Sense Organs
Sense Organs
Animals require a constant inflow of information from the environment to regulate their lives. Sense organs are specialized receptors designed for detecting environmental status and change. An animal’s sense organs are its first level of environmental perception; they are channels for bringing information to the brain.
A stimulus is some form of energy —electrical, mechanical, chemical, or radiant. A sense organ transforms energy from a stimulus into nerve impulses, the common language of the nervous system. In a very real sense, then, sense organs are biological transducers. A microphone, for example, is a transducer that converts mechanical (sound) energy into electrical energy. Like the microphone, which is sensitive only to sound, sense organs are, as a rule, specific for one kind of stimulus. Thus eyes respond only to light, ears to sound, pressure receptors to pressure, and chemoreceptors to chemical molecules. But again, all forms of energy are converted into nerve impulses.
Since all nerve impulses are qualitatively alike, how do animals perceive and distinguish different sensations of varying stimuli? The answer is that real perception of sensation is done in localized regions of the brain, where each sensory organ has its own hookup. This concept of “labeled lines” of communication to specific brain regions was first described by Johannes Müller in the 1830s, who called this the law of specific nerve energies. Impulses arriving at a particular sensory area of the brain can be interpreted in only one way. For example, pressure on the eye causes us to see “stars” or other visual patterns; mechanical distortion of the eye initiates impulses in the optic nerve fibers that are perceived as light sensations. Although such an operation probably could never be done, a deliberate surgical switching of optic and auditory nerves would cause the recipient literally to see thunder and hear lightning!
Animals require a constant inflow of information from the environment to regulate their lives. Sense organs are specialized receptors designed for detecting environmental status and change. An animal’s sense organs are its first level of environmental perception; they are channels for bringing information to the brain.
A stimulus is some form of energy —electrical, mechanical, chemical, or radiant. A sense organ transforms energy from a stimulus into nerve impulses, the common language of the nervous system. In a very real sense, then, sense organs are biological transducers. A microphone, for example, is a transducer that converts mechanical (sound) energy into electrical energy. Like the microphone, which is sensitive only to sound, sense organs are, as a rule, specific for one kind of stimulus. Thus eyes respond only to light, ears to sound, pressure receptors to pressure, and chemoreceptors to chemical molecules. But again, all forms of energy are converted into nerve impulses.
Since all nerve impulses are qualitatively alike, how do animals perceive and distinguish different sensations of varying stimuli? The answer is that real perception of sensation is done in localized regions of the brain, where each sensory organ has its own hookup. This concept of “labeled lines” of communication to specific brain regions was first described by Johannes Müller in the 1830s, who called this the law of specific nerve energies. Impulses arriving at a particular sensory area of the brain can be interpreted in only one way. For example, pressure on the eye causes us to see “stars” or other visual patterns; mechanical distortion of the eye initiates impulses in the optic nerve fibers that are perceived as light sensations. Although such an operation probably could never be done, a deliberate surgical switching of optic and auditory nerves would cause the recipient literally to see thunder and hear lightning!
Support our developers
