Nervous System CHAPTER 8. 2 Nervous System Overview Nervous System –Brain –Spinal cord –Nerves...
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Transcript of 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