CHAPTER 8 Nervous System Nervous System Overview Nervous

CHAPTER 8 Nervous System

Nervous System Overview • Nervous System – Brain – Spinal cord – Nerves • Functions of nervous system – Regulates and coordinates all body activities – Center of all mental activity, including thought, learning, and memory 2

Nervous System Divisions • Central Nervous System (CNS) – Brain – Spinal Cord • Processes and stores sensory and motor information • Controls consciousness 3

Nervous System Divisions • Peripheral Nervous System (PNS) – 12 Pairs of Cranial Nerves – 31 Pairs of Spinal Nerves • Transmits sensory and motor impulses back and forth between CNS and rest of body 4

Nervous System Divisions 5

Peripheral Nervous System • Afferent (sensory) nerves – Carry impulses from the body to the central nervous system • Efferent (motor) nerves – Carry impulses from the central nervous system to muscles and glands – Cause the target organs to do something in response to commands 6

Peripheral Nervous System • Somatic Nervous System (SNS) – Provides voluntary control over skeletal muscle contractions • Autonomic Nervous System (ANS) – Provides involuntary control over smooth muscle, cardiac muscle, and glandular activity and secretions in response to the commands of the central nervous system 7

Autonomic Nervous System • Sympathetic nerves – – Increase heart rate Constrict blood vessels Raise blood pressure Fight-or-flight response • Parasympathetic nerves – – Slow heart rate Increase peristalsis of intestines Increase glandular secretions Relax sphincters 8

Cells of the Nervous System • Neuron – Cell body • Contains the nucleus and cytoplasm – Axon • Conducts impulses away from the cell body • Some axons are covered with a myelin sheath – Dendrite • Conducts impulses toward the cell body – Synapse • Space between two nerves which the impulse must cross 9

Cells of the Nervous System 10

Cells of the Nervous System • Neuroglia – Connective tissue • Support system for neurons – Do not conduct impulses – Protect nervous system through phagocytosis • Types of Neuroglia Cells – Astrocytes – Microglia – Oligodendrocytes 11

Central Nervous System • Brain – Surrounded by bone for protection – Enclosed in cranium • Spinal cord – Surrounded by vertebrae for protection – Surrounded by meninges and cerebrospinal fluid 12

Meninges • Dura mater – Outermost layer of meninges – Tough, white connective tissue – Epidural space • Located outside of the dura mater • Contains supporting cushion of fat and connective tissue – Subdural space • Located beneath the dura mater • Cavity is filled with serous fluid 13

Meninges • Arachnoid membrane – Middle layer of the meninges – Resembles a spider web – Subarachnoid space immediately beneath • Contains cerebrospinal fluid • Pia mater – Innermost layer of the meninges – Tightly bound to the surface of the brain and spinal cord 14

Structures of the Brain • Cerebrum – Largest and uppermost portion of the brain – Controls consciousness, memory, sensations, emotions, voluntary movements – Cortex = outer surface • Gyri = elevations • Sulci = grooves • Longitudinal fissure divides cerebrum into two hemispheres 15

Structures of the Brain • Cerebellum – Attached to the brain stem – Maintains muscle tone – Coordinates normal movement and balance • Diencephalon – Located between cerebrum and midbrain – Consists of thalamus, hypothalamus, and pineal gland 16

Structures of the Brain • Brain Stem – Region between diencephalon and spinal cord – Consists of midbrain, pons, and medulla oblongata – Serves as pathway for impulses between brain and spinal cord – Controls respiration, blood pressure, and heart rate 17

Spinal Cord • Pathway for impulses traveling to and from brain • Carries 31 pairs of spinal nerves – Affects limbs and lower part of body 18

PATHOLOGICAL CONDITIONS Nervous System

Alzheimer’s Disease • Pronounced – (ALTS-high-merz dih-ZEEZ) • Defined – Progressive and extremely debilitating deterioration of a person’s intellectual functioning 20

Amyotrophic Lateral Sclerosis (ALS) • Pronounced – (ah-my-oh-TROFF-ik LAT-er-al skleh-ROHsis) • Defined – Severe weakening and wasting of the involved muscle groups • Usually begins with hands • Progresses to shoulders, upper arms, then legs 21

Anencephaly • Pronounced – (an-en-SEFF-ah-lee) • Defined – Absence of the brain and spinal cord at birth • Condition is incompatible with life 22

