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Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Chapter 5
The Central Nervous System
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Nervous System Organization
Central nervous system (CNS)
Consists of brain and spinal cord
Peripheral nervous system (PNS)
Afferent division
Carries information to the CNS Two branches
Sympathetic
Parasympathetic
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Nervous System Organization
Efferent division
Carries information away from CNS to effector organs(muscles and glands)
Divided into
Somatic nervous system
Consists of fibers of motor neurons that supplyskeletal muscles
Autonomic nervous system
Consists of fibers that innervate smooth muscle,
cardiac muscle, and glands
Two divisions:Sympathetic nervous system
Parasympathetic nervous system
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Nervous System Organization
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Functional Classes of Neurons
Afferent neurons
Inform CNS about conditions in both the externaland internal environment
Efferent neurons
Carry instructions from CNS to effector organs
muscles and glands Interneurons
Found entirely within CNS
Responsible for Integrating afferent information and formulating an
efferent response
Higher mental functions associated with the mind
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Functional Classes of Neurons
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Neuroglia
Also called glial cells
Physically, metabolically, and functionallysupport interneurons
Four major types of cells
Astrocytes Oligodendrocytes
Microglia
Ependymal cells
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Neuroglia
Astrocytes
Main glue of CNS holds neurons together
Guide neurons during fetal brain development
Aid in establishment of blood-brain barrier
Important in repair of brain injuries and in neuralscar formation
Play role in neurotransmitter activity
Take up excess K+from brain ECF
Along with other glial cellsenhance synapseformation and modify synaptic transmission
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Neuroglia
Oligodendrogytes
Form myelin sheaths around axons in CNS
Microglia
Immune defense cells of the CNS
In resting state release low levels of growthfactors that help neurons and other glial cells
survive and thrive
Ependymal cells
Line internal, fluid-filled cavities of the CNS
In ventricles of brain, help form and circulate
cerebrospinal fluid
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Neuroglia
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Protection of CNS
Enclosed by hard, bony structures
Wrapped by three protective and nourishingmembranesmeninges
Dura mater
Arachnoid mater Pia mater
Floats in cushioning fluidcerebrospinal fluid
(CSF)
Blood-brain barrier limits access of blood-borne
materials into brain tissue
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Cerebrospinal Fluid (CSF)
Surrounds and cushions brain and spinal cord
Formed primarily by choroid plexuses
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Cerebrospinal Fluid
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Blood-Brain Barrier (BBB)
Protects brain from chemical fluctuations in
blood Minimizes possibility that harmful blood-borne
substances might reach central nervous tissue
Prevents certain circulating hormones that couldalso act as neurotransmitters from reaching
brain
Limits use of drugs for treatment of brain and
spinal cord disorders Many drugs cannot penetrate BBB
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Central Nervous System
Enables you to:
Subconsciously regulate your internalenvironment by neural means
Experience emotions
Voluntarily control your movements
Be consciously aware of your own body and your
surroundings
Engage in other higher cognitive processes such
as thought and memory
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Brain Anatomy
Brain components
Brain stem Cerebellum
Forebrain
Diencephalon
Hypothalamus
Thalamus
Cerebrum
Basal nuclei
Cerebral cortex
B i t
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Table 5-2 (1), p. 140
Hypothalamus
Brain stem
Cerebral cortex
Thalamus
(medial)
Basal nuclei
(lateral to thalamus)
Cerebellum
Spinal cord
Midbrain
Pons
Medulla
Bra in com ponent
Cerebral cortex
Basal nuclei
Thalamus
Hypothalamus
Cerebellum
Brain stem(midbrain, pons,
and medulla)
M j F ti B i t
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Major Functions
1. Sensory perception2. Voluntary control of movement3. Language4. Personality traits5. Sophisticated mental events, such as thinking memory,
decision making, creativity, and self-consciousness
1. Inhibition of muscle tone2. Coordination of slow, sustained movements3. Suppression of useless patterns of movements
1. Relay station for all synaptic input2. Crude awareness of sensation
3. Some degree of consciousness4. Role in motor control
