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BIOL 2401
Fundamentals of Anatomy and Physiology
Chapter 14: The Brain & Cranial Nerves
Mrs. Willie Grant
[email protected]
(210) 486-2870
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Chapter 14
The Brain and
Cranial Nerves
Lecture Presentation by
Lee Ann Frederick
University of Texas at Arlington
© 2012 Pearson Education, Inc.
An Introduction to the Brain and Cranial Nerves
Learning Outcomes
14-1 Name the major brain regions, vesicles, and ventricles, and describe the
locations and functions of each.
14-2 Explain how the brain is protected and supported, and discuss the formation,
circulation, and function of cerebrospinal fluid.
14-3 Describe the anatomical differences between the medulla oblongata and the
spinal cord, and identify the main components and functions of the medulla
oblongata.
14-4 List the main components of the pons, and specify the functions of each.
14-5 List the main components of the cerebellum, and specify the functions of each.
14-6 List the main components of the midbrain, and specify the functions of each.
14-7 List the main components of the diencephalon, and specify the functions of
each.
14-8 Identify the main components of the limbic system, and specify the locations
and functions of each.
14-9 Identify the major anatomical subdivisions and functions of the cerebrum, and
discuss the origin and significance of the major types of brain waves seen in
an electroencephalogram.
14-10 Describe representative examples of cranial reflexes that produce somatic
responses or visceral responses to specific stimuli.
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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)
Six Regions of the Brain
Cerebrum
Cerebellum
Diencephalon
Mesencephalon
Pons
Medulla oblongata
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14-1 The Brain
Cerebrum—Largest part of the brain
Controls higher mental functions
Divided into left and right cerebral hemispheres
Surface layer of gray matter (neural cortex)
Neural cortex (cerebral cortex)
Folded surface increases surface area
Elevated ridges (gyri)
Shallow depressions (sulci)
Deep grooves (fissures)
Cerebellum—second largest part of the brain
Coordinates repetitive body movements
Two hemispheres covered with cerebellar cortex
1 Which part of the brain is the largest?
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14-1 The Brain
Diencephalon
Located under cerebrum and cerebellum
Links cerebrum with brain stem
Three divisions of the diencephalon
Left and right thalamus (relays and processes sensory information)
Hypothalamus (hormone production, emotion, and autonomic function)
Pituitary gland (major endocrine gland connected to hypothalamus) via the
infundibulum (stalk).
Interfaces nervous and endocrine systems
The Brain Stem
Processes information between: spinal cord and cerebrum or cerebellum
Includes: Midbrain
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Pons
Medulla oblongata
14-1 The Brain
Midbrain (mesencephalon)
Processes sight, sound, and associated reflexes
Maintains consciousness
Pons
Connects cerebellum to brain stem
Is involved in somatic and visceral motor control
Medulla Oblongata
Connects brain to spinal cord
Relays information
Regulates autonomic functions
Heart rate, blood pressure, and digestion
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Figure 14-1 An Introduction to Brain Structures and Functions
DIENCEPHALON
THALAMUS
• Relay and processing
centers for sensory
information
HYPOTHALAMUS
• Centers controlling
emotions, autonomic
functions, and
hormone production
MIDBRAIN
Brain
stem
• Processing of visual
and auditory data
• Generation of reflexive
somatic motor
responses
• Maintenance of
consciousness
PONS
• Relays sensory
information to
cerebellum and
thalamus
• Subconscious
somatic and visceral
motor centers
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MEDULLA OBLONGATA
• Relays sensory information to thalamus and
to other portions of the brain stem
• Autonomic centers for regulation of visceral
function (cardiovascular, respiratory, and
digestive system activities)
Table 14-1 Development of the Brain
Embryological Development
Determines organization of brain structures. Neural tube is origin of brain
Forebrain
Midbrain
Hindbrain
2 Which primary brain vesicle does not develop into a secondary brain vesicle?
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14-1 The Brain
Ventricles of the Brain
Origins of ventricles
Neural tube encloses neurocoel which expands to form chambers
(ventricles) lined with ependyma
Each cerebral hemisphere contains one large lateral ventricle (I and II)
separated by a thin medial partition, the septum pellucidum.
