Nervous System: Definition, Types and Sample Questions

The nervous system is the part of an animal's body that controls and sends information between different parts of the body. The central nervous system (CNS) and the peripheral nervous system (PNS) are the two primary elements of the nervous system in vertebrates (PNS). The spinal cord and the brain are present in the CNS. In this article, we will learn more about the nervous system, its working, and related sample questions.

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What is the Nervous System?

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The nervous system, often known as the neural system, is a sophisticated network of neurons dedicated to the transmission of messages. As we progress up the food chain, the neurological system becomes more sophisticated.

Cnidarians like jellyfish, for example, have basic neural nets that run throughout their bodies. Crabs have a more complex neurological system with two nerve centers termed the dorsal and ventral ganglions. Furthermore, it is one of the most tightly connected structures in the animal kingdom, including billions of neurons.

The neurological system in the human body combines the activity of organs based on stimuli that neurons perceive and communicate. They send and receive messages in the form of electrical impulses from and to the sense organs. As a result, the sense organs, nerves, spinal cord, and brain all play a role in neurological coordination.

The presence of a unique type of cell called a neuron, sometimes known as a "nerve cell," defines the nervous system at the cellular level. Neurons have unique features that enable them to convey signals to neighboring cells quickly and precisely. They deliver these messages in the form of electrochemical waves that travel along 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 can be stimulated, inhibited, or otherwise regulated.

Function

The nervous system's most basic job is to govern the organism's movement and to influence the environment (e.g., through pheromones). This is accomplished by transmitting signals from one cell to another, or from one body component 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 circulation or other internal fluids to cause the nervous system's output. 

Sensory cells of many sorts provide information to the nervous system, converting physical modalities such as light and sound into neuronal activity. Internally, the nervous system has intricate webs of connections between nerve cells that allow it to generate activity patterns that are only partially dependent on sensory input. By dynamically altering the strength of connections between neurons, as well as other methods, the nervous system is also capable of retaining information over time.

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Human Nervous System

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The human nervous system, which is one of the most sophisticated organ systems to have ever evolved, is divided into two parts:

• Central Nervous System, known as CNS (includes the spinal cord and the brain)
• Peripheral Nervous System of the Periphery (includes all the nerves of the body)

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Central Nervous System

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The Primary Nervous System (CNS) is commonly referred to as the body's central processing unit. It is made up of two parts: the brain and the spinal cord.

• Brain

The brain is the largest and most essential organ in the human neurological system. It is the neurological system's control unit, and it aids us in learning new things, retaining and comprehending information, making decisions, and much more. It is encased within the skull, which protects it from the front, sides, and back. The human brain is divided into three sections:

• The cerebrum, Hypothalamus, and Thalamus make up the forebrain, which is located in the front of the brain.
• Tectum and Tegmentum make up the midbrain, which is the smaller and central region of the brainstem.
• Cerebellum, Medulla, and Pons make up the hindbrain, which is the brain's center portion.

• Spinal Cord

The spinal cord is a cylindrical bundle of nerve fibers and accompanying tissues that connects all regions of the body to the brain and is encased within the spine. It starts from the medulla and extends downwards. It is encased in a bone cage called the vertebral column, which is surrounded by meninges. The spinal cord is responsible for spinal reflex actions as well as nerve impulse transmission to and from the brain.

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Peripheral Nervous System

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The peripheral nervous system (PNS) is a branch of the nervous system that branches off from the central nervous system and connects various regions of the body to the CNS. With the support of peripheral nerves, we may perform both voluntary and involuntary activities. It also contains the enteric nervous system, which is a semi-independent component of the nervous system that governs the gastrointestinal system, as well as peripheral ganglia, sympathetic and parasympathetic ganglia. 

PNS has two types of nerve fibers:

• Afferent nerve fibers are important for conveying messages from tissues and organs to the central nervous system.
• Efferent nerve fibers carry messages from the central nervous system to the associated peripheral organ.

Classification

• The somatic neural system (SNS) is a neural system formed of somatic nerves that transmits impulses from the central nervous system to skeletal muscle cells to govern voluntary actions in the body. 
• The autonomic nervous system (ANS) is involved in involuntary behaviors such as the regulation of physiological functions (digestion, respiration, salivation, etc.). It's a self-regulating system that sends impulses from the central nervous system to smooth muscles and involuntary organs (heart, bladder, and pupil). The autonomic neural system is further subdivided into the following categories:

- Sympathetic nervous system

- Parasympathetic nervous system

Neuron

A neuron is an organized and functioning element of the nervous system that is irregular in shape and capable of conducting electrochemical impulses, unlike other cells. 

• The shortest fiber in a neuron's cell body is the dendrite, which spreads out from the cell body.
• The longest thread on the cell body of a neuron is the axon, which is surrounded by an insulating and protecting sheath of myelin.
• The cytoplasm and nucleus make up the cell body.
• A synapse is a small space between two adjacent neurons through which nerve impulses pass as they travel from one neuron to the next.

Nerves

Nerves arise from the brain and spinal cord as thread-like structures. It is in charge of sending messages to all regions of the body. Some of these neurons can fire messages at speeds of up to 428 km/h (119 m/s). Nerves are divided into three categories. 

• Sensory nerves convey information from the brain to all of the senses.
• Motor nerves transport messages from the brain to all of the muscles.
• Sensory and motor nerves are carried by mixed nerves.

Cranial nerves originate in the brain and carry impulses that originate in the central nervous system. Certain cranial nerves are classified as mixed nerves, whereas others are classified as sensory nerves. Spinal nerves originate in the spinal cord. Mixed nerves include all spinal nerves that convey impulses to and from the central nervous system.

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Things to Remember based on Nervous System

• The nervous system is split into two parts: the peripheral nervous system and the central nervous system. 
• The brain and spinal cord are two parts of the central nervous system.
• To limit the effects of damage caused by accidents, the central and peripheral nervous systems are protected by a robust internal skeleton, such as the skull and vertebral column.

• The peripheral nervous system is made up of neurons that transmit signals between the body's various components and the central nervous system. 

• A neuron is an organized and functioning element of the nervous system that is irregular in shape and capable of conducting electrochemical impulses, unlike other cells.

• With the support of peripheral nerves, we may perform both voluntary and involuntary activities.

• The nervous system can range in size from a few hundred cells in the tiniest worms to over 100 billion cells in humans.

• The autonomic nervous system (ANS) is involved in involuntary behaviors such as the regulation of physiological functions: