These questions ask you to identify how hormonal messages travel, why some cells respond, and which gland or control loop matches a stated body function. Follow the chain from releasing structure to hormone, target, effect, and feedback.
Build the signalling chain
A hormone is a chemical messenger released by cells and carried through body fluids to target cells, often elsewhere in the body. Endocrine release is ductless: the chemical enters surrounding fluid and can reach the blood, rather than travelling through an outlet tube to a surface or cavity. Arrival is not enough by itself. A cell responds only when it has a receptor that matches the hormone. This gives a dependable method: identify the source, the signal, the route, the receptor-bearing target, and the regulated effect.
| Control clue | Link to make |
|---|---|
| Neural information influencing endocrine control | The hypothalamus regulates signals affecting the pituitary. |
| Growth and influence over several other glands | The pituitary releases multiple regulating hormones but remains linked to hypothalamic control. |
| Rate of energy use by many cells | Thyroid hormones influence metabolic activity. |
| Calcium concentration in body fluids | Parathyroid hormone contributes to its regulation. |
| Blood glucose moving in opposite directions | The endocrine pancreas supplies insulin and glucagon as counteracting signals. |
| A response shrinking as stability returns | Negative feedback is counteracting the earlier departure. |
Other glands fit the same source-to-effect method. Adrenal hormones support stress responses and regulation that includes salt balance. Ovaries and testes release hormones involved in puberty and reproductive function. The pineal gland releases melatonin, contributing to sleep-wake timing. Match a gland to the complete functional clue, not to a nearby organ system or to a single familiar word.
Common wrong turns
| Tempting shortcut | How to reject it |
|---|---|
| Calling hormones electrical impulses or purely local signals | Hormones are chemical messages that can travel in body fluids. Nerve impulses use a different signalling route. |
| Assuming every reached cell must respond | Specific response requires a matching receptor; mere exposure does not give every cell the same reaction. |
| Matching glands to unrelated transport or digestive jobs | Thyroid hormones affect energy use, parathyroid hormone helps regulate calcium, and adrenal hormones support stress and other regulation; they do not filter lymph, carry oxygen, or make bile. |
| Pairing the pineal gland with haemoglobin, or assigning a sleep hormone to muscle or the bladder | Follow the source and the signal together: the pineal gland releases melatonin, which contributes to sleep-wake timing. |
Try it
Which statements correctly classify endocrine secretion? Select all that apply.
- It always uses a duct to a body surface
- It releases hormones without an outlet duct
- Its messages travel only along nerves
- Its hormones can enter tissue fluid and blood
Which statements correctly describe insulin and glucagon as endocrine signals? Select all that apply.
- They have opposing effects on blood glucose
- Both can only raise blood glucose
- The endocrine pancreas releases both
- The gallbladder releases glucagon
A regulated condition moves back toward its set range, and the hormonal response becomes smaller. What mechanism does this illustrate?
- Permanent amplification
- Absence of regulation
- Negative feedback
- Hormone digestion