Chapter13
The Brain and Cranial Nerves
Nervous System: Brain and Cranial Nerves
• The Brain
– Average weight
of 1.35 to 1.4
kilograms
– Outer surface
folded in on
itself
– Four major
regions:
•
•
•
•
cerebrum
diencephalon
brainstem
cerebellum
– Cranial nerves
originating here
Overview of Brain Anatomy
• Brain anatomy
– With spinal cord,
composes central
nervous system
– Outer surface
• exhibits folds, gyri
• shallow depressions,
sulci
• deeper grooves,
fissures
– Two common directional
terms
• anterior = rostral
(“toward the nose”)
• posterior = caudal
(“toward the tail”)
Brain Development and Organization:
Overview of Brain Anatomy
Brain Development and Organization
Clinical View—Traumatic Brain Injuries:
Concussion and Contusion
– Traumatic brain injury
• acute brain damage occurring as a result of trauma
– Concussion
•
•
•
•
most common type
temporary loss of consciousness after blow to head
headache, drowsiness, confusion, and amnesia possible
may have a cumulative effect on intellectual abilities, personality, or mood
– Contusion
• bruising of brain due to trauma
• loss of consciousness < 5 minutes
– Second impact syndrome
• individual with second injury prior to resolution of first trauma
• develop severe brain swelling
Gray Matter and White Matter Distribution
• Two tissue areas of brain and
spinal cord:
– gray matter
• color from motor and interneuron cell
bodies, dendrites, and unmyelinated
axons
– white matter
– color from myelin on axons
– E.g., the cerebrum
• superficial region of gray matter,
termed cerebral cortex
• covers surface
• white matter deep to gray matter
Protection and Support of the Brain
• Brain protected and isolated by multiple structures
–
–
–
–
The cranium provides rigid support
The meninges surround and partition
Cerebrospinal fluid cushions
Blood-brain barrier prevents entry of harmful materials
Cranial Meninges
• Cranial meninges
– Three connective tissue
layers
– Separate and support soft
tissue of brain
– Enclose and protect blood
vessels supplying the
brain
– Help contain and circulate
cerebrospinal fluid
– From deep to superficial:
• pia matter
• arachnoid mater
• dura mater
Cranial Meninges
Pia Mater
– Innermost of cranial meninges Thin layer of areolar connective tissue
– Tightly adheres to brain Follows contours of brain surface
Arachnoid Mater
–
–
–
–
Lies external to pia mater
Partially composed of collagen and elastic fibers
Extend through subarachnoid space contains cerebrospinal fluid
Subdural space potential space between arachnoid and overlying dura mater
• becomes actual space if blood or fluid accumulates there - subdural hematoma
Dura Mater
– Lies external to arachnoid mater
– Tough, dense irregular connective tissue
– Epidural space
• potential space between dura mater and bones of the skull
• contains arteries and veins nourishing meninges and cranium
• becomes real space if blood or fluid accumulates
Clinical View: Epidural and Subdural Hematomas
– Epidural hematoma
• pool of blood in epidural space of brain
• usually due to severe blow to the head
• adjacent brain tissue distorted and compressed
• severe neurological injury or death unless bleeding
stopped and blood removed
– Subdural hematoma
• hemorrhage in subdural space
• typically from ruptured veins from fast rotational head
movement
• compression of brain tissue, more slowly than epidural
hematoma
Protection and Support of the Brain:
Cranial Meninges
Clinical View: Meningitis
– Inflammation of the meninges
– Typically caused by contagious viral or bacterial infections
– Symptoms of fever, headache, vomiting, and stiff neck
• pain from meninges sometimes referred to posterior
neck
– May result in brain damage and death if untreated
– Bacterial meningitis with more severe symptoms
– Vaccine for most common bacterial strains causing
meningitis
Protection and Support of the Brain:
Cranial Meninges
Cranial Dural
Septa
– Double layers of
dura mater
– Extend as flat
partitions into the
cranial cavity
– Separate specific
parts of the brain
– Stabilize and
support the brain
– Four locations
Protection and Support of the Brain:
Brain Ventricles
• Ventricles
– Cavities within the brain
– Derived from neural
canal
– Contain cerebrospinal
fluid
Cerebrospinal Fluid
• Cerebrospinal fluid - Formed by choroid plexus
–
–
–
–
Clear, colorless liquid
Originates from blood plasma
Circulates in ventricles and subarachnoid space
