Chapter 10
The Nervous System
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Objectives
List the organs and divisions of the nervous system and describe the generalized functions
Identify the major types of cells in the nervous system and discuss the function of each
Identify the major anatomical components of the brain and spinal cord and briefly comment on the function of each
Identify and discuss the coverings and fluid spaces of the brain and spinal cord
Compare and contrast spinal and cranial nerves
Discuss the structure and function of the two divisions of the autonomic nervous system
Describe major nervous system disorders
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Nervous System
1. Central nervous system (CNS) - brain and spinal
cord
2. Peripheral nervous
system (PNS) - all nerves
Autonomic nervous system
(ANS)
Somatic nervous system
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Central Nervous System
Contains:
Brain
Spinal cord
Made of gray and white matter
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Brainstem
Made up of 3 parts: medulla oblongata, pons, and midbrain
Medulla- regulates the vital functions of heart rate, breathing,
and BP; regulates reflexes of coughing, sneezing, swallowing,
and vomiting
Pons- contains respiratory centers that work with those in
medulla
Midbrain- contains centers for visual reflexes, auditory reflexes,
and righting (equilibrium) reflexes
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Cerebellum
Second largest part of the
human brain
Function
Regulates coordination of
voluntary movement, muscle
tone, stopping movements, and
equilibrium
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Diencephalon
Consist of hypothalamus, thalamus, and pineal gland
Control the functioning of most internal organs
Controls hormone secretion by anterior and posterior pituitary glands
Contains centers for controlling appetite, wakefulness, pleasure, etc.
Hypothalamus
Contributes to healthy survival
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Thalamus
Dumbbell-shaped mass of gray
matter extending into each
cerebral hemisphere
Superior to the hypothalamus
Inferior to the cerebrum
Relays and integrates sensory
impulses to cerebrum
Produces emotions of
pleasantness or unpleasantness
associated with sensations
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Cerebrum
Largest part of the human brain
Consists of two hemispheres
separated by longitudinal fissure
Outer layer of gray matter is the
cerebral cortex
Interior composed mainly of white
matter
Functions of the cerebrum:
mental processes of all types, including sensations,
consciousness, memory, and
voluntary control of movements
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Central Nervous System
Outer portion: Columns of white matter, composed of
bundles of myelinated nerve fibers
Interior portion: Gray matter made up mainly of neuron dendrites and cell bodies
Spinal cord tracts provide two-way conduction paths - ascending and descending
Spinal cord contains all spinal cord reflexes; sensory and motor tracts conduct impulses to and from the brain
Spinal Cord:
Cross-section of spinal cord
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Peripheral nervous system
Also known as (PNS) - all nerves outside of brain
and spinal cord
Contains:
1. Autonomic nervous system (ANS)
2. Somatic nervous system
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Autonomic Nervous System
The ANS- consists of motor neurons that conduct impulses
from the spinal cord or brainstem to the following tissues:
1. Cardiac muscle tissue
2. Smooth muscle tissue
3. Glandular epithelial tissue
Consists of two main divisions:
Sympathetic nervous system- “Fight or Flight”
Parasympathetic nervous system
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Autonomic Nervous System
Sympathetic nervous system
Serves as the emergency or stress system,
controlling visceral effectors during strenuous
exercise and when strong emotions (anger, fear,
hate, or anxiety) are elicited
Group of changes induced by sympathetic control
is called the fight-or-flight response
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Autonomic Nervous System
Parasympathetic nervous system
Function - dominates control of many visceral
effectors under normal, everyday conditions
What are visceral effectors referring to?
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Autonomic Nervous System
Motor neurons that conduct impulses from the central nervous system to cardiac muscle, smooth muscle, and glandular epithelial tissue
Regulates body’s automatic or involuntary functions
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Autonomic Nervous System
Autonomic neurotransmitters
Cholinergic fibers – pre-ganglionic axons of
parasympathetic and sympathetic systems release
acetylcholine
Adrenergic fibers - axons of sympathetic postganglionic
neurons release norepinephrine (noradrenaline)
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Somatic Nervous System
Also part of peripheral nervous system
Voluntary action signaling of the nervous system
to the voluntary muscles
https://www.youtube.com/watch?v=pEezpi9g6_w
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Peripheral Nervous System
Cranial nerves 12 pairs - attached to undersurface of the brain
Connect brain with the neck and structures in the thorax and abdomen
The Cranial Nerves
I Olfactory
II Optic
III Oculomotor
IV Trochlear
V Trigeminal
VI Abducens
VII Facial
VIII Acoustic
IX Glossopharyngeal
X Vagus
XI Spinal accessory
XII Hypoglossal
“On Old Olympus’ Tiny
Tops, A Finn And German
Viewed Some Hops”
The Cranial Nerves
I Olfactory Sense of smell
II Optic Vision
III Oculomotor Eye movements
IV Trochlear Eye movements
V Trigeminal Sensation of face, scalp, teeth
VI Abducens Eye movements
VII Facial Sense of taste
VIII Acoustic Hearing, sense of balance
IX Glossopharyngeal Swallowing
X Vagus Sensations of throat, slowing of HR
XI Spinal accessory Shoulder shrug
XII Hypoglossal Tongue movements
NERVE FUNCTION
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Peripheral Nervous System
Spinal nerves: contain dendrites of sensory neurons and axons of motor neurons
