Human Anatomy, Part 2 - K. A. Dyubenko, A. K. Kolomiysev, Yu. B. Chaykovsky 2008

Special Part
Sense organs, organa sensuum

During the Evolution of the animal kingdom, specialized Organs capable of perceiving stimuli from the external and internal environments emerged and developed. These organs are directly connected to the Central Nervous System, where stimuli are analyzed and synthesized.

Studying the physiology of Sensory Organs, I. P. Pavlov established that they act as peripheral parts of sensory analyzers, thereby ensuring the perceptive awareness of the external world and internal environment. The Biological Significance of analyzers lies in their ability to maximize the detection of stimuli, thus facilitating the Organism's adaptation to changes in both external and internal environments.

Each analyzer (in recent years, the term sensory system is widely used) consists of three parts: peripheral (receptor), intermediate (conductive), and central (cortical). The peripheral part includes specialized receptor elements that convert Various Forms of energy (light, sound, thermal, etc.) into The process of neural excitation—an impulse-coded type of information transmission. The intermediate part ensures the transmission of impulses to the Cerebral Cortex, where the highest level of information analysis and synthesis takes place.

Depending on the origin, Structure, and function of the receptor part, Sense Organs (as well as Sensory systems) are divided into three main types. The first type includes the organs of Vision and Olfaction, in which specialized neurosensory Cells (primary sensory cells) act as receptors, directly generating nerve impulses in response to appropriate stimuli. The second type includes the Organs of taste, Hearing, and equilibrium, where specialized sensory-epithelial cells (secondary sensory cells) serve as receptors. From these cells, the transformed stimulus arising in response to relevant triggers is transmitted to the dendrites of sensory Neurons. The third type comprises the cutaneous (exteroceptive), musculoskeletal (proprioceptive), and visceral (interoceptive) sensory systems, in which the peripheral parts lack a distinct organ structure and are instead represented by nerve endings in the Skin, Muscles, Internal Organs, and Blood Vessels.