Third ventricle (III) is ventricle of the diencephalon
Lateral ventricles communicate with third ventricle via the
interventricular foramen (Foramen of Monroe)
Fourth ventricle (IV) extends into medulla oblongata and becomes
continuous with the central canal of the spinal cord.
Connects with third ventricle via the cerebral aqueduct
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3 Which brain region is anterior to the fourth ventricle? Which is posterior to it?
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14-1 The Brain
The Brain
The brain is a large, delicate mass of neural tissue
Containing internal passageways and chambers filled with cerebrospinal fluid
Each of the six major brain regions has specific functions
Ascending from the medulla oblongata to the cerebrum, brain functions become
more complex and variable
Conscious thought and intelligence
Physical Protection of the Brain
Bones of the cranium
Cranial meninges (stabilize brain in cranial cavity)
Cerebrospinal fluid (protects against sudden movement and provides nutrients and
removes wastes)
Biochemical Isolation
Blood–brain barrier and Blood-CSF barrier are produced in the neural cortex of the
cerebral hemispheres. Selectively isolate brain from chemicals in blood
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14-2 Brain Protection and Support
The Cranial Meninges
Three layers: Dura mater
Arachnoid mater
Pia mater
Dura mater (inner fibrous layer—meningeal layer)
Outer fibrous layer (endosteal layer) fused to periosteum
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
Dural Folds (folded inner layer of dura mater that stabilizes and supports
brain)
4 What are the three layers of the cranial meninges, from superficial to deep?
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The relationship among the Brain, Cranium, and Meninges
5 Where is CSF reabsorbed?
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14-2 Brain Protection and Support
Cerebrospinal Fluid (CSF) surrounds all exposed surfaces of CNS and
interchanges with interstitial fluid of brain
Functions: Cushions delicate structures, supports brain, transports
Choroid plexus—specialized ependymal cells and capillaries
Secrete CSF into ventricles—remove waste products from CSF—
adjusts composition of CSF—produces about 500 mL of CSF/day
CSF circulates: From choroid plexus—through the ventricles—to the
central canal of spinal cord—into subarachnoid space via two lateral
apertures and one meian aperture around the brain, spinal cord, and
cauda equina
Blood Supply to the Brain—supplies nutrients and oxygen to brain.
Delivered by internal carotid arteries and vertebral arteries and removed
from dural sinuses by internal jugular veins
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14-2 Brain Protection and Support
Blood–Brain Barrier (BBB)
Isolates CNS neural tissue from general circulation
Lipid-soluble compounds (O2, CO2), steroids, and prostaglandins
Diffuse into interstitial fluid of brain and spinal cord
Astrocytes control blood–brain barrier Blood–CSF Barrier
Formed by special ependymal cells
Surrounds capillaries of choroid plexus
Limits movement of compounds transferred
Allows chemical composition of blood and CSF to differ
Valerie Harper has cancer of the Blood-Brain Barrier
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14-2 Brain Protection and Support
Four Breaks in the Blood Brain Barrier
Portions of hypothalamus
Secrete hypothalamic hormones
Posterior lobe of pituitary gland
Secretes hormones ADH and oxytocin
Pineal gland
Pineal secretions
Choroid plexus
Where special ependymal cells maintain blood–CSF barrier
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Review These Summary Tables
The Medulla Oblongata (page 472)
The Pons (page 473)
The Cerebellum (page 474)
The Midbrain (page 476)
The Thalamus (page 478)
The Hypothalamus (page 479)
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14-3 The Medulla Oblongata
The Medulla Oblongata
Allows brain and spinal cord to communicate
Coordinates complex autonomic reflexes
Controls visceral functions
Nuclei in the Medulla
Autonomic nuclei control visceral activities
Sensory and motor nuclei of cranial nerves
Relay stations along sensory and motor pathways
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14-3 The Medulla Oblongata
The Medulla Oblongata
Includes three groups of nuclei
Autonomic Nuclei Controlling Visceral Activities (Reticular formation
mass of gray matter that contains embedded nuclei.)
