Detecting Stimulus

Detecting & responding to stimulus results in communication.

Dot points covered on this page

1.1 identify the role of receptors in detecting stimuli

1.1.1 Identify data sources, gather and process information from secondary sources to identify the range of senses involved in communication.

1.2 explain that the response to a stimulus involves:

  • stimulus

  • receptor

  • messenger

  • effector

  • response


What is a stimulus? How do we detect them?

A stimulus is a detectable change in the internal or external environment.


The roles of receptors are to detect stimuli within the surrounding environment. Once a stimulus has been detected by the organism it can respond.


For example if the thermoreceptors on your skin detect cold air you will begin to shiver to maintain your body heat.
Receptors are also classified on the basis of their function, they are as follows:

  • Chemoreceptors: detect chemicals.
  • Electromagnetic receptors: change in electromagnetic field, E.G. light receptors in eye.
  • Mechanoreceptors: detect mechanical features such as pressure, touch, stretch.
  • Pain receptors: detect pain.
  • Thermoreceptors: detect change in temperature.

The stimulus - response pathway

In order to respond to a stimulus a certain pathway in the body must be followed.


For example if you were suddenly exposed to bright light (stimulus) the photo - receptors
in the eye (receptor) send a message to the central nervous system (CNS - messenger) which then in turn sends a message to the muscles in the eye (effector)
for the muscles to contract which then elicits the response of blinking (response). This process applies to all stimulus/response actions.

What senses and sensory organs are involved in detecting stimuli?

There are five main senses which are involved in communication, which are seeing, hearing, touch, taste and smell.

  • Seeing (OCCULAR): or sight involves the use of an eye. An eye contains many structures which allow certain amounts of light as well as different electromagnetic waves to pass in and out of the eye. The organism reacts to these changes by relaying a message via the optic nerve to the brain to either allow more or less light/electromagnetic waves into the eye.
  • Hearing (AUDITORY): involves the use of ears. The ear contains many structures which allow certain frequencies of noise to enter the ear to be deciphered by the brain.
  • Touch (SOMATOSENSORY SYSTEM): involves the use of mechanoreceptors, pain receptors and thermoreceptors. These receptors are usually found on the skin of the organism and enable the organism to enjoy certain stimulus and to avoid certain stimulus.
  • Taste (GUSTATION): refers to the ability of being able to taste foods and chemicals entering the mouth. Taste involves the use of chemoreceptors which detect chemicals within the food. There is said to be aspects of taste; sweet, sour, salty, bitter, and umami.
  • Smell (OLFACTION): smell is the ability of an organism to perceive odours or smells. Chemoreceptors are found in the nose which has the ability of detecting these smells.