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
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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
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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
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Cells of the Nervous System
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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
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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
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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
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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
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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
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Spinal Cord
• Pathway for impulses traveling to and from
brain
• Carries 31 pairs of spinal nerves
– Affects limbs and lower part of body
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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
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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
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Brain Abscess
• Pronounced
– (BRAIN AB-sess)
• Defined
– Accumulation of pus located anywhere in the
brain tissue
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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
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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
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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
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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
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Cerebral Palsy
• Spastic
– Damage to cortex of the brain
• Tense muscles
• Very irritable muscle tone
• Ataxic
– Damage to cerebellum
• Affects equilibrium
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Cerebral Palsy
• Athetoid
– Damage to basal ganglia
• Causes sudden jerking
• Rigidity
• Causes child to be in continual state of tension
• Mixed cerebral palsy
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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
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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
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Epilepsy
• Pronounced
– (EP-ih-lep-see)
• Defined
– Syndrome of recurring episodes of excessive
irregular electrical activity of the central
nervous system, called seizures
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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