The Nervous System 1
1What You Will Learncentral nervous system proc Theesses and responds to all messages coming from the peripheral nervoussystem.The somatic nervous system controls voluntary movements. Theautonomic nervous system controlsfunctions that are involuntary.The brain is made of many partsthat function together as the controlcenter of the nervous system.Why It MattersWithout a nervous system, you wouldnot be able to sense or respond toyour environment.Vocabulary central nervous systemperipheral nervous systemneuronnervebrainClarifying Concepts Take turnsreading this section out loud with apartner. Stop to discuss ideas thatseem confusing.The Nervous SystemKey Concept Your nervous system is an organ system thatgathers, interprets, and responds to sensory information.What is one thing that you have done today that did NOTinvolve your nervous system? This is a trick question! In fact,your nervous system controls almost everything that you do.Two Systems Within a SystemThe nervous system acts as the body’s central commandpost. It has two basic functions. First, it gathers and interpretsinformation. This information comes from inside your bodyand from the world outside your body. Then, the nervoussystem responds to that information as needed.The nervous system has two parts: the central nervous systemand the peripheral nervous system. The central nervous system(CNS) is the brain and spinal cord. The CNS processes andresponds to all messages coming from the peripheral nervoussystem. The peripheral nervous system (PNS) includes all of theparts of the nervous system except for the brain and the spinalcord. The PNS connects all parts of the body to the CNS. ThePNS uses specialized structures called nerves to carry informationbetween your body and your CNS. Figure 1 shows the majordivisions of the nervous system.Describe the difference between the function ofthe CNS and the function of the PNS.7.5.aFigure 1 The CNS (in orange)acts as the control center for yourbody. The PNS (in purple) carriesinformation to and from theCNS. How do these parts of thenervous system work together?7.5.a Students know plants and animals have levelsof organization for structure and function, includingcells, tissues, organs, organ systems, and the wholeorganism.7.5.b Students know organ systems functionbecause of the contributions of individual organs,tissues, and cells. The failure of any part can affectthe entire system.526Chapter 17
NucleusCell bodyAxonterminalFigure 2 Neurons are specializednerve cells that transfer electricalmessages throughout the body.ls eAxonDendriteD ir e c ti o nimofpuThe Peripheral Nervous SystemMessages about your environment travel through the nervous system along neurons. A neuron is a nerve cell that isspecialized to transfer messages in the form of fast-movingelectrical energy. These electrical messages are called impulses.Impulses may travel as fast as 150 m/s or as slow as 0.2 m/s.Figure 2 shows a typical neuron transferring an impulse.Neuron StructureIn many ways, a neuron is similar to other cells. A neuron has a large region called the cell body. The cell body hasa nucleus and cell organelles. But neurons also have specialstructures called dendrites and axons. Dendrites are usually short,branched extensions of the cell. A neuron receives information from other cells through its dendrites. A neuron mayhave many dendrites, which allows it to receive impulses fromthousands of other cells.Impulses are carried away from the cell body by axons.Axons are elongated extensions of a neuron. They can be veryshort or quite long. Some long axons extend almost 1 m fromyour lower back to your toes. The end of an axon often hasbranches that allow information to pass to other cells. The tipof each branch is called an axon terminal.central nervous system(SEN trahl NUHR vuhs SIS tuhm) thebrain and the spinal cordperipheral nervous system(puh RIF uhr uhl NUHR vuhs SIS tuhm)all of the parts of the nervous systemexcept for the brain and the spinalcordWordwise The root peri- means“around” or “near.” The root phermeans “to bear” or “to go.”neuron (NOO RAHN) a nerve cell thatis specialized to receive and conductelectrical impulsesIn your own words, describe the structure of aneuron.7.5.aSection 1The Nervous System527
