non-REM sleep

When we are sleeping, about 75-80% of the time is spent in the inactive Quiet/Non-REM (NREM) stages that provide the body’s much-needed relaxation and rejuvenation and are also vital to proper development.

Stage 1: Drowsiness (1-7 minutes)

With heavy eyelids, we begin to drift off. Our body temperature begins to drop, muscles relax, and eyes often move slowly from side to side. We lose awareness of our surroundings but can wake easily since our brain is still quite active.

Stage 2: Light sleep (10-25 minutes)

Our brain activity slows further as we descend into a light sleep. Our eyes stop moving, and our heart rate and breathing are slower than when awake. Our brain disconnects from outside sensory input and begins the process of memory consolidation and organizing for long-term storage.

Stage 3: Moderate sleep (20-40 minutes)

Our breathing becomes more regular, blood pressure falls, and pulse slows to about 20-30% below our waking rate. Blood flow is directed less toward our brain, which cools measurably. We become less responsive to external stimuli and much more difficult to wake up.

Stage 4: Deep sleep (20-40 minutes)

Our brain quiets further as we transition into deep sleep. Our muscles relax and our breathing becomes slow and rhythmic. We become extremely hard to wake and may snore.

The time of peak growth hormone release in the body, during this deepest stage of sleep the pituitary gland releases a pulse of growth hormone that stimulates tissue growth and muscle repair. “Growth hormone is primarily secreted during deep sleep,” says Judith Owens, M.D., director of sleep medicine at Children’s National Medical Center, in Washington, D.C. Babies spend about 50% of their time in this deep sleep, considered to be essential for adequate growth.

In addition to being critical for cell reproduction and rejuvenation, deep sleep helps the body defends itself against infection. During deep sleep, researchers have detected increased blood levels of proteins known as cytokines. As part of the immune response, cytokines exert their influence over various white blood cells which the body relies on to fight infection, illness, and stress.

Cytokines also make us sleepy, forcing us to rest, which further aids the body’s ability to heal and explains why having the flu or a cold feels so exhausting. Too little sleep appears to impact the number of cytokines on hand, illustrating why it is easier to catch and more difficult to fight viruses with too little sleep.

Dreaming/REM sleep

Just as deep sleep restores our body, scientists believe that active Dreaming/REM sleep restores our mind by transferring short-term memories into long-term storage and helps clear out irrelevant information and facilitates learning and memory.

Stage 5: Active sleep (10-60 minutes)

After deep sleep, our brain activity increases again. About 3-5 times a night, or about every 90 minutes, we enter active, or REM sleep. The first such episode usually lasts for only a few minutes, but REM time increases progressively over the course of the night. The final period of REM sleep may last a half-hour.

This is the period of the night when most dreams happen. Our muscles are temporarily paralyzed, and our eyes dart back and forth, giving this stage its name. Our body temperature rises, blood pressure increases, and our heart rate and breathing speed up to daytime levels. The sympathetic nervous system, which creates the fight-or-flight response, is twice as active as when we are awake.

Research indicates that decluttering—sorting, storing, and filing away information, memories, and experiences—may be one of the central functions our brain performs during REM sleep. This is also when we repackage neurotransmitters, the chemicals that enable our brain cells to communicate. Additionally, experts have demonstrated that REM sleep allows brain cells to flushing out disease-causing toxins.

When we sleep after a period of sleep deprivation, we pass quickly through the lighter sleep stages into the deeper stages and spend a greater proportion of sleep time there. This suggests that deep sleep plays a large part in restoring alertness and fills an essential role in a our optimal functioning.

So, how can we prioritize to optimize?

For the most part, we can indeed control how much sleep we get—if we want to. It all starts with creating the time necessary for sleep and an environment conducive to sleep. Making sleep a priority means that our families have the opportunity to sleep as much as they need to in a safe, quiet, comfortable environment.

By reducing pressures on our limited time we can prioritize and optimize our family’s sleep. Even if we realize that our child could use more sleep, “…it can be very difficult to recognize all the ways that after-school and evening activities sabotage bedtime, and the damaging effects of allowing electronics into your kid’s bedroom,” says Parents advisor Jodi Mindell, Ph.D., associate director of the Sleep Center at the Children’s Hospital of Philadelphia.

“The bedroom should be a haven for rest and recovery, not a place to be distracted,” echoes Wendy Troxel, a behavioral scientist at RAND, a think tank that helps improve public policy through research.

10 ways to build a better bedtime

1. For babies, encourage self-soothing

Try not to let babies fall asleep while eating, and put them to bed when they are still awake.

2. For kids, create a solid routine

Children should have an age-appropriate, clear and consistent bedtime ritual, with the same bedtime and wake up schedule all week long —no sleeping in.

3. Add another bedtime story

Listening to storybooks is a great way to ease kids towards sleep. “Of all activities, reading printed books appears to be most relaxing,” says Michael Gradisar, a clinical psychologist at Flinders University, in Adelaide, Australia.

4. Keep electronics out of the bedroom

Avoid having a television, computer, tablet or cell phone in the bedroom in the hour before bed as electronics can stimulate young brains. Blue light from devices such as iPads also suppresses melatonin release.

5. Make sure the bedroom is cool and quiet

6. Keep the bed for sleeping only

Not confusing the bed with playtime teaches children to respects it as the place for rest, establishing a habit that can provide life lon benefits.

7. Keep allergens out of the bedroom

Keeping the bedrooms clean can go a long way to ensuring an allergen-free bedroom.

8. Encourage a nighttime snack before brushing teeth

A snack that’s high in protein and low in sugar, like a glass of milk, can promote better sleep. However, eating sweets near bedtime causes a spike in blood sugar followed later by a drop, leading to a feeling of hunger that may wake kids in the middle of the night.

9. Establish talk time

Including 10 or 15 minutes of undivided attention when we are available to listen to our child talk about whatever they want can provide an opportunity for our kids to unload anything that might be preventing them from sleeping.

10. Teach kids to practice a form of mindfulness or prayer before bed

Meditation and prayer can quiet the mind, reduce stress and improve sleep.

Of course, every child varies in the amount of sleep they need. Some kids have high sleep needs and others don’t. As parents, we are the best judge of whether or not our kids are getting enough sleep.

It’s important to remember that our kids are human, too. And just like our behavior can disintegrate when we are overtired, so can theirs. We can’t expect our kids to function when they are sleep deprived when don’t expect the same from ourselves.

And just as it is our responsibility to feed, love and keep our kids safe, it is also our responsibility to recognize how important sleep is for all of us and ensure that all the elements are in place to enable everyone to enjoy the amazing benefits of sleep. Otherwise, we’ll all be just. so. tired.