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Chapter 12 Part C
The Central
Nervous
System
© Annie Leibovitz/Contact Press Images
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PowerPoint® Lecture Slides
prepared by
Karen Dunbar Kareiva
Ivy Tech Community College
12.6 Functional Brain Systems
• Networks of neurons that work together but
span wide areas of brain
– Limbic system
– Reticular formation
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Limbic System
• Structures on medial aspects of cerebral
hemispheres and diencephalon
• Fornix: fiber tract that links limbic system
regions
• Includes parts of diencephalon and some
cerebral structures that encircle brain stem
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Limbic System (cont.)
• Large part of emotional or affective brain
– Amygdaloid body: recognizes angry or fearful
facial expressions, assesses danger, and elicits
fear response
– Cingulate gyrus: plays role in expressing
emotions via gestures and resolves mental
conflict
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Figure 12.17 The limbic system.
Septum
pellucidum
Diencephalic structures
of the limbic system
• Anterior thalamic
nuclei (flanking
3rd ventricle)
• Hypothalamus
• Mammillary body
Olfactory
bulb
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Corpus callosum
Fiber tracts connecting
limbic system structures
• Fornix
• Anterior commissure
Cerebral structures
of the limbic system
• Cingulate gyrus
• Septal nuclei
• Amygdaloid body
• Hippocampus
• Dentate gyrus
• Parahippocampal
gyrus
Limbic System (cont.)
• Limbic system puts emotional responses to
odors
– Example: skunks smell bad
• Most output relayed via hypothalamus
– Hypothalamus plays a role in psychosomatic
illnesses
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Limbic System (cont.)
• Limbic system interacts with prefrontal lobes
– Allows us to react emotionally to things we
consciously understand to be happening
– Makes us consciously aware of emotional
richness in our lives
• Hippocampus and amygdaloid body also play
a role in memory
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Reticular Formation
• Extends through central core of brain stem
• Three broad columns run length of brain stem
– Raphe nuclei
– Medial (large cell) group of nuclei
– Lateral (small cell) group of nuclei
• Has far-flung axonal connections with
hypothalamus, thalamus, cerebral cortex,
cerebellum, and spinal cord
– Connections allow it to govern brain arousal
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Reticular Formation (cont.)
• Reticular activating system (RAS)
– Sends impulses to cerebral cortex to keep it
conscious and alert
– Filters out repetitive, familiar, or weak stimuli
(~99% of all stimuli is not relayed to
consciousness)
– Inhibited by sleep centers, alcohol, drugs
– Severe injury can result in permanent
unconsciousness (coma)
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Reticular Formation (cont.)
• Motor function of reticular formation helps
control coarse limb movements via
reticulospinal tracts
• Reticular autonomic centers regulate visceral
motor functions
– Vasomotor centers
– Cardiac center
– Respiratory centers
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Figure 12.18 The reticular formation.
3 The continuous
stream of sensory
stimuli keeps the
cerebrum aroused
and alert.
Radiations
to cerebral
cortex
2 RAS neurons
relay sensory
stimuli to the
cerebrum through
the thalamus.
1 Sensory axons
synapse on
reticular activating
system (RAS)
neurons in the
brain stem.
Reticular activating
system (RAS)
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Visual
impulses
Reticular
formation
nuclei in
brain stem
Auditory impulses
Ascending general
sensory tracts
(touch, pain, temperature)
Descending projections
• From reticular formation
nuclei to the spinal cord
• Help regulate skeletal
and visceral muscle activity
Table 12.1-1 Functions of Major Brain Regions
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Table 12.1-2 Functions of Major Brain Regions (continued)
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Table 12.1-3 Functions of Major Brain Regions (continued)
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Table 12.1-4 Functions of Major Brain Regions (continued)
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12.7 Higher Mental Functions
• Analysis of higher mental functions include:
– Language
– Memory
– Brain waves and EEGs
– Consciousness
– Sleep and sleep-wake cycles
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Language
• Language implementation system involves
association cortex of left hemisphere
• Main areas include:
– Broca’s area: involved in speech production
• Patients with lesions in Broca’s understand words, but
cannot speak
– Wernicke’s area: involved in understanding
spoken and written words
• Patients with lesions in Wernicke’s can speak, but
words are nonsensible
• Corresponding areas on right side are involved
with nonverbal language components
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Figure 12.7a Functional and structural areas of the cerebral cortex.