Sensory Neurons: Collecting InformationRemember that neurons are a type of nerve cell that carries impulses. Some neurons are sensory neurons. These neurons gather information about what is happening in andaround your body. They have specialized nerve endings calledreceptors. Receptors detect changes inside and outside the body.For example, receptors in your eyes detect light. Sensory neurons then send this information to the CNS for processing.Motor Neurons: Delivering Ordersnerve (NUHRV) a collection of nervefibers through which impulses travelbetween the central nervous systemand other parts of the bodyNeurons that send impulses from the brain and spinal cordto other systems are called motor neurons. When muscles getimpulses from motor neurons, the muscles respond by contracting. For example, motor neurons cause muscles around youreyes to contract when you are in bright light. These musclesmake you squint so that less light enters your eyes. Motorneurons also send messages to glands, such as sweat glands.These messages tell sweat glands when to make sweat.NervesThe central nervous system is connected to the rest ofyour body by nerves. A nerve is a collection of axons bundledtogether with blood vessels and connective tissue. Nerves arefound everywhere in your PNS. Most nerves have axons ofboth sensory neurons and motor neurons. Axons are parts ofnerves, but nerves are more than simply axons. Figure 3 showsthe structure of a nerve. The axon in this nerve transmitsinformation from the spinal cord to muscle fibers.Spinal cordWhat would happen if your nerves veFigure 3 A message from the brain travels downthe spinal cord and then along the axon of amotor neuron inside a nerve to the muscle. Themessage makes the muscle contract.528Chapter 17Communication and Control
Somatic and AutonomicNervous SystemsRemember, the peripheral nervous system (PNS) connectsthe central nervous system (CNS) to the rest of the body. Andthe PNS includes two main kinds of neurons: sensory neuronsand motor neurons. You know that sensory neurons collectinformation from your senses and send that information tothe CNS. You also know that motor neurons carry out theCNS’s responses to that sensory information. The PNS has twotypes of motor neurons to carry out these responses: somaticneurons and autonomic neurons.Somatic Nervous SystemMost of the neurons that are part of the somatic nervous systemare under your conscious control. These neurons stimulateskeletal muscles. So, the neurons control voluntary movements,such as writing, talking, smiling, or jumping.Time to TravelTo calculate how long animpulse takes to travel acertain distance, you can usethe following equation:time distancespeedIf an impulse travels 100 m/s,about how long will it takethe impulse to travel 10 m?Record your work in yourScience Journal.Autonomic Nervous SystemAutonomic neurons do not need your conscious control.These neurons are part of the autonomic nervous system. Theautonomic nervous system controls body functions that you donot think about, such as digestion and heart rate (the numberof times that your heart beats per minute).The main job of the autonomic nervous system is tokeep all of the body’s functions in balance. Depending onthe situation, the autonomic nervous system can speedup or slow down these functions. The autonomic nervoussystem has two divisions: the sympathetic nervous system andthe parasympathetic nervous system. These two divisions worktogether to maintain a stable internal state, called homeostasis.Table 1 shows some effects of these divi SmellCerebellumBreathingHeartrateMedullaSection 1The Nervous System531
The Spinal CordSpinal cordVertebraMotorinformationSensoryinformationYour spinal cord, which is part of your central nervous system, is about as big around as your thumb. The spinal cord ismade of neurons and bundles of axons that pass impulses toand from the brain. As shown in Figure 7, the spinal cord is surrounded by protective bones called vertebrae (VUHR tuh BRAY).The axons in your spinal cord allow your brain to communicate with your PNS. The axons of sensory neurons in yourskin and muscles carry impulses to your spinal cord. The spinalcord relays these impulses to your brain. The brain interpretsthese impulses as pain, temperature, or other sensations. Then,the brain responds to the situation. Impulses moving from thebrain down the spinal cord are relayed to motor neurons. Theaxons of motor neurons carry the impulses to muscles andglands all over your body.Describe the path of an impulse from the skinto the brain and the path of the response.7.5.aSpinal Cord InjuryFigure 7 The spinal cord carriesinformation to and from the brain.Vertebrae protect the spinal cord.A spinal cord injury may block all information to and fromthe brain. Sensory information coming from below the injurymay not get to the brain. For example, a spinal cord injurymay block all sensory impulses from the feet and legs. Peoplewho have such an injury can not sense pain, touch, or temperature with their feet. And motor commands from the brainto the injured area may not reach the peripheral nerves. So,the person may not be able to move his or her legs.Each year, thousands of people are paralyzed by spinal cordinjuries. Among young people, spinal cord injuries are sometimes related to sports or other activities. These injuries maybe prevented by wearing proper safety equipment.Quick LabBuilding a Neuron1. Your teacher will provide at least four colorsof modeling clay. Build a model of a neuronby using various colors of clay for the variousparts of the neuron.2. Use tape to attach your model to a piece ofplain white paper.3. On the paper, label each part of the neuron.Draw an arrow from the label to the part.7.5.a7.7.d4. Use a colored pencil, marker, or crayon todraw arrows showing the path of an impulsetraveling in your neuron. Tell whether theimpulse is a sensory impulse or a motorimpulse. Then, describe what will happenwhen the impulse reaches its destination.20 min532Chapter 17Communication and Control
