Download Chapter 14 - Brain and Spinal Cord

Chapter
14
The Brain
and Cranial
Nerves
PowerPoint® Lecture Slides
prepared by Jason LaPres
Lone Star College - North Harris
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Copyright © 2009 Pearson Education, Inc.,
publishing as Pearson Benjamin Cummings
An Introduction to the Brain and Cranial
Nerves
 The Adult Human Brain
 Ranges from 750 cc to 2100 cc
 Contains almost 97% of the body’s neural tissue
 Average weight about 1.4 kg (3 lb)
 Male brains are typically larger but there is no
correlation between brain size and intelligence.
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The Brain
 Six Regions of the Brain
 Cerebrum
 Cerebellum
 Diencephalon
 Mesencephalon
 Pons
 Medulla oblongata
3D Peel-Away of the Brain
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The Brain
 Cerebrum
 Largest part of brain
 Controls higher mental functions
 conscious thoughts, sensations, intellect, memory,
and skeletal muscle contractions all occur in the
cerebrum
 Divided into left and right cerebral hemispheres
 Surface layer of gray matter (neural cortex)
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The Brain
 Cerebrum
 Neural cortex
 Also called cerebral cortex
 Folded surface increases
surface area
 Elevated ridges (gyri)
 Shallow depressions (sulci)
 Deep grooves (fissures)
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The Brain
 Cerebellum
 Second largest part of brain
 Coordinates repetitive body movements
 Two hemispheres
 Covered with cerebellar cortex
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The Brain
 Diencephalon
 Located under cerebrum and cerebellum
 Links cerebrum with brain stem

Composed of:
 L & R thalamus
– Relays and processes sensory information
 Hypothalamus
– Contains centers involved with emotions, autonomic function, and hormone
control.
– Connected to the pituitary gland by infundibulum (stalk)
 Epithalamus
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The Brain
 The Brain Stem
 Processes information between
 Spinal cord and cerebrum or cerebellum
 Includes
 Mesencephalon
 Pons
 Medulla oblongata
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The Brain
 The Brain Stem
 Mesencephalon
 Also called midbrain
 Processes sight, sound, and associated reflexes
– Closing your eyes at loud noises
 Maintains consciousness
 Pons
 Connects cerebellum to brain stem
 Is involved in somatic and visceral motor control
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The Brain
 The Brain Stem
 Medulla oblongata
 Connects brain to spinal cord
 Relays sensory information
 Regulates autonomic functions:
– heart rate, blood pressure, and digestion
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The Brain
Figure 14–1 An Introduction to Brain Structures and Functions.
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The Brain
 Embryological Development
 Determines organization of brain structures
 Neural tube
 Origin of brain
 Hollow cylinder filled with neurocoel
 Enlarges into three primary brain vesicles
– Prosencephalon - forebrain
– Mesencephalon - midbrain
– Rhombencephalon - hindbrain
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The Brain
 Origins of Brain Structures
 The prosencephalon and rhombencephalon are further
subdivided forming the secondary brain vesicles.
 Prosencephalon forms the:
 Telencephalon – forms the cerebrum
 Diencephalon – composed of L & R thalamus, and hypothalamus
 Rhombencephalon forms the:
 Metencephalon
 It will ultimately form the cerebellum and pons
 Myelencephalon
 It will ultimately form the medulla oblongata.
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The Brain
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The Brain
 Ventricles of the Brain
 Origins of ventricles
 Neural tube encloses neurocoel
 Neurocoel expands to form chambers (ventricles) lined with
ependymal cells
 Each cerebral hemisphere contains one large lateral
ventricle
 Separated by a thin medial partition (septum pellucidum)
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The Brain
 Ventricles of the Brain
 Third ventricle
 Ventricle of the diencephalon
 Lateral ventricles communicate with third ventricle:
– via interventricular foramen (foramen of Monro)
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The Brain
 Ventricles of the Brain
 Fourth ventricle
 Extends into medulla oblongata
 Becomes continuous with central canal of the
spinal cord
 Connects with third ventricle:
– via narrow canal in mesencephalon
– aqueduct of midbrain
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The Brain
Figure 14–2 Ventricles of the Brain.
