Your nervous system affects every aspect of your health, including your: Thoughts, memory, learning, and feelings. Movements, such as balance and coordination. Senses, including how your brain interprets what you see, hear, taste, touch and feel. Sleep, healing and aging. Heartbeat and breathing. Definition of nervous system.: the bodily system that in vertebrates is made up of the brain and spinal cord, nerves, ganglia, and parts of the receptor organs and that receives and interprets stimuli and transmits impulses to the effector organs — see autonomic nervous system, central nervous system, peripheral nervous system.
Nervous systemorganized group of cells specialized for the conduction of electrochemical stimuli from sensory receptors through a network to the site at which a response occurs. All living organisms are able to detect changes within themselves and in their environments. Changes in the external environment include those of lighttemperaturesoundmotion, and odourwhile changes in the internal environment include those in the position of the head and limbs as well as in the internal organs.
Once detected, nfrvous internal and external changes must be analyzed and acted upon in order to survive. As life on Earth evolved and the environment became more complex, the survival of organisms depended upon how well they could respond to changes in their surroundings. One factor necessary for survival was bg speedy reaction or response.
Since communication from one cell to another by chemical means was too slow to be adequate for survival, a system evolved that allowed for faster reaction. That system was the nervous system, which is based upon the almost instantaneous transmission of wuat impulses from one region of the body to another along specialized nerve cells called neurons. Nervous systems hy of two general types, diffuse and centralized. In the diffuse type of system, found in lower invertebratesthere is no brainand neurons are distributed throughout the organism in a netlike pattern.
In the centralized systems of higher invertebrates and vertebratesa portion of the nervous system has a dominant role in coordinating information sysstem directing responses. This centralization reaches its culmination in vertebrates, which have a well-developed brain and spinal cord. Impulses nervus carried to and from the brain and spinal cord by nerve fibres that make up the peripheral nervous system.
This whaat begins with a discussion of the general features of nervous systems—that is, their function of responding to stimuli and the rather how to use a paddle boat electrochemical processes by which they generate a response.
Following that is a discussion of the various types of nervous systems, from the simplest to the most complex. The simplest type of response is a direct one-to-one stimulus-response reaction. A change in the environment is the stimulus ; the reaction of the organism to it is the response. In single-celled organisms, the response is the result of a property of the cell fluid called irritability. In simple organisms, such as algaeprotozoansand fungia response in which the organism moves toward or away from the stimulus is called taxis.
In larger and more complicated organisms—those in which response involves the synchronization and integration of events in different parts of the body—a control mechanism, or controller, is located between the stimulus and the response. In multicellular organisms, this controller consists of two basic mechanisms by which integration is achieved—chemical regulation and nervous regulation. In chemical regulation, substances called hormones are produced by well-defined groups of cells and are either diffused or carried by the blood to other areas of the body where they act on target cells and influence metabolism or induce synthesis of other substances.
The changes resulting from hormonal action are expressed in the organism as influences on, or alterations in, form, growthreproductionand behaviour. Plants respond to a variety of external stimuli by utilizing hormones as controllers in a stimulus-response system. Directional responses of movement are known as tropisms and are positive when the movement is toward the stimulus and negative when it is away from the stimulus.
When a seed germinates, the growing stem turns upward toward the light, and the roots turn downward away from the light. Thus, the stem shows positive phototropism and negative geotropism, whar the roots show negative phototropism and positive geotropism. In this example, light and gravity are the stimuli, and directional growth is the response.
The controllers are certain hormones synthesized by cells in the tips of the plant stems. These hormones, known as auxinsdiffuse through the tissues beneath the stem tip and concentrate toward the shaded side, causing elongation of these cells and, thus, a bending of the tip toward the light.
The end result is the maintenance of the plant in an optimal condition with respect to light. In animalsin addition to chemical regulation via the endocrine systemthere is another integrative system bby the nervous system. A nervous system can be defined as an organized group of cells, called neurons, specialized for the conduction of an impulse—an excited state—from a sensory receptor through a nerve network to an effector, the site at which the response occurs.
