Who is the creator of the theory of functional systems and the concept of the action acceptor?

The theory of functional systems was developed and described by Academician Pyotr Anokhin. Functional systems are defined as morphofunctional organizations that ensure self-regulation in the organism. The architecture of a behavioral act utilizes the concept of the action acceptor: an apparatus for anticipating, predicting, and evaluating future results. The formation of the action acceptor is based on mechanisms of afferent synthesis and decision-making, reflecting goal-setting and higher motivation.

Which types of receptors belong to proprioceptors forming guidance afferentation?

Proprioceptors providing guidance reverse afferentation include receptors of the musculoskeletal system. These specialized encapsulated structures include muscle spindles (responding to muscle stretch) and neurotendinous spindles (responding to muscle contraction). The Golgi tendon organ is also involved in reflex arcs, responding to muscle tension. Guidance reverse afferentation regulates movement execution: the correct distribution of muscle contractions and limb position at any given moment.

What is the difference between reverse afferentation and the fourth link of the reflex arc?

The reflex arc with its fourth link (afferent feedback from muscles) is merely a partial, executive component. Reverse afferentation within a functional system evaluates the result of holistic behavior rather than just the status of an individual muscle.

Which parameters in the action acceptor are rigidly programmed?

Only the parameters of the required result (the final goal) are rigidly programmed. The methods for achieving it and environmental conditions are programmed probabilistically, providing behavioral flexibility.

What are the functions of guidance and resultant afferentation in movement?

Guidance afferentation originates from proprioceptors and continuously monitors the correctness of muscle contractions during the action. Resultant afferentation originates from sense organs and informs the organism whether the final goal has been achieved.

Home › Physiology › Reverse Afferentation

Reverse Afferentation

For medical students2 min readUpdated 2026-10-10

Reverse afferentation is the continuous stream of sensory information sent to the central nervous system to evaluate the achieved results of a behavioral act. It allows the organism to compare the actual outcome of an action with the expected result and correct errors when necessary.

Main objectiveEvaluation of the achieved adaptive result

PropertyMulti-parametric (reflects physical, chemical, and informational properties)

Obligatory componentProprioceptive impulses (from contracting muscles)

PathologyDisruption of receptors impairs the behavioral act

Multi-parametric Nature and Species Specificity

Signals returning to the brain from receptors are never homogeneous. They are always multi-parametric, as they gather data from various sensory systems: vision, hearing, olfaction, touch, taste, and thermoreception.

These parameters reflect the physical, chemical, and informational properties of the obtained result. In humans, informational properties play a key role, and the evaluation of many actions relies on a speech-based (written or oral) foundation.

Additionally, the significance of specific parameters depends on the biological species. For example, birds rely predominantly on vision, whereas olfaction and tactile sensations are critically important for the mole. Regardless of the species, information from proprioceptors—receptors of the musculoskeletal system—always enters the brain.

Role in the Systemic Organization of Behavior

It is important not to confuse the reverse afferentation of a functional system with the "fourth link" of the classical reflex. A reflex is merely a partial component of holistic behavior. Reverse afferentation operates more broadly and plays a creative role in organizing actions.

Its main functions include:

Guiding the subject's behavior and spatial orientation.
Actively influencing the dominant functional system.
Correcting errors during activity.
Restructuring plans when encountering obstacles.
Triggering emotions (positive upon success or negative upon failure).

Connection with the Action Acceptor

The experience of successfully achieving a goal is recorded in the CNS. When an animal or human obtains an adaptive result, its parameters are "imprinted" in the structures of the action acceptor.

Subsequently, when the need arises again, motivation triggers feedforward excitation within the action acceptor. The brain "recalls" the parameters of past successes and directs the organism to satisfy the need.

Various elements are programmed within the action acceptor, but with varying degrees of strictness:

Strictly (rigidly) programmed are only the parameters of the required result (the goal).
Probabilistically programmed are environmental parameters (both facilitating and hindering) and specific methods for achieving the goal.

Control of Motor Acts

Any movement (from walking to speech) is impossible without sensory control via centripetal impulses. There are three levels of such control:

Exteroceptive — signals from sense organs.
Proprioceptive — data from muscles, ligaments, and joints.
Intracerebral reafferentation — internal feedback loops within the CNS from lower centers to higher ones.

During the execution of phased movements, reverse afferentation is divided into guidance (from proprioceptors, regulating the muscle contraction process in real time) and resultant (from sense organs, reporting on the final outcome).

Motor control includes long-loop feedback (informing the cortex about movement execution via long-loop feedback), spinal reflex arcs (automatic load compensation at the segmental level of the spinal cord), and sensory correction (Nikolai Bernstein's principle, where multisensory integration enables complex voluntary actions).

Frequently asked questions

Who is the creator of the theory of functional systems and the concept of the action acceptor?: The theory of functional systems was developed and described by Academician Pyotr Anokhin. Functional systems are defined as morphofunctional organizations that ensure self-regulation in the organism. The architecture of a behavioral act utilizes the concept of the action acceptor: an apparatus for anticipating, predicting, and evaluating future results. The formation of the action acceptor is based on mechanisms of afferent synthesis and decision-making, reflecting goal-setting and higher motivation.
Which types of receptors belong to proprioceptors forming guidance afferentation?: Proprioceptors providing guidance reverse afferentation include receptors of the musculoskeletal system. These specialized encapsulated structures include muscle spindles (responding to muscle stretch) and neurotendinous spindles (responding to muscle contraction). The Golgi tendon organ is also involved in reflex arcs, responding to muscle tension. Guidance reverse afferentation regulates movement execution: the correct distribution of muscle contractions and limb position at any given moment.
What is the difference between reverse afferentation and the fourth link of the reflex arc?: The reflex arc with its fourth link (afferent feedback from muscles) is merely a partial, executive component. Reverse afferentation within a functional system evaluates the result of holistic behavior rather than just the status of an individual muscle.
Which parameters in the action acceptor are rigidly programmed?: Only the parameters of the required result (the final goal) are rigidly programmed. The methods for achieving it and environmental conditions are programmed probabilistically, providing behavioral flexibility.
What are the functions of guidance and resultant afferentation in movement?: Guidance afferentation originates from proprioceptors and continuously monitors the correctness of muscle contractions during the action. Resultant afferentation originates from sense organs and informs the organism whether the final goal has been achieved.

Go deeper

Mechanism of alpha-gamma coactivation at the spinal level
Sensory correction of complex voluntary movements according to Nikolai Bernstein
Multisensory integration (vision, proprioception, touch) in fine motor skills
The role of long-loop feedback in cortical control