What is the Nervous System?

The nervous system is the portion of an animal's body that controls and transmits signals between various parts of the body. The central nervous system (CNS) and the peripheral nervous system (PNS) are the two primary components of the nervous system in vertebrates. The brain and spinal cord are housed in the CNS. The PNS is made up primarily of nerves, which are long fibers that link the CNS to every other part of the body, but it also includes peripheral ganglia, sympathetic and parasympathetic ganglia, and the enteric nervous system, which is a semi-independent part of the nervous system that regulates the gastrointestinal system.

When a ball comes your way, you swing your bat. When a large dog leaps in front of you, you start to perspire. You step past a bakery and the delicious scent tempts your taste buds. If you have a functioning nervous system, you will perform any of these tasks. Your nervous system is a complex network of nerves and cells that transmit information and regulate behavior.

The nervous system's most basic function is to regulate the organism's movement and to influence the environment (example, through pheromones). This function is accomplished by transmitting signals from one cell to another, or from one body part 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 bloodstream or other internal fluids to cause the nervous system's output. Sensory cells of various types provide feedback to the nervous system, converting physical modalities such as light and sound into neural activity.

Evolution of Nervous System

The existence of a particular form of cell called a neuron, also known as a "nerve cell," defines the nervous system at the cellular level. Neurons have unique properties that enable them to send signals to other cells quickly and precisely. They send these signals in the form of electrochemical waves that pass through thin fibers known as axons, causing chemicals known as neurotransmitters to be released at synapses, or junctions between neurons. A cell (a postsynaptic neuron) that receives a synaptic signal from a neuron may be excited, inhibited, or otherwise modulated. Neural circuits are formed by the interactions between neurons and can produce very complex patterns of dynamical activity. Glial cells (or simply glia) are specialized cells in the nervous system that provide structural and metabolic support in addition to neurons. Glia can also play a significant signaling function, according to new evidence.

Nervous systems can be found in nearly all multicellular animals, but their complexity varies greatly. Sponge and microscopic bloblike species called placozoans and mesozones are the only multicellular creatures without a nervous system. Ctenophores (comb jellies) and cnidarians (example, anemones, hydras, corals, and jellyfishes) have a diffuse nerve net in their nervous systems. Except for echinoderms and a few varieties of worms, all other species have a nervous system that consists of a brain, a central cord (or two cords running parallel to each other), and nerves radiating from the central cord and the brain.

Central Nervous System and Peripheral Nervous System

Nerves that migrate to and from the central nervous system make up the peripheral nervous system, or PNS. These nerves notify the brain and spinal cord of any sensory changes and then execute instructions. As a result, one might compare the PNS to the jobs.

Divisions of the Peripheral Nervous System

The peripheral nervous system is subdivided once more, resulting in two major subdivisions. This is simple to understand if you note that some of the PNS nerves migrate into the brain and others away from it. The sensory division, also known as the afferent division, is made up of nerves that migrate toward the brain. This division's nerves bring information from sensory receptors to the CNS, such as the alarming sound of a dog barking or the delicious aroma of freshly baked bread. To put it another way, the sensory division enables a person to perceive the world around him.

The motor division, or efferent division, of the peripheral nervous system, is made up of nerves that migrate away from the CNS. This division's nerves send messages to the muscles and glands, instructing them to carry out the brain's commands. Some of these orders, like throwing a bat in an attempt to hit a home run, are something that someone deliberately wants to do. Other stuff, such as mouth-watering or sweating, happens without a person’s knowledge. The motor division of the PNS can be further split into two additional subdivisions since certain body reactions are voluntary and others are not.

Somatic and Autonomic Nervous System

The somatic nervous system is a branch of the motor division that helps to regulate the skeletal muscles consciously. Every voluntary movement, such as brushing the teeth or swatting a fly off the arm, falls into this category.

The autonomic nervous system is a subset of the motor division that enables the body to perform activities that are not regulated by the conscious mind. In other words, even though someone is sound asleep, it's the mechanism that controls involuntary movements like digestion, sweating, and heartbeat.

The autonomic nervous system is a control system that controls bodily functions such as heart rate, digestion, respiratory rate, pupillary response, urination, and sexual arousal in a mostly unconscious manner. The primary control mechanism for the fight-or-flight response is this system.

Sensory and motor pathways exist in the somatic nervous system, while motor pathways exist only in the autonomic nervous system. Internal organs and glands are regulated by the autonomic nervous system, while muscles and movement are controlled by the somatic nervous system.

Context and Applications

This topic is significant in the professional exams for both undergraduate and graduate courses, especially for      

• Bachelor of Science in Anatomy and Physiology
• Master of Science in Anatomy and Physiology
• Bachelor of Medicine and Bachelor of Surgery