Organisms that possess a nervous system are capable of much more complex behaviour than are organisms that do not. The nervous system, specialized for the conduction of impulses, allows rapid responses to environmental stimuli. Many responses mediated by what do you mean by nervous system nervous system are directed toward preserving the status quo, or homeostasisof the animal. Stimuli that tend to displace or disrupt some part of the organism call forth a response that results in reduction of the adverse effects and a return to a more normal condition.
Organisms with a nervous system are also capable of a second group of functions that initiate a variety of behaviour patterns. Animals may go through periods of exploratory or appetitive behaviour, nest building, and migration. Although these activities are beneficial to the survival of the species, they are not always performed by the individual in response to an individual need or stimulus.
Finally, learned behaviour can be superimposed on both the homeostatic and initiating functions of the nervous system. All living cells nedvous the property of irritability, or responsiveness to environmental stimuli, which can affect the cell in nsrvous ways, producing, how to make textures on paper by hand example, electrical, chemical, or mechanical how to make handmade dolls video. The responsiveness of a single cell can be illustrated by the behaviour of the relatively simple amoeba.
Unlike some other protozoans, an amoeba lacks highly developed structures that function in the reception of stimuli and in the production or conduction of a response. The amoeba behaves as though it had a nervous system, however, because the general responsiveness of its cytoplasm serves the functions of a nervous system. An excitation produced by a stimulus is conducted to other parts of bj cell and evokes whzt response by the animal. An amoeba will move to a region of a certain level of light.
It will be attracted by chemicals given off by foods and exhibit a feeding response. It will also withdraw from a region with noxious chemicals and exhibit an avoidance reaction upon contacting other objects.
Nervous system. Videos Images. Additional Info. Print print Print. Table Of Contents. While every effort has been made to follow citation style rules, there what do you mean by nervous system be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions. Facebook Twitter. Give Feedback External Websites. Let us know if you have suggestions to improve this article requires login.
External Websites. Articles from Britannica Encyclopedias for elementary and high school students. Thomas L. Author of Primitive Nervous Systems. See Article History. In a myelinated axon, the myelin sheath prevents the local current small black arrows from flowing across the membrane.
This forces the current to travel down the nerve fibre to the unmyelinated nodes of Ranvier, which have a high concentration of ion channels. Upon stimulation, these ion channels propagate the action potential large green arrows to the next node. Thus, the action potential jumps along the fibre as it is regenerated at each node, a process called saltatory conduction.
In an unmyelinated axon, jou action potential is propagated along the entire membrane, fading as it diffuses back through the membrane to the original depolarized region. Follow the electrical and chemical changes undergone to transmit an impulse through the human nervous system. The movement of impulses through the nerve cell, involving both chemical and biological changes.
Nervous systems of a flatworm Planaria and a grasshopper order Orthoptera. In primitive animals such as Hydraa marine organism related to jellyfish and sea anemones, the nervous system consists of a diffuse net of individual nerve cells and fibres. In the brain of mammals such as the cat, the olfactory bulb is still how to download effects for windows live movie maker, but the greatly expanded cerebrum has assumed the higher neural functions of correlation, association, and learning.
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The nervous system of vertebrates is a complex information-processing system that consists mainly of the brain, spinal cord, and peripheral and autonomic nerves. It receives chemical information from hormones in the circulating blood and can also regulate secretions of the endocrine system by the action of neurohormones. Jan 18, · Fibers called nerves carry important messages back and forth between your body and your brain. That network -- your nervous system -- has two parts: Your brainand spinal cord Author: Danny Bonvissuto. A nervous system can be defined as an organized group of cells, called neurons, specialized for the conduction of an impulse—an excited state—from a sensory receptor through a nerve network to an effector, the site at which the response occurs.
Your nervous system guides almost everything you do, think, say or feel. It controls complicated processes like movement, thought and memory. It also plays an essential role in the things your body does without thinking, such as breathing, blushing and blinking. This complex system is the command center for your body. A vast network of nerves sends electrical signals to and from other cells, glands, and muscles all over your body. These nerves receive information from the world around you.
Then the nerves interpret the information and control your response. The nervous system has two main parts. Each part contains billions of cells called neurons, or nerve cells. These special cells send and receive electrical signals through your body to tell it what to do. Your nervous system uses specialized cells called neurons to send signals, or messages, all over your body.