Motor areas
Primary motor cortex
Sensory areas and related
association areas
Central sulcus
Primary somatosensory
cortex
Somatosensory
association cortex
Premotor cortex
Frontal eye field
Broca’s area
(outlined by dashes)
Anterior association area
(prefrontal cortex)
Working memory for
spatial tasks
Executive area for task
management
Solving complex,
multitask problems
Gustatory cortex
(in insula)
Primary visual
cortex
Visual
association area
Auditory
association area
Primary
auditory cortex
Lateral view, left cerebral hemisphere
Motor association cortex
Sensory association cortex
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Taste
Wernicke’s area
(outlined by dashes
within the posterior
association area)
Working memory for
object-recall tasks
Primary motor cortex
Somatic
sensation
Primary sensory cortex
Multimodal association cortex
Vision
Hearing
Memory
• Memory: storage and retrieval of information
• Different kinds of memory
– Declarative memory of facts (names, faces,
words, dates)
– Procedural memory of skills (playing piano)
– Motor memory memory of motor skills (riding a
bike)
– Emotional memory memory of experiences
linked to an emotion (heart pounding when you
hear rattlesnake)
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Memory (cont.)
• Two stages of declarative memory storage:
– Short-term memory (STM, or working memory):
temporary holding of information
• Limited to seven or eight pieces of information
– Long-term memory (LTM) has limitless capacity
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Memory (cont.)
• Factors affecting transfer from STM to LTM
– Emotional state: best if alert, motivated,
surprised, or aroused
– Rehearsal: repetition and practice
– Association: tying new information with old
memories
– Automatic memory: subconscious information
stored in LTM
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Memory (cont.)
• Memory consolidation involves fitting new
facts into categories already stored in cerebral
cortex
• Hippocampus, temporal cortical areas,
thalamus, and prefrontal cortex are involved in
consolidation
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Figure 12.19 Memory processing.
Outside stimuli
General and special sensory receptors
Afferent inputs
Temporary storage
(buffer) in
cerebral cortex
Data selected
for transfer
Automatic
memory
Short-term
memory (STM)
Retrieval
Forget
Forget
Data transfer
influenced by:
Excitement
Rehearsal
Associating new
data with stored
data
Long-term
memory
(LTM)
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Data
permanently lost
Data unretrievable
Clinical – Homeostatic Imbalance 12.5
• Damage to hippocampus or surrounding
temporal lobe structures on either side result in
only slight memory loss
• Bilateral destruction causes widespread
amnesia
• Anterograde amnesia: consolidated memories
are not lost, but new inputs are not associated
with old one
– Person lives in the here and now
– Memory of conversations from just 5 minutes
before would not be remembered
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Clinical – Homeostatic Imbalance 12.5
• Retrograde amnesia: loss of memories formed
in the distant past
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Brain Wave Patterns and the EEG
• Brain waves reflect electrical activity of higher
mental functions
– Normal brain functions are continuous and hard
to measure
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Brain Wave Patterns and the EEG (cont.)
• Electroencephalogram (EEG) records electrical
activity that accompanies brain function
– Used for diagnosing epilepsy and sleep disorders
– Localizes lesions, tumors, infarcts, infections,
abscesses
– Used in research and also to determine brain
death
– Electrodes placed on scalp measure electrical
potential differences between various cortical
areas
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Figure 12.20a Electroencephalography (EEG) and brain waves.
