What is your nervous system?
From Wikipedia…
In biology, the classical doctrine of the nervous system determines that it is a highly complex part of an animal that coordinates its actions (behavior) and sensory information by transmitting signals to and from different parts of its body.
(sense: A sense is a biological system used by an organism for sensation, the process of gathering information about the world and responding to stimuli. For example, in the human body, the brain receives signals from the senses, which continuously receive information from the environment, interprets these signals, and causes the body to respond, either chemically or physically.
Although traditionally around five human senses were known (namely sight, smell, touch, taste, and hearing), it is now recognized that there are many more.[1] Senses used by other non-human organisms are even greater in variety and number. During sensation, sense organs collect various stimuli (such as a sound or smell) for transduction, meaning transformation into a form that can be understood by the brain.
Sensation and perception are fundamental to nearly every aspect of an organism’s cognition, behavior and thought.
The nervous system detects environmental changes that impact the body, then works in tandem with the endocrine system to respond to such events.[1]
The Central Nervous System (CNS)
In humans, the CNS contains two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS).
The CNS consists of the brain and spinal cord.
The Peripheral Nervous System (PNS)
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 nerves or efferent nerves, while those nerves that transmit information from the body to the CNS are called sensory nerves or afferent.
Spinal nerves are mixed nerves that serve both functions.
The PNS is divided into three separate subsystems, the somatic, autonomic, and enteric nervous systems. Somatic nerves mediate voluntary movement.
Autonomic Nervous System (ANS)
The ANS autonomic nervous system is further subdivided into the
sympathetic and the parasympathetic nervous systems.
Sympathetic Nervous System
The sympathetic nervous system is activated in cases of emergencies to mobilize energy.
Parasympathetic Nervous System
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
Nerves that exit from the cranium are called cranial nerves
while those exiting from the spinal cord are called spinal nerves.
The vagus nerve
The 10th cranial nerve is called the vagus nerve. The vagus nerve, historically cited as the pneumogastric nerve, is the tenth cranial nerve or CN X, and interfaces with the parasympathetic control of the heart, lungs, and digestive tract. It actually comprises two nerves—the left and right vagus nerves—but they are typically referred to collectively in the singular. The vagus is the longest nerve of the autonomic nervous system in the human body and comprises sensory and motor fibers.
Neurons (Cellular Biology)
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 electrochemical impulses traveling along thin fibers called axons, which can be directly transmitted to neighboring cells through electrical synapses or cause chemicals called neurotransmitters to be released at chemical 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 pathways, neural circuits, and larger 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.
References
- Tortora, G.J., Derrickson, B. (2016). Principles of Anatomy and Physiology (15th ed.). J. Wiley. ISBN 978-1-119-34373-8.
- Wikipedia
Resources on Nervous System Function
Dr. Andrew Huberman: The Huberman Lab Podcast
How your nervous system works and changes
Dan Seigel: The PocketGuide to Interpersonal Neurobiology and Mindsight.
Dr. Bessel van der Kolk: The Body That Keeps the Score
