Which component of a reflex arc connects the sensory neuron to the motor neuron within the spinal cord?
Correct answer: D. Associative neuron
- A. Receptor
- B. Effector
- C. Muscle fiber
- D. Associative neuron
Explanation
The associative or relay neurone sits in the grey matter of the spinal cord and passes the impulse straight from the sensory to the motor neurone, which is what allows the response to happen before the brain is even informed. The receptor detects the stimulus at the start of the arc and the effector, usually a muscle or gland, produces the response at the end. A muscle fibre is part of the effector rather than a link in the pathway.
This question appeared on the UHS MDCAT 2025 paper, which you can sit online with every answer explained.
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About Reflexes and the Reflex Arc
A reflex arc shows how a rapid, automatic response travels from a receptor through a sensory neuron, relay neuron and motor neuron to an effector. The topic covers synapses, the spinal cord's role, and the difference between an involuntary reflex action and a slower voluntary response.
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