How do the nervous system and endocrine system work together? apex?

The nervous and the endocrine system are tightly linked together.
The main reason for this linkage is due to the connection of the hypothalamus (nervous system) and the hypophysis (a gland in the endocrine system)
The hypophysis is the ''controller'' of all of the other endocrine glands.
The connection between the hypothalamus and the hypophysis enables the nervous system to control the hormone levels of all of the major endocrine glands in the body.
The hypothalamus releases hormones into the bloodstream that leads to the hypophysis. These hormones induce a release of hypophysis hormones that enter the bloodstream and when they reach the target gland (for example pancreas) these hormones induce the release of the hormones of that gland (in the case of the pancreas, insulin).
The hypothalamus monitors the concentration of hormones in the blood, and a high level of a certain hormone blocks the release of the hypothalamus' hormones. Therefore, a high level of insulin blocks a cascade of hormone release that starts in the hypothalamus that leads to its release in the pancreas.