Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
*See separate FlexArt PowerPo...
Introduction
• The human brain is complex
• Brain function is associated with life
• This chapter is a study of brain and ...
14-3
Introduction
• Aristotle thought brain was “radiator” to cool blood
• Hippocrates was more accurate: “from the brain ...
Overview of the Brain
• Expected Learning Outcomes
– Describe the major subdivisions and anatomical
landmarks of the brain...
14-5
Major Landmarks
• Rostral—toward the
forehead
• Caudal—toward the spinal
cord
• Brain weighs about 1,600 g
(3.5 lb) i...
14-6
Major Landmarks
• Three major portions of the
brain
– Cerebrum is 83% of brain
volume; cerebral hemispheres,
gyri and...
14-7
Major Landmarks
• Longitudinal fissure—deep
groove that separates
cerebral hemispheres
• Gyri—thick folds
• Sulci—sha...
14-8
Major Landmarks
• Occupies posterior
cranial fossa
• Marked by gyri, sulci,
and fissures
• About 10% of brain
volume
...
14-9
Major Landmarks
• Brainstem—what
remains of the brain
if the cerebrum and
cerebellum are
removed
• Major components
–...
14-10
Major Landmarks
Figure 14.2a
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or dis...
14-11
Major Landmarks
Figure 14.2b
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or dis...
14-12
Gray and White Matter
• Gray matter—the seat of neuron cell bodies,
dendrites, and synapses
– Dull white color when ...
14-13
Embryonic Development
• Nervous system develops from ectoderm
– Outermost tissue layer of the embryo
• Early in thir...
14-14
Embryonic Development
• By fourth week, creates a hollow channel—neural
tube
– Neural tube separates from overlying ...
14-15
Embryonic Development
Cont.
• Neural crest—formed from ectodermal cells that lay
along the margins of the groove and...
14-16
Embryonic Development
• By fifth week, it subdivides into five secondary vesicles
– Forebrain divides into two of th...
Embryonic Development
14-17
Figure 14.3
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction o...
14-18
Embryonic Development
• Fourth week
– Forebrain
– Midbrain
– Hindbrain
• Fifth week
– Telencephalon
– Diencephalon
–...
Meninges, Ventricles, Cerebrospinal
Fluid, and Blood Supply
• Expected Learning Outcomes
– Describe the meninges of the br...
14-20
Meninges
• Meninges—three connective tissue
membranes that envelop the brain
– Lies between the nervous tissue and b...
14-21
Meninges
• Dura mater
– In cranial cavity; has two layers
• Outer periosteal—equivalent to periosteum of cranial bon...
14-22
Meninges
Cont.
– Folds inward to extend between parts of the brain
• Falx cerebri separates the two cerebral hemisph...
14-23
Meninges
• Arachnoid mater and pia mater are similar to those in the
spinal cord
• Arachnoid mater
– Transparent mem...
14-24
Meninges
Figure 14.5
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Su...
14-25
Meningitis
• Meningitis—inflammation of the meninges
– Serious disease of infancy and childhood
– Especially between...
14-26
Ventricles and Cerebrospinal Fluid
Figure 14.6a,b
Copyright © The McGraw-Hill Companies, Inc. Permission required fo...
Choroid plexus
Thalamus
Gyrus
Sulcus
Caudate nucleus
Frontal lobe
White matter
Lateral ventricle
Temporal lobe
Third ventr...
14-28
Ventricles and Cerebrospinal Fluid
• Ventricles—four internal chambers within the brain
– Two lateral ventricles: on...
14-29
Ventricles and Cerebrospinal Fluid
Cont.
• Choroid plexus—spongy mass of blood capillaries on the
floor of each vent...
14-30
Ventricles and Cerebrospinal Fluid
• Cerebrospinal fluid (CSF)—clear, colorless liquid that fills
the ventricles and...
14-31
Ventricles and Cerebrospinal Fluid
• CSF continually flows through and around the CNS
– Driven by its own pressure, ...
14-32
Ventricles and Cerebrospinal Fluid
• Small amount of CSF fills the central canal of the spinal
cord
– All escapes th...