Bathes and completely surrounds surfaces of CNS
• functions:
– buoyancy
• brain floating here
• reduces apparent weight by 95%
• prevents collapse of brain through foramen magnum
– protection
• provides liquid cushion
• protects delicate neural structures from sudden movements
– environmental stability
• transports nutrients and chemical messengers to brain
• removes waste products (to venous circulation)
• protects tissue from chemical fluctuations
Figure 13.9a
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CSF flow
Arachnoid villi
5
Superior sagittal sinus
(dural venous sinus)
4
Venous fluid
flow
Pia mater
Choroid plexus of
third ventricle
1
Choroid plexus of
lateral ventricle
Interventricular foramen
2
Cerebral aqueduct
Lateral aperture
Choroid plexus
of fourth ventricle
3
Median aperture
Dura mater
Subarachnoid space
Central canal of spinal cord
(a) Midsagittal section
Protection and Support of the Brain:
Cerebrospinal Fluid
Clinical View: Hydrocephalus
–
–
–
–
–
–
Pathologic condition of excessive CSF
Often leads to brain distortion
May result from obstruction in CSF restricting reabsorption
May result from intrinsic problem with arachnoid villi
In a young child, head enlarged with possible neurological damage
May be treated surgically
• implant shunts that drain CSF to other body regions
Protection and Support of the Brain:
Blood-Brain Barrier
• Blood-brain barrier (BBB)
– Strictly regulates which substances enter brain’s interstitial fluid
– Helps prevent neuron exposure to harmful substances
• e.g., drugs
• blood waste products
• variations in levels of normal substances
– e.g., ions, hormones
• Barrier not absolute
– Lipid-soluble compounds
•
•
•
•
can diffuse across endothelial plasma membranes
e.g., nicotine
alcohol
some anesthetics
– Can be damaged by drugs such as cocaine
Protection and Support of the Brain:
Blood-Brain Barrier
Brain: 2% of body wt, 15% of blood consumption, 20% of O2 and glucose consumptio
Brain barrier system- strictly regulates what substances can get from bloodstream into
brain tissue
Blood-brain-barrier (BBB)tight junctions b/t brain and capillaries
Astrocytes completely seal off gaps
Exclude harmful substances
Allow necessary ones to pass
• Missing or reduced in 3 locations:
– choroid plexus
• needs to be permeable to produce CSF
– hypothalamus and pineal gland
• produce hormones requiring access to bloodstream
Cerebrum
• Cerebrum
– Origin of all complex intellectual functions
– Two large hemispheres on superior aspect of brain
– Center of:
• intelligence and reasoning
• thought, memory, and judgment
• voluntary motor, visual, and auditory activities
• Cerebrum composition
– Composed of two halves, left and right cerebral
hemispheres
– Separated by deep cleft, longitudinal fissure
– Hemispheres separate, except at a few locations
– Largest tract, corpus callosum
• provides main method of communication between
hemispheres
Cerebrum: Cerebral Hemispheres
• Cerebrum characteristics
– Usually difficult to assign precise function to specific region
• overlapping and indistinct boundaries
• some aspects not easily assigned to any single region
– e.g., memory
– Innervation
• hemispheres receiving information from opposite side of body
• hemispheres projecting motor commands to opposite side of body
• e.g., right cerebral hemisphere controlling the left side of body
– Functional differences between hemispheres
• termed cerebral lateralization
• e.g., regions of brain responsible for speech in left cerebral hemisphere
• primarily affects higher-order function
Cerebrum: Lobes of the Cerebrum
• Five Lobes
– Four visible on external surface
– Named for overlying cranial bones
• frontal, parietal, temporal, and occipital
• insula, not visible at surface (fifth lobe)- memory and taste
Frontal lobe
• Voluntary motor functions, motivation, foresight, planning, memory, mood,
emotion, social judgment, aggression, decision making, personality
Parietal lobe
• receive and interpret signals
of general senses – shape texture
• Taste, touch, some visual
Occipital lobe
• Principal visual centervisual memory
Temporal lobe
• hearing, smell, learning,
memory, some vision and emotion
Cerebrum: Functional Areas of the Cerebrum
• Structure and functions
– Specific structural areas with distinct motor and sensory functions
– Higher mental functions dispersed over large areas
– Three categories of functional areas:
