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ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION Chapter 3 © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learnin NOT FOR SALE OR DISTRI Introduction to the Structure and Function of the Nervous System © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION Structure and Function of the Nervous System makes possible complex activities, such as walking, running, playing a piano, and a computer, as well as simple ones & BartlettThe Learning, LLC is a complex regulatory© Jones using & Bartlett Learning, LLC activinervous system ties, such as maintaining muscle tone and system that, along with the endocrine system (see T FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION posture while at rest. Chapter 23), controls and coordinates activities • Monitoring and recognizing stimuli (and and functions throughout the body, internally information) within the environment, and and externally, by sending, receiving, and sortthen directing an appropriate response to ing electrical impulses. Disruption of any part of the stimuli. This function makes possible © Jones & Bartlett Learning, LLC © Jones & Bartlett Learnin the nervous system affects body function in some reflex actions, such as pulling away NOT FORone’s SALE OR DISTRI FOR SALE OR DISTRIBUTION way, either NOT internally or externally. hand from a hot surface, as well as perceivThe nervous system consists of the central ing music being played in the next room. nervous system, which includes the brain and • Monitoring and coordinating internal body spinal cord, and the peripheral nervous system, states so that internal organs function as a which includes nerve fibers extending from the © Jones & Bartlett Learning, LLC © Jones Bartlett(homeostaLearning, LLC unit, internal body&constancy brain and spinal cord that carry information NOT between FOR SALE OR DISTRIBUTION FORand SALE OR action DISTRIBUTION sis) isNOT maintained, protective is the central nervous system and the rest taken. For example, in response to a lack of of the body. The peripheral nervous system is furoxygen, more rapid breathing occurs; the ther divided into two parts: the afferent (sensory) body shivers in response to cold; and when system, which carries messages from other parts threat or danger is encountered, the heart the body to theLLC central nervous system, and the ones & Bartlettof Learning, © Jones beats & Bartlett Learning, LLC more rapidly. efferent (motor) system, which carries messages T FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION from the central nervous system to other parts of the body (see Table 3-1). Other functions, such as display of personality traits, language, speech, learning, remembering, feeling emotion, reasoning, and generating and relaying thoughts, are also controlled by the nerLLC vous system—specifically, by © theJones brain. & Bartlett Function of the Nervous System © Jones & Bartlett Learning, Functions of the nervous system include the following: NOT FOR SALE OR DISTRIBUTION Nerve Cells • Organizing and directing motor responses Learnin NOT FOR SALE OR DISTR Specialized cells called neurons are the functional units of the nervous system. Neurons transmit messages to and the brain. They © Jones & from Bartlett Learning, LLC consist of NOT a cell FOR body and processes (nerve SALE OR DISTRIBUTION of the voluntary muscle system, enabling the body to move more effectively as a whole and to achieve purposeful movement. © Jones & Bartlett Learning, LLC This coordination of voluntary muscles NOT FOR SALE OR DISTRIBUTION 31 ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION. © Jones & Bartlett Learning, LLC ones & Bartlett Learning, LLC 32 Chapter 3 • Introduction to the Structure and Function of the Nervous System NOT FOR SALE OR DISTRIBUTION T FOR SALE OR DISTRIBUTION process begins again (see Figure 3-1). After neurotransmitters are released, they are either taken up again by the neuron or destroyed. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learnin I. Central nervous system Longer axons are generally grouped in bunNOT FOR SALE OR DISTRI NOT FOR SALE OR DISTRIBUTION A. Brain dles. When they are transmitting impulses within the central nervous system, these bundles are B. Spinal cord referred to as tracts. Those bundles located outII. Peripheral nervous system side the central nervous system are referred to A. Afferent (sensory) as nerves. © Jones & Bartlett Learning, LLC Jones & Bartlett Learning, LLC Table 3-1 The Nervous System (Central and Peripheral) © B. Efferent (motor) NOT FOR SALE OR DISTRIBUTION 1. Somatic nervous system 2. Autonomic nervous system a. Sympathetic nervous system b. Parasympathetic nervous system ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION The Central Nervous System The central