Our bodies are incredible!
The human body has an innate ability to adapt and heal. The lungs exchange oxygen, the heart beats, pupils react to light, papillae on the skin become erect when you encounter cold, fear, or a sudden feeling of excitement.
All superbly orchestrated by billions of nerve cells And billions of miles of genetic information, in combinations that make each of us unique.
A nerve is a bundle of individual neurons. There are approximately 100 billion neurons in the human body (about the same number of stars in our Milky Way galaxy), and over 90,000 miles of neural tissue.
The nervous system is a complex network of nerves and cells that carry messages to and from the brain and spinal cord to various parts of the body.
The nervous system coordinates actions and responses to stimulus by transmitting signals to and from different parts of the body. It detects environmental changes that impact the body, then works in tandem with the other body systems to respond to such events.
The human nervous system consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers or axons, that connect the CNS to every other part of the body.
Nerves that transmit signals from the brain are called motor or efferent nerves, while those nerves that transmit information from the body to the CNS are called sensory or afferent nerves. Spinal nerves serve both functions and are called mixed nerves. The PNS is divided into three separate subsystems, the somatic, autonomic, and enteric nervous systems. Somatic nerves mediate voluntary movement. The autonomic nervous system is further subdivided into the sympathetic and the parasympathetic nervous systems. The sympathetic nervous system is activated in cases of emergencies to mobilize energy, while the parasympathetic nervous system is activated when organisms are in a relaxed state. The enteric nervous system functions to control the gastrointestinal system. Both autonomic and enteric nervous systems function involuntarily. Nerves that exit from the cranium are called cranial nerves while those exiting from the spinal cord are called spinal nerves.
At the cellular level, the nervous system is defined by the presence of a special type of cell, called the neuron, also known as a “nerve cell”. Neurons have special structures that allow them to send signals rapidly and precisely to other cells. They send these signals in the form of electro-chemical waves traveling along thin fibers called axons, which cause chemicals called neurotransmitters to be released at junctions called synapses. A cell that receives a synaptic signal from a neuron may be excited, inhibited, or otherwise modulated. The connections between neurons can form neural circuits and neural networks that generate an organism’s perception of the world and determine its behavior. Along with neurons, the nervous system contains other specialized cells called glial cells (or simply glia), which provide structural and metabolic support. Every sensation, every process, everything your body does, is controlled by your nervous system. If your nervous system is not able to function correctly, your body will not function correctly.