February 20, 2014
Specific Brain Cells Found That Determine When Its Sleepy Time
[ Watch the Video: What Triggers Sleepiness? ]
Ranjini Raghunath for redOrbit.com - Your Universe Online
Researchers at Oxford University have figured out which nerve cells in the brain alert us to the fact that it is time to sleep. These nerve cells, or neurons, fire when we are tired and cool down once we are rested.
The findings could help scientists develop drugs that target these regions in the brain and help treat sleep disorders such as insomnia.
The study, published in the journal Neuron, was carried out in fruit flies, but the researchers believe that similar regions in the human brain control when we need to go to sleep.
“When you're tired, these neurons in the brain shout loud and they send you to sleep,” senior author and Oxford scientist Gero Miesenböck said in a statement.
The researchers found that mutant fruit flies with these regions turned off had trouble sleeping even after being kept up all night. Lack of sleep also affected their learning and memory, similar to how sleep loss affects humans.
Two mechanisms in the body work in concert to keep track of how long you are awake and active and when you need to go to sleep: the homeostatic and circadian systems. The former keeps track of how many hours you have been up, and the latter – also called the body clock – makes your body adjust to the 24-hour cycle.
“The sleep homeostat is similar to the thermostat in your home,” Miesenböck explained. “A thermostat measures temperature and switches on the heating if it's too cold. The sleep homeostat measures how long a fly has been awake and switches on a small group of specialized cells in the brain if necessary. It's the electrical output of these nerve cells that puts the fly to sleep.”
The sleep-promoting neurons identified by the researchers act as the effector arm – the part that responds to a particular signal or stimuli -- of the homeostatic system, the authors wrote.
A lot of research has been carried out on the circadian cycles, but scientists know very little about how the homeostatic system works, the authors point out.
Many questions are still unanswered, the authors acknowledge, such as why does the human body need sleep in the first place and what signals the sleep “switch” to turn on or off.
“If we knew what happens in the brain during waking that requires sleep to reset, we might get closer to solving the mystery of why all animals need to sleep,” Miesenböck added.