A dialled up sympathetic nervous system gets in the way of easy baby sleep

There are two biological hungers which dial up your baby’s sympathetic nervous system. These are your baby's

Hunger for milk, and
Hunger for richer sensory motor experience (which could be contact with your or another loving adult’s body, or a change in sensory environment).

A dialled up sympathetic nervous system makes it more difficult for one of your baby’s sleep regulators, the rising sleep pressure, to do its work of switching on sleep. You can find out about your baby's two sleep regulators, the body clock and sleep pressure, here and here.

When you use your baby sleep superpowers to dial your baby down, his sleep regulators do their job of sending him to sleep easily. Knowing how to use these two superpowers of

Frequent flexible feeds (whether your baby is breastfed or bottle fed), and
Rich and changing sensory motor experience

is vital for enjoyable and easy sleep in your family.

Why does a dialled up sympathetic nervous system interfere with sleep?

I often use an example to show how this works physiologically in my own body. Let's say I go to bed at night knowing I need to give a big presentation the next day. When I feel stressed, I can find it difficult to go to sleep. My sympathetic nervous system dials up even more as I lie there, imagining the next day. My body might feel tense and my mind becomes busy. These high levels of sympathetic nervous system activity override the neurohormones of my building sleep pressure. I can't go to sleep.

This is what happens in babies who are dialling up. Eventually baby's sleep pressure might kick in anyway after a period of fussing and crying, and baby goes to sleep, but it could all have been so much easier.

Sometimes you might find yourself in a pattern of lying awake even when your baby is asleep, despite your exhaustion and sleep deprivation. It's awful when this happens. You can find out what to do if you're in this situation here.