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The Brain
 Cerebrospinal Fluid (CSF)
 All of the ventricles are filled with CSF which
continuously circulates from the ventricles and
central canal into the subarachnoid space of
the surrounding meninges.
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Brain Protection and Support
 Physical protection in the brain is done by:
 Bones of the cranium
 Cranial meninges
 Cerebrospinal fluid
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Brain Protection and Support
 The Cranial Meninges
 Made of three layers:
 Dura mater
 Arachnoid mater
 Pia mater
 All are continuous with spinal meninges
 Protect the brain from cranial trauma
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Brain Protection and Support
 The Cranial Meninges
 Dura mater
 Inner fibrous layer (meningeal layer)
 Outer fibrous layer (endosteal layer) fused to periosteum
 Venous sinuses between two layers
 Arachnoid mater
 Covers brain
 Contacts epithelial layer of dura mater
 Subarachnoid space: between arachnoid mater and pia mater
 Pia mater
 Attached to brain surface by astrocytes
 Extends into every fold
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Brain Protection and Support
 Dural Folds
 Folded inner layer of dura mater
 Extend into cranial cavity
 Stabilize and support brain
 Contain collecting veins (dural sinuses)
 Three largest dural folds are:
 falx cerebri
 tentorium cerebelli
 falx cerebelli
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Brain Protection and Support
 Dural Folds
 Falx cerebri
 Projects between the cerebral hemispheres
 Contains superior sagittal sinus and inferior sagittal
sinus
 Tentorium cerebelli
 Separates cerebellum and cerebrum
 Contains transverse sinus
 Falx cerebelli
 Divides cerebellar hemispheres below the tentorium cerebelli
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Brain Protection and Support
Figure 14–3a The Relationship among the Brain, Cranium, and
Meninges.
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Brain Protection and Support
Figure 14–3b The Relationship among the Brain, Cranium, and
Meninges.
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Brain Protection and Support
 Cerebrospinal Fluid (CSF)
 Surrounds all exposed surfaces of CNS
 Interchanges with interstitial fluid of brain
 Functions of CSF
 Cushions delicate neural structures
 Supports brain
 Transports nutrients, chemical messengers, and
waste products
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Brain Protection and Support
 Cerebrospinal Fluid (CSF)
 Produced in the choroid plexus
 Consists of a combination of specialized ependymal cells and
permeable capillaries.
 About 500 ml of CSF is made per day
 It circulates from the choroids plexus through the ventricles,
central canal of the spinal cord, subarachnoid space, brain, spinal
cord, and cauda equina.

It is then absorbed into the venous circulation at the arachnoid
granulations (formed from arachnoid villi).
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Brain Protection and Support
 Cerebrospinal Fluid (CSF)
 Hydrocephalus
 Failure of infants to reabsorb CSF
– causes – “Water on the brain”
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Brain Protection and Support
Figure 14–4 The Formation and Circulation of Cerebrospinal Fluid.
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The Medulla Oblongata
 The Medulla Oblongata
 Connects the brain to the spinal cord
 All communication between the brain and
spinal cord involve tracts that ascend or
descend through here
 Center for coordination of relatively complex
autonomic reflexes and the control visceral
functions
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The Medulla Oblongata
 The Medulla Oblongata
 Includes three groups of nuclei
 Autonomic nuclei
 Sensory and motor nuclei of cranial nerves
 Relay stations along sensory and motor pathways
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The Medulla Oblongata
 Autonomic Nuclei of the Medulla Oblongata
 Reticular formation
 Gray matter with embedded nuclei
 Regulates autonomic functions
 Reflex centers
 Control peripheral systems:
– cardiovascular centers:
» cardiac center
» control blood flow through peripheral tissues
– respiratory rhythmicity centers
sets pace for respiratory movements
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The Medulla Oblongata
 Sensory and Motor Nuclei of the Medulla
Oblongata
 Associated with 5 of 12 cranial nerves (VIII,
IX, X, XI, XII)
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The Medulla Oblongata
 Relay Stations of the Medulla Oblongata
 Nucleus gracilis and nucleus cuneatus
 Pass somatic sensory information to thalamus
 Solitary nucleus
 Receives visceral sensory information
 Olivary nuclei (olives)
 Relay information about somatic motor commands
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The Medulla Oblongata
Figure 14–6a The Medulla Oblongata and Pons.