nervous system is made up of the brain and spinal cord. Bony coverings protect both the and the spinal cord.LLC On the inte© Jones & brain Bartlett Learning, rior of these bony coverings are three membranes NOT(meninges) FOR SALE OR DISTRIBUTION that provide additional protection: • The dura mater is the outer membrane, fibers) that extend beyond the cell body. In most lying closest to the bony covering of the cases, a single long nerve fiber called an axon brain and spinal cord. conducts nerve impulses&(and information) away © Jones Bartlett Learning, LLC• The arachnoid membrane © Jones & Bartlett Learnin is the middle from the cell body to other neurons. Smaller, NOT FOR SALE OR DISTRI NOT FOR SALE OR DISTRIBUTION membrane, a cobweb-appearing membrane. shorter nerve fibers called dendrites conduct • The pia mater is the inner membrane, which nerve impulses toward the cell body after receivlies closest to the brain and spinal cord. ing information from other neurons. Fibers that carry information from parts of the body to the Between each of the membrane layers are spaces. © Jones Learning, © Jones & Bartlett LLC brain & areBartlett called afferent neuronsLLC (sensory neuThe space between the dura mater andLearning, the inner NOT rons). FOR Fibers SALEthat ORcarry DISTRIBUTION FOR SALEis OR DISTRIBUTION information from the surface of NOT the bony covering the epidural brain to other parts of the body are called efferspace. T; the space between the dura mater and ent neurons (motor neurons). the arachnoid membrane is the subdural space; Surrounding neurons is a fatty sheath called and the space between the arachnoid membrane myelin, which, much like the covering of elecand the pia mater is the subarachnoid space. ones & Bartletttrical Learning, LLC insulation, ensuring that © Jones Bartlett Learning, LLC cords, provides The¢ral nervous system is also protected T FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION electrical impulses are able to flow smoothly and and cushioned by cerebrospinal fluid (CSF), reliably. Information is passed from neuron to which is formed by specialized capillaries called neuron by both electrical and chemical impulses. the choroids plexus in inner chambers within the The electrical impulse, which has been picked up brain called ventricles. The cerebrospinal fluid by the dendrites, is passed through the cell body bathes the brain and spinal cord, circulating from © Jones & Bartlett Learning, LLC © Jones & Bartlett Learnin to the axon. The electrical impulse then moves the ventricles into the subarachnoid space (see NOT FOR SALE OR DISTR NOT FOR SALE OR DISTRIBUTION down the full length of the axon until it reaches Figure 3-2). From the subarachnoid space it the its tip. At the tip of the axon are tiny processes, CSF flows to the back of the brain, down around which release chemicals known as neurotransthe spinal cord, and then back to the brain, mitters. Neurotransmitters, through chemical where it is reabsorbed into the blood through the means, transfer the impulse from one neuron arachnoid membrane. amounts ofLearning, cerebro© Jones & Bartlett Learning, LLC © JonesThe & Bartlett LLC to another across a space between the two neuspinal fluid produced and absorbed are equally NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION rons called the synapse. The electrical impulse, balanced, so that under normal conditions, the through the vehicle of neurotransmitters, then amount of CSF within the central nervous system moves to the next neuron’s dendrites and the remains constant. ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION. ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC Structure andSALE Function of the Nervous System 33 NOT FOR OR DISTRIBUTION Figure 3-1 Neurons © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION © Jones & Bartlett Learnin NOT FOR SALE OR DISTRI © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION Copyright Jane Tinkler Lamm. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learnin harmful substances, such as toxins, are prevented Another protective device is the blood–brain NOT FOR SALE OR DISTRI NOT FOR SALE OR DISTRIBUTION from crossing into the brain. barrier, a structural arrangement of capillaries The central nervous system is composed of that selectively determines which substances can white matter and gray matter. White matter move from the blood into the brain. While submakes up the inner part of the brain and the outer stances such as oxygen and glucose are necessary portion of the cord&and consists of myelinto brain survival and consequently move freely © Jones & Bartlett Learning, LLC © spinal Jones Bartlett Learning, LLC ated covered axons that conduct nerve impulses. across the blood–brain barrier, other potential NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Figure 3-2 Circulation of Cerebrospinal Fluid ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learnin NOT FOR SALE OR DISTR © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION Copyright Jane Tinkler Lamm. ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION. © Jones & Bartlett Learning, LLC ones & Bartlett Learning, LLC 34 Chapter 3 • Introduction to the Structure and Function of the Nervous System NOT FOR SALE OR DISTRIBUTION T FOR SALE OR DISTRIBUTION It is called white matter because of its whitish • The associational cortex is involved in cogappearance due to the myelin covering. Gray nitive functions such as memory, reasoning, matter makes up the thin outer layer of the brain © Jones & Bartlett Learning, LLC abstract thinking, and consciousness. © Jones & Bartlett Learnin and the inner portion of the spinal cord. Small FORcalled SALE OR DISTRI NOT FOR SALE OR DISTRIBUTION The cerebrum is divided into NOT two halves, segments of gray matter are also embedded deep the right hemisphere and the left hemisphere. within certain parts of the white matter of the These two hemispheres communicate with each brain. Gray matter consists of groups of neuron other. Dividing the hemispheres and connecting cell bodies; it gets its name from . It is called gray specific areas of the two hemispheres are bundles matter&because of itsLearning, grayish appearance. © Jones Bartlett LLC Gray © Jones & Bartlett Learning, LLC of nerve fibers called the corpus callosum. Each matter of the brain receives, sorts, and processes NOT FOR SALE OR DISTRIBUTION FORfor SALE ORinformaDISTRIBUTION hemisphereNOT has centers receiving nerve messages, while gray matter of the spinal tion and for initiating responses. The left hemicord serves as a center for reflex action (automatic sphere mostly receives information from and response to stimuli). sends information to the right side of the body, whereas right hemisphere mostly ones & Bartlett Learning, LLC © Jones & the Bartlett Learning, LLCreceives from and sends information to the Structure and Function of T FOR SALE OR DISTRIBUTION NOTinformation FOR SALE OR DISTRIBUTION left side of the body. the Brain Deep within the cerebral hemispheres are The brain is directly connected to the spinal cord groups of gray matter called basal ganglia, which and serves as the primary center for the integraare part of the extrapyramidal system. (“Extrapytion, coordination, initiation, and interpretation ramidal” denotes nerve fiber tracts that lie outside © Jones & Bartlett Learning, LLC © Jones & Bartlett Learnin of most nerve messages. It regulates and monithe pyramidal tract, a relatively compact group of NOT FOR SALE OR DISTRI NOT FORbody SALE OR DISTRIBUTION tors many unconscious functions, such as nerve fibers that originate from cells in the outer heart and respiratory rate, and coordinates most layer of the brain.) Extrapyramidal function is voluntary movements. In addition, it is the site concerned with postural adjustment and gross of higher cognitive processes such as learning, voluntary and automatic muscular movements. generating and relaying thoughts, reasoning, © Jones & Bartlett Learning, LLC © Jones &maintain Bartlett Learning, LLC The basal ganglia help to tone in musjudgment, memory, consciousness, and emotion. NOT FOR SALE OR DISTRIBUTION NOTand FOR SALE enabling OR DISTRIBUTION cles in the trunk extremities, indiThe brain also has a sensory function, which is viduals to maintain balance and posture and to responsible for vision, hearing, touch, taste, and engage in movements such as walking. The basal smell. Language function, including the ability ganglia also play a role in enabling individuals to to communicate and to comprehend, is also conreact swiftly, appropriately, and automatically to by the brain as well. Finally, the brain conones & Bartletttrolled Learning, LLC © Jones Bartlett Learning, LLC such stimuli&that demand an immediate response, trolsDISTRIBUTION basic behavior patterns and the display of T FOR SALE OR NOTasFOR SALE OR DISTRIBUTION after tripping, enabling the individual to adjust general personality traits, which are characterishis or her movement to avoid a fall. tic of how each individual responds to stimuli. Each hemisphere of the cerebrum is divided The brain is protected by the bony covering of into lobes that contain areas related to specific the skull (cranium or cranial bones). The largest functions (see Figure 3-3). The frontal lobe is © Jones & Bartlett Learning, LLC © Jones & Bartlett Learnin part of the brain, the cerebrum, is covered with a located in the front of each hemisphere and conthin outer layer of FOR gray matter called cortex, NOT FOR SALE OR DISTR NOT SALE ORtheDISTRIBUTION tains motor areas that initiate voluntary movewhich contains billions of nerve