Bell’s Palsy • Pronounced – (BELLZ PAWL-zee) • Defined – Temporary or permanent unilateral weakness or paralysis of muscles in the face 23

Brain Abscess • Pronounced – (BRAIN AB-sess) • Defined – Accumulation of pus located anywhere in the brain tissue 24

Carpal Tunnel Syndrome • Pronounced – (CAR-pal TUN-el SIN-drom) • Defined – Pinching or compression of median nerve within the carpal tunnel – Inflammation and swelling of tendons cause intermittent or continuous pain 25

Cerebral Concussion • Pronounced – (seh-REE-bral con-KUSH-un) • Defined – Brief interruption of brain function usually with loss of consciousness lasting for a few seconds 26

Cerebral Contusion • Pronounced – (seh-REE-bral con-TOO-zhun) • Defined – Small, scattered venous hemorrhages in the brain – Bruise of the brain tissue – Occurs when brain strikes the inner skull 27

Cerebral Palsy • Pronounced – (seh-REE-bral PAWL-zee) • Defined – Collective term used to describe congenital brain damage that is permanent but not progressive • Characterized by the child’s lack of control of voluntary muscles 28

Cerebral Palsy • Spastic – Damage to cortex of the brain • Tense muscles • Very irritable muscle tone • Ataxic – Damage to cerebellum • Affects equilibrium 29

Cerebral Palsy • Athetoid – Damage to basal ganglia • Causes sudden jerking • Rigidity • Causes child to be in continual state of tension • Mixed cerebral palsy 30

Cerebrovascular Accident (CVA) • Pronounced – (seh-REE-broh-VASS-kyoo-lar AK-sih-dent) • Defined – Death of a specific portion of brain tissue • Results from decreased blood flow to that area of the brain • Also called a stroke 31

Cerebrovascular Accident • Causes – Transient ischemic attacks (TIAs) • Also known as mini strokes – Cerebral thrombosis • Occurs largely in individuals older than 50 – Cerebral embolism • Embolus causes an occlusion – Cerebral hemorrhage • Cerebral vessel ruptures 32

Degenerative Disk • Pronounced – (deh-JEN-er-ah-tiv disk) • Defined – Deterioration of the intervertebral disk • Usually due to constant motion and wear on the disk 33

Encephalitis • Pronounced – (En-seff-ah-LYE-tis) • Defined – Inflammation of the brain or spinal cord tissue • Virus enters CNS when person experiences viral disease such as mumps, measles, or through tick or mosquito bite 34

Epilepsy • Pronounced – (EP-ih-lep-see) • Defined – Syndrome of recurring episodes of excessive irregular electrical activity of the central nervous system, called seizures 35

Grand Mal Seizure • Pronounced – (grand MALL SEE-zyoor) • Defined – Epileptic seizure characterized by sudden loss of consciousness and generalized involuntary muscular contraction • Vacillates between rigid body extension and an alternating contracting and relaxing of muscles 36

Petit Mal Seizure • Pronounced – (pet-EE MALL SEE-zyoor) • Defined – Small seizures in which there is a sudden, temporary loss of consciousness • Lasts only a few seconds • Also known as absence seizures 37

Guillain-Bàrré Syndrome • Pronounced – (GEE-yon bah-RAY SIN-drom) • Defined – Acute polyneuritis of the peripheral nervous system • • • Myelin sheaths on the axons are destroyed Decreased nerve impulses Loss of reflex response Sudden muscle weakness Usually follows viral gastrointestinal or respiratory infection 38

Headache (Cephalalgia) • Pronounced – (seff-ah-LAL-jee-ah) • Defined – Pain anywhere within the cranial cavity varying in intensity from mild to severe • May be chronic or acute • May occur as result of a disease process • May be totally benign 39

Migraine Headache • Pronounced – (MY-grain headache) • Defined – Recurring, pulsating, vascular headache developing on one side of the head • Characterized by slow onset • May be preceded by an aura during which sensory disturbance occurs 40

Cluster Headache • Pronounced – (KLUSS-ter headache) • Defined – Headache occurring typically two to three hours after falling asleep • Described as extreme pain around one eye that wakens the person from sleep 41

Tension Headache • Pronounced – (TEN-shun headache) • Defined – Headache that occurs from long, endured contraction of the skeletal muscles around the face, scalp, upper back, and neck 42