14-33
Ventricles and Cerebrospinal Fluid
• Functions of CSF
– Buoyancy
• Allows brain to attain considerable size without ...
14-34
Ventricles and Cerebrospinal Fluid
Figure 14.7
Copyright © The McGraw-Hill Companies, Inc. Permission required for r...
14-35
Blood Supply and the Brain
Barrier System
• Brain is only 2% of the adult body weight, and receives 15%
of the blood...
14-36
Blood Supply and the Brain
Barrier System
• Blood is also a source of antibodies, macrophages,
bacterial toxins, and...
14-37
Blood Supply and the Brain
Barrier System
• Blood–brain barrier—protects blood capillaries
throughout brain tissue
–...
14-38
Blood Supply and the Brain
Barrier System
• Blood–CSF barrier—protects the brain at the choroid
plexus
– Forms tight...
14-39
Blood Supply and the Brain
Barrier System
• Obstacle for delivering medications such as antibiotics
and cancer drugs...
The Hindbrain and Midbrain
• Expected Learning Outcomes
– List the components of the hindbrain and midbrain and
their func...
14-41
The Medulla Oblongata
• Embryonic myelencephalon
becomes medulla oblongata
• Begins at foramen magnum of
the skull
•...
14-42
The Medulla Oblongata
• Olive—a prominent bulge
lateral to each pyramid
• Posteriorly, gracile and
cuneate fasciculi...
14-43
The Medulla Oblongata
• Cardiac center
– Adjusts rate and force of heart
• Vasomotor center
– Adjusts blood vessel d...
14-44
The Medulla Oblongata
• Pyramids contain descending fibers called corticospinal tracts
– Carry motor signals to skel...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Diencephalon:
Midbrain:
Thala...
14-46
The Pons
Figure 14.8b
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
D...
Thalamus
Hypothalamus
Frontal lobe
Corpus callosum
Cingulate gyrus
Optic chiasm
Pituitary gland
Mammillary body
Midbrain
P...
14-48
The Pons
• Ascending sensory tracts
• Descending motor tracts
• Pathways in and out of cerebellum
• Cranial nerves V...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Reticular formation
Trigemina...
14-50
The Midbrain
• Mesencephalon becomes one mature brain
structure, the midbrain
– Short segment of brainstem that conn...
14-51
The Midbrain
• Mesencephalon (cont.)
– Tectum: rooflike part of the midbrain posterior to
cerebral aqueduct
• Exhibi...
14-52
The Midbrain
Cont.
– Cerebral peduncles: two stalks that anchor the
cerebrum to the brainstem anterior to the cerebr...
14-53
The Midbrain
– Substantia nigra
• Dark gray to black nucleus pigmented with melanin
• Motor center that relays inhib...
14-54
The Midbrain
Figure 14.9a
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or displa...
14-55
The Reticular Formation
• Loosely organized web of
gray matter that runs
vertically through all levels of
the brains...
14-56
The Reticular Formation
• Networks
– Somatic motor control
• Adjust muscle tension to maintain tone, balance, and
po...
14-57
The Reticular Formation
Cont.
– Cardiovascular control
• Includes cardiac and vasomotor centers of medulla
oblongata...
14-58
The Reticular Formation
– Sleep and consciousness
• Plays central role in states of consciousness, such as
alertness...
14-59
The Cerebellum
• The largest part of the hindbrain and the second largest part of the brain as
a whole
• Consists of...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Superior colliculus
Posterior...
14-61
The Cerebellum
• Monitors muscle contractions and aids in motor coordination
• Evaluation of sensory input
– Compari...
14-62
The Cerebellum
Cont.
• Hearing
– Distinguish pitch and similar-sounding words
• Planning and scheduling tasks
• Lesi...
The Forebrain
• Expected Learning Outcomes
– Name the three major components of the diencephalon
and describe their locati...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Diencephalon
Mesencephalon
Fo...
14-65
The Diencephalon: Thalamus
• Thalamus—ovoid mass on each side of the brain perched at the
superior end of the brains...
