Download The Brain and Cranial Nerves

Chapter
14
The Brain
and Cranial
Nerves
PowerPoint® Lecture Slides
prepared by Jason LaPres
Lone Star College - North Harris
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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)
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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
 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
 Three divisions
 Left thalamus
 Right thalamus
 Hypothalamus
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The Brain
 Diencephalon
 Thalamus
 Relays and processes sensory information
 Hypothalamus
 Hormone production
 Emotion
 Autonomic function
 Pituitary gland




Major endocrine gland
Connected to hypothalamus
Via infundibulum (stalk)
Interfaces nervous and endocrine systems
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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
 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 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
 Enlarges into three primary brain vesicles
– prosencephalon
– mesencephalon
– rhombencephalon
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The Brain
 Five Secondary Brain Vesicles
 Telencephalon
 Diencephalon
 Mesencephalon
 Metencephalon
 Myelencephalon
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The Brain
 Origins of Brain Structures
 Diencephalon and mesencephalon persist
 Telencephalon:
 Becomes cerebrum
 Metencephalon
 Forms cerebellum and pons
 Myelencephalon
 Becomes 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
 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 are produced in the
neural cortex of the cerebral hemispheres
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Brain Protection and Support
 Physical protection
 Bones of the cranium
 Cranial meninges
 Cerebrospinal fluid
 Biochemical isolation
 Blood–brain barrier
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Brain Protection and Support
 The Cranial Meninges
 Have three layers:
 Dura mater
 Arachnoid mater
 Pia mater
 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
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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)
 Falx cerebri, tentorium cerebelli, and 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)
 Choroid plexus
 Specialized ependymal cells and capillaries:
– secrete CSF into ventricles
– remove waste products from CSF
– adjust composition of CSF
 Produces about 500 mL of CSF/day
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Brain Protection and Support
 Cerebrospinal Fluid (CSF)
 CSF circulates
 From choroid plexus
 Through ventricles
 To central canal of spinal cord
 Into subarachnoid space around the brain, spinal cord, and
cauda equina
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Brain Protection and Support
 Cerebrospinal Fluid (CSF)
 CSF in subarachnoid space
 Arachnoid villi:
– extensions of subarachnoid space
– extend through dura mater to superior sagittal sinus
 Arachnoid granulations:
– large clusters of villi
– absorb CSF into venous circulation
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Brain Protection and Support
Figure 14–4 The Formation and Circulation of Cerebrospinal Fluid.
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Brain Protection and Support
Figure 14–4a The Formation and Circulation of Cerebrospinal Fluid.
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Brain Protection and Support
Figure 14–4b The Formation and Circulation of Cerebrospinal Fluid.
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Brain Protection and Support
 Blood Supply to the Brain
 Supplies nutrients and oxygen to brain
 Delivered by internal carotid arteries and
vertebral arteries
 Removed from dural sinuses by internal
jugular veins
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Brain Protection and Support
Figure 21–22 Arteries of the Neck and Head.
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Brain Protection and Support
Figure 21–23 Arteries of the Brain.
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Brain Protection and Support
Figure 21–28 Major Veins of the Head, Neck, and Brain.
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Brain Protection and Support
Figure 21–28 Major Veins of the Head, Neck, and Brain.
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Brain Protection and Support
 Cerebrovascular Disease
 Disorders interfere with blood circulation to brain
 Stroke or cerebrovascular accident (CVA)
 Shuts off blood to portion of brain
 Neurons die
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Brain Protection and Support
 Blood–Brain Barrier
 Isolates CNS neural tissue from general circulation
 Formed by network of tight junctions
 Between endothelial cells of CNS capillaries
 Lipid-soluble compounds (O2, CO2), steroids, and
prostaglandins diffuse into interstitial fluid of brain and
spinal cord
 Astrocytes control blood–brain barrier by releasing
chemicals that control permeability of endothelium
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Brain Protection and Support
 Blood–CSF Barrier
 Formed by special ependymal cells
 Surround capillaries of choroid plexus
 Limits movement of compounds transferred
 Allows chemical composition of blood and CSF to
differ
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Brain Protection and Support
 Four Breaks in the BBB
 Portions of hypothalamus
 Secrete hypothalamic hormones
 Posterior lobe of pituitary gland
 Secretes hormones ADH and oxytocin
 Pineal glands
 Pineal secretions
 Choroid plexus
 Where special ependymal cells maintain blood–
CSF barrier
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Brain Protection and Support
 Meninges stabilize brain in cranial cavity
 Cerebrospinal fluid protects against sudden
movement
 CSF provides nutrients and removes wastes
 Blood–brain barrier and blood–CSF barrier
 Selectively isolate brain from chemicals in blood that
might disrupt neural function
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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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The Medulla Oblongata
Figure 14–5a The Diencephalon and Brain Stem.
