Every living organism reacts and responds to its surroundings. External conditions affect and impact them, which consequently leads 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 behaviour of the living organism is called stimulus, and the change it causes in the organism is called Response.
Stimulus vs Response
The main difference between stimulus and response is that the 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 leaves of the plant, they tend to close themselves. The touch is called the stimulus, and the plants closed its leaf as a response to the human touch.
Stimulus is something that triggers, causes, or initiates action. It is a detectable influence or change in the environment, may it be physical or chemical modification either inside the organism’s body or in its surrounding. The organisms possess the ability to identify the change and responding to the trigger factor. Its ability is known as sensitivity.
The Response is a change or reaction produced by the organism in accordance with the stimulus. When the stimulus happens, the organism’s receptors sense the change and sends 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 the given stimuli.
Comparison Table Between Stimulus and Response
| Parameters of Comparison | Stimulus | Response |
| Definition | It is an obvious and detectable change or modification inside the body of the living organism or in its external environment and surroundings. | It is the act of the living organism that is in accordance with the stimulus. |
| Factors and Types | It is influenced by factors like location, time, and the intensity level of stimulus. | It is either 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 response is carried by the efferent or effector nerves. |
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 direction of growth which is named tropism. In animals and humans, the central nervous system is responsible for acting upon the stimulus, but in plants, the interaction of 2 or more two 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 major change that plants bring about to themselves as a response to the stimulus is losing or gaining water that 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. Senses of humans and animals detect the stimulus.
What is Response?
Whenever the organism is affected by a change in a trigger called stimulus a result electric signals or impulse signals are transferred to the receptors of the organism, and it reaches the brain. The central nervous system analyses the stimulus and causes the organism to act accordingly by sending the decision signals to the effectors that are 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 that is obvious and detectable. An interesting fact is that all these steps take place almost in an instant and the Response to a stimulus happens immediately.
There is a common misconception that plants are stationary and they do not move. It is completely wrong, plants also have movement, and along with humans and animals, they also respond to stimulus instantly.
A few examples of Response 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 some common 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 an external factor as well as 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.
Conclusion
Touch me not is also called the shame plant, and biologically it is Mimosa pudica. This introverted plant is a good example of stimulus and Response. The Response is highly dependent on the stimulus.
Surprisingly stimulus-response action is also found in unicellular organisms. In unicellular organisms, it occurs due to what is called irritability, but in multicellular organisms, it is due to sensitivity.
In multicellular, organisms it occurs as a combined result of both chemical and nervous regulations. In plants, the process is done by hormones, whereas in animals, it is done by the brain. This process commonly occurs in every type of living organism.
References
- https://www.lifescied.org/doi/abs/10.1187/cbe.02-12-0062
- https://books.google.com/books?hl=en&lr=&id=nnDpCAAAQBAJ&oi=fnd&pg=PA1&dq=stimulus+and+response+in+biology&ots=IbVowSyVbw&sig=vxnMiGicDlGT9C7o8x0NlqcrQ_c