Question

In reflex action, the reflex arc is formed by
A. Brain→ spinal cord→ muscle
B. Receptor→ spinal cord→muscles
C. Muscle→ receptor→ brain
D. Muscles→ spinal cord→ receptor

Answer 1

Reflex actions are very rapid, automatic, stereotyped behaviour or responses in which the same kind of stimulus evokes a short-lived response. It is a process of response to a peripheral nervous stimulation that occurs involuntarily, without conscious effort or thought and requires the involvement of a part of the central nervous system.

Complete answer:
- In a withdrawal reflex, the following actions are carried out:
1. The stimulus is detected by sensory receptors present in the skin.
2. These initiate nerve impulses in the sensory or afferent neurons leading from them to the spinal cord.
3. These impulses enter the spinal cord and initiates impulses in one or more interneurons.
4. Interneurons initiate impulses in one or more motor or efferent neurons.
5. The motor neurons then carry these impulses to the effectors or skeletal muscles in which response will be shown.
- The muscles called flexors are stimulated to contract so that they withdraw the body part whereas the muscles called extensors are inhibited so that they do not extend the body part. The result is that the body part is suddenly, involuntarily withdrawn from the irritating stimulus.
- This entire pathway from sensory receptor to sensory neuron to spinal cord to motor neuron to effectors is called the reflex arc.

Therefore, the answer is (B) Receptor→spinal cord→muscles

Note:
- The reflex pathway comprises at least one afferent neuron (coming from receptor) and one efferent neuron (going to effector or excitor) appropriately arranged in a series.
- Reflexes can be classified one the basis of the number of synapses in the reflex path (Monosynaptic and Polysynaptic reflexes) and their conditioning (Unconditioned and Conditioned reflexes).