• motor areas
• sensory areas
• association areas
Cerebrum: Functional Areas of the Cerebrum
Motor Areas
– Control voluntary motor function
– Housed within frontal lobes
– Primary motor cortex located in precentral gyrus of lobe
• control voluntary skeletal muscle activity
• project contralaterally (opposite side) within brainstem or spinal cord
• e.g., left primary motor cortex controlling right-side voluntary muscles
– Motor speech area
• also known as Broca area
• located in inferolateral portion of left frontal lobe (in most people)
• controls muscular movement for vocalization
– Frontal eye field
• on superior surface of middle frontal gyrus
• regulates eye movements needed for reading and binocular visions
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Primary motor cortex
(within precentral gyrus)
Trunk
Hip
Knee
Ankle
Toes
Figure 13.13a
Pharynx
Lateral
Medial
(a) Primary motor cortex
(somatic motor area)
Cerebrum: Functional Areas of the Cerebrum
Sensory Areas
– Primary somatosensory cortex
• housed within postcentral gyrus of parietal lobes
• receives somatic sensory information from:
– proprioceptors, touch, pressure pain, and temperature receptors
– Primary visual cortex
• located within occipital lobe
• receives and processes incoming visual information
– Primary auditory cortex
• located within temporal lobe
• receives and processes auditory information
– Primary olfactory cortex
• located within temporal lobe
• provides conscious awareness of smells
– Primary gustatory cortex
• located within insula
• involved in processing taste information
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Leg
Neck
Hip
Trunk
Primary somatosensory cortex
(within postcentral gyrus)
Foot
Toes
Genitals
Figure 13.13b
Intra-abdominal
Medial
Lateral
(b) Primary somatosensory cortex
Cerebrum: Functional Areas of the Cerebrum
Association Areas
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–
–
–
Connected to adjacent motor and sensory regions
Process and interpret data or coordinate motor response
Integrate new sensory inputs with memories
Premotor cortex
• within frontal lobe anterior to precentral gyrus
• responsible for coordinating skilled motor activities
– e.g., playing the piano
Association Areas
– Somatosensory association area
•
•
•
•
within parietal lobe posterior to primary somatosensory complex
integrates sensory information
determines texture, temperature, pressure, and shape of objects
allows us to identify known objections without seeing them
Association Areas
– Visual association area
•
•
•
•
within occipital lobe
surrounds primary visual area
helps process visual information
helps us identify things we see
– Auditory association area
• within temporal lobe
• interprets characteristics of sound
• stores memories of sound heard in the past
– Functional brain regions
• multi-association area between lobes
• integrates information from individual association areas
– Wernicke area, one example
• typically located only in left hemisphere
• involved in recognizing, understanding, comprehending language
– Gnostic area, another functional brain region
• composed of regions of parietal, occipital, and temporal lobes
• provides comprehensive understanding of current activity
Figure 13.12b
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(b) Motor Areas
Primary motor cortex
Premotor cortex
Motor speech area
Control voluntary
skeletal muscle
activity
Regulate
skeletal muscle
movements
Involved with
speech
Plan and coordinate
learned, skilled motor activities
Figure 13.12c
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(c) Sensory and Association Areas
Primary visual cortex
Primary gustatory cortex
Visual association area
Primary olfactory cortex
Process taste
information
and provide
conscious
awareness
of smells,
respectively
Process, integrate,
and store visual
information
Primary auditory cortex
Primary somatosensory cortex
Auditory association area
Somatosensory association area
Process, interpret
sounds, and store
auditory memories
Receive and
interpret somatic
information
from receptors
Figure 13.12d
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(d) Functional Brain Regions
Wernicke area
Gnostic area
Integrates all information being processed
in adjacent lobes to
provide a comprehensive understanding of a
current activity
This multi-association
area helps understand
spoken or written
language.