Epidural Hematoma • Pronounced – (eh-pih-DOO-ral hee-mah-TOH-mah) • Defined – Collection of blood located above the dura mater and just below the skull 43

Subdural Hematoma • Pronounced – (sub-DOO-ral hee-mah-TOH-mah) • Defined – Collection of blood below the dura mater and above the arachnoid layer of the meninges 44

Herniated Disk • Pronounced – (HER-nee-ay-ted disk) • Defined – Rupture or herniation of the disk center through the disk wall and into the spinal canal • Causes pressure on the spinal cord or nerve roots 45

Huntington’s Chorea • Pronounced – (HUNT-ing-tonz koh-REE-ah) • Defined – Inherited neurological disease characterized by rapid, jerky, involuntary movements and increased dementia • Progressive, degenerative disease 46

Hydrocephalus • Pronounced – (high-droh-SEFF-ah-lus) • Defined – Abnormal increase of cerebrospinal fluid in the brain that causes the ventricles of the brain to dilate • Results in increased head circumference in infant with open fontanel • Congenital disorder 47

Intracranial Tumors • Pronounced – (in-trah-KRAY-nee-al TOO-morz) • Defined – Tumors occurring in any structural region of the brain • May be malignant or benign • Classified as primary or secondary • Named according to the tissue from which they originate 48

Primary Intracranial Tumors • Pronounced – (PRIGH-mah-ree in-trah-KRAY-nee-al TOOmorz) • Defined – Tumors that arise from gliomas and the meninges • Gliomas = malignant glial cells that are a support for nerve tissue 49

Primary Intracranial Tumors • Glioblastoma multiforme – Most rapidly growing of the gliomas • Astrocytomas – Tend to invade surrounding structures • Ependymomas – Occur more commonly in children and adolescents – Usually encapsulated and benign 50

Metastatic Intracranial Tumors (Secondary) • Pronounced – (met-ah-STAT-ik in-trah-KRAY-nee-al TOOmorz) • Defined – Tumors occurring as a result of metastasis from a primary site such as the lung or breast 51

Meningitis (Acute Bacterial) • Pronounced – (men-in-JYE-tis ah-KYOOT back-TEE-ree-al) • Defined – Serious bacterial infection of the meninges • Can have residual debilitating effects or even a fatal outcome • Must be diagnosed and treated promptly with appropriate antibiotic therapy 52

Multiple Sclerosis (MS) • Pronounced – (MULL-tih-pl SKLEH-roh-sis) • Defined – Degenerative inflammatory disease of the central nervous system attacking the myelin sheath in the spinal cord and brain • Leaves area sclerosed (hardened) or scarred 53

Myasthenia Gravis • Pronounced – (my-ass-THEE-nee-ah GRAV-is) • Defined – Chronic progressive neuromuscular disorder • Causes skeletal muscle weakness (without atrophy) and fatigue • Occurring at different levels of severity 54

Narcolepsy • Pronounced – (NAR-coh-lep-see) • Defined – Rare syndrome of uncontrolled, sudden attacks of sleep – Main features of narcolepsy are daytime sleepiness and cataplexy – Sudden loss of muscle tone 55

Neuroblastoma • Pronounced – (noo-roh-blass-TOH-mah) • Defined – Highly malignant tumor of the sympathetic nervous system • Most commonly occurs in the adrenal medulla with early metastasis to liver, lungs, lymph nodes, and bone 56

Parkinson’s Disease • Pronounced – (PARK-in-sons dih-ZEEZ) • Defined – Degenerative, slowly progressive deterioration of nerves in the brain stem’s motor system, characterized by a gradual onset of symptoms • Classic Symptoms: stooped posture with body flexed forward, bowed head, shuffling gait, pillrolling gestures, expressionless mask-like facial appearance 57

Peripheral Neuritis • Pronounced – (per-IF-er-al noo-RYE-tis) • Defined – Inflammation of one or more peripheral nerves – Effects are dependent upon particular nerve involved 58

Poliomyelitis • Pronounced – (poh-lee-oh-my-ell-EYE-tis) • Defined – Infectious viral disease that affects the ability of spinal cord and brain motor neurons to receive stimulation • Virus enters through the upper respiratory tract • Muscles affected become paralyzed without the motor nerve stimulation 59

