Hormones and Negative Feedback

Hormones

Definition and Function

Hormones are chemical messengers produced by glands in the endocrine system.
They are secreted directly into the bloodstream and travel to specific target cells or tissues to elicit a response.
Hormones play a vital role in many physiological processes, including growth and development, metabolism, and reproduction.
Examples of hormones include insulin, adrenaline, and progesterone.

Categories of Hormones

Hormones can be categorised into three types based on their chemical structure: steroid hormones, peptide hormones, and amino acid derivatives.
Steroid hormones (like cortisol and sex hormones) are lipid-soluble and can cross the cell membrane to act on receptors inside the cell.
Peptide hormones (like insulin and glucagon) are water-soluble and act on receptors on the cell surface.
Amino acid derivative hormones (like adrenaline and thyroxine) can be either water-soluble or lipid-soluble.

Negative Feedback

Definition and Mechanism

Negative feedback is a control mechanism employed by the body to maintain homeostasis or stable internal conditions.
This mechanism works by counteracting any deviation from the normal state. When the level of a particular hormone increases or decreases beyond the set point, negative feedback triggers responses to restore the balance.

Examples of Negative Feedback

The regulation of blood glucose levels is an example of negative feedback. When blood glucose levels rise (after a meal, for instance), the pancreas secretes insulin which promotes glucose uptake by cells, thus reducing the blood glucose levels.
Conversely, if blood glucose levels fall (e.g., during fasting), glucagon encourages the conversion of glycogen to glucose in the liver, thereby raising blood glucose levels.
Another example is the regulation of body temperature. If the body temperature rises, sweat glands are stimulated to produce sweat, which evaporates and cools the body.

In conclusion, hormones and negative feedback are both crucial elements in maintaining the body’s internal stability. Both allow the body to respond to changes and adapt accordingly.