1. Regulation of many homeostatic functions, such as temperaturecontrol, thirst, urine output, and food intake
2. Important link between nervous and endocrine systems3. Extensive involvement with emotion and basic behavioral patterns
1. Maintenance of balance
2. Enhancement of muscle tone3. Coordination and planning of skilled voluntary muscle activity
1. Origin of majority of peripheral cranial nerves
2. Cardiovascular, respiratory, and digestive control centers
3. Regulation of muscle reflexes involved with equilibrium and posture
4. Reception and integration of all synaptic input from spinal cord;
arousal and activation of cerebral cortex5. Role in sleep-wake cycle
Bra in com ponent
Cerebral cortex
Basal nuclei
Thalamus
Hypothalamus
Cerebellum
Brain stem
(midbrain, pons,
and medulla)
Table 5-2, p. 141
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Brain Stem
Oldest region of the brain
Continuous with spinal cord
Controls many life-sustaining processes, such
as respiration, circulation, and digestion
Consists of Midbrain
Pons
Medulla
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Cerebellum
Attached at top rear portion of brain stem
Maintains proper position of the body in space
Subconscious coordination of motor activity
(movement)
Plays key role in learning skilled motor tasks
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Diencephalon
Houses two brain components
Hypothalamus Controls many homeostatic functions important in
maintaining stability of internal environment
Thalamus
Performs some primitive sensory processing
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Cerebrum
Highly developed
Makes up about 80% of total brain weight(largest portion of brain)
Inner core houses basal nuclei
Outer surface is highly convoluted cerebralcortex
Highest, most complex integrating area of the
brain
Plays key role in most sophisticated neuralfunctions
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Cerebral Cortex
Organized into six well-defined layers
Layers are organized into functional verticalcolumns
Each half of cortex divided into four major lobes
Occipital Temporal
Parietal
Frontal
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Cerebral cortex
Occipital lobe
Carries out initial processing of visual input
Temporal lobe
Initial reception of sound sensation
Parietal lobe Somatosensory processing
Frontal lobe
Responsible for
Voluntary motor activity
Speaking ability
Elaboration of thought
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Cerebral Cortex
Primary motor cortex
Located in frontal lobe Confers voluntary control over movement
produced by skeletal muscles
Primarily controls muscles on the opposite side of
the body
Motor homunculus
Depicts location and relative amount of motor cortex
devoted to output to muscles of each body part
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Cerebral Cortex
Supplementary motor area
Plays preparatory role I n programming complexsequences of movement
Premotor cortex
Important in orienting the body and arms toward a
specific target
Posterior parietal cortex
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Chapter 5 The Central Nervous SystemHuman Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Cerebral Cortex
Primary areas of cortical specialization for
language Brocas area
Governs speaking ability
Wernickes area
Concerned with language comprehension Responsible for formulating coherent patterns of
speech
Language disorders
Aphasias Speech impediments
Dyslexia
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Cerebral Hemispheres
Left cerebral hemisphere
Excels in logical, analytic, sequential, and verbaltasks
Math, language forms, philosophy
Right cerebral hemisphere
Excels in nonlanguage skills
Spatial perception and artistic and musical talents
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Cerebral Cortex
Schematic Linking
of Various Regions
of the Cortex
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Electroencephalogram (EEG)
Record of postsynaptic activity in cortical
neurons Brain waves
Three major uses
Clinical tool in diagnosis of cerebral dysfunction Used in legal determination of brain death
Used to distinguish various stages of sleep
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Electroencephalogram (EEG)
B l N l i
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Basal Nuclei
Act by modifying ongoing activity in motor
pathways Primary functions
Inhibiting muscle tone throughout the body
Selecting and maintaining purposeful motoractivity while suppressing useless or unwanted
patterns of movement
Helping monitor and coordinate slow, sustained
contractions, especially those related to postureand support
Th l
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Thalamus
Part of diencephalon
Serves as relay station and synaptic integratingcenter for processing sensory input on its way to
cerebral cortex
Along with brain stem and cortical association
