Question

A reflex action is a quick involuntary response to stimulus. Which of the following is both, unconditioned and conditioned reflex?
A.Knee jerk reflex
B.Secretion of saliva in response to the aroma of food
C.Sneezing reflex
D.Contraction of the pupil in response to bright light

Answer 1

Reflex action is considered as an involuntary process because the reflex arcs act on the signals caused by the stimulus before the signals can even reach the brain.

Complete answer:
1)The reflex action can be of two types that are the conditioned reflex action and the unconditioned reflex action.
2)Conditioned reflex action is also known as acquired reflex action because these reflexes are not present from the time of birth but are acquired in the lifetime and depend on experiences, learning, and training that causes the conditioned reflex action whereas the inborn reflexes are known as unconditioned reflexes.

Option A: Knee jerk is an unconditioned reflex. Therefore, this is the incorrect option.

Option B: Secretion of saliva is normally an unconditioned reflex but it was seen in Pavlov's experiment that this reflex can also be a conditioned reflex. Therefore, this is the correct option.

Option C: Sneezing reflex is an unconditioned reflex. Therefore, this is the incorrect option.

Option D: Contraction of pupils in presence of bright light is an unconditioned reflex. Therefore, this is the incorrect option.

Hence, the correct answer is option (B)

Note: Normally dogs have receptors in their tongue which stimulates the secretion of saliva on receiving the aroma of the food. But Ivan Pavlov, a physiologist carried out an experiment where he provided food to the dog only after the ringing of the bell. After some days, the dog started salivating only on hearing the sound of the bell even if the food was not given to the dog. This was possible only through the unconditioned reflex that the dog developed by learning and experiences.