Essence and Historical Significance of the Theory
The reflex theory is based on extending the reflex principle to all forms of vital activity, ranging from the simplest responses to complex behavioral acts. Historically, the concept was shaped by the work of many scientists. In Western Europe, its origins trace back to J. Procházka and M. Hall, while I.M. Sechenov and I.P. Pavlov made fundamental contributions.
The significance of this theory for normal physiology is profound:
- It provided physiological phenomena with a solid material structural basis — the reflex arc.
- It provided compelling experimental evidence regarding how reflex processes are organized.
- It established the principle of strict determinism: every reflex response is material in nature and occurs exclusively within cause-and-effect relationships (an external stimulus acts upon a receptor, predictably leading to a response).
Contributions of Renowned Physiologists
The development of the reflex theory is inextricably linked to the names of prominent researchers.
I.M. Sechenov made a breakthrough in understanding nervous system function:
- He was the first to apply the reflex principle to the functions of the higher parts of the brain, thereby explaining the physiological nature of mental functions.
- He highlighted the extreme variability of reflexes occurring in the brain, in contrast to more primitive responses.
- He made a vital discovery — the phenomenon of central inhibition of reflex activity.
I.P. Pavlov continued and deepened these studies. He divided all cerebral reflexes into two large groups (conditioned and unconditioned) and detailed the mechanisms of nervous system function.
A special place in Pavlov's work is held by the concept of the temporary connection (association). The mechanism of its formation is that repeated pairings between the arcs of conditioned and unconditioned reflexes forge a functional link. Reinforcement plays a key role in this process. If reinforcement is canceled or completely absent, the formed temporary connection breaks down, and the conditioned reflex itself undergoes extinction and disappears.
The Principle of Signaling and Anticipatory Reflection
A crucial aspect of higher nervous activity is the principle of signaling. Its essence is that a conditioned stimulus, acting upon the organism, carries advance information regarding the properties of a future unconditioned (reinforcing) stimulus.
The primary function of such a conditioned stimulus is to serve as a signal that an unconditioned reflex will soon follow. The physiological significance of this mechanism is enormous: it represents the activity of the organism directed toward a future, life-sustaining event. In physiology, this phenomenon is often referred to as the anticipatory reflection of reality.
Classical Postulates of the Reflex Theory
The logical culmination of the development of reflex ideas was the formulation of four basic postulates that fully describe reflex activity:
- Determinism. External stimuli always play the leading role in shaping absolutely any reflex activity. Without an initial stimulus, a reflex does not occur.
- Structure. The excitation process is strictly tied to anatomical structures. It propagates progressively along the reflex arc — from the receptor apparatus to the effector organs (transmission of impulses from point to point).
- Resultativeness. Any reflex act does not simply terminate arbitrarily; it necessarily culminates in a specific action. This can be muscle contraction, a secretory response of a gland, or a bioelectrical reaction.
- Constancy versus Variability.
- Spinal reflexes are characterized by constancy. They operate stereotypically upon presentation of an adequate stimulus.
- Cerebral reflexes are characterized by high variability, allowing the organism to adapt flexibly to changing conditions.