An example of a direct connection: thus, the production by the glands of internal secretion of some biologically active substances (hormones) is under constant control of the nervous system. In turn, fluctuations in the content of hormones in the blood affect the nervous system, increasing or decreasing its level of excitability. This is an example of feedback.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.