areas, important in ability to direct attention to
stimuli of interest
Capable of crude awareness of various types of
sensation but cannot distinguish their location orintensity
H th l
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Hypothalamus
Brain area most involved in directly regulating internal
environment Functions
Controls body temperature
Controls thirst and urine output
Controls food intake Controls anterior pituitary hormone secretion
Produces posterior pituitary hormones
Controls uterine contractions and milk ejection
Serves as a major ANS coordinating center Plays role in emotional and behavioral patterns
Participates in sleep-wake cycle
Li bi S t
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Limbic System
Includes portions of the hypothalamus and other
forebrain structures that encircle brain stem Responsible for
Emotion
Basic, inborn behavioral patterns related to
survival and perpetuation of the species
Plays important role in motivation and learning
M
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Memory
Storage of acquired knowledge for later recall
Memory trace Neural change responsible for retention or storage ofknowledge
Short-term memory
Lasts for seconds to hours
Long-term memory Retained for days to years
Consolidation
Process of transferring and fixing short-term memory
traces into long-term memory stores Working memory
Temporarily holds and interrelates various pieces ofinformation relevant to a current mental task
Comparison of Long Term and Short Term Memory
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Comparison of Long-Term and Short-Term Memory
C b ll
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Cerebellum
Important in balance and in planning and
executing voluntary movement Three different parts
Vestibulocerebellum Important in maintaining balance and controls eye
movements Spinocerebellum
Enhances muscle tone and coordinates skilled,voluntary movements
Cerebrocerebellum Plays role in planning and initiating voluntary activity by
providing input to cortical motor areas
Stores procedural memories
B i St
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Brain Stem
Critical connecting link between rest of brain and
spinal cord Consists of
Medulla
Pons
Midbrain
B i St
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Brain Stem
Functions
Most of cranial nerves arise from brain stem Neuronal clusters within brain stem control heart
and blood vessel function, respiration, and manydigestive functions
Plays role in regulating muscle reflexes involvedin equilibrium and posture
Reticular formation within brain stem receivesand integrates all incoming sensory synaptic input
Centers that govern sleep are in brain stem(evidence suggests center promoting slow-wavesleep lies in hypothalamus)
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Cranial
Nerves
Sl
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Sleep
Function of sleep is unclear
Sleep-wake cycle Normal cyclic variation in awareness of
surroundings
Active process consisting of two types of sleep
characterized by different EEG patterns and
different behaviors
Slow-wave sleep
Paradoxical, or REM sleep
Comparison of Slow Wave and Paradoxical Sleep
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Comparison of Slow-Wave and Paradoxical Sleep
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
EEG
Patterns
During
DifferentTypes of
Sleep
Spinal Cord
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Spinal Cord
Extends from brain stem through vertebral canal
31 pairs of spinal nerves emerge from spinalcord through spaces formed between arches of
adjacent vertebrae
Named for region of vertebral column from which
they emerge
8 pairs cervical (neck) nerves
12 pairs thoracic (chest) nerves
5 pairs lumbar (abdominal) nerves
5 pairs sacral (pelvic) nerves
1 pair coccygeal (tailbone) nerves
Spinal Nerves
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Spinal Nerves
Spinal Cord
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Spinal Cord
Two vital functions
Neuronal link between brain and PNS Integrating center for spinal reflexes
Reflex
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Reflex
Reflex
Any response that occurs automatically withoutconscious effort
Two types of reflexes
Simple, or basic, reflexes
Built-in, unlearned responses
Acquired, or conditioned, reflexes
Result of practice and learning
Reflex Arc
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Chapter 5 The Central Nervous System
Human Physiologyby Lauralee Sherwood 2007 Brooks/Cole-Thomson Learning
Reflex Arc
Neural pathway involved in accomplishing reflex
activity Five basic components
Receptor
Afferent pathway
Integrating center
Efferent pathway
effector
Crossed Extensor Reflex Coupled with the
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Chapter 5 The Central Nervous System
Crossed Extensor Reflex Coupled with the
Withdrawal Reflex