Question

Which is not a reflex action?
A. Swallowing of food
B. Shivering in cold
C. Salivation at choicest food
D. Closure of the eyelid by flashing light

Answer 1

Hint:
Reflex action is done unknowingly in an animal. From the above actions, the one in which the animal reacts automatically without thinking is the reflex action.

Complete answer:
Reflex action is a spontaneous mechanical response to a stimulus without the knowledge of the animal. The afferent neuron receives a signal from a sensory organ and transmits the impulse to the CNS through a dorsal root. The signal is transmitted via efferent neurons from CNS to the effector. The reflex arc is formed by the stimulus and response.
In the options given above:
Swallowing of food is not a reflex action as the animal purposefully or knowingly swallows the food.
Shivering in the cold is a reflex action. When the body senses cold in the surrounding, it activates some functions which helps the body to maintain the temperature, shivering is one of them.
The salvation of the choicest food is also a reflex action.
Closure of the eyelid by light is a reflex action to minimize the amount of light passing through the cornea.
From the above options, swallowing the good is not a reflex action.
Other examples of reflex action.
1. Withdrawal of limbs when they are touched by hot things.
2. Opening of mouth on hearing a loud sound.
3. Withdrawal of limbs in a decapitated frog (whose head has been cut) when dipped in warm water or touched with acid.

Option ‘A’ is correct

Note:
There are two types of Reflexes:
Unconditioned reflexes are inborn reflexes that are transmitted through heredity
Conditioned reflexes are acquired reflexes during the lifetime of an individual. They are not shared by heredity.