irritability

Irritability, in a physiological context, refers to the inherent property of living organisms and protoplasm to react to stimuli. This responsiveness allows cells to undergo changes, such as electrical, chemical, or mechanical alterations, which manifest as a response. For instance, gland cells might release secretions, muscle cells contract, or ciliated cells move their cilia.12

In simpler organisms like amoebas, this general responsiveness of the cytoplasm functions similarly to a nervous system, enabling reactions to stimuli like light or chemicals. In more complex multicellular organisms, irritability is a foundational property that, alongside specialized systems like the nervous and endocrine systems, allows for coordinated responses to environmental changes.2