how do mother's do it?

Last Night, I was on call all night for a software vendor of a client who was installing an update to an EHR program.  They require when this is performed after normal office hours that they have someone they can reach by phone.  This person was designated to be me.  I set my ringer to the lowest setting.  I activated the setting that tells you who is calling as the call comes in so if it wasn't one I needed I could swipe the phone to ignore it.  I turned off all other settings for emails, text messages and like alerts and reminders to avoid being disturbed all night long.  The project got started at 11.30pm.  The first call was at 3.30am.  Then 4.am, 5.45am and 6.00am...at this point I decided to get up and get ready and head to the office because I wasn't sleeping and the issues they were having really needed someone onsite to get them completed.

As I got ready at the hotel to head in, I wondered how mother's do it?  They get up at all hours of the night.  They never know when their sleep is going to be interrupted.  How do they do this?  How do doctor's do it when they are on call?  They never know when a phone call is going to come in or how many they will get a night?  

I have found I do not go back to sleep.  I wondered, is this a learned pattern of sleeping that you train yourself for?  I don't know, but I know that I got a LARGE cup of coffee from McDonald's to make it through my day...and I know that being on call during my normal sleep hours isn't something I want to add to my portfolio!