Review6 Evaluating Explain how a severe injury to the7.5.a, 7.5.bSummarycentral nervous system (CNS) is the brain Theand the spinal cord.peripheral nervous system (PNS) is all of Thethe parts of the nervous system except for thebrain and spinal cord.in the peripheral nervous system are Nervesbundles of axons, blood vessels, and connectivetissue.neurons have receptors that detect Sensoryinformation about the body and its environment.Motor neurons carry messages from the brainand spinal cord to other parts of the body.spinal cord can affect other parts of the body.7 Applying Concepts Some medications slow aperson’s nervous system. These drugs are oftenlabeled “May cause drowsiness.” Explain why aperson needs to know about this side effect.8 Predicting Consequences Explain how yourlife would change if your autonomic nervoussystem suddenly stopped working.9 Making Inferences Briefly explain why thenervous system is made up of many smallerparts that have specialized functions.INTERPRETING GRAPHICS Use the figure belowto answer the next two questions.PNS has two types of motor neurons: Thesomatic neurons and autonomic neurons.cerebrum is the largest part of the brain Theand controls thinking, sensing, and voluntarymovement.cerebellum is the part of the brain that Thekeeps track of the body’s position and thathelps maintain balance. The medulla controls involuntary processes,such as breathing and the regulation of heartrate, blood pressure, and body temperature.0 Identifying Relationships Which hemisphereof the brain recognizes and processes words,numbers, and letters? faces, places, and objects?q Analyzing Processes For a person whose lefthemisphere is primarily in control, would it beeasier to learn to play a new computer game byreading the rules and following instructions or bywatching a friend play and imitating his actions?1 Write an original definition for neuron and nerve.2 Use brain and peripheral nervous system inthe same sentence.3 Describing What is one function of each of thethree main parts of the brain?w Analyzing Relationships The nervous systemis one of eleven systems of the human body.Describe how the other body systems dependon the nervous system to function. How doesthe nervous system depend on the otherbody systems?4 Comparing How are the somatic nervoussystem and the autonomic nervous systemrelated?5 Analyzing What is the relationship betweenthe peripheral nervous system and the centralnervous system?Internet ResourcesFor a variety of links related to thischapter, go to www.scilinks.orgTopic: Nervous SystemSciLinks code: HY71023533
The main job of the autonomic nervous system is to keep all of the body’s functions in balance. Depending on the situation, the autonomic nervous system can speed up or slow down these functions. The autonomic nervous system has two divisions: thesympathetic nervous system and the parasympathetic nervous s
I. Central Nervous System vs Peripheral Nervous System II. Peripheral Nervous System A. Somatic Nervous System B. Autonomic Nervous System III. Autonomic Nervous System A. Parasympathetic Nervous System B. Sympathetic Nervous System IV. Reflex Actions V. Central Nervous Sys
May 02, 2018 · D. Program Evaluation ͟The organization has provided a description of the framework for how each program will be evaluated. The framework should include all the elements below: ͟The evaluation methods are cost-effective for the organization ͟Quantitative and qualitative data is being collected (at Basics tier, data collection must have begun)
Silat is a combative art of self-defense and survival rooted from Matay archipelago. It was traced at thé early of Langkasuka Kingdom (2nd century CE) till thé reign of Melaka (Malaysia) Sultanate era (13th century). Silat has now evolved to become part of social culture and tradition with thé appearance of a fine physical and spiritual .
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peripheral nervous system is subdivided into the a. sensory-somatic nervous system and the autonomic nervous system (ANS). The peripheral nervous system carry information to and from the central nervous system. The central nervous system is composed of the brain and spinal cord. Figure 1 The Human Nervous System
nervous system is separated into two major divisions: the central nervous system and the peripheral nervous system. The central nervous system is the control center of the body. The functions of the central nervous system are similar to those of the central processing unit of a computer. The central nervous system relays messages, processes .