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The Pons
 The Pons
 Links cerebellum with mesencephalon, diencephalon,
cerebrum, and spinal cord
 Contains four groups of components:
 sensory and motor nuclei of cranial nerves V, VI, VII, and VIII
– They innervate the jaw muscles, the anterior surface of the face,
one of the extraocular muscles, and the sense organs of the inner
ear.
 Nuclei involved with the control of respiration
 nuclei and tracts that process and relay information heading to
or from the cerebellum
 Ascending, Descending, and Transverse Tracts
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The Cerebellum

Autonomic processing center

Functions of the Cerebellum

adjusting the postural muscles of the body


coordinates rapid, automatic adjustments that maintain
balance and equilibrium
programming and fine-tuning movements
controlled at the conscious and
subconscious levels
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The Cerebellum
 Structures of the Cerebellum
 Folia
 Surface of cerebellum
 Highly folded neural cortex
 Anterior and posterior lobes
 Separated by primary fissure
 Cerebellar hemispheres:
 Separated at midline by vermis
 Vermis
 Narrow band of cortex
 Flocculonodular lobe
 Below fourth ventricle
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The Cerebellum
 Structures of the Cerebellum
 Purkinje cells
 Large, branched cells
 Found in cerebellar cortex
 Receive input from up to 200,000 synapses
 Arbor vitae
 Highly branched, internal white matter of cerebellum
 Cerebellar nuclei: embedded in arbor vitae:
– relay information to Purkinje cells
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The Cerebellum
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The Mesencephalon
 Tectum
 roof of the mesencehalon and area posterior to mesencephalic
aqueduct
 It contains two pairs of sensory nuclei collectively known as the
corpora quadrigemina
– process visual and auditory sensations.
 Tegmentum
 area anterior to the mesencephalic aqueduct
On each side, the tegmentum contains:
 Red nucleus- gives red color because of numerous blood vessels. It
issues subconscious motor commands that affect upper limb position
and background muscle tone.
 Substantia nigra – the gray matter in this region give it a black color
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The Mesencephalon
 Structures of the Mesencephalon
 Cerebral peduncles
 Nerve fiber bundles on ventrolateral surfaces
 Contain:
– descending fibers to cerebellum
– motor command fibers
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The Mesencephalon
Figure 14–8a The Mesencephalon.
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The Mesencephalon
Figure 14–8b The Mesencephalon.
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The Diencephalon
 Integrates sensory information and motor
commands
 Includes
 epithalamus
 thalamus
 hypothalamus
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The Diencephalon

Epithalamus



Is the roof of the diencephalon superior to
the third ventricle
The anterior portion contains an extensive
area of choroids plexus
The posterior portion contains the pineal
gland
– endocrine structure that secretes melatonin
» important in the regulation of day-night cycles and
also in the regulation of reproductive functions.
