Upon completion of this chapter the participant will be able to:

Transcription

1 Chapter 7 The Nervous System Chapter Objectives Upon completion of this chapter the participant will be able to: 1. Name the divisions of the nervous system. 2. Describe the major functions of the nervous system. 3. Discuss the function of the nerve cell. 4. Label a diagram of the nerve cell and the brain. 5. Discuss the function of the various divisions of the brain. 6. List the protective coverings of the brain. 7. Discuss the function of the spinal cord. 8. Analyze, define, spell and pronounce the common terms associated with the nervous system. 9. Successfully complete the exercises at the end of the chapter. The nervous system allows the body to adjust to the requirements of both the inside and outside of our bodies. As soon as a change in either environment is detected the brain is notified and it decides what would be the appropriate response and then brings about that change. This may sound simple but in actual fact it is a very complex process. The nervous system is more complex than the most sophisticated computer. Anatomy and Physiology of the Nervous System Nerves The nervous system is made up of nervous tissue that consists of bundles of fibers that carry impulses throughout the body. The root word for nerve is neur/i or neur/o. There are two different types of nerve cells that are found in the nervous system: neurons: carry nerve impulses back and forth through the body neuroglia: found between the neurons and act as a protection for the neuron. Neuron Neurons are made up of three main parts, each with a very distinct role. These parts are: Cell Body: Contains all the structures that maintain the cell. Dendrites: Root like structures that receive impulses and conduct them toward the cell body. The root for dendrites is dendr/o. Revised September

2 Axon: Extends away from the cell body and conducts the impulse away from the nerve body. Some axons are protected by a white fatty substance called myelin. The root for axon is axo/. Nucleus Axon Dendrite Cell body Myelin bead Myelin sheath Direction of Impulse Flow The nervous system is divided into three major structures: Central Nervous System: Consists of the brain and spinal cord which is protected by fluid and a series of membranes. Protection from trauma in the environment is obtained by the skull and the bones of the vertebrae. The brain is the information processing area and the spinal cord is the body s information super-highway. Peripheral Nervous System: Consists of cranial nerves which extend from the brain, and spinal nerves which come from the spinal cord. Autonomic Nervous System: Consists of ganglia on either side of the spinal cord. Nerves of the autonomic nervous system control involuntary actions of the body which we are not able to control; e.g. heart rate, breathing. Revised September

3 Impulse Transmission In order for the nervous system to carry on its many functions there must be transmission of messages back and forth from one part of the body to another. The nerves allow for this and the process occurs smoothly with the help of neurotransmitters. Neurotransmitters are chemical substances that make it possible for the impulse to jump from one nerve cell to another. We know of at least 40 neurotransmitters in the body, each with a very specific function. The space between the nerve cells is referred to as the synapse. An impulse will travel down a neuron to a synapse and then a neurotransmitter is released that allows the impulse to jump to the next neuron. Central Nervous System The Central Nervous System is made up of the brain and spinal cord. The root for brain is either encephal/o or cerebr/o. The root for spine is spin/o and for spinal cord is myel/o. The brain which is encased in the skull is made up of the following parts: Cerebrum: The largest part of the brain which receives impulses from all areas of the body. It is the area of the brain that holds our intellectual ability. The cerebrum is divided into two hemispheres by a gap that extends down the middle of the tissue. These two areas are connected by bundles of nerves that allow the two hemispheres to function together. If for some reason the hemispheres become spilt each can function independently but there isn t the integration of functions that normally occurs. The outer layer of the cerebrum is a thin gray layer called the cerebral cortex. The cerebrum is involved in sensory and motor function as well as thought, judgment and our perception. Each of the two hemispheres of the brain is divided into lobes: frontal lobe, parietal lobe, temporal lobe and occipital lobe. Thalamus: The thalamus acts as a relay station for impulses coming into the brain. This area is responsible for detection of touch, temperature and pain. The root for thalamus is thalam/o. Hypothalamus: Located below the thalamus. It helps regulate the functions of the autonomic nervous system. It helps regulate appetite, thirst, temperature, sleep cycles and the amount of water retained by the body. Brain Stem: This area is sometimes referred to as the animal brain because it is the site of the basic life functions of breathing, heart beat, blood pressure, ability to see and ability to hear. It is also responsible for the responses of coughing, sneezing and swallowing. Revised September