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The Medulla Oblongata
Figure 14–5b The Diencephalon and Brain Stem.
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The Medulla Oblongata
Figure 14–5c The Diencephalon and Brain Stem.
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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 Medulla Oblongata
Figure 14–6b The Medulla Oblongata and Pons.
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The Pons
 The Pons
 Links cerebellum with mesencephalon,
diencephalon, cerebrum, and spinal cord
 Sensory and motor nuclei of cranial nerves V,
VI, VII, VIII
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The Pons
 The Pons
 Nuclei involved with respiration
 Apneustic center and pneumotaxic center:
– modify respiratory rhythmicity center activity
 Nuclei and tracts
 Process and relay information to and from
cerebellum
 Ascending, descending, and transverse tracts:
– transverse fibers (axons):
» link nuclei of pons with opposite cerebellar
hemisphere
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The Pons
Figure 14–6a The Medulla Oblongata and Pons.
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The Pons
Figure 14–6b The Medulla Oblongata and Pons.
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The Pons
Figure 14–6c The Medulla Oblongata and Pons.
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The Pons
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The Pons
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The Cerebellum
 Functions of the Cerebellum
 Adjusts postural muscles
 Fine-tunes conscious and subconscious
movements
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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
 Structures of the Cerebellum
 The peduncles
 Tracts link cerebellum with brain stem, cerebrum, and spinal
cord:
– superior cerebellar peduncles
– middle cerebellar peduncles
– inferior cerebellar peduncles
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The Cerebellum
 Disorders of the Cerebellum
 Ataxia
 Damage from trauma or stroke
 Intoxication (temporary impairment)
 Disturbs muscle coordination
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The Cerebellum
Figure 14–7a The Cerebellum.
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The Cerebellum
Figure 14–7b The Cerebellum.
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The Cerebellum
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The Mesencephalon
 Structures of the Mesencephalon
 Tectum
 Two pairs of sensory nuclei (corpora quadrigemina):
– superior colliculus (visual)
– inferior colliculus (auditory)
 Tegmentum
 Red nucleus (many blood vessels)
 Substantia nigra (pigmented gray matter)
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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 Mesencephalon
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The Diencephalon
 Integrates sensory information and motor
commands
 Thalamus, epithalamus, and hypothalamus
 The pineal gland
 Found in posterior epithalamus
 Secretes hormone melatonin
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The Diencephalon
 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
 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
Figure 14–9a The Thalamus.
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The Diencephalon
Figure 14–9b The Thalamus.
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The Diencephalon
[INSERT Table. 14.5]
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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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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
 Provides subconscious control of skeletal muscle
 Controls autonomic function
 Coordinates activities of nervous and endocrine
systems
 Secretes hormones
 Antidiuretic hormone (ADH) by supraoptic nucleus
 Oxytocin (OT; OXT) by paraventricular nucleus
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The Diencephalon
 Eight Functions of the Hypothalamus
 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)
 Suprachiasmatic nucleus
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The Diencephalon
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The Limbic System
 The Limbic System
 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
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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
 Limbic lobe of cerebral hemisphere
 Cingulate gyrus
 Dentate gyrus
 Parahippocampal gyrus
 Hippocampus
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The Limbic System
 Components of the Limbic System
 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
Figure 14–11a The Limbic System.
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The Limbic System
Figure 14–11b The Limbic System.
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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
 Gray matter
 In cerebral cortex and basal nuclei
 White matter
 Deep to basal cortex
 Around basal nuclei
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The Cerebrum
 Structures of the Cerebrum
 Gyri of neural cortex
 Increase surface area (number of cortical neurons)
 Insula (island) of cortex
 Lies medial to lateral sulcus
 Longitudinal fissure
 Separates cerebral hemispheres
 Lobes
 Divisions of hemispheres
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The Cerebrum
 Structures of the Cerebrum
 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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The Cerebrum
Figure 14–12a The Brain in Lateral View.
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The Cerebrum
Figure 14–12b The Brain in Lateral View.
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The Cerebrum
Figure 14–12c 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
 White Matter of the Cerebrum
 Association fibers
 Commissural fibers
 Projection fibers
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The Cerebrum
 White Matter of the Cerebrum
 Association fibers
 Connections within one hemisphere:
– arcuate fibers:
» are short fibers
» connect one gyrus to another
– longitudinal fasciculi:
» are longer bundles
» connect frontal lobe to other lobes in same hemisphere
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The Cerebrum
 White Matter of the Cerebrum
 Commissural fibers
 Bands of fibers connecting two hemispheres:
– corpus callosum
– anterior commissure
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The Cerebrum
 White Matter of the Cerebrum
 Projection fibers
 Pass through diencephalon
 Link cerebral cortex with:
– diencephalon, brain stem, cerebellum, and spinal cord
 Internal capsule:
– all ascending and descending projection fibers
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The Cerebrum
Figure 14–13a Fibers of the White Matter of the Cerebrum.