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The Diencephalon
 The Thalamus
 Filters ascending sensory information for primary sensory
cortex
 Called “sensory relay center”
 Final relay point for ascending sensory information
 Relays information between basal nuclei and cerebral cortex
 The third ventricle
 Separates left thalamus and right thalamus
 Interthalamic adhesion (or intermediate mass):
– projection of gray matter
– extends into ventricle from each side
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The Diencephalon
 The Thalamus
 Thalamic nuclei
 Are rounded masses that form thalamus
 Relay sensory information to basal nuclei and
cerebral cortex
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The Diencephalon
 Five Groups of Thalamic Nuclei
 Anterior group
 Anterior nuclei
 Part of limbic system (emotions)
 Medial group
 Provides awareness of emotional states
 Ventral group
 Relays sensory information
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The Diencephalon
 Five Groups of Thalamic Nuclei
 Posterior group
 Pulvinar nucleus (sensory)
 Lateral geniculate nucleus (visual)
 Medial geniculate nucleus (auditory)
 Lateral group
 Affects emotional states
 Integrates sensory information
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The Diencephalon
Figure 14–9 The Thalamus.
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The Diencephalon
 Hypothalamus
 Extends from the area superior to the optic chiasm (crossover of optic
tracts from the eyes) to the posterior margins of the mamillary bodies
 Mamillary bodies
– Process olfactory and other sensory information
– Control reflex eating movements
» chewing, licking, swallowing
 Infundibulum
– A narrow stalk
– Connects hypothalamus to pituitary gland
 Tuberal area
– Located between the infundibulum and mamillary bodies
– Helps control pituitary gland function
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The Diencephalon
Figure 14–10a The Hypothalamus in Sagittal Section.
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The Diencephalon
Figure 14–10b The Hypothalamus in Sagittal Section.
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The Diencephalon
 Eight Functions of the Hypothalamus
1. The subconscious control of skeletal muscle contractions such
as those associated with rage, pleasure, pain, and sexual
arousal.
2. The control of autonomic function such as heart rate, blood
pressure, and respiration
3. The coordination of activities of the nervous and endocrine
systems
4. The secretion of two hormones
 antidiuretic hormone (ADH) which restricts water loss in the
kidneys
 oxytocin (OT) which stimulates smooth muscle contractions in the
uterus and mammary glands of females and the prostate of males.
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The Diencephalon

Eight Functions of the Hypothalamus
5. The production of emotions and behavioral drives
such as the sensation of hunger and thirst.
6. Coordination between voluntary and autonomic
functions
7. Regulation of body temperature
8. The control of circadian rhythms which tells you
when to sleep.
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The Limbic System
 The Limbic System
 Is a functional grouping (not anatomical) that
 Establishes emotional states
 Links conscious functions of cerebral cortex with autonomic
functions of brain stem
 Facilitates memory storage and retrieval
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The Limbic System
 Components of the Limbic System
 Amygdaloid body
 Acts as interface between the limbic system, the cerebrum, and various
sensory systems
 Regulation of heart rate, “fight or flight response”, and linking emotions with
specific memories
 Limbic lobe of cerebral hemisphere
* Consists of the superficial folds (gyri) and underlying structures
adjacent to the diencephalon.
* There are three gyri in the limbic lobe:
-cingulated gyrus
-dentate gyrus
-parahippocampal gyrus
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The Limbic System
 Components of the Limbic System
 Hippocampus
 important in learning and the storage and retrieval of longterm memories
 Fornix
 Tract of white matter
 Connects hippocampus with hypothalamus
 Anterior nucleus of the thalamus
 Relays information from mamillary body to cingulate gyrus
 Reticular formation
 Stimulation or inhibition affects emotions (rage, fear, pain,
sexual arousal, pleasure)
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The Limbic System
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The Cerebrum
 The Cerebrum
 Is the largest part of the brain
 Controls all conscious thoughts and
intellectual functions
 Processes somatic sensory and motor
information
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The Cerebrum
 Cerebral cortex
 The cortical surface contains gyri (elevated ridges)
separated by sulci (shallow depressions) or fissures
(deeper grooves).
 The two cerebral hemispheres are almost completely
separated by a deep longitudinal fissure.
