Reflex action is an involuntary and rapid response to a stimulus that bypasses conscious thought. It involves a simple neural pathway called a reflex arc, which includes a sensory neuron, interneuron, and motor neuron. Walking, on the other hand, is a voluntary and coordinated movement involving various muscle groups controlled by the brain's motor cortex and cerebellum. Unlike reflex actions, walking requires conscious intention and coordination between different parts of the brain and muscles.

At the synapse between two neurons, neurotransmitters are released from the presynaptic neuron into the synaptic cleft. These neurotransmitters then bind to receptors on the postsynaptic neuron, causing a change in its membrane potential. This results in the propagation of the electrical signal across the synaptic gap from one neuron to the next.

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.