Scalp electrodes are used to record brain
wave activity.
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Brain Wave Patterns and the EEG (cont.)
• EEG measures patterns of neuronal electrical
activity generated by synaptic activity in cortex
– Each person's brain waves are unique
– Patterns change with age, sensory stimuli, brain
disease, and chemical state of body
• Measures wave frequency in Hertz (Hz),
numbers of peaks per second (1 Hz = 1 peak
per second)
• Can be grouped into four classes based on Hz:
– Alpha, beta, theta, or delta waves
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Brain Wave Patterns and the EEG (cont.)
• Alpha waves: (8–13 Hz)—regular and rhythmic,
low-amplitude, synchronous waves indicating an
“idling” brain
• Beta waves: (14–30 Hz)—rhythmic, less
regular waves occurring when mentally alert
• Theta waves: (4–7 Hz)—more irregular;
common in children and uncommon in awake
adults
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Brain Wave Patterns and the EEG (cont.)
• Delta waves: (4 Hz or less)—high-amplitude
waves of deep sleep and when reticular
activating system is suppressed, as during
anesthesia; indicates brain damage in awake
adult
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Figure 12.20b Electroencephalography (EEG) and brain waves.
1-second interval
Alpha waves — awake but relaxed
Beta waves — awake, alert
Theta waves — common in children
Delta waves — deep sleep
Brain waves shown in EEGs
fall into four general classes.
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Clinical – Homeostatic Imbalance 12.6
• Epileptic seizure: torrent of electrical
discharges by groups of neurons
– Prevent any other messages from getting
through
• Victim of epilepsy may lose consciousness, fall
stiffly, and have uncontrollable jerking
• Epilepsy is not associated with intellectual
impairments
• Epilepsy occurs in 1% of population
– Genetic factors play a role, but brain injuries,
stroke, infections, or tumors can also be causes
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Clinical – Homeostatic Imbalance 12.6
• Aura (sensory hallucination) may precede
seizure
• Absence seizures (formerly petit mal)
– Mild seizures of young children: expression goes
blank for few seconds
• Tonic-clonic seizures (formerly grand mal)
– Most severe; last few minutes
– Victim loses consciousness, bones broken
during intense convulsions, loss of bowel and
bladder control, and severe biting of tongue
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Clinical – Homeostatic Imbalance 12.6
• Control of epilepsy includes anticonvulsive
drugs, vagus nerve stimulator or deep brain
stimulator implantations that deliver pulses to
vagus nerve or directly to brain to stabilize brain
activity
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Consciousness
• Consciousness involves:
– Perception of sensation
– Voluntary initiation and control of movement
– Capabilities associated with higher mental
processing (memory, logic, judgment, etc.)
• Clinically defined on continuum that grades
behavior in response to stimuli: alertness,
drowsiness (lethargy), stupor, and coma
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Consciousness (cont.)
• Current suppositions on consciousness
– Involves simultaneous activity of large cortical
areas
– Superimposed on other neural activities
– Holistic and totally interconnected
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Clinical – Homeostatic Imbalance 12.7
• Except during sleep, loss of consciousness
signals that brain function is impaired
• Fainting or syncopy: brief loss of
consciousness
– Most often due to inadequate cerebral blood flow
– Due to low blood pressure or ischemia from
hemorrhage or sudden, severe emotional stress
• Coma: unconsciousness for extended period
– Not the same as deep sleep; oxygen
consumption is lowered
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Clinical – Homeostatic Imbalance 12.7
• Brain death: irreversible coma
– Ethical and legal issues surround decisions on
whether person is dead or alive
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Sleep and Sleep-Wake Cycles
• Sleep: state of partial unconsciousness from
which person can be aroused by stimulation
• Cortical activity is depressed, but brain stem
activity doesn’t change
• Types of sleep:
– Two major types of sleep (defined by EEG
patterns)
• Non–rapid eye movement (NREM) sleep
– Broken into four stages
• Rapid eye movement (REM) sleep
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Sleep and Sleep-Wake Cycles (cont.)