 Each hemisphere can be divided into lobes (regions)
– Central sulcus (a deep grove) divides the frontal lobe from the
parietal lobe
– Lateral suclus separates the frontal lobe from the temporal
lobe
– Parieto-occipital sulcus separates the parietal lobe from the
occipital lobe
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The Cerebrum
Figure 14–12b The Brain in Lateral View.
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The Cerebrum
 Three Functional Principles of the Cerebrum
 Each cerebral hemisphere receives sensory
information from, and sends motor commands to, the
opposite side of the body
 The two hemispheres have different functions,
although their structures are alike
 Correspondence between a specific function and a
specific region of cerebral cortex is not precise
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The Cerebrum
 The interior of the cerebrum consists
primarily of white matter
 The axons can be classified as:
 Association fibers
– interconnect areas of neural cortex within a single cerebral
hemisphere
 Commissural fibers
– interconnect and permit communication between the cerebral
hemispheres.
» Includes the corpus callosum and anterior commissure
 Projection fibers
– link the cerebral cortex to the diencephalons, brain stem,
cerebellum, and spinal cord
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The Cerebrum
 The Basal Nuclei
 Also called cerebral nuclei
 Are masses of gray matter
 Are embedded in white matter of cerebrum
 Involved with
 The subconscious control of skeletal muscle tone
 The coordination of learned movement patterns (walking,
lifting)
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The Cerebrum
 Structures of Basal Nuclei
 Caudate nucleus
 Curving, slender tail
 Lentiform nucleus
 Globus pallidus
 Putamen
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The Cerebrum
Figure 14–14c The Basal Nuclei.
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The Cerebrum
 Motor and Sensory Areas of the Cortex
 Central sulcus separates motor and sensory
areas
 Motor areas
 Precentral gyrus of frontal lobe:
– directs voluntary movements
 Primary motor cortex:
– is the surface of precentral gyrus
 Pyramidal cells:
– are neurons of primary motor cortex
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The Cerebrum
 Motor and Sensory Areas of the Cortex
 Sensory areas
 Postcentral gyrus of parietal lobe:
– receives somatic sensory information (touch, pressure,
pain, vibration, taste, and temperature)
 Primary sensory cortex:
– surface of postcentral gyrus
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The Cerebrum
 Special Sensory Cortexes
 Visual cortex
 Information from sight receptors
 Auditory cortex
 Information from sound receptors
 Olfactory cortex
 Information from odor receptors
 Gustatory cortex
 Information from taste receptors
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The Cerebrum
Figure 14–15a Motor and Sensory Regions of the Cerebral Cortex.
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The Cerebrum
 Association Areas
 Sensory association areas
 Monitor and interpret arriving information at sensory areas of
cortex
 Somatic motor association area (premotor cortex)
 Coordinates motor responses (learned movements)
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The Cerebrum
 Sensory Association Areas
 Somatic sensory association area
 Interprets input to primary sensory cortex (e.g., recognizes
and responds to touch)
 Visual association area
 Interprets activity in visual cortex
 Allows you to understand that c + a + t = cat
 Auditory association area
 Monitors auditory cortex
 Word recognition
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The Cerebrum
 General Interpretive Area
 Also called Wernicke area
 Present in only one hemisphere (usually left)
 Receives information from all sensory association
areas
 Coordinates access to complex visual and auditory
memories
 Plays an essential role in your personality
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The Cerebrum
 Other Integrative Areas
 Speech center
 Also called Broca’s area
 Is associated with general interpretive area
 Coordinates all vocalization functions (breathing and
vocalization needed for speech)
 Prefrontal cortex of frontal lobe
 Integrates information from sensory association areas
 Performs abstract intellectual activities (e.g.,
predicting consequences of actions)
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The Cerebrum
Figure 14–15b Motor and Sensory Regions of the Cerebral Cortex.
