"Sleepy..."

All moms put passion in singing"cradle song". Animals also sleep, even the plants. Everything that's alive needs sleep to survive. In the resting hours, the body makes internal repairs such as relaxation of muscles, the neurons repair themselves, the brain sorts things out, replaces chemicals and solve problems, the immune system increases and so. In the past, most people thought of sleep as a passive time. Today we know that sleep holds the mind and the body together. The lack of sleep can destroy our health. The more sleep-deprived we are, the more stressed we become and overtired.
Nerve-signaling chemicals called neurotransmitters control whether we are asleep or awake by acting on different groups of nerve cells, or neurons, in the brain. Neurons in the brainstem, which connects the brain with the spinal cord, produce neurotransmitters such as serotonin and norepinephrine that keep some parts of the brain active while we are awake. Other neurons at the base of the brain begin signaling when we fall asleep. These neurons appear to "switch off" the signals that keep us awake. Research also suggests that a chemical called adenosine builds up in our blood while we are awake and causes drowsiness. This chemical gradually breaks down while we sleep.
How do our bodies know when it is time to sleep? We all have an internal circadian clock that provides cues for when it is time to sleep and time to wake. This clock is sensitive to light and time of day, which is why having a good bedtime routine and a quiet dark place to sleep is so important. At the same time, a chemical messenger called adenosine builds up during the day as our bodies are busy using energy. The more adenosine builds up in the brain, the sleepier you will feel. Adenosine combined with the circadian clock sends a powerful message of sleepiness to your body. 
Insomnia almost always affects job performance and well-being the next day.
I hope I helped you a bit.