The need for sleep goes far beyond simply replenishing our energy levels every 12 hours. Our brains actually change states when we sleep to clear away the toxic byproducts of neural activity left behind during the day.
Weirdly enough, the same process starts to occur in brains that are chronically sleep-deprived too - except it's kicked into hyperdrive.
Researchers have found that persistently poor sleep causes the brain to clear a significant amount of neurons and synaptic connections, and recovering sleep might not be able to reverse the damage.
A team led by neuroscientist Michele Bellesi from the Marche Polytechnic University in Italy examined the mammalian brain's response to poor sleeping habits, and found a bizarre similarity between the well-rested and sleepless mice.
Like the cells elsewhere in your body, the neurons in your brain are being constantly refreshed by two different types of glial cell - support cells that are often called the glue of the nervous system.
The microglial cells are responsible for clearing out old and worn out cells via a process called phagocytosis - meaning "to devour" in Greek.
The astrocytes' job is to prune unnecessary synapses (connections) in the brain to refresh and reshape its wiring.
We've known that this process occurs when we sleep to clear away the neurological wear and tear of the day, but now it appears that the same thing happens when we start to lose sleep.
But rather than being a good thing, the brain goes overboard with the clearing, and starts to harm itself instead.
Think of it like the garbage being cleared out while you're asleep, versus someone coming into your house after several sleepless nights and indiscriminately tossing out your television, fridge, and family dog.