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The Cerebrum
 Hemispheric Lateralization
 Functional differences between left and right
hemispheres
 Each cerebral hemisphere performs certain
functions that are not ordinarily performed by
the opposite hemisphere
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The Cerebrum
 The Left Hemisphere
 In most people, left brain (dominant hemisphere)
controls
 Reading, writing, and math
 Decision making
 Speech and language
 The Right Hemisphere
 Right cerebral hemisphere relates to
 Senses (touch, smell, sight, taste, feel)
 Recognition (faces, voice inflections)
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The Cerebrum
Figure 14–16 Hemispheric Lateralization.
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The Cerebrum
 Monitoring Brain Activity
 Brain activity is assessed by an
electroencephalogram (EEG)
 Electrodes are placed on the skull
 Patterns of electrical activity (brain waves) are
printed out
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The Cerebrum
 Four Categories of Brain Waves
 Alpha waves
 Found in healthy, awake adults at rest with eyes closed
 Beta waves
 Higher frequency
 Found in adults concentrating or mentally stressed
 Theta waves
 Found in children
 Found in intensely frustrated adults
 May indicate brain disorder in adults
 Delta waves
 During sleep
 Found in awake adults with brain damage
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The Cerebrum
Figure 14–17a-d Brain Waves.
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The Cerebrum
 Synchronization
 A pacemaker mechanism
 Synchronizes electrical activity between
hemispheres
 Brain damage can cause desynchronization
 Seizure
 Is a temporary cerebral disorder
 Changes the electroencephalogram
 Symptoms depend on regions affected
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Cranial Nerves
 12 pairs connected to brain
 Four Classifications of Cranial Nerves
 Sensory nerves: carry somatic sensory information,
including touch, pressure, vibration, temperature, and
pain
 Special sensory nerves: carry sensations such as
smell, sight, hearing, balance
 Motor nerves: axons of somatic motor neurons
 Mixed nerves: mixture of motor and sensory fibers
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Cranial Nerves
 Cranial nerves are classified by primary
functions
 May also have important secondary functions
 Distributing autonomic fibers to peripheral ganglia
 The 12 cranial nerve groups are identified by
 Primary function
 Origin
 Pathway
 Destination
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Cranial Nerves
Figure 14–18 Origins of the Cranial Nerves.
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Cranial Nerves
 Olfactory Nerves (I)
 The olfactory nerve is composed of axons
from the olfactory receptors in the nasal
sensory epithelium.
 It carries olfactory information (sense of
smell) to the olfactory bulb of the brain.
 This is a pure sensory nerve fiber.
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Cranial Nerves
 Olfactory Nerve Structures
 Olfactory bulbs
 Located on either side of crista galli
 Olfactory tracts
 Axons of postsynaptic neurons
 Leading to cerebrum
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Cranial Nerves
 Optic Nerves (II)
 The optic nerve is composed of axons of the
ganglion cells in the eye.
 It carries visual information to the brain.
 This is a pure sensory nerve fiber.
 This nerve travels posteromedially from the
eye, exiting the orbit at the optic canal in the
lesser wing of the sphenoid bone. The optic
nerves join each other in the middle cranial
fossa to form the optic chiasm.
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Cranial Nerves
 Optic Nerve Structures
 Optic chiasm
 Where sensory fibers converge
 And cross to opposite side of brain
 Optic tracts
 Reorganized axons
 Leading to lateral geniculate nuclei
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Cranial Nerves
 Oculomotor Nerves (III)
 This is a pure motor nerve.
 It provides somatic motor innervation to four of the extrinsic
eye muscles:
–
–
–
–
the superior rectus
inferior rectus
medial rectus
inferior oblique muscles.
 It also innervates the muscles of the upper eyelid and the
intrinsic eye muscles (the pupillary eye muscle.)
 Together, CN III, CN IV and CN VI control the six muscles of
the eye.
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Cranial Nerves
 The Trochlear Nerves (IV)
 The trochlear nerve provides somatic motor
innervation to the superior oblique eye
muscle.
