Everything comes to us by means of our sense organs. These sense organs may be thought of as receiving station for stimuli which comes from outside or from inside our body. Like Human beings have five sensory organs i.e. eyes for seeing, ears for hearing, tongue for taste, nose to smell and touching. 


The process through which the senses pick up visual, auditory, and other sensory stimuli and transmit them to the brain; sensory information that has registered in the brain but has not been interpreted is called sensation. In this process, an organism’s sense organs respond to a stimulus (A source of physical energy that produces a response in a sense organ).
If sensation is to occur, a stimulus must activate the receptor cells, from which nerve impulses travel through the nervous system to the sensory areas of the brain. The only stimuli that are above the threshold can activate the receptors. The organizational process and characteristics of sensation may be divided into four stages:

  • Stimulus

  • Receptors

  • Transduction and codes

  • Sensory Adaption


A stimulus is the source of energy that produces a response in a sense organ. Stimuli may vary in both type and intensity. Different types of stimuli activate different sense organs.
Psychophysics is the study of relationship between physical nature of stimuli and person’s sensory responses to them.
The smallest intensity of a stimulus by which it can be detected is called Absolute Threshold. It is the minimum amount of physical energy required to produce a sensation.


All sense organs in the body have receptors that are located more deeply within the body. Receptors in each of the sense organs are specialized structures that are sensitive to a particular type of physical energy, such as light waves, sound waves, pressure, temperature or chemical reaction.


When a receptor is stimulated, the function of transduction starts. Transduction is the process of changing the stimulus energy from the environment into neural impulses/codes. The receptor is a biological transducer. Once the receptors are stimulated, they transform the energy into electrical neural impulses.

Sensory Adaption

Sensory adaption is the tendency of the sense organs to adjust to continuous, unchanging stimulation by reducing their functionality. In other words, a stimulus that once caused a sensation may become less effective.

In the light of above discussion we can define sensation as a process in which stimuli are received by sense receptors and transformed into neural impulses by the process of transduction that can be carried through the nervous system.

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