The Diencephalon: Thalamus
Cont.
– “Gateway to the cerebral cortex”: nearly all input to the
cerebrum passes by way of syn...
14-67
• Hypothalamus—forms part
of the walls and floor of the
third ventricle
• Extends anteriorly to optic
chiasm and pos...
The Diencephalon: Hypothalamus
• Infundibulum—a stalk that attaches the pituitary gland to the
hypothalamus
• Major contro...
The Diencephalon: Hypothalamus
Cont.
– Hormone secretion
• Controls anterior pituitary
• Regulates growth, metabolism, rep...
The Diencephalon: Hypothalamus
Cont.
– Food and water intake
• Hunger and satiety centers monitor blood glucose and amino
...
The Diencephalon: Epithalamus
• Epithalamus—very small mass of tissue composed of:
– Pineal gland: endocrine gland
– Haben...
The Telencephalon: Cerebrum
• Cerebrum—largest and most conspicuous part of the human
brain
– Seat of sensory perception, ...
Brainstem
Cerebellum
Cerebrum
Spinal cord
Rostral Caudal
Central sulcus
Lateral sulcus
Gyri
(b) Lateral view
Temporal lobe...
14-74
• Frontal lobe
– Voluntary motor functions
– Motivation, foresight,
planning, memory, mood,
emotion, social judgment...
14-75
Tracts of Cerebral White Matter
Figure 14.14
Copyright © The McGraw-Hill Companies, Inc. Permission required for rep...
14-76
The Cerebral White Matter
• Most of the volume of cerebrum is white matter
– Glia and myelinated nerve fibers transm...
14-77
The Cerebral White Matter
• Three types of tracts
– Projection tracts
• Extends vertically between higher and lower ...
14-78
The Cerebral White Matter
Cont.
– Association tracts
• Connect different regions within the same cerebral
hemisphere...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
I
II
III
IV
V
VI
Cortical sur...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
I
II
III
IV
V
VI
Cortical sur...
The Cerebral Cortex
• Contains two principal types of neurons
– Stellate cells
• Have spheroid somas with dendrites projec...
The Cerebral Cortex
• Neocortex—six-layered tissue that constitutes about
90% of the human cerebral cortex
– Relatively re...
14-83
The Basal Nuclei
• Basal nuclei—masses of cerebral gray matter buried deep
in the white matter, lateral to the thala...
The Basal Nuclei
• At least three brain centers form basal nuclei
– Caudate nucleus
– Putamen
– Globus pallidus
• Lentifor...
14-85
The Limbic System
• Limbic system—important
center of emotion and
learning
• Most anatomically prominent
components ...
14-86
The Limbic System
• Limbic system components
are connected through a
complex loop of fiber tracts
allowing for somew...
Integrative Functions of the Brain
• Expected Learning Outcomes
– List the types of brain waves and discuss their relation...
14-88
Integrative Functions of the Brain
• Higher brain functions—sleep, memory, cognition,
emotion, sensation, motor cont...
14-89
The Electroencephalogram
• Alpha waves 8 to 13 Hz
– Awake and resting with eyes closed and mind wandering
– Suppress...
14-90
The Electroencephalogram
• Electroencephalogram (EEG)—monitors surface electrical activity
of the brain waves
– Usef...
The Electroencephalogram
Cont.
• Brain waves—rhythmic voltage changes resulting from
synchronized postsynaptic potentials ...
14-92
Sleep
• Sleep occurs in cycles called circadian rhythms
– Events that reoccur at intervals of about 24 hours
• Sleep...
14-93
Sleep
Cont.
• Restorative effect
– Brain glycogen and ATP levels increase in non-REM sleep
– Memories strengthened i...
14-94
Sleep
Cont.
– Stage 2
• Pass into light sleep
• EEG declines in frequency but increases in amplitude
• Exhibits slee...
14-95
Sleep
Cont.
– Stage 4
• Called slow-wave sleep (SWS)—EEG dominated by low-
frequency, high-amplitude delta waves
• M...