Reflex centers that control peripheral systems, cardiovascular centers,
cardiac center, blood flow through peripheral tissues, respiratory
rhythmicity centers
Sensory and motor nuclei of cranial nerves (VIII, IX, X, Xi, and XII
control the pharynx, neck, back and visceral organs of thoracic and
peritoneal cavities)
Relay stations along sensory and motor pathways (pass somatic
sensory information to the thalamus)
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14-4 The Pons
The Pons
Sensory and motor nuclei of cranial nerves (V, VI, VII, VIII)
Nuclei involved with respiration
Apneustic center of the lower pons appears to promote inspiration by
stimulation of the neurons in the medulla oblongata providing a
constant stimulus.
Pneumotaxic center : a neural center in the upper part of the pons that
provides inhibitory impulses on inspiration and thereby prevents
overdistension of the lungs and helps to maintain alternately
recurrent inspiration and expiration
Nucei that process and relay information to and from cerebellum
Ascending, descending, and transverse tracts
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Figure 14-6c The Medulla Oblongata and Pons
Tracts
Ascending tracts
Respiratory Centers
Descending tracts
Pneumotaxic center
Apneustic center
Transverse fibers
Cerebellum
Midbrain
Fourth
ventricle
Pons
Medulla oblongata
Medulla
oblongata
Reticular formation
Olivary nucleus
Spinal cord
Lateral view
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14-5 The Cerebellum
Functions of the Cerebellum
Adjusts postural muscles
Fine-tunes conscious and subconscious movements
Structures of the Cerebellum
Folia (surface of cerebellum that is 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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14-5 The Cerebellum
Structures of the Cerebellum
Purkinje cells are large branched cells found in the cerebellar cortex. They receive
input from up to 200,00 synapses
Arbor vitae (“tree of life”)
Highly branched, internal white matter of cerebellum
Cerebellar nuclei embedded in arbor vitae
Relay information to Purkinje cells
Disorders of the Cerebellum
Ataxia (a disturbance in muscular coordination. If severe, the individual cannot sit
or stand without assistance)
Damage from trauma or stroke
Intoxication (temporary impairment)
Disturbs muscle coordination
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14-6 The Midbrain
Structures of the Midbrain
Tectum (roof of midbrain)
Two pairs of sensory nuclei (corpora quadrigemina—process visual and
auditory sensations)
Tegmentum
Cerebral peduncles
Nerve fiber bundles on ventrolateral surfaces
Contain:
Descending fibers to cerebellum carrying voluntary motor
commands from cerebral hemispheres
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Figure 14-8a The Midbrain
Thalamus
Pineal
gland
Red nucleus
Substantia
nigra
Corpora
quadrigemina
Cerebral
peduncle
Superior
colliculus
Inferior
colliculus
Reticular
formation
A posterior view. The underlying
nuclei are colored only on the right.
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14-7 The Diencephalon
The Diencephalon
Integrates sensory information and motor commands
Thalamus, epithalamus, and hypothalamus
The pineal gland is found in the posterior epithalamus. It secretes
melatonin
The Thalamus
Filters ascending sensory information for primary sensory cortex
Relays information between basal nuclei and cerebral cortex
The third ventricle
Separates left thalamus and right thalamus
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14-7 The Diencephalon
The Hypothalamus
Mamillary bodies
Process olfactory and other sensory information
Control reflex eating movements
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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14-7 The Diencephalon
Eight Functions of the Hypothalamus
Provides subconscious control of skeletal muscle
Controls autonomic function
Coordinates activities of nervous and endocrine systems
Secretes hormones Antidiuretic hormone (ADH) and Oxytocin (OT; OXT)
Produces emotions and behavioral drives
The feeding center (hunger)
The thirst center (thirst)
Coordinates voluntary and autonomic functions
Regulates body temperature
Preoptic area of hypothalamus
Controls circadian rhythms (day–night cycles)
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Table 14-7 The Limbic System
The Limbic System
The Limbic System includes nuclei and tracts along the border between the cerebrum and
diencephalon.
It is a functional grouping that:
Establishes emotional states
Links conscious functions of cerebral cortex with autonomic functions of brain stem
Facilitates memory storage and retrieval
Components of the Limbic System: Fornix—tract of white matter that connects hippocampus with
hypothalamus
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Stopping Point?