• Types of sleep (cont.):
– We pass through first two stages of NREM
during the first 30–45 minutes of sleep, then
move into stages 3 and 4, referred to as slowwave sleep
• Frequency of waves declines, but amplitude increases
• EEG, heart rate, respiratory rate, blood pressure, and
GI motility change
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Sleep and Sleep-Wake Cycles (cont.)
• Types of sleep (cont.):
– At ~90 minutes in, fourth stage ends, and REM
sleep begins abruptly
• Temporary paralysis, except for rapid eye movements
• Oxygen consumption, heart rate, and breathing
increase; increase can be greater than when awake
• Most dreaming occurs in REM
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Figure 12.21a Types and stages of sleep.
Awake
REM: Skeletal muscles (except
ocular muscles and diaphragm)
are actively inhibited; most
dreaming occurs.
NREM stage 1: Relaxation
begins; EEG shows alpha
waves; arousal is easy.
NREM stage 2: Irregular EEG
with sleep spindles (short highamplitude bursts); arousal is
more difficult.
NREM stage 3: Sleep
deepens; theta and delta
waves appear; vital signs
decline.
NREM stage 4: EEG is
dominated by delta waves;
arousal is difficult; bedwetting, night terrors, and
sleepwalking may occur.
Typical EEG patterns
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Sleep and Sleep-Wake Cycles (cont.)
• How sleep is regulated
– Alternating cycles of sleep and wakefulness
reflect natural circadian (24-hour) rhythm
– RAS activity is inhibited during sleep, but RAS
also mediates sleep stages
– Suprachiasmatic and preoptic nuclei of
hypothalamus time sleep cycle
• Hypothalamus releases orexins that help cortex to
wake up
– Typical sleep pattern alternates between REM
and NREM sleep
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Figure 12.21b Types and stages of sleep.
Awake
REM
Stage 1
NREM
Stage 2
Stage 3
Stage 4
1
2
3
4
5
Time (hrs)
6
Typical progression of an adult through one
night’s sleep stages
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7
Sleep and Sleep-Wake Cycles (cont.)
• Importance of sleep
– Slow-wave sleep (NREM stages 3 and 4)
presumed to be restorative stage
– People deprived of REM sleep become moody
and depressed
– REM sleep may:
1. Give brain opportunity to analyze day’s events and
work through emotional events or problems
2. Eliminate unneeded synapses that were formed
(dream to forget)
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Sleep and Sleep-Wake Cycles (cont.)
– Daily sleep requirements decline with age
• Stage 4 sleep declines steadily and may disappear
after age 60
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Clinical – Homeostatic Imbalance 12.8
• Sleep disorders include:
• Narcolepsy: abrupt lapse into sleep from
awake state
– Orexins (“wake-up” chemicals from
hypothalamus) may be being destroyed by
immune system
• Offer key to possible treatment
• Insomnia: chronic inability to obtain amount or
quality of sleep needed
– May be treated by blocking orexin action
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12.8 Protection of Brain
Meninges
• Function of meninges:
– Cover and protect CNS
– Protect blood vessels and enclose venous
sinuses
– Contain cerebrospinal fluid (CSF)
– Form partitions in skull
• Consists of three layers (from external to
internal): dura mater, arachnoid mater, and
pia mater
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Figure 12.22 Meninges: dura mater, arachnoid mater, and pia mater.
Superior
sagittal sinus
Subdural
space
Subarachnoid
space
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Skin of scalp
Periosteum
Bone of skull
Dura mater
• Periosteal layer
• Meningeal layer
Arachnoid mater
Pia mater
Arachnoid granulation
Blood vessel
Falx cerebri
(in longitudinal
fissure only)
Meninges (cont.)
