This quick response is called a reflex, and reflexes occur without conscious thinking or planning, meaning the brain is not involved in them.

Which part of the brain controls reflex action?

The brain stem, which consists of the medulla (an enlarged portion of the upper spinal cord), pons and midbrain (lower animals have only a medulla). The brain stem controls the reflexes and automatic functions (heart rate, blood pressure), limb movements and visceral functions (digestion, urination).

Why is the brain not involved in the reflex action?

It is because most sensory neurons do not pass directly into the brain but synapse in the spinal cord which allows reflex actions to occur relatively quickly by activating spinal motor neurons without the delay of routing signals through the brain, although the brain receives sensory input while the reflex action ...