 This cranial nerve originates at the trochlear
nucleus located in the tegmentum of the
midbrain at the inferior colliculus level and
exits the posterior side of the brainstem.
 A pure motor nerve fiber.
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Cranial Nerves
 The Trigeminal Nerves (V)
 the largest cranial nerve .
 It provides sensory information from the face,
forehead, nasal cavity, tongue, gums and
teeth (touch, and temperature) and provides
somatic motor innervation to the muscles of
mastication or “chewing”.
 It is composed of both sensory and motor
axons.
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Cranial Nerves
Figure 14–22 The Trigeminal Nerve.
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Cranial Nerves
 The Abducens Nerves (VI)
 The abducens nerve carries somatic motor
innervation to one of the extrinsic eye
muscles, the lateral rectus muscle.
 It is another pure motor nerve fiber and
originates from the abducens nucleus located
in the caudal pons at the facial colliculus level.
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Cranial Nerves
Figure 14–21 Cranial Nerves Controlling the Extra-Ocular Muscles.
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Cranial Nerves
 The Facial Nerves (VII)
 The facial nerve carries somatic motor
innervation to the many muscles for facial
expression.
 It carries sensory information form the face
(deep pressure sensation) and taste
information from the anterior two thirds of the
tongue.
 It is composed of both sensory and motor
axons.
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Cranial Nerves
Figure 14–23a The Facial Nerve.
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Cranial Nerves
Figure 14–23b The Facial Nerve.
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Cranial Nerves
 The Vestibulocochlear Nerves (VIII)
 The vestibulocochlear nerve innervates
the hair cell receptors of the inner ear.
– balance
– hearing
 It is pure sensory nerve fiber.
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Cranial Nerves
Figure 14–24 The Vestibulocochlear Nerve.
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Cranial Nerves
 The Glossopharyngeal Nerves (IX)
 The glossopharyngeal nerve innervates the pharynx (upper part
of the throat), the soft palate and the posterior one-third of the
tongue.
 sensory information (touch, temperature, and pressure) from the
pharynx and soft palate
 taste sensation from the taste buds
 swallowing
 salivary glands
 supplies the carotid sinus and reflex control to the heart
 It is composed of both sensory and motor axons and originates
from the nucleus ambiguous in the reticular formation of the
medulla.
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Cranial Nerves
Figure 14–25 The Glossopharyngeal Nerve.
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Cranial Nerves
 The Vagus Nerves (X)
 Consists of many rootlets that come off of the brainstem just
behind the glossopharyngeal nerve.
 Longest cranial nerve
 Innervates many structures in the throat, including the muscles
of the vocal cords, thorax and abdominal cavity.
 Sensory information (touch, temperature and pressure) from the
external auditory meatus (ear canal) and a portion of the external
ear.
 Taste sensation from taste buds in the pharynx.
 Sensory information from the esophagus, respiratory tract, and
abdominal viscera (stomach, intestines, liver, etc.).
 It provides visceral motor innervation to the heart, stomach,
intestines, and gallbladder.
 It is composed of both sensory and motor axons.
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Cranial Nerves
Figure 14–26 The Vagus Nerve.
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Cranial Nerves
Figure 14–26 The Vagus Nerve.
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Cranial Nerves
 The Accessory Nerves (XI)
 The spinal accessory nerve has two
branches.
 Cranial branch provides somatic motor innervation
to some of the muscles in the throat involved in
swallowing.
 The spinal branch provides somatic motor
innervation to the trapezius muscles, providing
muscle movement for the upper shoulders head
and neck.
 It is pure motor nerve fiber.
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Cranial Nerves
 The Hypoglossal Nerves (XII)
 The hypoglossal nerve provides somatic
motor innervation to the muscles of the
tongue.
 This pure motor nerve originates from the
hypoglossal nucleus located in the
tegmentum of the medulla.
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Cranial Nerves
Figure 14–27 The Accessory and Hypoglossal Nerves.
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