nervous system chapter 8. 2 nervous system overview nervous system –brain –spinal cord –nerves...

Nervous System

CHAPTER 8

2

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

3

• Central Nervous System (CNS)– Brain– Spinal Cord

• Processes and stores sensory and motor information

• Controls consciousness

Nervous System Divisions

4

• 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

Nervous System Divisions

5

Nervous System Divisions

6

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

7

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

8

• 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

Autonomic Nervous System

9

• 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

Cells of the Nervous System

10

Cells of the Nervous System

11

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

12

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

13

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

14

• 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

Meninges

15

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

16

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

17

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

18

Spinal Cord

• Pathway for impulses traveling to and from brain

• Carries 31 pairs of spinal nerves– Affects limbs and lower part of body

PATHOLOGICAL CONDITIONS

Nervous System

20

Alzheimer’s Disease

• Pronounced– (ALTS-high-merz dih-ZEEZ)

• Defined– Progressive and extremely debilitating

deterioration of a person’s intellectual functioning

21

Amyotrophic Lateral Sclerosis (ALS)

• Pronounced– (ah-my-oh-TROFF-ik LAT-er-al skleh-ROH-

sis)

• Defined– Severe weakening and wasting of the involved

muscle groups• Usually begins with hands • Progresses to shoulders, upper arms, then legs

22

Anencephaly

• Pronounced– (an-en-SEFF-ah-lee)

• Defined– Absence of the brain and spinal cord at birth

• Condition is incompatible with life

23

Bell’s Palsy

• Pronounced– (BELLZ PAWL-zee)

• Defined– Temporary or permanent unilateral weakness

or paralysis of muscles in the face

24

Brain Abscess

• Pronounced– (BRAIN AB-sess)

• Defined– Accumulation of pus located anywhere in the

brain tissue

25

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

26

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

27

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

28

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

29

• Spastic– Damage to cortex of the brain

• Tense muscles• Very irritable muscle tone

• Ataxic– Damage to cerebellum

• Affects equilibrium

Cerebral Palsy

30

• Athetoid– Damage to basal ganglia

• Causes sudden jerking

• Rigidity• Causes child to be in continual state of tension

• Mixed cerebral palsy

Cerebral Palsy

31

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

32

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

33

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

34

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

35

Epilepsy

• Pronounced– (EP-ih-lep-see)

• Defined– Syndrome of recurring episodes of excessive

irregular electrical activity of the central nervous system, called seizures

36

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

37

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

38

• 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

Guillain-Bàrré Syndrome

39

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

40

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

41

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

42

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

43

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

44

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

45

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

46

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

47

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

48

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

49

Primary Intracranial Tumors

• Pronounced– (PRIGH-mah-ree in-trah-KRAY-nee-al TOO-

morz)

• Defined– Tumors that arise from gliomas and the

meninges• Gliomas = malignant glial cells that are a support

for nerve tissue

50

• 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

Primary Intracranial Tumors

51

• Pronounced– (met-ah-STAT-ik in-trah-KRAY-nee-al TOO-

morz)

• Defined– Tumors occurring as a result of metastasis

from a primary site such as the lung or breast

Metastatic Intracranial Tumors (Secondary)

52

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

53

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

54

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

55

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

56

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

57

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, pill-rolling gestures, expressionless mask-like facial appearance

58

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

59

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

60

Post Polio Syndrome

• Pronounced– (POST POH-lee-oh SIN-drom)

• Defined– Progressive weakness occurring at least 30

years after the initial poliomyelitis attack

61

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

62

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

63

Shingles

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

64

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

65

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 5th lumbar or 1st sacral vertebrae

• Congenital defect of the CNS

66

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

67

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

68

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

69

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

70

• 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 5th and 8th cervical vertebrae

• The higher the trauma, the more debilitating the motor and sensory impairments

Quadriplegia

71

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

72

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

DIAGNOSTIC TECHNIQUES, TREATMENTS, AND

PROCEDURES

Nervous System

74

• 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

Diagnostic Techniques, Treatments, and Procedures

75

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

76

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

77

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

78

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

79

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

80

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

81

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

82

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

83

• Laminectomy– Surgical removal of the bony arches from one

or more vertebrae in order to relieve pressure from the spinal cord

Diagnostic Techniques, Treatments, and Procedures

84

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

85

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

86

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

87

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

88

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)

89

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

90

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

91

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

92

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

93

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