The nervous system of living organisms, due to its properties, not only regulates the activity of the whole organism and reactions to internal or external changes, but also provides an opportunity for the development of the psyche. One of the key functions of nerve cells is irritability. What is it for?
Irritability (excitability) is the property of cells, tissues, organs and intracellular formations to respond to various changes in the factors of the internal and external environment (stimuli) by a shift in functions and structures. Perception of irritation is designated using the term reception (perception). This property ensures the adaptability of living organisms to changing environmental conditions. The irritability of primitive organisms (microbes, protozoa), as well as some cells (spermatozoa, leukocytes) is reflected in taxis - the ability to move in relation to the stimulus. In plants, excitability manifests itself in the form of motor reactions, as well as in reactions to gravity, the chemical composition of the environment, electrical or mechanical stimuli, light, and the Earth's magnetic field. Plants, as you know, do not have the sense organs inherent in animals and humans, but they have receptor proteins and cells with the help of which plants respond to stimuli. An example of irritability in plants is a sunflower that follows the sun with its head. In the normal state, the plant cell has a negative electrical potential ranging from -50 to -200 mV. In response to the stimulus, a positive reaction arises that can exceed the resting potential or equal it. If the external influence on the cells was super strong, this can lead to the death of the plant. People and animals are characterized by a variety of reactions to various kinds of stimuli, which is provided by reflexes, higher nervous activity and consciousness. The excitability of complex organisms is manifested primarily in the sensitive perception of events in the surrounding world with the help of the sense organs (receptors). Influences on receptors through nerve impulses transmit information to the appropriate parts of the brain. And then the brain gives "orders" to certain organs, effectively regulating vital processes. Thus, irritability is one of the indicators of the body's reactivity. Reactivity is a mechanism laid down by nature itself, aimed at preserving and developing not only each type of living organism, but also its specific individual.
