Nervous System

Jai Ganesh · Yesterday 17:54:16

Nervous System

Gist

The nervous system is the body's primary command center, controlling actions, sensory information, and involuntary functions by transmitting electrical signals between the brain, spinal cord, and body. Divided into the central (brain/spinal cord) and peripheral (nerves) systems, it enables movement, thought, memory, and, together with the endocrine system, maintains homeostasis.

Core Components

Central Nervous System (CNS): Comprises the brain and spinal cord, which act as the main processing center for information.
Peripheral Nervous System (PNS): Consists of all nerves outside the brain and spinal cord, connecting the CNS to limbs and organs.
Neurons: The basic structural units (nerve cells) that send messages via electrical impulses, featuring axons for transmission and dendrites for reception.

Summary

In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes that impact the body, then works in tandem with the endocrine system to respond to such events. Nervous tissue first arose in wormlike organisms about 550 to 600 million years ago. In vertebrates, it 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 nerves (efferent), while those nerves that transmit information from the body to the CNS are called sensory nerves (afferent). The PNS is divided into two separate subsystems, the somatic and autonomic nervous systems. The autonomic nervous system is further subdivided into the sympathetic, parasympathetic and enteric 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. Nerves that exit from the brain are called cranial nerves while those exiting from the spinal cord are called spinal nerves.

The nervous system consists of nervous tissue which, at a cellular level, is defined by the presence of a special type of cell, called the neuron. 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. Many of the cells and vasculature channels within the nervous system make up the neurovascular unit, which regulates cerebral blood flow in order to rapidly satisfy the high energy demands of activated neurons.

Nervous systems are found in most multicellular animals, but vary greatly in complexity. The only multicellular animals that have no nervous system at all are sponges, placozoans, and mesozoans, which have very simple body plans. The nervous systems of the radially symmetric organisms ctenophores (comb jellies) and cnidarians (which include anemones, hydras, corals and jellyfish) consist of a diffuse nerve net. All other animal species, with the exception of a few types of worm, have a nervous system containing a brain, a central cord (or two cords running in parallel), and nerves radiating from the brain and central cord. The size of the nervous system ranges from a few hundred cells in the simplest worms, to around 300 billion cells in African elephants.

The central nervous system functions to send signals from one cell to others, or from one part of the body to others and to receive feedback. Malfunction of the nervous system can occur as a result of genetic defects, physical damage due to trauma or toxicity, infection, or simply senescence. The medical specialty of neurology studies disorders of the nervous system and looks for interventions that can prevent or treat them. In the peripheral nervous system, the most common problem is the failure of nerve conduction, which can be due to different causes including diabetic neuropathy and demyelinating disorders such as multiple sclerosis and amyotrophic lateral sclerosis. Neuroscience is the field of science that focuses on the study of the nervous system.

Details

Your nervous system plays a role in everything you do. The three main parts of your nervous system are your brain, spinal cord and nerves. It helps you move, think and feel. It even regulates the things you do but don’t think about like digestion. It contains the central nervous system and the peripheral nervous system.

Overview:

What is the nervous system?

Your nervous system is your body’s command center. It’s made up of your brain, spinal cord and nerves. Your nervous system works by sending messages, or electrical signals, between your brain and all the other parts of your body. These signals tell you to breathe, move, speak and see, for example. Your nervous system keeps track of what’s going on inside and outside of your body and decides how to respond to any situation you’re in.

Your nervous system regulates complicated processes like thoughts and memory. It also plays an essential role in the things your body does without thinking, like blushing, sweating and blinking.

Function:

What does the nervous system do?

Your nervous system’s main function is to send messages from various parts of your body to your brain, and from your brain back out to your body to tell your body what to do. These messages regulate your:

* Thoughts, memory, learning and feelings.
* Movements (balance and coordination).
* Senses (how your brain interprets what you see, hear, taste, touch and feel).
* Wound healing.
* Sleep.
* Heartbeat and breathing patterns.
* Response to stressful situations, including sweat production.
* Digestion.
* Body processes, such as puberty and aging.

