Operating principles and stages of activity
Any analyzer is an exclusively afferent system. This means that the flow of information always has a strict direction: from the perceiving structures at the periphery to the processing centers in the CNS.
In the course of its work, the analyzer sequentially implements three key stages:
- 'Decomposition' of the external world into elements. The system breaks down the complex picture of the environment into separate basic signals (light, sound, pressure, etc.).
- Transformation of stimulation. At this stage, the physical or chemical impact is converted into a nerve impulse, which ultimately leads to the emergence of a primary sensation taking into account sensitivity thresholds.
- Formation of behavioral tactics. Based on the information received, the organism decides on further actions.
The phenomenon of psychological reflection
Incoming stimuli trigger specific reactions in the CNS that underlie the phenomenon of psychological reflection. According to the teachings of I.P. Pavlov, it is the cells of the cerebral cortex that undertake the most complex work — the highest analysis and synthesis of incoming information.
The process of reflecting reality occurs in stages and includes three levels:
- Sensation. This is the basic level at which only isolated, individual properties of a particular stimulus are reflected.
- Perception. A more complex process. Here, the CNS analyzes and synthesizes individual sensations, necessarily comparing them with previously accumulated experience.
- Representation. The highest level, allowing the formation of full-fledged images even when the stimulus is not directly affecting the sense organs at the moment.
Thus, the final function of the entire structure is a detailed analysis of external events followed by the synthesis of a unified mental image.
Role in the systemic organization of behavior
Within the framework of the systemic organization of physiological functions, analyzers cannot be viewed as static wires for transmitting current. On the contrary, they are dynamic, self-tuning, and self-regulating organizations.
Each afferent flow of excitation has an absolutely specific functional significance in the architecture of a behavioral act. The central nervous system uses these flows for complex processes such as afferent synthesis and the operation of the apparatus for anticipating the results of action.
Depending on their role in behavior, afferent flows are classified into three types:
- Situational afferentation — informs about current environmental conditions.
- Trigger afferentation — serves as a direct signal to initiate action.
- Feedback afferentation — reports the results of an action already performed, completing the self-regulation cycle.
Briefly: answers to topical questions
What three anatomical and physiological parts does the analyzer consist of according to I.P. Pavlov?
According to I.P. Pavlov, the analyzer consists of three anatomical, physiological, and functional parts.
- Peripheral part — includes receptors, an accessory apparatus, and the primary afferent neuron; performs signal detection and encoding.
- Conductor part — includes sensory nerves and specific afferent pathways (in the spinal cord and brainstem).
- Central part (cortical) — areas of the sensory cortex of the brain that receive excitation of a specific modality (primary and secondary areas).
What is the property of analyzer adaptation?
Receptor adaptation consists in the process of changing receptor sensitivity against the background of ongoing stimulus application. This process can occur at the pre-receptor, receptor, conductor, and cortical levels.
According to the rate of adaptation, the following are distinguished:
- Fast-adapting receptors — form a short response to a rapid stimulus.
- Slow-adapting receptors — respond with a train of impulses throughout the entire duration of the stimulus.
One form of adaptation is sensitization, which manifests as a decrease in thresholds and an increase in receptor excitability.
Where is the cortical end of the visual analyzer localized?
The cortical end of the visual analyzer is localized in the occipital lobe of the brain. The primary visual cortex is located along the banks of the calcarine sulcus (sulcus calcarinus), which corresponds to area 17.
Light stimuli, converted into nerve impulses, travel along the conductor and reach this cortical area via the optic radiation. The cortical end has a strictly crossed organization: the left hemisphere receives impulses from the right visual field, and the right hemisphere from the left.
To remember the levels of psychological reflection, use the abbreviation SPR: Sensation (details) → Perception (synthesis + experience) → Representation (image without stimulus).
Class and exam questions
What is the main function of the cerebral cortex in the work of the analyzer?
According to I.P. Pavlov, cortical cells are responsible for the highest analysis and synthesis of information coming from both the external and internal environment of the organism.
How does perception fundamentally differ from sensation?
Sensation reflects only individual properties of a stimulus. Perception, on the other hand, combines these sensations and necessarily compares them with the person's previous experience.
What types of afferent flows participate in a behavioral act?
Three main types are distinguished: situational, trigger, and feedback afferentation. They differ in their role in the mechanisms of anticipation and synthesis.
What else to study on this topic
- Mechanisms of transforming stimulation into a nerve impulse
- The concept of sensitivity thresholds in the work of sensory systems
- The role of feedback afferentation in evaluating the results of action
- The apparatus for anticipating the results of action (action result acceptor)
- Stages of afferent synthesis in systemic architectonics
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