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The Cerebrum
Figure 14–13b Fibers of the White Matter of the Cerebrum.
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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
 Direct subconscious activities
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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 14–14a The Basal Nuclei.
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The Cerebrum
Figure 14–14b The Basal Nuclei.
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The Cerebrum
Figure 14–14c The Basal Nuclei.
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The Cerebrum
 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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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
 Auditory association area
 Monitors auditory cortex
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The Cerebrum
 Integrative Centers
 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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The Cerebrum
 General Interpretive Area
 Also called Wernicke area
 Present in only one hemisphere
 Receives information from all sensory association
areas
 Coordinates access to complex visual and auditory
memories
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The Cerebrum
 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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The Cerebrum
Figure 14–15b Motor and Sensory Regions of the Cerebral Cortex.
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The Cerebrum
 Interpretive Areas of Cortex
 Brodmann areas
 Patterns of cellular organization in cerebral cortex
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The Cerebrum
Figure 14–15c Motor and Sensory Regions of the Cerebral Cortex.
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The Cerebrum
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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)
 Primary function
 Special sensory (smell)
 Origin
 Receptors of olfactory epithelium
 Pathway
 Olfactory foramina in cribriform plate of ethmoid
 Destination
 Olfactory bulbs
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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
Figure 14–19 The Olfactory Nerve.
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Cranial Nerves
 Optic Nerves (II)
 Primary function
 Special sensory (vision)
 Origin
 Retina of eye
 Pathway
 Optic canals of sphenoid
 Destination
 Diencephalon via 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
Figure 14–20 The Optic Nerve.
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Cranial Nerves
 Oculomotor Nerves (III)
 Primary function
 Motor (eye movements)
 Origin
 Mesencephalon
 Pathway
 Superior orbital fissures of sphenoid
 Destination
 Somatic motor:
– superior, inferior, and medial rectus muscles
– inferior oblique muscle
– levator palpebrae superioris muscle
 Visceral motor:
– intrinsic eye muscles
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Cranial Nerves
 Oculomotor Nerve Structures
 Oculomotor nerve
 Controls four of six eye-movement muscles
 Delivers autonomic fibers to ciliary ganglion:
– ciliary ganglion: controls intrinsic muscles of iris and
lens
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Cranial Nerves
 The Trochlear Nerves (IV)
 Primary function
 Motor (eye movements)
 Origin
 Mesencephalon
 Pathway
 Superior orbital fissure of sphenoid
 Destination
 Superior oblique muscle
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Cranial Nerves
 The Abducens Nerves (VI)
 Primary function
 Motor (eye movements)
 Origin
 Pons
 Pathway
 Superior orbital fissures of sphenoid
 Destination
 Lateral rectus muscle
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Cranial Nerves
Figure 14–21 Cranial Nerves Controlling the Extra-Ocular Muscles.
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Cranial Nerves
 The Trigeminal Nerves (V)
 Primary function
 Mixed (sensory and motor) to face
 Origin
 Ophthalmic branch (sensory):
– orbital structures
– nasal cavity
– skin of forehead, upper eyelid, and eyebrow
– part of nose
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Cranial Nerves
 The Trigeminal Nerves (V)
 Origin
 Maxillary branch (sensory):
–
–
–
–
lower eyelid
upper lip, gums, and teeth
cheek and nose
palate and part of pharynx
 Mandibular branch (sensory):
– lower gums, teeth, and lips
– palate and part of tongue
 Mandibular branch (motor):
– motor nuclei of pons
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Cranial Nerves
 The Trigeminal Nerves (V)
 Pathway
 Ophthalmic branch:
– superior orbital fissure
 Maxillary branch:
– foramen rotundum
 Mandibular branch:
– foramen ovale
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Cranial Nerves
 The Trigeminal Nerves (V)
 Destination
 Sensory nerves:
– sensory nuclei in pons
 Motor nerves of mandibular branch:
– muscles of mastication
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Cranial Nerves
 Trigeminal Nerve Structures
 Trigeminal nerves
 Largest cranial nerves
 With three major branches
 Semilunar ganglion
 Contains cell bodies of sensory neurons
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Cranial Nerves
Figure 14–22 The Trigeminal Nerve.
