The Endocrine System
The glands, the hormones that matter in emergency care, how blood glucose is actually controlled by insulin and glucagon, and how thyroid and adrenal problems present. Slow control, in contrast to the nervous system’s fast control.
9 min read · Updated September 10, 2026
Slow Control
The nervous system sends fast electrical signals down defined wires to specific targets. The endocrine system does the same job with chemistry: glands release hormones into the bloodstream, and those hormones act on any cell carrying the matching receptor.
That difference explains the timing. A nerve impulse acts in milliseconds and stops the moment the signal stops. A hormone takes seconds to days to have its effect and lingers afterward. The endocrine system handles growth, metabolism, reproduction, fluid balance and the long term stress response.
Most of it runs on negative feedback. A hormone's own effect signals the gland to stop producing it, which holds the level in a narrow range.
Quick check
What does negative feedback do in the endocrine system?
Frequently asked questions
What do insulin and glucagon do?
Both come from the pancreas. Insulin comes from the beta cells and moves glucose out of the blood and into the cells, lowering blood sugar. Glucagon comes from the alpha cells and pulls stored glucose out of the liver, raising blood sugar. They pull in opposite directions and hold blood glucose in a narrow range.
Which gland releases epinephrine?
The adrenal medulla, the inner part of the adrenal gland sitting on top of each kidney. It releases epinephrine and norepinephrine on a signal from the sympathetic nervous system, which is why the hormonal response and the nerve response produce the same picture.
Why does a diabetic patient breathe deeply and rapidly in ketoacidosis?
Without insulin the cells burn fat instead of glucose and the byproduct is ketoacid. Blowing off carbon dioxide is the fastest way the body has to shed acid, so the breathing becomes deep and fast. That pattern is called Kussmaul respirations and the sweet or fruity smell on the breath is the ketones leaving the same way.
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