Slow Chemistry and the Master Gland
While the nervous system fires fast millisecond signals across synapses, the endocrine system releases hormones into the bloodstream to affect distant organs for minutes, hours, or longer.
The pituitary gland is controlled by the hypothalamus. Its anterior pituitary synthesizes its own hormones, while the posterior pituitary only stores and releases oxytocin and vasopressin produced by the hypothalamus.
| Pituitary Part | Function | Examples |
|---|---|---|
| Anterior | Synthesizes and releases own hormones | ACTH, Growth Hormone |
| Posterior | Stores and releases hypothalamic hormones | Oxytocin, Vasopressin |
Stress Axes and Metabolic Glands
The HPA axis is the central stress pathway: the hypothalamus triggers the anterior pituitary, which prompts the adrenal cortex to release cortisol, with negative feedback shutting it down.
The thyroid sets baseline metabolic rate via thyroxine, and gonads release sex hormones.
| Adrenal Part | Control Pathway | Response Time & Chemical |
|---|---|---|
| Medulla | Direct sympathetic nervous system | Instant, adrenaline |
| Cortex | Slow HPA cascade | Minutes to hours, cortisol |
Common pitfall: Confusing the fast adrenaline surge with the slow cortisol response. Both come from the adrenal gland, but via different pathways and timescales.