14-96
Sleep
Cont.
– Vital signs increase, brain uses more oxygen than when
awake
– Sleep paralysis stronger to prevent sle...
14-97
Sleep
• Rhythm of sleep is controlled by a complex interaction
between the cerebral cortex, thalamus, hypothalamus,
...
14-98
Sleep
• Suprachiasmatic nucleus (SCN)—another important
control center for sleep
– Above optic chiasma in anterior h...
14-99
Sleep
• Sleep has a restorative effect, and sleep deprivation can be
fatal to experimental animals
– Bed rest alone ...
14-100
Sleep Stages and Brain Activity
Figure 14.19
Copyright © The McGraw-Hill Companies, Inc. Permission required for re...
14-101
Cognition
• Cognition—the range of mental processes by
which we acquire and use knowledge
– Such as sensory percept...
14-102
Cognition
• Studies of patients with brain lesions, cancer, stroke,
and trauma yield information on cognition
– Par...
14-103
Memory
• Information management entails:
– Learning: acquiring new information
– Memory: information storage and re...
14-104
Memory
• Hippocampus—important memory-forming center
– Does not store memories
– Organizes sensory and cognitive in...
14-105
Memory
Cont.
– Vocabulary and memory of familiar faces stored in superior
temporal lobe
– Memories of one’s plans a...
14-106
Accidental Lobotomy
• Phineas Gage—railroad
construction worker; severe
injury with metal rod
• Injury to the ventr...
14-107
Emotion
• Emotional feelings and memories are interactions
between prefrontal cortex and diencephalon
• Prefrontal ...
14-108
Emotion
• Amygdala receives input from sensory systems
– Role in food intake, sexual behavior, and drawing
attentio...
14-109
Sensation
• Primary sensory cortex—sites
where sensory input is first
received and one becomes
conscious of the sti...
14-110
The Special Senses
• Special senses—limited to the head and employ relatively
complex sense organs
• Primary cortic...
14-111
The Special Senses
• Equilibrium
– Signals for balance and sense of motion project mainly to
the cerebellum and sev...
14-112
The General Senses
• General (somesthetic, somatosensory, or somatic)
senses—distributed over the entire body and e...
14-113
The General Senses
• Awareness of stimulation occurs in primary somesthetic
cortex
• Making cognitive sense of the ...
Thigh
Shoulder
Arm
V
(b)
Insula
Lateral sulcus
Genitalia
Leg
Hip
Trunk
Eye
Nose
Face
Upper lip
Lower lip
Thum
b
(I)
Hand
F...
14-115
Functional Regions of the Cerebral Cortex
Figure 14.21
Wernicke area
Broca area
Primary motor
cortex
Motor associat...
14-116
Motor Control
• The intention to contract a muscle begins in motor
association (premotor) area of frontal lobes
– W...
14-117
Motor Control
• Premotor area (cont.)
– Neurons send signals to the brainstem and spinal cord
– Ultimately resultin...
14-118
Motor Control
• Pyramidal cells of the precentral gyrus are called upper
motor neurons
– Their fibers project cauda...
14-119
Motor Control• Basal nuclei
– Determines the onset and cessation of intentional movements
• Repetitive hip and shou...
Fingers
Eye and eyelid
Tongue
Ankle
Lips
Face
Jaw
Pharynx
Salivation
Mastication
Swallowing
Neck
Brow
V
H
andW
rist
Elbow
...
14-121
Motor Pathways Involving the Cerebellum
Figure 14.24
Cerebrum
Cerebrum
Motor cortex
Cerebellum
Cerebellum
Brainstem...
14-122
Language
• Language include several abilities: reading, writing, speaking,
and understanding words assigned to diff...
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Precentral gyrus
Anterior Pos...
14-124
Aphasia
• Aphasia—any language deficit from lesions in same
hemisphere (usually left) containing the Wernicke and B...
14-125
Cerebral Lateralization
Figure 14.26
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproducti...
14-126
Cerebral Lateralization
• Cerebral lateralization—the difference in the structure and
function of the cerebral hemi...