cells. The cortex ment and skilled movements, such as those, has three specialized areas, which serve three involved in handwriting. Other areas in the fronmajor areas of function: tal lobe control higher intellectual functions such • The motor cortex coordinates voluntary as foresight,©analytical and Learning, judgment. © Jones & Bartlett Learning, LLC Jones thinking, & Bartlett LLC movements of the body. The parietal lobe is located in the middle of NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION • The sensory cortex is responsible for the each hemisphere and is primarily the sensory recognition or perception of sensory stimarea, integrating and interpreting sensation such uli, such as touch, pain, smell, taste, vision, as touch, pressure, pain, and temperature. Some and hearing. memory functions are also located in the parietal ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION. ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC Structure and Function of the Brain 35 NOT FOR SALE OR DISTRIBUTION Figure 3-3 Areas of Brain Function © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION Copyright Jane Tinkler Lamm. © Jones & Bartlett Learnin NOT FOR SALE OR DISTRI © Jones & Bartlett Learnin NOT FOR SALE OR DISTRI lobe, especially those responsible for storage of articulation. This area contributes to expressive sensory memory. The temporal lobe is located function (speech formation), or the ability to inteunder the frontal and parietal lobes and is prigrate and coordinate words so that the meaning © Jones Bartlett for Learning, LLC of and © Jones & Bartlett Learning, LLC marily&responsible the interpretation can be comprehended. NOT distinction FOR SALE ORauditory DISTRIBUTION NOT FOR SALE ORlies DISTRIBUTION between stimuli. The occipiA structure known as the thalamus within tal lobe is located at the back or posterior porthe center of the brain. The thalamus acts as a tion of each hemisphere; i. It is the primary area relay station that sorts, interprets, and directs for reception and interpretation of visual stimuli. sensory information. Below the thalamus is the Several parts of the cerebrum are involved hypothalamus, which coordinates neural and ones & Bartlettin Learning, LLC © Jones & Bartlett Learning, LLC the language function, which consists of the endocrine activities. It This structure helps reguT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION process of receiving, interpreting, and integratlate the body’s internal environment and behaving visual and auditory stimuli as well as the iors that are important to survival, such as eating, ability to express thoughts in a coordinated way drinking, and reproduction. Below the hypothalaso that others can comprehend them. Language mus is the pituitary gland, an endocrine gland that function is located in the left hemisphere of the will be discussed in more detail in a later chapter. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learnin cerebrum in most individuals, whether they are The limbic system is comprises a group of SALE OR DISTR NOT FOR SALE OR DISTRIBUTION right- or left-handed. An area located over the structures consisting of bothNOT gray FOR and white temporal and parietal lobes, called Wernicke’s matter that surround the thalamus. The limbic area, is the major area responsible for receptive system plays a role in expression of instincts, function (speech understanding), or the ability to drives, and emotions and as in the formation of integrate visual and auditory information so as memories. A of gray called the hip© Jones & Bartlett Learning, LLC ©band Jones & matter Bartlett Learning, LLC to understand communication received. An area pocampus is involved in learning and long-term NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION located in front of the temporal lobe and in the memory, helping to determine where important frontal cortex, called Broca’s area, is responsible and relevant aspects of facts will be stored. for speaking ability and is closely associated with Beneath the occipital lobe of the cerebrum is motor areas that control the muscles needed for a structure called the cerebellum. The cerebellum ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION. © Jones & Bartlett Learning, LLC ones & Bartlett Learning, LLC 36 Chapter 3 • Introduction to the Structure and Function of the Nervous System NOT FOR SALE OR DISTRIBUTION T FOR SALE OR DISTRIBUTION is primarily responsible for the coordination and fused (joined) bone. At the tip of the sacrum is integration of voluntary movement and for the the coccyx, or tailbone (see Figure 3-4). maintenance of equilibrium, posture, and balance © Jones & Bartlett Learning, LLCThe spinal cord conducts©impulses Jones to & and Bartlett Learnin of the body. It also regulates and coordinates fine from the