Cerebrum
Clinical View: The Case of Phineas Gage
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–
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–
–
Famous neurological case in 1848
Rod shot through Gage’s head, below left eye
Before accident, capable, well-balanced, and shrewd
After accident, was irreverant, fitful, and profane
Helped uncover link that frontal lobes are important in personality,
and linked to basic elements of decision making
Cerebrum: Cerebral Lateralization
• Hemispheric asymmetries
– Petalias, shape asymmetries of
frontal and occipital lobes
– Right frontal petalias
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Right frontal
petalia
Right-handed
• right frontal lobe projection
farther than the left frontal lobe
– Left occipital petalias
• left occipital lobe projecting
farther than right occipital lobe
– Right-handed individual with
these patterns
– Left-handed individual with left
frontal petalias and right occipital
petalias
Left occipital
petalia
(a) Petalias
Figure 13.15
Cerebrum: Cerebral Lateralization
• Hemisphere specialization
– Called cerebral lateralization
– Higher order centers with different but complementary functions
– Categorical hemisphere
•
•
•
•
•
specialized for language abilities
usually contains Wernicke area and motor speech area
involved in sequential and analytical reasoning tasks
the left hemisphere in most people
left-handed people with either hemisphere as categorical
Cerebrum: Cerebral Lateralization
• Hemisphere specialization
– Representational hemisphere, other hemisphere
• involved in visuospatial relationships
• seat of imagination, artistic skill, pattern perception
• right hemisphere in most people
– Hemisphere in constant contact through commissures
• especially corpus callosum
– Develops prior to 5-6 years of age
– Differs between sexes
• women with a thicker posterior corpus callosum
• adults with more lateralization
– Correlated with handedness
• right-handed and left-handed with different lateralization patterns
• right-handed individuals usually with left categorical hemisphere
• left-handed individuals with either categorical hemisphere
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Left eye
Right eye
Left Right
visual visual
field field
Left Right
visual visual
field
field
Left hand
Right hand
Right hemisphere
(representational hemisphere)
Left hemisphere
(categorical hemisphere)
Figure 13.15b
Verbal memory
Memory for shapes (limited
language comprehension)
Corpus callosum
Speech (motor
speech area)
Left hand
motor control
Right hand
motor control
Feeling shapes with
left hand
Feeling shapes
with right hand
Musical ability
Recognition of faces
and spatial relationships
Superior language and
mathematic comprehension
(Wernicke area)
Right visual field
Left visual field
Primary visual cortex
(b) Cerebral lateralization
Cerebrum
Clinical View: Hemispherectomies and Cerebral
Lateralization
– Epilepsy
•
•
•
•
•
neurological disorder
neurons transmitting action potentials too frequently and rapidly
most controlled by medications
may require surgical removal of part of brain
in most severe cases, may require hemispherectomy
– side of brain responsible for seizure activity removed
• hemisphere able to take over some functions of missing hemisphere
Cerebrum
Clinical View: Cerebrovascular Accident
– Cerebrovascular accident (CVA, or stroke)
•
•
•
•
reduced blood supply to part of brain
due to blocked arterial blood vessel or hemorrhage
my cause brain tissue death if greater than 10 minutes
symptoms of blurred vision, weakness, headache, dizziness, and walking
difficulty
• affect opposite side of body
• brief episode, transient ischemic attack (TIA)
Diencephalon
• Diencephalon
– Components of
diencephalon:
• epithalamus,
thalamus, and
hypothalamus
– Provides the relay
and switching
centers for:
• sensory and
motor pathways
• control of
visceral
activities
Figure 13.17
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Corpus callosum
Diencephalon
Septum pellucidum
Fornix
Choroid plexus in third ventricle
Thalamus
Habenular nucleus
Interthalamic adhesion
Pineal gland
Anterior commissure
Posterior commissure
Hypothalamus
Tectal plate
Frontal lobe
Mammillary body
Cerebral aqueduct
Optic chiasm
Infundibulum
Cerebellum
Pituitary gland
Fourth ventricle
Midsagittal section
Epithalamus
Diencephalon
• Epithalamus
– Partially forms posterior roof of diencephalon
– Posterior portion
• houses pineal gland - endocrine gland secreting melatonin
• helps regulate day-night cycles, circadian rhythm
• Thalamus
• functions
– Principal and final relay point for incoming sensory information
– Processed and projected to primary somatosensory cortex
– Information filter
