What is the Difference Between Stimulus and Response

The main difference between stimulus and response is that a stimulus is an event or condition which initiates a response whereas response is the organism’s reaction to a stimulus. Furthermore, the stimulus is a detectable change in the organism’s internal or external environment while a response is specific to a stimulus. Moreover, stimulus varies by its type, intensity, location, and duration while a response can be either cellular, physical or behavioral.

Stimulus and response are two aspects coordinated by the nervous system of the body. Both are responsible for gaining sensitivity to the body and helping to maintain homeostasis.

Key Areas Covered

1. What is a Stimulus
     – Definition, Sensory Organs, Role
2. What is a Response
     – Definition, Types, Role
3. What are the Similarities Between Stimulus and Response
     – Outline of Common Features
4. What is the Difference Between Stimulus and Response
     – Comparison of Key Differences

Key Terms

External Stimuli, Homeostasis, Internal Stimuli, Involuntary, Nervous System, Response, Voluntary

What is a Stimulus

A stimulus is an event, agent or condition capable of initiating a response. All living things tend to respond to various types of stimuli. Here, the stimulus should make an obvious change in the internal or external conditions of the organism. Also, different types of organisms have developed different types of sensory organs to capture stimuli. In humans, ears, eyes, nose, tongue, and skin are the main sensory organs which capture external stimuli such as hearing, vision, smell, taste, touch or heat, respectively. These sensory organs help the organism to respond to the changes in the environment.

Figure 1: Response to an External Stimuli

In addition, mechanoreceptors, chemoreceptors, thermoreceptors, and stretch receptors serve as sensory organs which capture internal stimuli. Thus, internal sensory organs help the body to mainly maintain the homeostasis.

What is a Response

A response is a behavior manifested by a living organism as a result of the recognition of either internal or external stimuli. A response can be either a physiological, cellular or behavioral based on the nature of the stimulus. Moreover, the central nervous system is responsible for coordinating stimuli and their corresponding responses. Its main components are the brain and spinal cord. Also, the brain coordinates voluntary responses while the spinal cord coordinates involuntary responses.

Figure 2: Involuntary Response

Generally, the sensory organs transmit nerve impulses to the central nervous system through afferent or sensory nerves. After processing the information, the brain transmits nerve impulses corresponding to the voluntary responses to the effector organs through the efferent or motor nerves. However, the stimuli transmitted to the spinal cord travel either through somatic or visceral reflexes to the effector organs since they generate involuntary responses.

Similarities Between Stimulus and Response

• Stimulus and response are two aspects of the nervous system of the animal body. Also, plants respond to stimulus through hormones.
• Both give sensitivity to an organism.
• Also, both help to maintain homeostasis or a constant internal environment in animals.

Difference Between Stimulus and Response

Definition

A stimulus refers to a detectable change in the internal or external environment while a response refers to any behavior of a living organism that results from an external or internal stimulus.

Correspondence

Hence, the main difference between stimulus and response is that a stimulus is an event or condition which initiates a response while a response is the organism’s reaction to the stimulus.

Types

A stimulus varies by its type, intensity, location, and duration while a response can be either cellular, physical or behavioral.

Types of Nerves Used

Afferent or sensory nerves transmit nerve impulses corresponding to the stimulus while efferent or motor nerves transmit nerve impulses corresponding to the response. Thus, this is another difference between stimulus and response.

The Direction of the Nerve Impulses

The direction of the nerve impulses is one other difference between stimulus and response. Nerve impulses corresponding to the stimulus transmit towards the central nervous system while the nerve impulses corresponding to the response transmits from the central nervous system.

Types of Organs

Moreover, the sensory organs including eyes, ears, nose, tongue, skin, and internal sensory system are responsible for detecting stimuli while effector organs including muscles in the internal organs and hands and legs are responsible for reacting to a stimulus.

Conclusion

Stimulus is the event or condition which initiates a response in the body. However, stimuli can be either internal or external. Sensory organs of the body of animals are responsible for capturing stimuli. Then, the nerve impulses are sent to the central nervous system, which then sents nerve impulses corresponding to the response. Generally, the response is the organism’s reaction to a specific stimulus. Both stimulus and response help to maintain a constant internal environment. Therefore, the main difference between stimulus and response is their role in the homeostasis.

References:

1. “Stimulus (Physiology).” Wikipedia, Wikimedia Foundation, 6 Dec. 2018, Available Here

Image Courtesy:

1. “1508 Autonomic Control of Pupil Size” By OpenStax College – Anatomy & Physiology, Connexions Web site. (CC BY 3.0) via Commons Wikimedia  
2. “Imgnotraçat arc reflex eng” By MartaAguayo – Own work (CC BY-SA 3.0) via Commons Wikimedia