Post Polio Syndrome • Pronounced – (POST POH-lee-oh SIN-drom) • Defined – Progressive weakness occurring at least 30 years after the initial poliomyelitis attack 60

Reye’s Syndrome • Pronounced – (RISE SIN-drom) • Defined – Acute brain encephalopathy along with fatty infiltration of the internal organs that may follow acute viral infections • Occurs in children under the age of 18; often with a fatal result • Linked to aspirin administration during a viral illness 61

Shingles (Herpes Zoster) • Pronounced – (SHING-lz) (HER-peez ZOSS-ter) • Defined – Acute viral infection characterized by inflammation of the underlying spinal or cranial nerve pathway producing painful, vesicular eruptions on the skin along these nerve pathways • Seen mainly in adults 62

Shingles Image courtesy of Robert A. Silverman, M. D. , Pediatric Dermatology, Georgetown University 63

Skull Fracture (Depressed) • Pronounced – (SKULL FRAK-chur, deh-PREST) • Defined – Broken segment of the skull bone thrust into the brain as a result of a direct force, usually a blunt object 64

Spina Bifida Cystica • Pronounced – (SPY-nah BIFF-ih-dah SISS-tih-kah) • Defined – Back portion of one or more vertebrae is not closed normally and a cyst protrudes through the opening in the back, usually at the level of the 5 th lumbar or 1 st sacral vertebrae • Congenital defect of the CNS 65

Meningocele • Pronounced – (men-IN-goh-seel) • Defined – Cystlike sac covered with skin or a thin membrane protruding through the bony defect in the vertebrae containing meninges and CSF 66

Meningomyelocele • Pronounced – (men-in-goh-my-ELL-oh-seel) • Defined – Cystlike sac covered with skin or a thin membrane protruding through the bony defect in the vertebrae that contains meninges, CSF, and spinal cord segments 67

Spina Bifida Occulta • Pronounced – (SPY-nah BIFF-ih-dah oh-KULL-tah) • Defined – Congenital defect of the central nervous system in which the back portion of one or more vertebrae is not closed • A dimpling over the area may occur 68

Paraplegia • Pronounced – (pair-ah-PLEE-jee-ah) • Defined – Paralysis of the lower extremities caused by severe injury to the spinal cord in the thoracic or lumbar region – Results in loss of sensory and motor control below the level of the injury 69

Quadriplegia • Pronounced – (kwod-rih-PLEE-jee-ah) • Defined – Paralysis of the trunk, legs, and pelvic organs with partial or total paralysis in the upper extremities caused by severe injury to the spinal cord between the 5 th and 8 th cervical vertebrae • The higher the trauma, the more debilitating the motor and sensory impairments 70

Tay-Sachs Disease • Pronounced – (TAY SACKS dih-ZEEZ) • Defined – Congenital disorder caused by altered lipid metabolism, resulting from an enzyme deficiency • Accumulation of this type of lipid occurs in the brain, leading to progressive neurological deterioration with both physical and mental retardation 71

Trigeminal Neuralgia (Tic Douloureux) • Pronounced – (try-JEM-ih-nal noo-RAL-jee-ah), – (tik DOO-loh-roo) • Defined – Short periods of severe unilateral pain which radiates along the fifth cranial nerve (trigeminal nerve) • Heat, chewing, or touching of the affected area activates the pain 72

DIAGNOSTIC TECHNIQUES, TREATMENTS, AND PROCEDURES Nervous System

Diagnostic Techniques, Treatments, and Procedures • Babinski’s Reflex – Reflex tested by stroking the sole of the foot, beginning at mid-heel and moving upward and lateral to the toes. • Positive Babinski’s occurs when there is dorsiflexion of the great toe and fanning of the other toes 74

Diagnostic Techniques, Treatments, and Procedures • Brain scan – Nuclear counter scanning of cranial contents two hours after an intravenous injection of radioisotopes • Isotopes concentrate in abnormal tissue of brain, indicating a pathological process 75

Diagnostic Techniques, Treatments, and Procedures • Cerebral Angiography – Visualization of the cerebral vascular system via x-ray after injection of a radiopaque contrast medium into an arterial blood vessel • May use carotid, femoral, or brachial artery 76

Diagnostic Techniques, Treatments, and Procedures • Cerebrospinal fluid analysis – Laboratory analysis of cerebrospinal fluid – Obtained from a lumbar puncture for the presence of bacteria, blood, malignant cells, and amount of protein and glucose present 77