brain. The outer white matter of the NOT FOR SALE OR DISTRI NOT FOR SALE OR DISTRIBUTION movements of the extremities, which are initiated spinal cord, which consists of bundles or tracts of by the frontal lobe. myelinated fibers of sensory (afferent) and motor The brain stem, which is located beneath (efferent) neurons, conveys electrical impulses up the cerebellum at the base of the brain just above and down the spinal cord between the peripheral the spinal cord, actsLearning, as a relay station, nervous system (those nerves lying outside the © Jones & Bartlett LLCtransmit© Jones & Bartlett Learning, LLC ting nerve impulses between the spinal cord and central nervous system) and the brain. In most NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION the brain. It is the primary center of involuntary instances, sensory information traveling up the functions. Control of vital organ functions, such right side of the spinal cord crosses over to the as regulation of heartbeat or respiration, occurs in left side of the brain, so the left hemisphere of the brain would, for example, interpret pain in the brain stem. Areas in the brain stem also reguones & BartlettlateLearning, © Jones & hand. Bartlett Learning, LLC origithe diameterLLC of blood vessels, contributing to the right Conversely, motor impulses T FOR SALE OR DISTRIBUTION NOTnating FORinSALE the control of blood pressure. Reflex actions, such the leftOR brainDISTRIBUTION cross to the right side of as coughing and swallowing, are controlled in the the spinal cord and initiate a response to the right brain stem as well. Finally, the brain stem conside of the body. Because of this crossover effect, tains scattered groups of cells, called the reticudamage on one side of the brain typically causes lar formation, which are involved in the initiation manifestations itself on the opposite side of the © Jones & Bartlett Learning, LLC © Jones & Bartlett Learnin and maintenance of wakefulness and alertness. body. NOT FOR SALE OR DISTRI NOT FOR SALE The brain requires both oxygenOR and DISTRIBUTION nourishment in the form of glucose in order to function Figure 3-4 The Spine and to survive. Oxygen and glucose are transported to the brain by blood carried by four major arteries: two carotidLearning, arteries and LLC two vertebral © Jones & Bartlett © Jones & Bartlett Learning, LLC arteries. The vertebral arteries join to form the NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION basilar artery. The carotid and basilar arteries then connect at the base of the brain to form the circle of Willis, from which cerebral arteries branch out to carry blood to the rest of the brain. ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION Structure and Function © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION of the Spinal Cord and Peripheral Nervous System The Spinal Cord Jones LLC © Jones & Bartlett Learnin The spinal © cord is part&ofBartlett the centralLearning, nervous system andNOT extends fromSALE the brain stem to the NOT FOR SALE OR DISTR FOR OR DISTRIBUTION lower part of the back. Bony coverings called vertebrae surround the spinal cord and protect it. Taken as a whole, this bony covering, as a whole, forms the vertebral column. The vertebral © Jones & consists Bartlett LLC located © Jones & Bartlett Learning, LLC column of 7Learning, cervical vertebrae, NOT in FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION the neck area; 12 thoracic vertebrae, located in the upper and middle back; and 5 lumbar vertebrae, located in the lower back. The sacrum, Copyright Jane Tinkler Lamm. located below the lumbar vertebrae, consists of ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION. © Jones & Bartlett Learning, LLC ones & Bartlett Learning, LLC Structure and Function of theNOT SpinalFOR Cord SALE and Peripheral Nervous System 37 OR DISTRIBUTION T FOR SALE OR DISTRIBUTION The inner gray matter of the spinal cord, Many types of neurons work together to transwhich is composed of cell bodies and unmymit impulses through the spinal cord. Sensory elinated neurons, acts as coordinating center LLC impulses entering the spinal cord at the lumbar © Jones & aBartlett Learning, © Jones & Bartlett Learnin for reflex and other activities, such as voluntary region are relayed vertically to the brain through NOT FOR SALE OR DISTRI NOT FOR SALE OR DISTRIBUTION movements and control of internal functions. A a number of connecting sensory neurons. Motor reflex center in the gray matter of the spinal cord impulses from the brain to the peripheral nerves, is where sensory and motor neurons connect; this however, are conducted through two separate catpart of the spinal cord serves as a center for spinal egories of motor neurons. Upper motor neurons reflexes. reflex canLearning, be defined asLLC an automatic