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Question

Difficulty: MediumNervous Coordination and Sense Organs

A student involuntarily blinks when a sudden gust of wind blows dust toward their eye. Which of the following represents the correct sequence of neural structures involved in conducting the nerve impulse during this reflex action?

  1. Receptor → Sensory neuron → Relay neuron → Motor neuron → EffectorAnswer
  2. B
    Receptor → Motor neuron → Relay neuron → Sensory neuron → Effector
  3. C
    Receptor → Relay neuron → Sensory neuron → Motor neuron → Effector
  4. D
    Effector → Motor neuron → Relay neuron → Sensory neuron → Receptor

Answer

The correct sequence of neural structures in a reflex arc is Receptor → Sensory neuron → Relay neuron → Motor neuron → Effector.
The correct sequence begins at the sensory receptor where the stimulus is detected, travels along the sensory neuron to the central nervous system (relay neuron), and then exits via the motor neuron to trigger contraction in the effector muscle.

Step-by-Step Solution

1
Identify the point of stimulus detection
The stimulus (dust/wind) triggers the sensory receptor in the eye.
Reflex actions always originate at a sensory receptor that converts a physical stimulus into an electrical nerve impulse.
2
Trace the afferent pathway into the central nervous system
The impulse travels via the sensory (afferent) neuron into the central nervous system where it synapses with a relay (interneuron) neuron.
Sensory neurons conduct impulses toward the central nervous system.
3
Trace the efferent pathway to the response organ
The relay neuron passes the impulse to a motor (efferent) neuron, which conducts it to the effector muscle (eyelid muscle) causing it to contract.
Motor neurons carry commands from the central nervous system out to muscles or glands to execute the reflex response.

Key Concept

Reflex Arc Neural Pathway Sequence
Estimated Time:50s
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Topics

Nervous Coordination and Sense Organs

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