The cerebellum, located at the back of the brain, plays a crucial role in maintaining posture and equilibrium of the body. It receives sensory input from the vestibular system, which detects changes in head position and movement, and integrates this information to coordinate muscle activity and maintain balance.

The smell of an agarbatti (incense stick) is detected by specialized sensory cells called olfactory receptors in the nasal cavity. These receptors bind to odor molecules present in the air, initiating a cascade of chemical signals that are transmitted to the brain's olfactory bulb. The olfactory bulb then processes these signals, allowing us to perceive the smell.

The brain's role in reflex action is to process sensory information and coordinate motor responses. When a sensory stimulus is detected, sensory neurons transmit signals to the spinal cord or brainstem, where interneurons relay the information to motor neurons. The brain then sends signals back to the muscles to produce a reflexive motor response, often without conscious awareness.

The movement of leaves of the sensitive plant (Mimosa pudica) is known as thigmonasty and is triggered by touch or physical disturbance. In contrast, the movement of a shoot towards light, known as phototropism, is a directional response to light stimuli. Thigmonastic movement occurs rapidly and involves changes in turgor pressure within specialized cells, while phototropic movement occurs gradually and involves the differential growth of cells in response to light.