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Cranial Nerves
 The Facial Nerves (VII)
 Primary function
 Mixed (sensory and motor) to face
 Origin
 Sensory:
– taste receptors on anterior 2/3 of tongue
 Motor:
– motor nuclei of pons
 Pathway
 Internal acoustic meatus to facial canals
(stylomastoid foramina)
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Cranial Nerves
 The Facial Nerves (VII)
 Destination
 Sensory:
– sensory nuclei of pons
 Somatic motor:
– muscles of facial expression
 Visceral motor:
– tear and nasal mucous glands
– submandibular and sublingual salivary glands
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Cranial Nerves
 Facial Nerve Structures
 Facial nerve branches
 Temporal
 Zygomatic
 Buccal
 Mandibular
 Cervical branches
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Cranial Nerves
 Facial Nerve Structures
 Geniculate ganglia
 Hold cell bodies of sensory neurons
 Pterygopalatine ganglia
 Postganglionic fibers innervate glands (lacrimal, nasal cavity,
and pharynx)
 Submandibular ganglia
 Innervate salivary glands
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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)
 Primary function: special sensory
 Vestibular branch:
– balance and equilibrium
 Cochlear branch:
– hearing
 Origin
 Receptors of inner ear
 Pathway
 Internal acoustic meatus of temporal bones
 Destination
 Vestibular and cochlear nuclei of pons and medulla
oblongata
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Cranial Nerves
 Vestibulocochlear Nerve Structures
 Vestibular branch
 Originates at receptors of vestibule (balance)
 Connects to vestibular nuclei of pons and medulla oblongata
 Cochlear branch
 Originates at sensors of cochlea (hearing)
 Connects with cochlear nuclei of pons and medulla oblongata
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Cranial Nerves
Figure 14–24 The Vestibulocochlear Nerve.
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Cranial Nerves
 The Glossopharyngeal Nerves (IX)
 Primary function
 Mixed (sensory and motor) to head and neck
 Origins
 Sensory:
– posterior 1/3 of tongue
– part of pharynx and palate
– carotid arteries
 Motor:
– motor nuclei of medulla oblongata
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Cranial Nerves
 The Glossopharyngeal Nerves (IX)
 Pathway
 Jugular foramina between occipital and temporal
bones
 Destination
 Sensory:
– sensory nuclei of medulla oblongata
 Somatic motor:
– nerves involved in swallowing
 Visceral motor:
– parotid salivary gland
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Cranial Nerves
 Glossopharyngeal Nerve Structures
 Superior and inferior ganglion
 Sensory neurons of tongue and pharynx
 Otic ganglion
 Synapse visceral motor fibers
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Cranial Nerves
Figure 14–25 The Glossopharyngeal Nerve.
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Cranial Nerves
 The Vagus Nerves (X)
 Primary function
 Mixed (sensory and motor)
 Widely distributed in thorax and abdomen
 Origins
 Sensory:
–
–
–
–
part of pharynx
auricle and external acoustic meatus
diaphragm
visceral organs of thoracic and abdominopelvic cavities
 Motor:
– motor nuclei in medulla oblongata
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Cranial Nerves
 The Vagus Nerves (X)
 Pathway
 Jugular foramina
 Between occipital and temporal bones
 Destination
 Sensory:
– sensory nuclei and autonomic centers of medulla
oblongata
 Visceral motor:
– muscles of the palate and pharynx
– muscles of the digestive, respiratory, and cardiovascular
systems in thoracic and abdominal cavities
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Cranial Nerves
 Vagus Nerve Structures
 Vagus nerves
 Branch and radiate extensively
 Superior (jugular) ganglion and inferior
(nodose) ganglion
 Hold sensory neurons
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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)
 Primary function
 Motor to muscles of neck and upper back
 Origin
 Motor nuclei of spinal cord and medulla oblongata
 Pathway
 Jugular foramina between occipital and temporal bones
 Destination
 Internal branch:
– voluntary muscles of palate, pharynx, and larynx
 External branch:
– sternocleidomastoid and trapezius muscles
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Cranial Nerves
 Accessory Nerve Structures
 Spinal root
 Motor fibers that originate in anterior gray horns of first five
cervical segments of spinal cord
 Cranial root
 Motor fibers that originate in medulla oblongata
 Internal branch
 Joins the vagus nerve
 External branch
 Controls muscles of neck and back
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Cranial Nerves
 The Hypoglossal Nerves (XII)
 Primary function
 Motor (tongue movements)
 Origin
 Motor nuclei of medulla oblongata
 Pathway
 Hypoglossal canals of occipital bone
 Destination
 Muscles of tongue
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Cranial Nerves
Figure 14–27 The Accessory and Hypoglossal Nerves.
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Cranial Nerves
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Cranial Nerves
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Cranial Reflexes
 Cranial Reflexes
 Monosynaptic and polysynaptic reflex arcs
 Involve sensory and motor fibers of cranial nerves
 Clinically useful to check cranial nerve or brain
damage
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Cranial Reflexes
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