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14-9 The Cerebrum
The Cerebrum
Is the largest part of the brain
Controls all conscious thoughts and intellectual functions
Processes somatic sensory and motor information
Gray Matter
In cerebral cortex and basal nuclei
White Matter
Deep to basal cortex
Around basal nuclei
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14-9 The Cerebrum
Structures of the Cerebrum
Gyri of neural cortex (increase surface area - number of cortical neurons)
Insula (“island” of cortex)
Longitudinal fissure
Separates cerebral hemispheres
Lobes—Divisions of hemispheres
Central sulcus divides:
Anterior frontal lobe from posterior parietal lobe
Lateral sulcus divides:
Frontal lobe from temporal lobe
Parieto-occipital sulcus divides:
Parietal lobe from occipital lobe
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Figure 14-12b The Brain in Lateral View
Precentral
gyrus
Central
sulcus
Postcentral
gyrus
PARIETAL LOBE
FRONTAL
LOBE
OCCIPITAL
LOBE
TEMPORAL
LOBE
Lateral sulcus
Cerebellum
Pons
Medulla oblongata
Lateral view
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14-9 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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14-9 The Cerebrum
The Basal Nuclei
Are masses of gray matter
Are embedded in white matter of cerebrum
Direct subconscious activities
Functions of Basal Nuclei
Involved with:
The subconscious control of skeletal muscle tone
The coordination of learned movement patterns (walking, lifting)
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14-9 The Cerebrum
Association Areas
Sensory association areas (regions of the cortex that interpret and monitor
arriving information at sensory ares of cortex)
Somatic sensory association area
Interprets input to primary sensory cortex (e.g., recognizes and
responds to touch)
Sensory Association Areas
Visual association area—interprets activity in visual cortex
Auditory association area—monitors auditory cortex
Somatic motor association area (premotor cortex)—coordinates motor
responses (learned movements)
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14-9 The Cerebrum
Integrative Centers (areas that receive information from many
association areas and direct extremely complex motor activities).
Are located in lobes and cortical areas of both cerebral
hemispheres
Receive information from association areas
Direct complex motor or analytical activities
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14-9 The Cerebrum
General Interpretive Area (Wernicke’s area)
Present in only one hemisphere
Receives information from all sensory association areas
Coordinates access to complex visual and auditory memories
Other Integrative Areas
Speech center
Is associated with general interpretive area
Coordinates all vocalization functions
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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Figure 14-15b Motor and Sensory Regions of the Cerebral Cortex
Frontal eye field
Speech
center
Prefrontal
cortex
General
interpretive
area
The left hemisphere generally contains the
general interpretive area and the speech center.
The prefrontal cortex of each hemisphere is
involved with conscious intellectual functions.
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14-9 The Cerebrum
Hemispheric Lateralization (regional specialization in each of the two cerebral
hemispheres)
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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14-9 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
Four Categories of Brain Waves
Alpha waves
Beta waves
Theta waves
Delta waves
6 Which type of brain wave indicates emotional stress?
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14-9 The Cerebrum
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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Brain Waves
Alpha waves
Beta waves
Theta waves
Delta waves
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14-9 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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Clinical Case—The Neuroanatomist’s Stroke
How would you know, just based on signs and symptoms, which side of Dr. Taylor’s brain has been
Injured by a stroke?
What is neuroplasticity and why was it important in Dr. Taylor’s recovery?
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Figure 14-15a Motor and Sensory Regions of the Cerebral Cortex
Special Sensory Cortexes
Central sulcus
Primary motor cortex
(precentral gyrus)
Primary sensory cortex
(postcentral gyrus)
Somatic motor association
area (premotor cortex)
PARIETAL LOBE
Somatic sensory
association area
FRONTAL LOBE
Visual association area
Prefrontal cortex
OCCIPITAL LOBE
Gustatory cortex
(taste receptors)
Insula
Visual cortex (sight receptors)
Auditory association area
Lateral sulcus
Olfactory cortex
(odor receptors)
TEMPORAL
LOBE
Major anatomical landmarks on the surface of
the left cerebral hemisphere. The lateral sulcus
has been pulled apart to expose the insula.
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Auditory cortex
(sound receptors)