• Dura mater
– Strongest meninx
– Made up of two layers of fibrous connective
tissue
• Periosteal layer attaches to inner surface of skull
– Found only in brain, not spinal cord
• Meningeal layer: true external covering of brain
– Extends into vertebral canal as spinal dura mater
• Two layers are mostly fused, but separate in certain
areas to form dural venous sinuses
– Sinuses collect venous blood from brain, empty into
jugular veins of neck
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Meninges (cont.)
• Dura mater (cont.)
– Dura mater extends inward in several areas to
form flat partitions that divide cranial cavity
• Partitions referred to as dural septa
• Act to limit excessive movement of brain
• Three main septa:
– Falx cerebri: in longitudinal fissure; attached to crista
galli
– Falx cerebelli: along vermis of cerebellum
– Tentorium cerebelli: horizontal dural fold over
cerebellum and in transverse fissure
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Figure 12.23a Dural septa and dural venous sinuses.
Superior
sagittal sinus
Falx cerebri
Straight
sinus
Crista galli of
the ethmoid
bone
Pituitary
gland
Midsagittal view
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Tentorium
cerebelli
Falx cerebelli
Figure 12.23b Dural septa and dural venous sinuses.
Superior
sagittal sinus
Falx cerebri
Parietal
bone
Scalp
Occipital lobe
Tentorium
cerebelli
Dura mater
Falx cerebelli
Transverse
sinus
Cerebellum
Arachnoid mater
over medulla
oblongata
Posterior dissection
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Temporal
bone
Meninges (cont.)
• Arachnoid mater
– Middle layer with spiderweb-like extensions
– Separated from dura mater by subdural space
– Subarachnoid space contains CSF and largest
blood vessels of brain
– Arachnoid granulations protrude through dura
mater into superior sagittal sinus
• Permit reabsorption of CSF back into venous blood
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Figure 12.22 Meninges: dura mater, arachnoid mater, and pia mater.
Superior
sagittal sinus
Subdural
space
Subarachnoid
space
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Skin of scalp
Periosteum
Bone of skull
Dura mater
• Periosteal layer
• Meningeal layer
Arachnoid mater
Pia mater
Arachnoid granulation
Blood vessel
Falx cerebri
(in longitudinal
fissure only)
Meninges (cont.)
• Pia mater
– Delicate connective tissue that clings tightly to
brain, following every convolution
• Contains many tiny blood vessels that feed brain
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Figure 12.22 Meninges: dura mater, arachnoid mater, and pia mater.
Superior
sagittal sinus
Subdural
space
Subarachnoid
space
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Skin of scalp
Periosteum
Bone of skull
Dura mater
• Periosteal layer
• Meningeal layer
Arachnoid mater
Pia mater
Arachnoid granulation
Blood vessel
Falx cerebri
(in longitudinal
fissure only)
Clinical – Homeostatic Imbalance 12.9
• Meningitis: inflammation of the meninges
• May spread to CNS, which would lead to
inflammation of the brain, referred to as
encephalitis
• Meningitis is usually diagnosed by observing
microbes in a sample of CSF obtained via
lumbar puncture
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Cerebrospinal Fluid (CSF)
• Cerebrospinal fluid (CSF) forms a liquid
cushion of constant volume around brain
• Functions
– Gives buoyancy to CNS structures
• Reduces weight of brain by 97% by floating it so it is
not crushed under its own weight
– Protects CNS from blows and other trauma
– Nourishes brain and carries chemical signals
• Composed of watery solution formed from blood
plasma, but with less protein and different ion
concentrations from plasma
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Cerebrospinal Fluid (CSF) (cont.)
• Choroid plexus: cluster of capillaries that hangs
from roof of each ventricle, enclosed by pia
mater and surrounding layer of ependymal cells
– CSF is filtered from plexus at constant rate
– Ependymal cells use ion pumps to control
composition of CSF and help cleanse CSF by
removing wastes
– Cilia of ependymal cells help to keep CSF in
motion
• Normal adult CSF volume of ~150 ml is replaced
every 8 hours
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Slide 2
Figure 12.24 Formation, location, and circulation of CSF.
