The interrelationship of the nervous and endocrine system?

Well, the endocrine system is a glandular system. It's glands give off hormones that may help the nervous system. That's my guess. I guess certain hormones, like, help the nervous system develop and stuff... I don't know...

The nervous system would operate the endocrine system, on the occasions where they are intertwined. When you have an impulse from your brain it will travel through the nervous system to its target organ/tissue/etc. When the signal arrives it causes a consequence. This consequence can sometimes be caused the nervous system releasing a hormone, as is the case with norepinephrine and the heart.

Also, the endocrine system can operate independently of the nervous system (which is more common). The hormones released by tissues/organs simply act as messengers. So for example when women are pregnant, various hormones arising from the reproductive organs of the women cause various changes in the female body to prepare for the baby.

So they can be intertwined but aren't always.