Voluntary Movements and Reflexes

Much of the work of the nervous system is automatic or reflexive. For example, when someone pinches our arm, the pinch stimulates sensory receptors in the skin and the nerve transmits the impulse to the spinal cord. The neurons, through the motor nerves, return impulses to the arm muscles, which contract and cause us to withdraw our arm. This reflex process, or reflex arc, occurs due to the fact that the nerve impulse caught by the sensory receptors of the skin is not sent to the cerebral cortex to receive a response, but takes a shorter route to the spinal cord.

On the contrary, voluntary activity is associated with various areas of the cerebral cortex - motor areas. From these areas, impulses pass through the spinal cord and motor nerves to the muscles.

Our cerebral cortex is much more developed than that of other animals and has a greater number of neurons, even compared to chimpanzees. The structure of the brain corresponds to the evolutionary development achieved by a living being. Thus, insects have independent nerve centers, but no brain. In fish, the brain consists almost exclusively of the nerve centers of smell and taste, while in birds the largest center is the visual center. Reptiles have two brain hemispheres, like humans. Mammals have the largest brains. Most of them have a smooth cerebral cortex, but more advanced animals, such as chimpanzees, have a significant number of convolutions and sulci.