Principles of Coordination
This lesson covers:
- The role of the endocrine system
- How hormones act as chemical messengers
- Steroid and non-steroid hormones
- A comparison of hormonal and neuronal communication
The role of the endocrine system
The endocrine system uses hormones to send information about changes in the environment around the body to bring about a designated response. It consists of endocrine glands that secrete hormones directly into the bloodstream.
These glands include the pancreas, adrenal glands, and the pituitary gland. The pituitary gland, located at the brain's base, produces various hormones that regulate the release of other hormones from different glands.
The role of hormones
Hormones serve as chemical messengers. They bind to specific receptors on target cells. Target cells are cells that have specific receptors for a hormone. Once the hormone binds to the receptors, it stimulates the target cells to produce a response.
How hormones act as chemical messengers:
- Hormones are produced by endocrine gland cells.
- When stimulated, glands release hormones into the bloodstream.
- The blood carries hormones to their target cells.
- They attach to receptors on or inside the target cells.
- The cells then respond to the hormones.
Non-steroid and steroid hormones
Hormones fall into two classes: non-steroid (peptide) hormones and steroid hormones.
| Non-steroid (peptide) hormones | Steroid hormones | |
|---|---|---|
| Solubility | Water soluble (hydrophilic) | Lipid soluble (hydrophobic) |
| Can they diffuse across the phospholipid bilayer? | Cannot diffuse across the phospholipid bilayer | Can diffuse across the phospholipid bilayer |
| Mechanism of action | Bind to receptors on the cell-surface membrane of their target cells to activate second messengers | Bind to receptor molecules in the cytoplasm or the nucleus, forming a hormone-receptor complex that acts as a transcription factor |
| Example | Adrenaline | Oestrogen |
Comparing hormonal and neuronal communication
The nervous and endocrine systems work in tandem to maintain homeostasis. They have different features that allow them to do this effectively.
| Feature | Endocrine system | Nervous system |
|---|---|---|
| Signals | Hormones | Nerve impulses |
| Transmission | By blood | By neurones |
| Speed | Slow | Very rapid |
| Spread | Widespread | Localised |
| Duration of effect | Long | Short |