Diagnostic Techniques, Treatments, and Procedures • CT scan of the brain – Analysis of a three-dimensional view of brain tissue obtained as X-ray beams pass through successive horizontal layers of the brain • CT = computerized tomography • Images look down through the top of the head 78

Diagnostic Techniques, Treatments, and Procedures • Chordotomy – Neurosurgical procedure for pain control accomplished through a laminectomy • Surgical interference of pathways within the spinal cord that control pain 79

Diagnostic Techniques, Treatments, and Procedures • Cisternal puncture – Insertion of a short, beveled spinal needle into the cisterna magna in order to drain CSF or to obtain a CSF specimen • Cisterna magna = shallow reservoir of CSF between the medulla and the cerebellum 80

Diagnostic Techniques, Treatments, and Procedures • Craniotomy – Surgical procedure that makes an opening into the skull • Echoencephalography – Measurement of electrical activity produced by the brain and recorded through electrodes placed on the scalp 81

Diagnostic Techniques, Treatments, and Procedures • Electroencephalography (EEG) – Measurement of electrical activity in the brain and recorded through electrodes – Sleep-deprived EEG • Individual deprived of sleep for 24 hours before test – Ambulatory EEG • Provides prolonged readings of electrical activity of brain over a 24 -hour period of time, while person is awake or asleep 82

Diagnostic Techniques, Treatments, and Procedures • Laminectomy – Surgical removal of the bony arches from one or more vertebrae in order to relieve pressure from the spinal cord 83

Diagnostic Techniques, Treatments, and Procedures • Electromyography (EMG) – Process of recording electrical activity of muscle – Insert small needle into the muscle, deliver small current that stimulates the muscle 84

Diagnostic Techniques, Treatments, and Procedures • Lumbar puncture – Insertion of a hollow needle and stylet into subarachnoid space between third and fourth lumbar vertebrae below level of the spinal cord – Performed under strict aseptic technique 85

Diagnostic Techniques, Treatments, and Procedures • Magnetic Resonance Imaging (MRI) – Noninvasive scanning procedure that provides visualization of fluid, soft tissue, and bony structures without the use of radiation • Provides far more preciseness and accuracy than most diagnostic tools – Not limited to scans of the brain • May also be used to examine the abdomen, chest, joints, nervous system, pelvis, and spinal column 86

Diagnostic Techniques, Treatments, and Procedures • Myelography – Introduction of contrast medium into the lumbar subarachnoid space through a lumbar puncture in order to visualize the spinal cord and vertebral canal through x-ray examination 87

Diagnostic Techniques, Treatments, and Procedures • Neurectomy – Neurosurgical procedure to relieve pain in a localized or small area by incision of cranial or peripheral nerves • Pneumoencephalography – Process used to radiographically visualize one of the ventricles or fluid occupying spaces in the central nervous system (CNS) 88

Diagnostic Techniques, Treatments, and Procedures • Polysomnogram (PSG) – Sleep study or sleep test that evaluates physical factors affecting sleep • Physical activity and level of sleep are monitored by a technician while the patient sleeps – Useful in evaluating sleep disorders such as sleep apnea, sleep walking, night terrors, restless leg syndrome, insomnia, and narcolepsy 89

Diagnostic Techniques, Treatments, and Procedures • Positron Emission Tomography (PET Scan) – Computerized radiographic images of various body structures produced when radioactive substances are inhaled or injected • Romberg test – Examination used to evaluate cerebellar function and balance 90

Diagnostic Techniques, Treatments, and Procedures • Stereotaxic Neurosurgery – Neurosurgery on a precise location of an area within the brain that controls specific function(s) • May involve destruction of brain tissue with various agents such as heat, cold, and sclerosing or corrosive fluids 91

Diagnostic Techniques, Treatments, and Procedures • Sympathectomy – Surgical procedure used to interrupt a portion of the sympathetic nerve pathway, for the purpose of relieving chronic pain • Trichotomy – Through a craniotomy, the anterolateral pathway in the brain stem is surgically divided in an attempt to relieve pain 92

Diagnostic Techniques, Treatments, and Procedures • Transcutaneous Electrical Nerve Stimulation (TENS) – Form of cutaneous stimulation for pain relief that supplies electrical impulses to the nerve endings of a nerve close to the pain site 93