Question

The correct sequence of events when someone’s hand touches a hot object (reflex action):

• A. Sensory neuron → Motor neuron → Relay neuron → Effector muscle
• B. Relay neuron → Sensory neuron → Motor neuron → Effector muscle
• C. Sensory neuron → Relay neuron → Motor neuron → Effector muscle in arm
• D. Motor neuron → Sensory neuron → Relay neuron → Effector muscle

Answer 1

The Correct Option is C

Step 1: Comprehend reflex action
A reflex action is a rapid, involuntary response to a stimulus that bypasses conscious brain processing. Its purpose is to prevent injury, exemplified by the swift withdrawal of a hand from a hot surface.

Step 2: Delineate the involved pathway (reflex arc)
Upon contact with a hot object, the following sequence of events is initiated:
1. The sensory neuron registers the stimulus (heat) via skin receptors and transmits a signal to the spinal cord.
2. Within the spinal cord, the signal is relayed to an interneuron (relay neuron).
3. The interneuron subsequently transmits the signal to a motor neuron.
4. The motor neuron directs the effector muscle in the arm to contract, executing the movement of the hand away.

Step 3: Conclusive Response
Sensory neuron → Relay neuron → Motor neuron → Effector muscle in arm