How does the nervous system work?

Your nervous system uses nerve cells called neurons to send signals, or messages, all over your body. These electrical signals travel among your brain, skin, organs, glands and muscles.

The messages help you move your limbs and feel sensations, like pain. Your eyes, ears, tongue, nose and the nerves all over your body take in information about your environment. Then, nerves carry that data to and from your brain.

There are different types of neurons. Each type of neuron has a different job:

* Motor neurons take signals from your brain and spinal cord to your muscles. They help you move. They also assist with breathing, swallowing and speaking.
* Sensory neurons take information from your senses (what you see, touch, taste, etc.) to your brain.
* Interneurons communicate between motor and sensory neurons. These neurons regulate your movement in response to sensory information (like moving away from a hot surface) and play a role in how you learn, think and remember.

Anatomy:

What are the parts of the nervous system?

The nervous system has two main parts:

* Central nervous system (CNS): Your brain and spinal cord make up your CNS. Your brain reads signals from your nerves to regulate how you think, move and feel.
* Peripheral nervous system (PNS): Your PNS is made up of a network of nerves. The nerves branch out from your spinal cord. This system relays information from your brain and spinal cord to your organs, arms, legs, fingers and toes.

There are two parts to your peripheral nervous system:

*The somatic nervous system guides your voluntary movements.
* The autonomic nervous system regulates the activities you do without thinking about them (involuntary movements).

What does the nervous system look like?

Nerve cells (neurons) are the basis of your nervous system. There are 100 billion neurons in your brain. These cells connect throughout your entire body.

Imagine your nervous system as a tree. Your central nervous system is the trunk of the tree that contains your brain and spinal cord. The tree branches are your peripheral nervous system (nerves). The branches extend from the truck (brain and spinal cord) to reach all parts of your body.

Conditions and Disorders:

What are common conditions or disorders that affect the nervous system?

There are many conditions that affect your nervous system. Some of the most common include:

* Alzheimer’s disease.
* Cancer.
* Cerebral palsy.
* Epilepsy.
* Huntington’s disease.
* Infection (meningitis).
* Parkinson’s disease.
* Stroke.
* Traumatic brain injury.

What are common signs or symptoms of nervous system conditions?

Signs and symptoms of nervous system conditions vary by type but may include:

* Movement and coordination changes.
* Memory loss.
* Pain, numbness or a pins and needles feeling.
* Behavioral and mood changes.
* Difficulty with thinking and reasoning.
* Seizures.

Some conditions, like a stroke, are medical emergencies that need treatment quickly. If you notice the following symptoms, contact 911 or your local emergency services number:

* Muscle weakness or paralysis in one side of your body.
* Sudden vision loss.
* Slurred speech.
* Confusion.

What tests check the health of your nervous system?

A healthcare provider may use one of the following tests to check the health of your nervous system:

* Computed tomography (CT) scan.
* Electrocardiogram (ECG or EKG).
* Electroencephalogram (EEG).
* Lumbar puncture (spinal tap).
* Magnetic resonance imaging (MRI) scans.

How are conditions that affect the nervous system treated?

A healthcare provider will review your symptoms to diagnose and treat any conditions that affect your nervous system. Treatment varies for each condition. So, your healthcare provider will take into consideration several factors, like your age and general health, to create your treatment plan. This plan may include:

* Taking medications.
* Having surgery.
* Participating in counseling for mental and emotional support.
* Receiving supportive care (to keep you comfortable).

Additional Information:

Key Facts

* The nervous system is made up of the brain, spinal cord and nerves.
* The nervous system is responsible for intelligence, learning, memory, movement, the senses and basic body functions such as your heartbeat and breathing.
* The basic building blocks of the nervous system are the nerve cells (neurons) which are responsible for carrying messages to and from different parts of the body.
* The brain is in constant communication with all parts of the body, sending instructions and receiving input from the senses.

What is the nervous system?

The nervous system is made up of the brain, spinal cord and nerves.