These electrical signals travel between your brain, skin, organs, glands and muscles. The messages help you move your limbs and feel sensations, such as 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. Different kinds of neurons send different signals. Motor neurons tell your muscles to move.
Sensory neurons take information from your senses and send signals to your brain. Other types of neurons control the things your body does automatically, like breathing, shivering, having a regular heartbeat and digesting food. Thousands of disorders and conditions can affect your nerves.
An injured nerve has trouble sending a message. Nerve injury can cause numbness, a pins-and-needles feeling or pain.
Your nervous system is the command center for your entire body. It needs care to keep working correctly. See your doctor regularly, eat a healthy diet, avoid drugs, and only drink alcohol in moderation.
The best way to avoid nerve damage from disease is to manage conditions that can injure your nerves, such as diabetes. Call your doctor right away if you have any sudden changes in your health, such as losing coordination or noticing severe muscle weakness. You should also see your doctor if you have:. Cleveland Clinic is a non-profit academic medical center.
Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Originating from your brain, it controls your movements, thoughts and automatic responses to the world around you. It also controls other body systems and processes, such as digestion, breathing and sexual development puberty. Diseases, accidents, toxins and the natural aging process can damage your nervous system.
Appointments What is the nervous system? Your nervous system affects every aspect of your health, including your: Thoughts, memory, learning, and feelings. Movements, such as balance and coordination. Senses, including how your brain interprets what you see, hear, taste, touch and feel. Sleep, healing and aging. Heartbeat and breathing patterns. Response to stressful situations. Digestion, as well as how hungry and thirsty you feel.
Body processes, such as puberty. What are the parts of the nervous system? Your brain uses your nerves to send messages to the rest of your body. Each nerve has a protective outer layer called myelin.
Myelin insulates the nerve and helps the messages get through. Peripheral nervous system : Your peripheral nervous system consists of many nerves that branch out from your CNS all over your body. This system relays information from your brain and spinal cord to your organs, arms, legs, fingers and toes.
Your peripheral nervous system contains your: Somatic nervous system , which guides your voluntary movements. Autonomic nervous system, which controls the activities you do without thinking about them. What does the nervous system do? What conditions and disorders affect the nervous system?
Nerve damage can happen in several ways. Some of the most common causes of nerve damage include: Disease: Many infections, cancers, and autoimmune diseases like diabetes , lupus and rheumatoid arthritis can cause nervous system problems.
Diabetes can lead to diabetic neuropathy, causing tingling and pain in the legs and feet. A condition called multiple sclerosis attacks the myelin around nerves in the CNS.
Without enough blood, part of the brain dies. A stroke can cause nerve damage ranging from mild to severe. Accidental injury: Nerves can be crushed, stretched, or cut in an accident. Car crashes and falls are common injuries that can damage nerves anywhere in the body.
Nerves can be pinched or trapped for many reasons, such as overuse as in carpal tunnel syndrome , a tumor, or structural problems like sciatica. Toxic substances: Chemotherapy medicines, illegal drugs, excessive alcohol and poisonous substances can cause peripheral neuropathy , or nerve damage. People with kidney disease are more likely to develop nerve damage because their kidneys have a hard time filtering out toxins.
You may feel weaker, and your reflexes may slow down. Some people lose sensation in their fingers, toes or other parts of the body. How common are these conditions? Some causes of nerve damage occur more frequently than others. They include: Diabetes: This disorder of the endocrine system causes nerve damage called diabetic neuropathy. Diabetic neuropathy usually affects the arms, legs, hands, feet, fingers and toes.
Lupus: About 1. Rheumatoid arthritis: People with rheumatoid arthritis can also develop neuropathy. Rheumatoid arthritis affects more than 1. Stroke: Around , Americans have a stroke every year.
Strokes occur more often in people over age How do I keep my nervous system healthy? When should I call my doctor? You should also see your doctor if you have: Vision problems or headaches. Slurred speech. Numbness, tingling, or loss of sensation in your arms or legs. Tremors or tics random muscle movements. Changes in behavior or memory. Problems with coordination or moving your muscles.