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.
Sensation
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
Stimulus
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.
Receptors
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.
Transduction
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.