Involuntary action is the set of muscle movement which do not require thinking. But it is controlled by brain for example beating of heart beat while on the other hand, the reflex action is rapid and spontaneous action in response to any stimulus. For example closing of eyes immediately when bright light is focused.
The human nervous system is responsible for controlling and coordinating all the activities of the human body.
The Central Nervous System (CNS) comprises the brain and spinal cord.
The Peripheral Nervous System (PNS) comprises sensory/motor neurons and ganglion.
The nervous system, often known as the neural system, is a sophisticated network of neurons dedicated to the transmission of messages. As we progress up the food chain, the neurological system becomes more sophisticated.
The nervous system's most basic job is to govern the organism's movement and to influence the environment (e.g., through pheromones). This is accomplished by transmitting signals from one cell to another, or from one body component to another. Signals that travel to muscle cells cause muscles to contract, and signals that travel to endocrine cells cause hormones to be released into the circulation or other internal fluids to cause the nervous system's output.