4 Cerebellum: Lies just below the occipital lobe of the cerebrum. It is responsible for balance, coordination and equilibrium. Root for cerebellum is cerebell/o. Skull Parietal Lobe Dura Mater Frontal Lobe Arachnoid Mater Pia Mater Temporal Lobe Hypothalamus sthalamus Brain Stem Cerebellum Spinal Cord The human brain weights a mere three pounds and looks like a gray, unshelled walnut, yet it is the most complex structure in our world and the body's most vital organ. It encases some 100 billion or more nerve cells, and is capable of sending signals to thousands of other cells at speeds of more than 200 miles an hour. It defines who we are, yet is influenced by what we do. It holds the secrets to conditions that have perplexed mankind for centuries. Protection for the Brain Skull: The bones that make up our skull protect the brain tissue from external trauma. The root for skull is crani/o. Meninges: A series of three membranes that cover the brain tissue. The root for meninges is mening/o and meningi/o. The three membranes are the dura mater, arachnoid mater and pia mater. In the space below the arachnoid mater and above the pia mater (subarachnoid) there is a fluid called the Revised September

5 cerebrospinal fluid that acts as a cushion to absorb trauma during a head injury. This fluid absorbs a great deal of the impact so the brain tissue doesn t become bruised. Blood-Brain Barrier: A mechanism that prevents dangerous or toxic substances from leaving the blood stream and moving into brain tissue. It does allow necessary substances like oxygen and nutrition to pass through, into the brain. Spinal Cord The spinal cord extends from the base of the brain down the back in a canal referred to as the spinal canal. The cord consists of nerves that are encased in 31 vertebrae for protection. The spinal cord branches into 31 pairs of spinal nerves that extend from the cord to the limbs and lower parts of the body. The root for spinal cord is myel/o. Like the brain it is protected by the three layers of meninges and the cerebrospinal fluid. Peripheral Nervous System The peripheral nervous system consists of the cranial nerves which extend from the brain and the spinal nerves which extend from the spinal cord. We have 12 pairs of cranial nerves and they are named for the area they affect or the function they are responsible for such areas of the body as the: eyes, face, throat, mouth, tongue, thorax. Revised September

6 There are 31 pairs of spinal nerves, which are generally named for the artery they accompany or the body part they affect; e.g. the femoral nerve affects the muscles along the femur. Autonomic Nervous System This aspect of the nervous system is divided into two parts; the parasympathetic and sympathetic. Each division acts as a balancer of the activities of the other. This allows a state of homeostasis to exist in the body. The sympathetic system is concerned with preparing the body for emergency/stressful situations. To prepare you to react quickly in these situations, your breathing rate, heart rate and blood circulation to the muscles is greatly increased. It also decreases the rate of your digestion as this is not a necessity in an emergency situation. The parasympathetic system, in contrast, returns your body to a state of calm after a stressful situation has passed. It also maintains normal body functions during ordinary daily circumstances. Diagnostic Procedures The most common procedures used to diagnose problems of the nervous system involve the use of sound and dyes to create graphic pictures. The advances in technology have allowed for two very specific procedures to be developed: Magnetic Resonance Imaging (MRI) uses a combination of radio waves and a strong magnetic field to create images in any part of the body. This procedure is used in diagnosing brain problems, as well as other problems in the body. The second procedure is the Computerized Axial Tomography (CAT Scan). During this procedure an X-Ray beam rotates around the patient and details the structure to be examined at various depths. The information is then computerized and converted to a picture of that part of the body. Pathology of Diseases of the Nervous System Injuries to the nervous system may be the result of one or a combination of the following: Inflammation Trauma Decrease in blood circulation to the tissue resulting in death of tissue Congenital injuries Revised September