Superior
sagittal sinus
Arachnoid
granulation
Choroid plexus
Subarachnoid space
Arachnoid mater
Meningeal dura mater
1
Periosteal dura mater
Right lateral ventricle
(deep to cut)
Interventricular
foramen
Third ventricle
Choroid plexus
of fourth ventricle
Cerebral aqueduct
Lateral aperture
Fourth ventricle
Median aperture
Central canal
of spinal cord
1 The choroid plexus of each ventricle produces CSF.
CSF circulation
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Slide 3
Figure 12.24 Formation, location, and circulation of CSF.
Superior
sagittal sinus
Arachnoid
granulation
Choroid plexus
Subarachnoid space
Arachnoid mater
Meningeal dura mater
Periosteal dura mater
1
Right lateral ventricle
(deep to cut)
Interventricular
foramen
Third ventricle
Choroid plexus
of fourth ventricle
Cerebral aqueduct
Lateral aperture
Fourth ventricle
Median aperture
Central canal
of spinal cord
1 The choroid plexus of each ventricle produces CSF.
2 CSF flows through the ventricles and into the
subarachnoid space via the median and lateral apertures.
CSF circulation
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2
Slide 4
Figure 12.24 Formation, location, and circulation of CSF.
Superior
sagittal sinus
Arachnoid
granulation
Choroid plexus
Subarachnoid space
Arachnoid mater
Meningeal dura mater
Periosteal dura mater
1
Right lateral ventricle
(deep to cut)
Interventricular
foramen
Third ventricle
3
Choroid plexus
of fourth ventricle
Cerebral aqueduct
Lateral aperture
Fourth ventricle
Median aperture
Central canal
of spinal cord
1 The choroid plexus of each ventricle produces CSF.
2 CSF flows through the ventricles and into the
subarachnoid space via the median and lateral apertures.
3 CSF flows through the subarachnoid space.
CSF circulation
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2
Slide 5
Figure 12.24 Formation, location, and circulation of CSF.
4
Superior
sagittal sinus
Arachnoid
granulation
Choroid plexus
Subarachnoid space
Arachnoid mater
Meningeal dura mater
Periosteal dura mater
1
Right lateral ventricle
(deep to cut)
Interventricular
foramen
Third ventricle
3
Choroid plexus
of fourth ventricle
Cerebral aqueduct
Lateral aperture
Fourth ventricle
Median aperture
Central canal
of spinal cord
1 The choroid plexus of each ventricle produces CSF.
2 CSF flows through the ventricles and into the
subarachnoid space via the median and lateral apertures.
3 CSF flows through the subarachnoid space.
4 CSF is absorbed into the dural venous sinuses via
the arachnoid granulations.
CSF circulation
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2
Figure 12.24b Formation, location, and circulation of CSF.
Ependymal
cells
Capillary
Section
of choroid
plexus
Connective
tissue of
pia mater
Wastes and
unnecessary
solutes absorbed
Cavity of
ventricle
CSF forms as a filtrate
containing glucose,
oxygen, vitamins, and ions
(Na+, Cl-, Mg2+, etc.)
CSF formation by choroid plexuses
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Clinical – Homeostatic Imbalance 12.10
• Hydrocephalus: obstruction blocks CSF
circulation or drainage, resulting in increased
pressure
• In newborns, skull bones are unfused, so
increased pressure causes head to enlarge
• In adults, rigidity of the skull keeps pressure
within, potentially leading to brain damage
– Can compress blood vessels and crush soft
nervous tissue
• Treatment is to drain CSF with ventricular shunt
to abdominal cavity
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Figure 12.25 Hydrocephalus in a newborn.
