Environmental Interaction and Physiological Isolation
The habitat represents a strictly organized space-time continuum. On Earth, it is defined by gravity, the atmosphere, temperatures, and the electromagnetic field. External phenomena are divided into episodic events (e.g., earthquakes) and periodically repeating events (alternation of day and night, seasons). Regular rhythmic influences play a key role in shaping biological properties across generations.
Despite their close connection with the environment, living organisms are isolated from non-living nature. This boundary is maintained by phospholipid membranes. Their structure is universal: the membranes of a human nerve cell and a sea urchin egg are structured almost identically. The emergence of such structures allowed living forms to separate from the primordial aqueous environment, complicate their internal organization, and begin actively influencing the surrounding world.
Stimuli and Types of Irritability
Any environmental factors acting on cell membranes are called stimuli. They can be physical (temperature, mechanical), chemical (hormones, acids), physico-chemical (pH changes, osmotic shifts), biological (viruses), and informational (speech, emotions).
The ability to respond to these factors by altering membrane and protoplasm structure is called irritability. There are two main types:
- Nonspecific (trigger) irritability. Independent of the stimulus type. The stimulus acts as a trigger that initiates internal membrane processes, bringing molecules to a threshold state.
- Specific (selective) irritability. Manifests in response to biologically active substances (ligands). Protein receptors on the cell membrane interact with stimuli via a lock-and-key mechanism, triggering a cascade of intracellular reactions. This selectivity is also regulated by the size of ion channels.
Memory and Anticipatory Reflection of Reality
The fixation of molecular changes resulting from stimuli is ensured by the universal genetic apparatus—the basis of biological memory. It is most vividly formed during repetitive exposures or single, strong emotional stimuli.
Based on memory, Academician P.K. Anokhin formulated the concept of anticipatory reflection of reality. This is the fundamental ability of an organism to foresee the course of external events and react to them faster than they actually occur.
The process is formed in three stages:
- Stage A (Primary Reaction): External events follow one another, eliciting isolated internal reactions. There is no connection between the reactions yet.
- Stage B (Chemical Continuum): With repeated external events, molecular changes in the organism are linked into a single sequential chain.
- Stage C (Realization): Now, the action of only the first triggering stimulus is sufficient. In response, the organism instantly launches the entire chain of internal chemical reactions, preparing for subsequent impacts before they actually happen.