It controls many aspects of what you think, how you feel and what your body does. It allows you to do things such as walk, speak, swallow, breathe and learn. It also controls how the body reacts in stressful situations. The nervous system interprets and responds to information gathered through the senses.

What is function of the nervous system?

The main function of the nervous system is to be the body's communication network. Its main job is to send and receive messages between you and the outside world, and within your own body.

The nervous system is responsible for:

* intelligence, learning and memory: your thoughts and feelings
* physical movement
* basic body functions such as the beating of your heart, breathing, digestion, sweating and shivering
* the senses: sight, hearing, taste, touch and smell

What are the parts of the nervous system?

The nervous system is made up of:

* the central nervous system (CNS), which consists of the brain and spinal cord
* the peripheral nervous system (PNS), which consists of nerves that connect the CNS to the rest of the body

The brain is made up of different parts. These include the:

* cerebrum
* cerebellum
* thalamus
* hypothalamus
* brainstem

The brain's cerebral cortex is the outermost layer of the brain that gives the brain its wrinkly appearance. The cerebral cortex is divided in half lengthways into two sides or hemispheres, the left hemisphere, and the right hemisphere. Each hemisphere specialises in different functions, but they share information and work together seamlessly.

Each brain hemisphere (parts of the cerebrum) has 4 different sections called lobes. These lobes are the frontal, parietal, temporal and occipital lobes. Each lobe carries out different brain functions.

Learn more about the structure of the central nervous system and how it works.

What are nerve cells?

The basic building blocks of the nervous system are the nerve cells, or neurons. The human brain has around 100 billion neurons. These cells are responsible for carrying messages to and from different parts of the body.

Neurons have a cell body which contain the cell's nucleus as well as special extension called dendrites and axons.

The synapse is the gap between the end of one neuron's axon and the tip of next neuron's dendrites. Messages travel from one neuron to the next across synapses.

A neuron and it's parts.

How does the nervous system work?

The brain is in constant communication with all parts of the body, sending instructions and receiving input from the senses.

Outgoing messages from the brain are sent along motor pathways, which carry messages from the brain to the muscles to tell them to move. The neurons that make up these motor pathways are called motor neurons.

Incoming messages from the body to the brain are sent along sensory pathways. The sensory pathways detect things such as light and sound and carry information about these to the brain. The neurons that make up these sensory pathways are called sensory neurons.

The spinal cord carries motor and sensory signals between the brain and nerves. The spinal cord also contains separate circuits for many reflexes.

One part of the nervous system, called the autonomic nervous system, controls a lot of the body processes that function automatically, for example, breathing, sweating or shivering.

There are 2 parts to the autonomic nervous system:

* the sympathetic nervous system, which controls how you respond in an emergency or when you are under stress (for example, it makes your heart beat faster and causes you to release adrenaline)
* the parasympathetic nervous system, which prepares the body for rest

These parts work together to manage how the body responds to your changing environment and needs. For example, your pupils change size to allow the right amount of light into your eyes to allow effective vision.

What medical conditions are related to the nervous system?

There are thousands of conditions that start in or affect the central nervous system, including:

* degenerative conditions such as Parkinson's disease, Alzheimer's disease and multiple sclerosis
* stroke
* seizure disorders, such as epilepsy
* cancer, such as brain tumours
* infections, such as meningitis
* brain injuries and spinal cord injuries
* spinal cord compression (spinal stenosis)

What are the symptoms of problems with the nervous system?

There are many different symptoms that could suggest a problem with the nervous system. They include:

* headaches
* blurry vision
* fatigue
* leg or arm numbness
* loss of coordination, weakness or loss of muscle strength
* slurred speech
* tremors

Other symptoms that might suggest a problem with the central nervous system include:

* emotional problems
* memory loss
* behavioural changes

There are also many diseases that affect the peripheral nervous system. The peripheral nerves include the nerves outside the brain and spinal cord such as nerves of the face, arms, legs and torso. Read more on diseases of the peripheral nervous system.

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Nervous System

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