The central and peripheral nervous systems are related to every bodily function, including heart beat. The primary relationship between the nervous stem and the heart lies with the autonomic nervous system. The autonomic nervous system continually tells the heart to pump blood through chemical and electrical signaling from the brain. As with the rest of the functions of the autonomic nervous system, this process is automatic and unconscious.
An important part of understanding the connection between the nervous system and the heart is understanding what the nervous system is. The nervous system is composed of the central nervous system, which is the brain and spinal cord, and the peripheral nervous system, which connects the rest of the body to the central nervous system. The peripheral nervous system can also be broken down into two subcategories, which are the somatic nervous system and the autonomic nervous system. The somatic nervous system is what controls musculoskeletal movement and provides sensory information to the central nervous system, but the main relationship between the nervous system and the heart lies with the autonomic nervous system.
The autonomic nervous system is one of the oldest systems of the body in evolutionary terms. As the name suggests, it is responsible for all the automatic functions of the body, such as the heart beat. This is in contrast to much of the rest of the functions of the nervous system, where a person has to consciously think about a body command, such as walking or raising a hand, before the signals are sent to the muscles. The autonomic nervous system and the heart work together unconsciously to keep blood pumping through the body, effectively keeping its owner alive.
Another important aspect of understanding the relationship between the nervous system and the heart is understanding how the heart works. The heart is protected within the rib cage and shares the left side of the chest with the left lung. It is a complex and vital system made up of four chambers. Used blood is collected from tissue throughout the body and pumped into the right side of the heart, where it is pumped through the lungs and supplied with fresh oxygen and then pumped back into the left side of the heart and back out into the body. The only way the heart can continue this important function is from electrical and chemical signals it receives from the brain via the autonomic nervous system.