• e.g., “filters out” sounds in a busy cafeteria while you study
Figure 13.18
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Medial group
Interthalamic adhesion
Lateral group
(a ) Location of thalamus within brain
Pulvinar nucleus
Lateral geniculate
nucleus
Anterior group
Ventral anterior Ventral lateral
nucleus
nucleus
Ventral posterior
nucleus
Ventral group
(b) Thalamus, superolateral view
Posterior group
Diencephalon
Clinical View: Brain Disorders
– Headache
• due to dilated blood vessels in skull or muscle contraction
• migraine headaches, very severe, affect one side of head
• not true brain disorder, but may accompany them
– Cerebral palsy
• group of neuromuscular disorders
• result from damage to infant brain before, during, or right after birth
• impairment of skeletal muscle, sometimes mental retardation
– Encephalitis
• acute inflammatory disease of brain, usually due to virus
• drowsiness, fever, headache, possibly coma and death
Diencephalon
Clinical View: Brain Disorders (continued)
– Huntington disease
•
•
•
•
hereditary disease affecting cerebral nuclei
Rapid, jerky, involuntary movements
also with intellectual deterioration
fatal within 10 to 20 years after onset
– Parkinson disease
• affects muscle movement and balance
• stiff posture, slow voluntary movements, resting tremor
• caused by decreased dopamine production in substantia nigra
Diencephalon: Hypothalamus
• Hypothalamus
– Infundibulum
• thin stalk extending inferiorly from hypothalamus
• attaches to pituitary gland
• Functions of the hypothalamus
– Master control of the autonomic nervous system
• influences heart rate, blood pressure, digestive activities, and respiration
• Hunger thirst
– Regulation of sleep-wake rhythms
• directs pineal gland to secrete melatonin
• regulates circadian rhythms
– Master control of the endocrine system
•
•
•
•
oversees most of endocrine system
secretes hormones that control activities in posterior pituitary gland
produces antidiuretic hormone(water balance)
and oxytocin(labor)
Figure 13.19
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Paraventricular nucleus
Dorsomedial nucleus
Preoptic area
Posterior nucleus
Anterior nucleus
Supraoptic nucleus
Mammillary body
Suprachiasmatic nucleus
Ventromedial nucleus
Arcuate nucleus
Optic chiasm
Infundibulum
Posterior pituitary
Anterior pituitary
Sagittal section of hypothalamus
Pituitary gland
Brainstem
• Brainstem
– Connects cerebrum,
diencephalon, and
cerebellum to spinal cord
– Bidirectional
passageway
– Contains many
autonomic centers and
reflex centers
– Houses nuclei of many
cranial nerves
– From superior to
inferior:
• midbrain
• pons
• medulla oblongata
Brainstem: Midbrain
• Components of midbrain
• houses neurons producing
dopamine
– involved in movement,
emotions, pleasure and pain
response
• pathology here in Parkinson
disease
- integrates information from cerebrum and
cerebellum
• issues involuntary motor
commands to erector spinae
– helps maintain posture
Brainstem: Pons
• Components of pons
– Bulging region on anterior
brainstem
– Sensory and motor tracts
located here
• connect to brain and spinal
cord
– respiratory center
• helps regulate skeletal muscles
of breathing
– Cranial nerve nuclei
• sensory and motor nuclei for:
– trigeminal, abducens, facial,
and vestibulocochlear nerves
Brainstem: Medulla Oblongata
• Medulla oblongata
– Most caudal part of the
brainstem
– Continuous with spinal
cord inferiorly
– All tracts between brain
and spinal cord passing
through here
– Pyramids
• most cross to opposite
side of brain
• cerebral hemisphere
controlling movement on
opposite side
Brainstem: Medulla Oblongata
• Autonomic nuclei of medulla
– Cardiac center
• regulates heart’s rate and strength of contraction
– Vasomotor center
•
•
•
•
controls blood pressure
alters diameters of arterioles
increased blood pressure when vessels constrict
decreased bp when vessels relax
– Medullar respiratory center
• regulates respiratory rate
• influenced by pontine respiratory center
– Other nuclei in the medulla
• involved in coughing, sneezing, and salivation
• swallowing, gagging, and vomiting
Cerebellum
• Cerebellum
– Second largest part of the brain
– Produces fine control over
muscular actions
– Helps maintain equilibrium and
posture
– Stores memories of movement
patterns
• e.g., playing scales on a piano
– Partitioned into three regions:
• cerebellar cortex, outer gray
matter of cortex
• internal region of white matter,
arbor vitae
• deepest gray matter layer of
cerebellar nuclei
Figure 13.25
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Primary motor cortex
Voluntary movements
The primary motor cortex and the basal nuclei
in the forebrain send impulses through the
nuclei of the pons to the cerebellum.
