Definition
The endocrine system is the body's network of hormone-producing glands — among them the hypothalamus, pituitary, thyroid, adrenal glands, pancreas, and gonads. Where the nervous system sends fast, targeted signals along wires, the endocrine system broadcasts slower chemical signals through the shared medium of the bloodstream.
In Behave, the endocrine system matters because it is one of the layers between a triggering event and a behavior. To explain why someone acted as they did, Sapolsky asks what hormonal climate the endocrine system had established in the hours and days before.
Why it matters
How it works
The hypothalamus sits at the interface of brain and endocrine system, translating neural signals into hormonal commands. It instructs the pituitary, often called the master gland, which in turn signals downstream glands such as the adrenals or gonads to release their hormones. Feedback loops — rising hormone levels reported back to the brain — keep the whole network self-regulating, switching production up or down to hold the body near a setpoint.