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Blood Brain Barrier
• Helps maintain stable environment for brain
– Chemical variations could lead to uncontrollable
neuron firings
• Exceptionally impermeable tight junctions keep
brain separated from many bloodborne
substances
• Substances must past through three layers
before gaining entry into neurons
1. Continuous endothelium of capillary walls
2. Thick basal lamina around capillaries
3. Feet of astrocytes surrounding neurons
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Figure 11.4a Neuroglia.
Capillary
Neuron
Astrocyte
Astrocytes are the most
abundant CNS neuroglia.
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Blood Brain Barrier (cont.)
• Barrier is selective, but not absolute
– Allows certain nutrients to move by facilitated
diffusion
– Metabolic wastes, proteins, toxins, most drugs,
small nonessential amino acids, K+ denied
– Allows any fat-soluble substances to pass,
including alcohol, nicotine, and anesthetics
• Absent in some areas, such as vomiting center
and hypothalamus
– Necessary to monitor chemical composition and
temperature of blood
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12.10 Brain Injuries and Disorders
Traumatic Brain Injuries
• Brain injuries include:
– Concussion: temporary alteration in function
– Contusion: permanent damage
– Subdural or subarachnoid hemorrhage:
pressure from blood may force brain stem
through foramen magnum, resulting in death
– Cerebral edema: swelling of brain associated
with traumatic head injury
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Cerebrovascular Accidents (CVAs)
• Also referred to as “strokes”
• Ischemia: tissue deprived of blood supply,
leading to death of brain tissue
– Can be caused by blockage of cerebral artery by
blood clot
– Glutamate acts as excitotoxin, worsening
condition
• Hemiplegia (paralysis on one side) or sensory
and speech deficits may result
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Cerebrovascular Accidents (CVAs) (cont.)
• Transient ischemic attacks (TIAs): temporary
episodes of reversible cerebral ischemia
• Tissue plasminogen activator (TPA) is only
approved treatment for stroke
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Degenerative Brain Disorders
• Alzheimer’s disease (AD)
– Progressive degenerative disease of brain that
results in dementia
• Key proteins appear to be misfolded and malfunction
– Memory loss, short attention span,
disorientation, eventual language loss, irritability,
moodiness, confusion, hallucinations
– Plaques of beta-amyloid peptides form in brain
– Neurofibrillary tangles inside neurons interfere
with transport mechanisms, eventually killing
neuron
– As brain cells die, brain shrinks
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Figure 12.26 Brain activity is decreased by Alzheimer’s disease.
Normal
Alzheimer
Anterior
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Degenerative Brain Disorders (cont.)
• Parkinson’s disease
– Degeneration of dopamine-releasing neurons of
substantia nigra
– Basal nuclei deprived of dopamine become
overactive, resulting in tremors at rest
– Cause unknown, but theories include
mitochondrial abnormalities or protein
degradation pathways
– Treatment includes L-dopa (dopamine
precursor), deep brain stimulation, gene therapy
• Research into stem cell transplants is promising
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Degenerative Brain Disorders (cont.)
• Huntington’s disease
– Fatal hereditary disorder caused by
accumulation of protein huntingtin in brain cells
• Leads to degeneration of basal nuclei and cerebral
cortex
– Initial symptoms include wild, jerky “flapping”
movements
– Later marked by mental deterioration
• Usually fatal within 15 years of onset
– Treated with drugs that block dopamine effects
– Stem cell implant research is promising
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Diagnostic Procedures for Assessing CNS
Dysfunction
• Simple test can include knee-jerk reflex with
hammer tapped against quadriceps tendon
– Abnormal responses may indicate intracranial
hemorrhage, multiple sclerosis, or hydrocephalus
• CT, MRI, and PET allow for quick identification of
tumors, lesions, plaque, or areas of infarct
– Radioactive tracers help visualize specific areas
• Cerebral angiography uses X rays with dye to
pinpoint any stroke causing clots
• Ultrasound can be used to evaluate blood flow
through arteries feeding the brain
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