The only way I can describe it is like a rush of something (like adrenaline) but a more relaxing, warm feeling rather than the spiking, energetic feeling of adrenaline.
As your body approaches sleep, your heart rate and blood pressure lower, muscles relax, and your brain chemicals change – an especially important change is that there’s more GABA, a neurotransmitter associated with relaxation. So your comparison to an adrenaline rush is very apt, you’re experiencing an increase in a neurotransmitter that does the opposite of what adrenaline does. 🙂
As your body approaches sleep, your heart rate and blood pressure lower, muscles relax, and your brain chemicals change – an especially important change is that there’s more GABA, a neurotransmitter associated with relaxation. So your comparison to an adrenaline rush is very apt, you’re experiencing an increase in a neurotransmitter that does the opposite of what adrenaline does. 🙂