originate in © theJones brain and contained entirely © Jones &A Bartlett &are Bartlett Learning, LLC response to a given stimulus. Spinal reflexes conwithin the central nervous system. Lower motor NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION trol not only muscle reflexes, but also the reflexes neurons, although originating in the central nerof internal organs. vous system, have fibers extending to the periphThe gray matter within the spinal cord resemeral nerves in voluntary muscles. Alteration of bles the letter “H.” The projections of the H are function of either upper or lower motor neurons ones & Bartlettnamed Learning, © Jones & Bartlett accordingLLC to the direction to which they can generally affect Learning, the voluntary LLC muscles. The T FOR SALE OR DISTRIBUTION NOTlocation FOR SALE OR DISTRIBUTION project. The posterior horns extend toward the of the alteration of function determines back, and the anterior horns project toward the nature of the manifestations. the front. Cerebrospinal fluid, which nourishes Structure and Function of the Peripheral and protects the spinal cord, fills both the cenNervous System tral canal, located within the center of the gray © Jones & Bartlett Learning, LLC © Jones & Bartlett Learnin A nerve is a bundle of fibers outside the cenmatter, and the subarachnoid space surrounding NOT information FOR SALE OR DISTRI NOTofFOR SALE tral nervous system that transmits the outer portion the spinal cord.OR DISTRIBUTION between the central nervous system and variMotor (efferent) impulses originate in the ous parts of the body. The peripheral nervous motor cortex of the brain, extend down the spinal system consists of all nerves that extend from cord through descending tracts, and exit through the brain and cord.&ToBartlett function effectively, motor spinal nerve roots that extend through © Jones & Bartlett Learning, LLC ©spinal Jones Learning, LLC the peripheral nerves must be connected to the openings between the vertebrae that surround the NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION central nervous system. Some peripheral nerves spinal cord. Sensory (afferent) impulses from the connect directly to the brain (cranial nerves); body enter the spinal cord through spinal nerve others connect directly to the spinal cord (spinal roots that also extend through openings between nerves). Cranial and spinal nerves are essential vertebrae and then travel up ascending tracts in links between the restLearning, of the body and the central the spinal cord to the brain. ones & Bartlett Learning, LLC © Jones & Bartlett LLC nervous system. Spinal nerve roots are named for the verteT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION The 12 pairs of peripheral nerves that conbral level from which they exit. For example, the nect and transmit messages directly to the brain nerve roots that leave the spinal cord at the cerviare called cranial nerves. Some cranial nerves cal level are labeled C1 through C8, and the nerve contain only sensory fibers, whereas others conroots that leave at the thoracic level are labeled Jones & Bartlett Learning, LLC © Jones & Bartlett Learnin tain both sensory and motor fibers. Cranial nerves T1 through© T12 (see Figure 3-5). The sensory mediate many aspects of sensation muscular (afferent) nerve outside theDISTRIBUTION central NOTand FOR SALE OR DISTR NOTfibers FORfrom SALE OR activity in and around the head and neck. Cranial nervous system carry body sensations into the nerves and their related functions are described sensory nerve roots (posterior roots) at the back in Table 3-2). of the spinal cord, where they are then carried The 31 pairs of peripheral nerves that conup the spinal cord to the brain. Motor (efferent) © Jones & Bartlett Learning, LLC © Jones & Bartlett LLC nect and transmit messages directly to Learning, the spinal impulses travel from the brain down the spinal NOT cord FORand SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION cord are called spinal nerves. Each nerve divides exit from motor nerve roots (anterior and then subdivides into a number of branches. roots) at the front of the spinal cord. Motor nerve Nerves at each level travel to specific parts of fibers then carry impulses to the voluntary musthe body, conveying information between those cles of the body. ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION. © Jones & Bartlett Learning, LLC ones & Bartlett Learning, LLC 38 Chapter 3 • Introduction to the Structure and Function of the Nervous System NOT FOR SALE OR DISTRIBUTION T FOR SALE OR DISTRIBUTION Figure 3-5 Spinal Nerves © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION © Jones & Bartlett Learnin NOT FOR SALE OR DISTRI © Jones & Bartlett Learnin NOT FOR SALE OR DISTRI © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION areas and the central nervous system. Spinal The autonomic nervous system integrates the © Jones & Bartlett Learning, LLC © Jones & Bartlett Learnin nerves and NOT their related functions are described work of vital organs, such as the heart and lungs. NOT FOR SALE OR DISTR FOR SALE OR DISTRIBUTION in Figure 3-5. Its primary function is to coordinate the activity Nerves control both voluntary and involunof internal organs so that they can make adaptary functions in the body. Nerves that control tive responses to changing external situations, voluntary functions (such as movement of the thereby maintaining internal equilibrium. Nerve © Jones & Bartlett Learning, LLC somatic fibers monitor © Jones & Bartlett Learning, LLC muscles in the extremities) are called the activities of internal organs Nerves that concerned with the conas well as changes in the SALE external OR environment. NOT nerves. FOR SALE ORare DISTRIBUTION NOT FOR DISTRIBUTION trol of involuntary functions are part of a subcatWhen changes are necessary to maintain interegory of the peripheral nervous system called the nal homeostasis (equilibrium) or to protect the autonomic nervous system. body, the autonomic nervous system stimulates ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION. © Jones & Bartlett Learning, LLC Bibliography 39 NOT FOR SALE OR DISTRIBUTION ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION Table 3-2 Cranial Nerves and Related Functions © Jones Cranial Nerve I. & Bartlett LLC Area of Learning, Function NOT FOR SALE OR DISTRIBUTION Smell Olfactory © Jones & Bartlett Learnin NOT FOR SALE OR DISTRI II. Optic Vision III. Oculomotor Movement of eye muscles IV. Trochlear Eyelids VII. Facial Taste, sensation of external ear, control of salivary glands, tears, muscles in facial expression VIII. Vestibulocochlear Sensation of sound, balance, orientation of head © Jones Bartlett Learning, LLCin head, face, and teeth, motor © activity Jonesof & Bartlett Learning, LLC V. & Trigeminal Sensation chewing NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION VI. Abducens Pupil dilation, focusing of lens ones & Bartlett IX. Learning, LLC Glossopharyngeal T FOR SALE OR X.DISTRIBUTION Vagus © Jones & Bartlett LLC Swallowing, sensation of pain, taste, touch fromLearning, tongue and throat NOT FOR SALErespiratory OR DISTRIBUTION Heartbeat, digestion, speech, swallowing, function, gland functions XI. Accessory Movement of head and shoulders, muscles of pharynx and larynx in throat, production of voice sounds XII. Hypoglossal Tongue movement, speech, swallowing © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION an immediate, involuntary response. For example, in response to a speck of dust in the eye, tears are produced; i. In response to a fearful situation, the heart beats faster. © JonesThe & autonomic Bartlettnervous Learning, LLC system is divided into NOT two FOR SALE OR DISTRIBUTION subsystems: • The sympathetic nervous system • The parasympathetic nervous system © Jones & Bartlett Learnin NOT FOR SALE OR DISTRI In contrast, the parasympathetic nervous system dominates when the body is a rest. It activates those mechanisms that focus on body conservation, such as decreasing the heart rate © Jones & Bartlett Learning, LLC and constricting the pupils of the eye. The paraFOR SALE DISTRIBUTION sympatheticNOT nervous system is alsoOR an important component of sexual arousal in both males and females. two systems work both together and in ones & BartlettThese Learning, LLC © Jones & Bartlett Learning, LLC Bibliography opposition to control internal organs and reguT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION late their function. Hormones and emotions can Falvo, R. E. (2001). Human physiology physiology 201 core curriculum. Champaign, IL: Stipes Publishing L.L.C. affect both systems. Sherwood, L. (2007). Human physiology: From cells to sysThe sympathetic nervous system becomes tems (6th ed.). Australia:. Thomson Brooks/Cole. active during periods of stress and in emergenTortora, G. J., & Derrickson, B. H. (Eds.). (2011).(13th ed) cies. It prepares the body action, deepening © Jones & for Bartlett Learning, LLC © Jones & Bartlett Learnin Principles of anatomy and physiology (13th ed.). Hoborespirations,NOT making the heart beat faster, dilating FOR SALE OR DISTRIBUTION ken, NJ:. John Wiley and Sons. NOT FOR SALE OR DISTR the pupils, stimulating production of stress horWidmaier, E., Raff, H., & Strang, K. (Eds.). (2010). Vander’s mones, and increasing blood supply to the large human physiology: The mechanisms of body function. muscles of the body. New York: McGraw-Hill. © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION ones & Bartlett Learning, LLC T FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. 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