Every living organism reacts and responds to its surroundings. External conditions affect and impact them, leading to their reaction and Response. Based on the various external factors, they may show a variety of responses.
These factors that tend to disturb or change the living organism’s behaviour are called stimulus, and the change it causes in the organism is called Response.
Stimulus vs Response
Stimulus is the cause, whereas the Response is the effect caused. For example, let’s consider a touch me, not a plant. When we touch the plant leaves, they tend to close themselves. The communication is called the stimulus, and the plants close its leaf in response to the human touch.
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A stimulus is something that triggers, causes or initiates action. It is a detectable influence or change in the environment, whether physical or chemical modification inside the organism’s body or in its surroundings.
The organisms can identify the change and respond to the trigger factor. Its ability is known as sensitivity.
The Response is a change or reaction the organism produces by the stimulus. When the stimulus happens, the organism’s receptors sense the change and send a signal to its brain in the form of impulses.
The impulse signals reach the central nervous system, which decides and signals the organism to respond to stimuli.
|Parameters of Comparison||Stimulus||Response|
|Definition||It is an evident and detectable change or modification in the living organism’s body or its external environment and surroundings.||It is the act of the living organism by the stimulus.|
|Factors and Types||Factors like location, time, and the intensity level of stimulus influence it.||It is either a physical or a behavioural change or sometimes even a cellular response.|
|Transmission||The impulse signals are transmitted to the central nervous system.||The impulse signals are transmitted from the central nervous system.|
|Organs||In animals, the organs that detect and analyze the stimulus are the eyes, ears, skin, tongue, mouth, and nose.||The organs responsible for response are muscles, cells, and limbs.|
|Nerves||In animals, the stimulus is carried by the receptor of afferent nerves.||The efferent or effector’s nerves carry the response.|
What is Stimulus?
Stimulus is the cause or the change that affects the organism and leads to a response. Every living organism is affected by stimulus. Once it recognizes the stimulus, it reacts and responds.
The stimulus is analyzed by set o organs that work hand in hand to help the organism respond.
The organs work systematically to analyze the stimulus and decide on the Response. In plants, the stimulus is received and acted upon by growth. Based on the stimulus, the plants change their development direction, which is named tropism.
The central nervous system is responsible for acting upon the stimulus in animals and humans. Still, in plants, the interaction of 2 or more hormones is responsible for initiating the Response.
Compared with humans and animals, plants take longer to respond to the stimulus they have been subjected to.
The significant change that plants bring about to themselves as a response to the stimulus is losing or gaining water, which leads to a change in shape and structure due to either shrinking or swelling of the plant parts.
Good examples of stimulus are the light falling on plants and the effect of gravity. The senses of humans and animals detect the stimulus.
What is Response?
Whenever the organism is affected by a change in a trigger called stimulus, electric signals or impulse signals are transferred to the receptors of the organism and reach the brain.
The central nervous system analyses the stimulus and causes the organism to act accordingly by sending the decision signals to the effectors responsible for responding or reacting to the stimulus.
The organism’s Response is either conscious or unconscious. Effectors are the part that is responsible for responding to the given stimulus. Based on the given stimulus, the organism changes something evident and detectable.
An interesting fact is that all these steps take place almost in an instant, and the Response to a stimulus happens immediately.
The common misconception is that plants are stationary and do not move. It is entirely wrong, plants also have movement, and along with humans and animals, they also respond to stimulus instantly.
A few examples of Responses in plants are geotropism, phototropism, and hydrotropism. These are the responses of plants to gravity, light, and water, respectively.
In humans, blinking when a dust particle falls on our eyes or yawning are typical examples of Response to a stimulus.
Main Differences Between Stimulus and Response
- Stimulus is the cause, and Response is the effect.
- Stimulus is caused by external and internal factors, whereas Response happens only internally in an organism.
- The sensory system plays a role in detecting the stimulus, and the nervous system is involved in responding to a stimulus.
- Example – Cold and adverse weather conditions are an example of stimulus. When the animal moves somewhere warm or to a shelter, it is the Response.
- Stimulus is carried to the CNS, whereas the Response is carried from the CNS.
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Piyush Yadav has spent the past 25 years working as a physicist in the local community. He is a physicist passionate about making science more accessible to our readers. He holds a BSc in Natural Sciences and Post Graduate Diploma in Environmental Science. You can read more about him on his bio page.