7 Word Parts for the Nervous System Roots ax/o axon cephal/o head cerebell/o cerebellum cerebr/o, encephal/o brain cortic/o cortex, outer covering dendr/o dendrite dur/o dura mater encephal/o, cerebr/o brain gangli/o, ganglion/o ganglion hydr/o water magnet/o magnet medull/o medulla, inner section mening/o, meningi/o meninges, membrane myel/o spinal cord, bone marrow narc/o numbness neur/o, neur/i nerve noct/i night radicul/o nerve root somn/i, somn/o sleep spin/o spine synaps/o, synapt/o synapse thalam/o thalamus ventricul/o ventricles Suffixes -algia, -dynia pain -cele hernia, protrusion -ectomy removal -esthesia sensation, feeling -graphy process of recording, producing images -kinesia, -kinesis movement, motion -oma tumor -phasia speech -plegia paralysis, loss of motor function -taxia order Prefixes de- lack of, removal epi- above, upon pachy- thick sub- below Revised September

8 Term Analysis and Definition Word Part Term Term Analysis Definition cerebell/o cerebellar cerebell = cerebellum -ar = pertaining to Pertaining to the cerebellum cerebellitis -itis = inflammation Inflammation of the cerebellum cerebr/o, encephal/o cerebral cerebr = brain -al = pertaining to Pertaining to the brain cerebrospinal spin = spine Pertaining to the brain and spine cerebrovascular vascul = vessel -ar = pertaining to Pertaining to the brain and blood vessels encephalitis encephalomalacia encephlopathy encephal = brain -itis = inflammation -malacia = softening -pathy = disease Inflammation of the brain Softening of the brain Any disease of the brain cortic/o cortical cortic = cortex, outer covering -al= pertaining to Pertaining to the cortex corticospinal spin = spine Pertaining to the cortex and spine dur/o epidural epi = on, upon, above dur = dura mater -al = pertaining to Pertaining to above the dura mater subdural sub = below, under Pertaining to under the dura mater hydr/o hydrocephalus hydr = water cephal = head -al = pertaining to Pertaining to an accumulation of fluid in the brain magnet/o magnetic resonance imaging magnet = magnet -ic = pertaining to magnification imaging = a picture A magnified picture of the brain made using magnetic waves. Revised September

9 Word Part Term Term Analysis Definition mening/o, meningi/o meningitis mening = meninges, -itis = inflammation Inflammation of the meninges meningoencephalitis encephal = brain Inflammation of the meninges and the brain myel/o myelogram myel = spinal cord, bone marrow -gram = record Record of the spinal cord poliomyelitis -itis = inflammation polio= gray Inflammation of the gray matter of the spinal cord neur/o, neur/i myoneural my = muscle -al = pertaining to neur = nerve Pertaining to the muscle and nerve neuralgia -algia = pain Nerve pain neurology -logy = study of Study of the nervous system neurologist -logist = one who specializes in the study of A specialist in the diagnosis and treatment of nervous system diseases neurolysis -lysis = destruction, breakdown Nerve destruction polyneuritis poly = many -itis = inflammation Inflammation of many nerves radicul/o myeloradiculitis myel = spinal cord radicul = nerve root -itis = inflammation spin/o spinal spin = spinal -al = pertaining to thalam/o thalamocortical thalam = thalamus cortic = cortex -al = pertaining to ventricul/o ventriculostomy ventric = ventricles -stomy = permanent new opening -algia cephalalgia cephal = head -algia = pain Inflammation of the spinal cord and nerve roots. Pertaining to the spine Pertaining to the thalamus and cerebral cortex Creating a permanentnew opening into the ventricles A pain in the head (Headache) Revised September

10 Word Part Term Term Analysis Definition -cele encephalocele encephal = brain Hernia of the brain -cele = hernia meningocele mening = meninges Hernia of the meninges myelomeningeocele myel = spinal cord Hernia of the spinal cord and meninges -ectomy lobectomy lobe = lobe -ectomy = surgical excision Surgical excision of a lobe of the brain craniectomy crani = skull Surgical removal of a part of the skull -esthesia anesthesia an = no, not -esthesia = sensation No sensation hypoesthesia hypo = below, under Decreased sensation hyperesthesia hyper- excessive, above Increased sensation dysesthesia dys = bad, difficult Irritating sensation paresthesia para = abnormal Abnormal sensation -graphy cerebral angiography cereb = brain -al = pertaining to angi = vessel -graphy = process of recording Graphic X-Ray image of the vessels in the brain.. computerized axial tomography tom/o = to cut X-Ray beam creates a picture of various depths of the brain encephalography encephal = brain Producing a graphic picture of the brain electroencephalography myelography elect= electric myel= spinal cord Process of recording the electric impulses of the brain X-Ray image of the spinal cord Revised September

