Deep Sleep
When are we at our deepest sleep?
Your deep sleep usually occurs in the first three hours. So over the two, one and a half hour cycles, there is a lot of deep sleep, then you awaken just that tiny bit and then go back and get a second block of deep sleep.
If we are unconscious when we sleep, how do we wake up?
In some ways we are not unconscious when we are asleep, we are in a state of sleep which means we can be aroused and awoken. When somebody is unconscious from another cause like being knocked out, you can't just wake them up. The thing about sleep is that, it's an orchestrated state, as far as the brain is concerned. It's a combination of the sleep promoting systems turning on and the 'wake from this' promoting systems turning off. And those 'wake from' promoting systems are associated with the internal clock. Now if something is going on, the 'wake from this' promoting systems will come on and try to switch sleep off. The reason we wake up is a good question. It's not a straight forward question to answer, but it's a combination of things. One is the pressure for sleep gradually dissipates and a lot of that pressure for sleep dissipates during deep sleep. So in the first 3 hours of the night, the pressure for sleep goes down. ‘Wake from this' carries on roughly at the same state. But the biological clock probably then comes on and says it's not time to wake up yet so it sort of lets the brain carry on the state of sleep. And, eventually the biological clock says ,well, dawn's arrived , it's time to wake up and get going. That's why we wake up.
What is the difference between sleeping and fainting?
The difference between sleeping and fainting is, there can be a variety of things. But let's say for some reason, blood pressure dropped down a little bit. It's a completely disorganized state as far as the brain is concerned. Whereas the state of sleep is one where the brain has made the decision that it's going to move into this different state of being.
What is the difference between sleeping and coma?
As far as coma is concerned, that also can be induced by various things but it's a disorganized state as far as the brain is concerned. Various parts have shut down which wouldn't normally won't be down, others are still working. Whereas, with sleep, the sleep systems have organized some parts to shut down, others in fact to keep on working. So if I use dreaming sleep as an example, with dreaming sleep when you're aware of dreams, that's part of the brain that's still working as if it were awake but it's not connected to the outside world.