Cerebral hemisphere
Assessment of voluntary movements
Proprioceptors in skeletal muscles and
joints report degree of movement to
the cerebellum.
Integration and analysis
The cerebellum compares the
planned movements (motor signals)
against the results of the actual
movements (sensory signals).
Corrective feedback
The cerebellum sends impulses
through the thalamus to the
primary motor cortex and to
motor nuclei in the brainstem.
Thalamus
Cerebellar cortex
Corpus callosum
Pontine nucleus
Pons
Direct (pyramidal) pathway
Sagittal section
Cerebellum: Functions
Clinical View: Effects of Alcohol and Drugs on the
Cerebellum
– Variety of drugs impairing cerebellar function
• include alcohol
• leads to:
– disturbance of gait
– loss of balance and posture
– inability to detect proprioceptive information
Functional Brain Systems: Limbic System
• Limbic system
–
–
–
–
Composed of multiple cerebral and diencephalic structures
Collectively process and experience emotions
Structures forming a ring around the diencephalon
Hippocampus
• nucleus superior to parahippocampal gyrus
• assists in storing memories and forming long-term memory
• connects to diencephalon
– Amygdaloid body
• connects to the hippocampus
• involved in several aspects of emotion, especially fear
• can help store emotions depending on emotional context
– Olfactory bulbs, olfactory tracts, olfactory cortex
• process odors that can provoke emotions
– Fornix
• thin tract of white matter
• connects hippocampus with other limbic structures
Figure 13.26
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Components of the limbic system
Cingulate gyrus
Corpus callosum
Fornix
Anterior thalamic nucleus
Anterior commissure
Septal nucleus
Mammillary body
Hippocampus
Amygdaloid body
Parahippocampal gyrus
Olfactory tract
Olfactory bulb
Midsagittal section
Functional Brain Systems: Limbic System
What are the main functions of the limbic system?
The limbic
system is
involved with
processing and
experiencing
emotions.
Functional Brain Systems:
Clinical View: Pathologic States of Unconsciousness
– Fainting
• brief loss of consciousness
• often signals inadequate cerebral blood flow due to low blood pressure
– Stupor
• arousable only to extreme stimuli
• with metabolic disorders, liver or kidney disease, brain trauma, or drugs
– Coma
• deep and profound unconsciousness alive but unable to respond
• from severe head injury, metabolic failure, very low blood sugar, or drugs
– Persistent vegetative state
• person without thinking and awareness of environment
• continuation of noncognitive brain functions some spontaneous movements
possible
– Electroencephalogram (EEG)
• diagnotic test where electrical activity of the brain is measured
• plots different types of brain waves
– waves varying with age, sleep, seizure, or pathology
Integrative Functions and
Higher-Order Brain Functions
• Higher-order mental functions
–
–
–
–
Include learning, memory, and reasoning
Occur within the cortex of cerebrum
Involve multiple brain regions
Both conscious and unconscious processing involved
• Cognition
– Mental processes
• e.g., awareness, knowledge, memory, perception, and thinking
– Association areas of the cerebrum responsible
• process and integrate information between sensory and motor areas
Integrative Functions and Higher-Order
Brain Functions: Memory
• Memory
– Requires higher-order mental functions
– Depends on complex interactions among brain regions
• Types of memory:
– sensory memory
• form important association based on sensory input
• lasts for seconds
– short-term memory (STM)
• limited capacity (about seven small pieces of information)
• brief duration (seconds to hours)
– long-term memory (LTM)
• can be converted from short-term memory if information repeated
– termed encoding
• may exist for limitless periods of time
• needs to be retrieved occasionally or can be “lost
Integrative Functions and Higher-Order Brain
Functions: Memory
Clinical View—Alzheimer Disease: The “Long
Goodbye”
–
–
–
–
–
–
–
–
Leading cause of dementia in developed world
Slow, progressive loss of higher intellectual function
Usually starts after age 65
Changes in mood and behavior
Eventual loss of memory and personality
