Which of the following is the correct order of events of a reflex arc?


a. Stimulus detection and delivery → motor response → integration in the CNS
b. Motor response → stimulus detection and delivery → integration in the CNS
c. Stimulus detection and delivery → integration in the CNS → delivery of motor response
d. Integration in the CNS → motor response → stimulus detection and delivery

Verified step by step guidance

1. Understand the components of a reflex arc: A reflex arc is the neural pathway that controls a reflex. It typically involves five main components: (1) a sensory receptor, (2) a sensory neuron, (3) integration in the central nervous system (CNS), (4) a motor neuron, and (5) an effector (muscle or gland).
2. Identify the sequence of events: The reflex arc begins with the detection of a stimulus by sensory receptors. This information is then transmitted via sensory neurons to the CNS for processing and integration.
3. Recognize the role of the CNS: In the CNS (spinal cord or brain), the sensory input is processed, and an appropriate motor response is determined. This step is crucial for coordinating the reflex action.
4. Understand the motor response: After integration, the CNS sends signals through motor neurons to the effector organs (muscles or glands) to produce a response, such as muscle contraction or gland secretion.
5. Compare the options: Based on the above understanding, the correct sequence is 'stimulus detection and delivery → integration in the CNS → delivery of motor response,' which matches option c.

Key Concepts

Reflex Arc

A reflex arc is a neural pathway that controls a reflex action. It typically involves a sensory neuron that detects a stimulus, an integration center in the central nervous system (CNS) that processes the information, and a motor neuron that triggers a response. This pathway allows for quick reactions to stimuli without the need for conscious thought.

Sensory Input

Sensory input refers to the information received by sensory receptors in response to external stimuli. In the context of a reflex arc, this is the initial step where a stimulus, such as heat or pain, is detected and converted into an electrical signal that travels along sensory neurons to the CNS for processing.

Motor Response

A motor response is the action taken by the body in reaction to a stimulus, initiated by the CNS after processing the sensory input. In a reflex arc, this response is typically executed by motor neurons that activate muscles or glands, resulting in a quick and involuntary action, such as pulling away from a hot surface.