We all have a pretty good idea of how it feels to have an awful night's sleep.
The second you woke up this morning, your cells started pumping out a sleep-promoting chemical called adenosine. It built up throughout the day and now, along with other substances, it's saturating your brain, making you drowsy.
As the sun set, your brain's pineal gland began producing the sleep hormone melatonin, which signals to your body it's time to snooze.
A neurochemical called GABA now activates the brain stem's sleep command center. Next stop, Zzzzzz…
After a Few Minutes
But first, you take a mental inventory of your day, thinking about what you should have said, could have done, still need to do. Big mistake. Though you're lying still, your mind has revved up your fight-or-flight stress response.
Your adrenal glands unleash adrenaline, which increases your heart rate, blood pressure, body temperature, and breathing rate.
Adrenaline recruits a partner, the stress hormone cortisol. Among other things, it raises blood sugar levels and mental alertness.
Game on. Your brain's sleep and wake centers are at war with each other.
After a Couple Hours
You glance at the clock. Grrr. Your frustration triggers another round of that adrenaline-cortisol cocktail. Some deep breathing could calm your agitated mind.
After About Three Hours
You give up and switch on your laptop. The screen's blue light squashes your melatonin levels and tricks your brain into thinking it's daytime. Also, your mind is likely engaged in whatever you're reading or watching, making you even more awake.
After About Five Hours
The brain's sleep center finally wins the tug-of-war, and you nod off. But instead of ebbing and flowing, your brain waves are stuck on high frequency, causing a fitful sleep.
After About Seven Hours
The alarm blares. Chances are, you're waking up when your brain waves are finally sliding into the delta phase associated with deep sleep, which is much harder to quickly snap out of.
You're up, but you haven't burned through enough of that adenosine, so your head feels foggy. Reaching for a java infusion might help–caffeine negates adenosine's effects.
Throughout the Morning
The lack of rest could make the amygdala, your brain's emotional center, more active than usual. You may feel grouchy or the opposite, unusually giddy.
Meanwhile, your brain's prefrontal cortex — your reasoning and concentration center — is dragging. You may feel like an unfocused, irritable hot mess. But if you hit the hay at your usual time tonight and do that relaxing deep breathing, you should be able to score a solid night's sleep.