Underlying cause unknown
No cure, some medications to help slow course
Identifiable with positron emission tomography (PET)
Integrative Functions and Higher-Order Brain
Functions: Memory
Clinical View: Amnesia
– Partial or complete loss of memory
– Usually temporary and affecting only a portion of experiences
– Causes:
• psychological trauma
• direct brain injury
– Type and degree of recovery
•
depends on part of the brain damaged
– Most serious kind
• results from damage to thalamus and limbic structures, especially
hippocampus
Integrative Functions and Higher-Order
Brain Functions: Emotion
• Brain regions involved in emotion
– Emotions interpreted by limbic system
– Expression controlled by prefrontal cortex
• decides appropriate way to show feelings
– Amygdaloid body and hippocampus important structures
• if damaged or artificially stimulated, get deadened or exaggerated
emotions
• Brain regions involved in language
– Includes functions of reading, writing, speaking, and understanding
– Wernicke area
• involved in interpreting writing and oral language
• in the categorical hemisphere in most people
Integrative Functions and Higher-Order
Brain Functions: Language
• Brain regions involved in language (continued)
– Broca area, motor speech area
• receive axons from Wernicke area
• regulates motor activities needed for speech
• sends signals to primary motor cortex
– innervate muscles of cheeks, larynx, lips, and tongue
– Angular gyrus
• posterior to Wernicke area
• processes words read into speakable form
– Region opposite Wernicke area in representational hemisphere
• recognizes the emotional content of speech
– Region opposite motor speech area in representational hemisphere
• responsible for producing speech with emotion
• lesion producing aprosodia, dull emotionless speech
Figure 13.29
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Primary motor cortex
Motor speech area
Wernicke area
(a) Lateral view
1 Auditory information about a sentence travels
to the primary auditory cortex. The Wernicke
area then interprets the sentence.
(b) PET scans
2
Information from the Wernicke area travels to
the motor speech area.
3
Information travels from the motor speech area
to the primary motor cortex, where motor
commands involving muscles used for speech
are given.
(left): © Wellcome Dept. of Cognitive Neurology/Photo Researchers, Inc.; (center): © WDCN/Univ. College London/Photo
Researchers, Inc.; (right): © Scientifica/ADEAR/Visuals Unlimited
Integrative Functions and Higher-Order Brain
Functions: Language
Clinical View: Dyslexia
–
–
–
–
–
–
Inherited learning disability
Problems with single-word decoding
Individuals with trouble reading, writing, and spelling
Level of reading competence below expected intelligence
Improvement in some individuals with time
May be form of disconnect syndrome
• impaired transfer of information through corpus callosum
Cranial Nerves
• Cranial nerves
– Part of the
peripheral
nervous system
– Originate on
inferior surface of
brain
– Numbered with
Roman numerals
according to their
position
• begin with most
anteriorly
placed nerve
– Name related to
function
On Old Olympus' Towering Top, A Finn
And German Viewed Some Hops
Oh, Oh, Oh, To Touch And Feel Virgin
Girl's Vagina And Hymen
Some Say Marry Money, But My Brother
Says Big Breasts Matter Most
• Cranial nerves
– Olfactory nerve (CNI)
• olfaction
– Optic nerve (CNII)
• vision
– Oculomotor (CNIII)
• four extrinsic eye muscles
• elevates eyelid, constricts pupils, rounds lens of eye
– Trochlear nerve (CNIV)
• superior oblique eye muscle
– Trigeminal nerve (CNV)
• sensory from anterior scalp, face, oral cavity, and others
• muscles of mastication and others
– Abducens (CNVI)
• lateral rectus eye muscle
– Facial nerve (CNVII)
• taste anterior tongue, muscles of facial expression, others
• gland secretions from lacrimal, submandibular, and salivary glands
• Cranial nerves
– Vestibulocochlear nerve (CNVIII)
• hearing, equilibrium
– Glossopharnygeal (CNIX)
• sensory and taste to posterior tongue
• sensory to part of pharynx and others
• secretions from parotid gland
– Vagus nerve (CNX)
•
•
•
•
