Anatomy and Physiology 12 · Biology · Lesson 10.1
Hormones & glands
- Level
- Grade 12
- Reading time
- 11 min reading
- Review
- Last reviewed 2026-09-03
- Standard
- Accuracy standard
- Errata
Abstract
Chemical messengers.
What are hormones?
Short answer
Hormones are chemical messengers secreted by endocrine glands directly into the bloodstream, which carries them to target cells elsewhere in the body. Only cells with the matching receptor respond, so a hormone can act on specific tissues far from its source. Hormones regulate slow, sustained processes such as growth, metabolism, and reproduction.
Concept preview
What you will be able to do
- 01Distinguish endocrine (ductless) glands from exocrine glands and give examples of each.
- 02Describe steroid, peptide/protein and amine hormone classes, and compare intracellular and cell-surface receptor signalling.
- 03Explain how target cells and receptor specificity decide which cells respond to a hormone.
- 04Compare the endocrine system with the nervous system in speed, spread and duration.
The nervous and endocrine systems coordinate the body through signals. Nerves conduct electrical impulses and release chemical messengers at their targets. Endocrine hormones enter the blood and act on cells with suitable receptors and downstream machinery. Nervous responses are often rapid, while hormone responses range from rapid effects to sustained regulation. This lesson compares steroid, peptide/protein and amine hormones and explains how receptor location shapes their action.
School Plan
Hormones & glands
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Related topics
Frequently asked questions
- How do hormones differ from nerve signals?
- Hormones travel in the blood and act slowly but with lasting effects; nerve impulses are fast and short-lived.
- Why does a hormone affect only certain cells?
- Only target cells carry the specific receptor that the hormone binds to, so only they respond.