Reflex theory

Essence and historical significance of the theory

The reflex theory is based on extending the reflex principle to all forms of the body's vital activity, from the simplest reactions to complex acts. Historically, the concept was shaped by the work of many scientists. In Western Europe, its origins lie with J. Procháska and M. Hall, while in Russia, I.M. Sechenov and I.P. Pavlov made fundamental contributions.

The significance of this theory for normal physiology is enormous:

• It provided physiological phenomena with a solid material structural foundation — the reflex arc.
• It provided convincing experimental evidence of exactly how reflex processes are organized.
• It established the principle of strict determinism: every reflex reaction is material in nature and arises exclusively within the framework of cause-and-effect relationships (an external stimulus acts on a receptor, which predictably leads to a response reaction).

Contribution of Russian physiologists

The development of the reflex theory is inextricably linked with the names of prominent Russian researchers.

I.M. Sechenov made a breakthrough in understanding the nervous system:

1. 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.
2. He pointed out the extreme variability of reflexes occurring in the brain, in contrast to more primitive reactions.
3. He made a major discovery — the phenomenon of central inhibition of reflex activity.

I.P. Pavlov continued and deepened these studies. He divided all brain reflexes into two large groups (conditioned and unconditioned) and described in detail the mechanisms of the nervous system.

A special place in Pavlov's work is held by the concept of temporary connection. The mechanism of its formation lies in the fact that, during repeated pairings between the arcs of conditioned and unconditioned reflexes, a functional connection is formed. 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 fades and disappears.

The principle of signaling and anticipatory reflection

The most important aspect of higher nervous activity is the principle of signaling. Its essence is that a conditioned stimulus, acting on the organism, carries information in advance about the properties of the future unconditioned (reinforcing) effect.

The main 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 colossal: it represents the activity of the organism directed toward a future, life-critical event. In physiology, this phenomenon is often called the anticipatory reflection of reality.

Classical postulates of the reflex theory

The logical completion of the development of ideas about reflexes was the formation of four basic postulates that fully describe reflex activity:

1. Determinism. The leading role in the formation of absolutely any reflex activity always belongs to external stimuli. Without an initial stimulus, the reflex does not occur.
2. Structurality. The excitation process is strictly tied to anatomical structures. It propagates along the reflex arc progressively — from the receptor apparatus to effector organs (transmission of the impulse from point to point).
3. Resultativeness. Any reflex act does not just stop; it necessarily ends with a specific action. This can be a muscle contraction, a secretory response of a gland, or a bioelectrical reaction.
4. Constancy versus variability.
5. Spinal reflexes are characterized by constancy. They operate stereotypically upon presentation of an adequate stimulus.
6. Brain reflexes are characterized by high variability, which allows the body to flexibly adapt to changing conditions.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Two groups of brain reflexes in I.P. Pavlov's classification
• The mechanism of central inhibition (discovered by I.M. Sechenov)
• Physiological bases of the anticipatory reflection of reality
• The role of reinforcement in the maintenance and extinction of a temporary connection

Other topics in the section "Correlation, regulation, reflexes, self-organization, self-regulation, functional systems"

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