The key difference between reaction and reflex depends on the type of response. A reaction is a voluntary response while a reflex is an involuntary response.
The human nervous system comprises of two major divisions; central nervous system (CNS) and peripheral nervous system (PNS). CNS comprises two components; namely, the spinal cord and the brain. PNS comprises of everything else other than the CNS. Both CNS and PNS involve in maintaining body homeostasis by responding to many stimuli generated from the environment through reflexes and reactions. Sensory organs and sensory neurons sense the signals generated from stimuli. Then, the motor neurons and effector organs generate actions accordingly. Therefore, the total nervous system functions with reactions and reflexes generated in response to stimuli.
CONTENTS
1. Overview and Key Difference
2. What is a Reaction
3. What is a Reflex
4. Similarities Between Reaction and Reflex
5. Side by Side Comparison – Reaction vs Reflex in Tabular Form
6. Summary
What is a Reaction?
In the context of physiology, a stimulus is a detectable change that occurs in the internal or external environments. The reaction or response is the ability of an organism to identify the stimulus and react accordingly. Hence, for a reaction to occur, the stimulus moves along the CNS through sensory organ, sensory neuron, brain, effector neuron and organ.
A reaction is a voluntary process that requires a conscious thought in responding to a stimulus. In comparison to a reflex, a reaction is a much slower process since the information received by the stimulus travels up to the brain and then to the effector organs to carry out the response. In other words, during a normal reaction, the sensory nerves carry the information from the sensory organs to the brain which perceives and organizes a signal and transfers to the motor neuron to carry the information to effector organs. Then the effector organ acts according to the information given by the motor neuron.
Figure 01: Reaction
For example, the voluntary reactions are carried out when an organism feel cold; the sensory nerves will sense it and send the information to the brain. The brain will inform relevant effector organs such as skeletal muscles to contract and generate heat accordingly.
What is a Reflex?
A reflex is an instantaneous movement that occurs involuntarily in response to a stimulus. This process also terms as reflex action that is facilitated by reflex arcs; the neural pathways present in living organisms. Thus, these reflex arcs have the ability to act on an impulse instantaneously without sending stimulus information to the brain. Accordingly, it is an automatic response that does not require any conscious thought in responding to the stimulus. For example, the immediate withdrawal of the foot in stepping on a nail is due to a reflex not due to a reaction. Consequently, reflex minimizes the physical harm since it is more instantaneous and faster than a reaction.
Figure 02: Reflex
The reflex arc consists of five different components. This includes, the receptor (present at the sensory organ), the sensory neuron (conducts the nerve impulses along an efferent pathway), integration centre (which consist of one or more synapses present in the CNS), motor neuron (conducts the nerve impulse along the efferent pathway from the CNS / integration centre to the effector) and effector organ (which responds to efferent nerve impulses). The minimum requirement of a reflex to take place is two neurons; a sensory and motor neuron.
What are the Similarities Between Reaction and Reflex?
- Both reaction and reflex involved in responding to a stimulus.
- In both types, the presence of a sensory and a motor neuron is compulsory.
- Also, both of them involve the nervous system .
- Besides, both in the maintenance of the body homeostasis.
What is the Difference Between Reaction and Reflex?
Reaction and reflex are two pathways that our nervous system executes in response to stimuli. The reaction is comparatively a slow action that goes via the brain. But, the reflex is a fast action that does not involve the brain. Thus, this is a key difference between reaction and reflex. Furthermore, compared to a reaction, the reflex is an instantaneous action which minimizes the harm.
Moreover, the reaction is a voluntary response while reflex is an involuntary response. Hence, this is another difference between reaction and reflex. The below infographic shows more details on the difference between reaction and reflex.
Summary – Reaction vs Reflex
Reaction and reflex are two ways of responding to a detectable stimulus generated both externally and internally. Reflex is a much instantaneous process that takes place involuntarily. Comparatively, the reaction is a much slow voluntary process. During a reaction, information from the stimulus reaches the brain, but during a reflex, it does not. Thus, this is the key difference between reaction and reflex. However, both processes are important in maintaining the body homeostasis.
Reference:
1.Phillips, Harry. “How Does the Body Respond to Touching Something Hot?” Health24, 24 Nov. 2014. Available here
2.“Stimulus-Response Theory.” Encyclopædia Britannica, Encyclopædia Britannica, Inc. Available here
Image Courtesy:
1.”Nervous system organization en”By JDifoolderivative work: Looie496 (talk) (CC BY-SA 3.0) via Commons Wikimedia
2.”Anatomy and physiology of animals A reflex arc”By By Ruth Lawson Otago Polytechnic (CC BY 3.0) via Commons Wikimedia