Conduct impulses necessary for sensations and voluntary movements
Skin surface area supplied by a single nerve is called a dermatome
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Neurons (nerve fibers)
1. Cell body: contains the
nucleus, essential for the life of
the neuron
2. Dendrites – processes that
transmit impulses toward the
cell body
3. Axon - elongated projection
that conducts impulses away
from the cell
4. Protected by the myelin
sheath: made of Schwann
cells
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Nerves
Bundle of peripheral axons
Tract – bundle of central
axons
White matter- brain or
cord tissue composed
primarily of myelinated
axons (tracts)
Gray matter- brain or
center of spinal cord
tissue composed
primarily of cell bodies
and unmyelinated fibers
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Neurons
Neurons classified according to function or direction of
impulse
Sensory neurons (afferent neurons): conduct
impulses to the spinal cord and brain
Motor neurons (efferent neurons): conduct impulses
away from brain and spinal cord to muscles and glands
Interneurons: conduct impulses from sensory neurons
to motor neurons; also called central or connecting
neurons
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Glia (neuroglia) Support cells: bring cells of nervous tissue together
structurally and functionally
Three main types of connective tissue cells of the CNS:
1. Astrocytes
2. Microglia
3. Oligodendrocytes
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Neuron signaling
1. Reception – the information is received
2. Transmission – an electrical process send
information from the afferent (sensory) neurons to
the interneurons in the CNS
3. Integration – the information is processed
4. Transmission – interneurons transmit information to
efferent (motor) neurons then to muscles or glands
5. Actual response
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The Synapse
Definition - the place where impulses are transmitted from one neuron to another
Synapse made of three structures - synaptic knob, synaptic cleft, and plasma membrane
Neurotransmitters bind to specific receptor molecules in the membrane of a postsynaptic neuron
http://www.news-medical.net/health/What-is-the-Nervous-System.aspx
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The Synapse
Names of neurotransmitters - acetylcholine,
(catecholamines; norepinephrine, dopamine,
and serotonin), endorphins, enkephalins, nitric
oxide (NO), and other compounds
Parkinson disease (PD) - characterized by
abnormally low levels of dopamine in motor
control areas of the brain; patients usually
exhibit involuntary trembling and muscle rigidity
Parkinsonism
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Reflex A reflex is an involuntary or automatic, one way action that
your body does in response to something - without you even having to think about it
Nerve impulses are conducted from afferent receptors to effector receptors over neuron pathways or reflex arcs
Five essential parts:
1. Receptors- detect a change and generate impulses
2. Sensory neurons- transmit impulses from receptors to the CNS
3. CNS- contains one or more synapses
4. Motor neurons- transmit impulses from the CNS to the effector
5. Effector- performs its characteristic action
Patellar reflex
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Disorders of nervous tissue Multiple sclerosis
Characterized by myelin loss in central nerve fibers and
resulting conduction impairments
Tumors
General name for nervous system tumors is neuroma
Most neuromas are gliomas, glial tumors
Multiple neurofibromatosis - characterized by numerous
benign tumors
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Brain disorders
Destruction of brain tissue
Cerebrovascular accident (CVA) – 2 types hemorrhage
from or cessation of blood flow through cerebral blood
vessels; a “stroke”
Cerebral palsy (CP) - condition in which damage to motor
control areas of the brain before, during, or shortly after birth
causes paralysis (usually spastic) of one or more limbs
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Brain disorders Dementia - progressive loss of memory, shortened
attention span, personality changes, reduced intellectual
capacity, motor control deficit
Alzheimer disease (AD) - brain disorder of the middle and
late adult years characterized by dementia
Huntington disease (HD) - inherited disorder characterized
by chorea (purposeless movement) progressing to severe
dementia
HIV (also causes AIDS) can infect neurons and thus cause
dementia
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Brain disorders Seizure disorders
Seizure - sudden burst of abnormal neuron activity that results in temporary changes in brain function
Epilepsy - many forms, all characterized by recurring seizures
Electroencephalogram - graphic representation of voltage changes in the brain used to evaluate brain activity
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Peripheral Nerve disorders
Neuritis - general term referring to nerve inflammation
Sciatica is inflammation of the sciatic nerve that innervates
the legs
Neuralgia, or muscle pain, often accompanies neuritis
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Peripheral Nerve disorders
Trigeminal neuralgia - recurring episodes of stabbing pain along one or more branches of the trigeminal (fifth cranial)
nerve in the head
Bell palsy - paralysis of facial features resulting from damage to the facial (seventh cranial) nerve
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Peripheral Nerve disorders
Herpes zoster or shingles
Viral infection caused by chickenpox virus that has invaded
the dorsal root ganglion and remained dormant until an
episode of shingles
Usually affects a single dermatome, producing characteristic
painful plaques or vesicles
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Disorders of the
Autonomic Nervous System Stress-induced disease
Prolonged or excessive response to stress can disrupt normal functioning throughout the body
Examples of stress-induced conditions include heart
disease, digestive problems, and reduced resistance to disease