visceral sensory from heart, lungs, and abdominal organs
general sensory from part of pharynx, larynx, others
most pharyngeal and all laryngeal muscles
smooth muscles and glands of heart, lungs, larynx, and most abdominal
organs
– Accessory nerve (CNXI)
• trapezius and sternocleidomastoid muscle
– Hypoglossal (CNXII)
• intrinsic and extrinsic tongue muscles
Figure 13.30
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cranial nerves
Olfactory bulb, termination
of olfactory nerve (CN I)
Olfactory tract
Optic chiasm
Optic nerve (CN II)
Infundibulum
Optic tract
Oculomotor nerve (CN III)
Trochlear nerve (CN IV)
Pons
Trigeminal nerve (CN V)
Pons
Abducens nerve (CN VI)
Facial nerve (CN VII)
Vestibulocochlear nerve (CN VIII)
Medulla
oblongata
Glossopharyngeal nerve (CN IX)
Vagus nerve (CN X)
Accessory nerve (CN XI)
Hypoglossal nerve (CN XII)
Spinal cord
(right): © The McGraw-Hill Companies, Inc./Rebecca Gray, photographer
Medulla
oblongata
I. Olfactory Nerve
• Function: Sense of smell
• Composition: Sensory
• Clinical Test: Determine
whether subject can
smell aromatic
substances
– Coffee, vanilla, clove, oil,
soap
• Effect of Damage:
impaired sense of smell
II. Optic Nerve
• Function: Vision
• Composition: Sensory
• Clinical Test: Test peripheral
vision and visual acuity
• Effect of Damage:
Blindness in part or all of
visual field
III. Oculomotor Nerve
• Functions: Controls muscles that
turn eyeballs up, down, medially
– Controls iris, lens, and upper lid
• Composition: Motor
• Clinical Test: Look for pupil
shape differences
– Test pupillary response to light
– Test ability to track moving
objects
• Effect of Damage: Drooping
eyelid, dilated pupil, inability to
move eye in some directions,
double vision, difficulty focusing
IV. Trochlear Nerve
• Function: Controls a muscle that rotates eyeball
medially
• Composition: Motor
• Clinical Test: Test ability of eye to rotate
inferolaterally
• Effect of Damage:
double vision,
inability to rotate eye
inferolaterally
V. Trigeminal Nerve
• Function: Important in facial
sensations
• Composition: Both
• Clinical Test: Test facial
sensation of forehead, cheeks,
and chin.
– Test subjects ability to open
mouth against resistance
• Effect of Damage: Loss of
sensation from face and
impaired chewing
VI. Abducens Nerve
• Function: Controls a
muscle that turns
eyeball laterally
• Composition: Motor
• Clinical Test: Test
lateral eye movement
• Effect of Damage:
Inability to turn eye
laterally, at rest eye
will turn medially
VII. Facial Nerve
• Function: Important
nerve of facial muscles
and taste
• Composition: Both
• Clinical Test: Test tongue
for taste response, test
ability to make facial
expressions
• Effect of Damage:
inability to control facial
muscles, sagging due to
loss of muscle tone,
distorted sense of taste
VIII. Vestibocochlear Nerve
• Function: Hearing and
equilibrium
• Composition: Sensory
• Clinical Test: Look for
nystagmus, test
hearing, balance,
ability to walk in a
straight line
• Effect of Damage:
deafness, dizziness,
nausea, loss of
balance, nystagmus
IX. Glossopharyngeal Nerve
• Function: Food ingestion,
salivation
– Sensations from the
tongue, throat, and outer
ear
• Composition: Both
• Clinical Test: Test gag
reflex, swallowing, and
coughing
• Effect of Damage:
impaired swallowing
X. Vagus Nerve
• Function: Control of cardiac,
pulmonary, digestive, and
urinary functions
• Composition: Both
• Clinical Test: Speech
abnormalities, swallowing
abnormalities, absence of gag
reflex, weak or hoarse voice,
inability to cough
• Effect of Damage: Hoarseness
or loss of voice, impaired
swallowing
XI. Accessory Nerve
• Function: Controls swallowing
and neck and shoulder
muscles
• Composition: Motor
• Clinical Test: Test ability to
rotate head and shrug
shoulders against resistance
• Effect of Damage: impaired
movement of head, neck, and
shoulders, difficulty shrugging
shoulder on damaged side
XII. Hypoglossal Nerve
• Function: Controls tongue
movements
• Composition: Motor
• Clinical Test: Note deviations
of the tongue as subject
protrudes and retracts it
• Effect of Damage: impaired
speech and swallowing,
inability to protrude tongue if
both sides damaged, deviation
of tongue toward injured side