Question

Reflex arcs, which involve no processing in the brain, are beneficial because they permit:
A. Instantaneous signalling to the motor neurons.
B. Avoidance of dangerous stimuli, without even a previously "learned" response.
C. Immediate response to the dangerous stimuli
D. All of the above

Answer 1

Hint: At some point in our life we may have experienced a sudden withdrawal of our body parts which may have come in contact with objects that are cold, hot or scary animals etc. This whole process of response to such stimulation that occurs without our conscious mind and involves the central nervous system is called reflex action and the pathway involved is called the reflex arc.

Complete Step by Step Answer:
The reflex arc is the nerve pathway involved in the reflex action. The pathway is composed of at least one afferent neuron (receptor) and one efferent neuron (effector or excitor) which are arranged in series. The sensory organs produces the signals that are received by the afferent neuron and is transmitted to the central nervous system (at the level of spinal cord) via a dorsal nerve root

Then, the signals are carried to the effector by an efferent neuron that generates the response. These responses are then sent to the sensory organs via a motor neuron. These signals are not processed in the brain and generate immediate or instant response to the motor neuron or to the dangerous neuron.

Hence, the correct answer is option D:- All of the above.

Note: The reflex arc can get impaired if the motor neurons suffer an injury. The signals will still reach the spinal cord and the response will be generated but these responses may not reach the sensory organs as motor neurons are damaged, thus the instant action will not take place against the dangerous stimuli.