11 Word Part Term Term Analysis Definition -kinesia, -kinesis hyperkinesis hyper = above, excessive -kinesis = movement Excessive movement, hyperactivity dyskinesia dys = difficult, bad -kinesia = movement Difficult movement hypokinesis hypo = slow Slow movement -oma glioma gli = glue Tumor of neuroglial cells meningioma mening = meninges Tumor of the meninges myeloma myel = spinal cord Tumor of the spinal cord -otomy neurotomy neur = nerve -tomy = Surgical incision Surgical incision into a nerve craniotomy crani = skull Creation of an opening into the skull -pathy encephalopathy encephal = brain -pathy = disease Disease of the brain neuropathy neur = nerve Disease of the nerve -phasia aphasia a = no, not phasia = speech No speech dysphasia dys = difficult, bad Difficult speech -plegia diplegia di = two -plegia = paralysis Paralysis of the like extremities on both sides of the body hemiplegia monoplegia paraplegia hemi = half mono = one para = beside, near Paralysis of either (half) the right side or left side of the body Paralysis of one extremity Paralysis of the lower part of the body and legs quadreplegia quad = four Paralysis of all four limbs Revised September

12 Word Part Term Term Analysis Definition -taxia ataxia a = no, not No muscular coordination -taxia = order de- demylination de- = lack of, removal mylin = myelin sheath -ion = process pachy- pachymeningitis pachy- = thick mening = meninges -itis = inflammation Loss of the myelin sheath. Inflammation of the thick meninges Summary Exercises Chapter 7 Exercise 7.1 Select the option that best answers the question. 1. Which term means to suture the ends of a severed nerve? 1. Neuroplasty 2. Neurotomy 3. Neurorrhaphy 2. Which term describes the space between two neurons, or between a neuron and a receptor organ? 1. Neurotransmitter 2. Synapse 3. Neuroglia 3. Which term describes a headache? 1. Cephalotomy 2. Cephalgia 3. Cephalitis 4. Which term best describes an inflammation of the membrane that covers the brain? 1. Meningitis 2. Encephalitis 3. Myelitis 5. Which division of the nervous system is concerned with the body s response to stress? Revised September

13 1. Central nervous system 2. Parasympathetic nervous system 3. Peripheral nervous system 4. Sympathetic nervous system 6. Which is the third layer of the meninges that is closest to the brain? 1. Dura mater 2. Pia mater 3. Arachnoid mater 7. The nerve structure that receives impulses and conducts them to the cell body is the? 1. Dendrite 2. Axon 3. Synapse 8. An inflammation of the nerve root is called? 1. Radiculitis 2. Myelitis 3. Neuritis 9. The largest and uppermost portion of th brain is the? 1. Cerebellum 2. Cerebrum 3. Brain stem 10. The medical term for inflammation of the brain is? 1. Encephalopathy 2. Cranitis 3. Encephalitis Exercise 8.2 Fill in the blanks with the most appropriate word or words. 1. Jane was diagnosed with pain in a nerve. The correct medical term for this is. 2. The medical term for recording the electrical activity of the brain is. 3. A condition where there is excessive stimulation is referred to as. 4. is a tumor of the spinal cord. 5. is the medical term for abnormal sensation. 6. is the process of maintaining a constant internal body environment. 7. is the absence of normal sensation. Revised September

14 8. is the inability to speak. 9. Abnormal softening of nerve tissue is referred to as. 10. An inflammation affecting many nerves is referred to as. Exercise 8.3 Build the medical term for each of the definitions listed below. 1. Nerve pain 2. A specialist in the study of nervous system diseases 3. Nerve destruction 4. Increase in sensation 5. Paralysis of all four limbs 6. Any disease of the brain 7. Inflammation of the brain 8. Surgical repair of the skull 9. Hernia of the spinal cord and meninges 10. Paralysis of one extremity Revised September