14-127
Cerebral Lateralization
• Highly correlated with handedness
– Left hemisphere is the categorical one in 96% of righ...
The Cranial Nerves
• Expected Learning Outcomes
– List the 12 cranial nerves by name and number.
– Identify where each cra...
14-129
The Cranial Nerves
• Brain must communicate with rest of body
– Most of the input and output travels by way of the ...
14-130
Cranial Nerve Pathways
• Most motor fibers of the cranial nerves begin in
nuclei of brainstem and lead to glands an...
14-131
Cranial Nerve Pathways
• Most cranial nerves carry fibers between
brainstem and ipsilateral receptors and effectors...
14-132
Cranial Nerve Classification
• Some cranial nerves are classified as motor,
some sensory, others mixed
– Sensory (I...
14-133
The Cranial Nerves
Figure 14.27a,b Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction...
14-134
The Olfactory Nerve (I)
• Sense of smell
• Damage causes impaired sense of smell
Figure 14.28
Copyright © The McGra...
14-135
The Optic Nerve (II)
• Provides vision
• Damage causes blindness in part or all of visual field
Figure 14.29
Copyri...
14-136
The Oculomotor Nerve (III)
• Controls muscles that turn the eyeball up, down, and medially, as
well as controlling ...
14-137
The Trochlear Nerve (IV)
• Eye movement (superior oblique muscle)
• Damage causes double vision and inability to ro...
14-138
The Trigeminal Nerve (V)
• Largest of the cranial
nerves
• Most important sensory
nerve of the face
• Forks into th...
14-139
The Abducens Nerve (VI)
• Provides eye movement (lateral rectus m.)
• Damage results in inability to rotate eye lat...
14-140
The Facial Nerve (VII)
• Motor—major motor nerve of facial muscles: facial expressions;
salivary glands and tear, n...
14-141
Five Branches of Facial Nerve
Clinical test: test anterior two-thirds of tongue with substances such as sugar,
salt...
Cochlear nerve
Cochlea
Semicircular
ducts
Vestibular ganglia
Vestibular nerve
Vestibulocochlear
nerve (VIII)
Internal
acou...
14-143
The Glossopharyngeal Nerve (IX)
• Swallowing,
salivation, gagging,
control of BP and
respiration
• Sensations from
...
14-144
The Vagus Nerve (X)
• Most extensive distribution of
any cranial nerve
• Major role in the control of
cardiac, pulm...
14-145
The Accessory Nerve (XI)
• Swallowing; head, neck, and shoulder movement
– Damage causes impaired head, neck, shoul...
14-146
The Hypoglossal Nerve (XII)
• Tongue movements for speech, food manipulation, and
swallowing
– If both are damaged:...
14-147
Cranial Nerve Disorders
• Trigeminal neuralgia (tic douloureux)
– Recurring episodes of intense stabbing pain in tr...
14-148
Images of the Mind
• Positron emission tomography (PET) and MRI
visualize increases in blood flow when brain areas ...
14-149
Images of the Mind
Figure 14.40
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or...
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Chapt14 lecture (4)

  1. 1. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. *See separate FlexArt PowerPoint slides for all figures and tables preinserted into PowerPoint without notes. Chapter 14 *Lecture PowerPoint The Brain and Cranial Nerves
  2. 2. Introduction • The human brain is complex • Brain function is associated with life • This chapter is a study of brain and cranial nerves directly connected to it • Will provide insight into brain circuitry and function 14-2
  3. 3. 14-3 Introduction • Aristotle thought brain was “radiator” to cool blood • Hippocrates was more accurate: “from the brain only, arises our pleasures, joys, laughter, and jests, as well as our sorrows, pains, griefs, and tears” • Cessation of brain activity—clinical criterion of death • Evolution of the central nervous system shows spinal cord has changed very little while brain has changed a great deal – Greatest growth in areas of vision, memory, and motor control of the prehensile hand
  4. 4. Overview of the Brain • Expected Learning Outcomes – Describe the major subdivisions and anatomical landmarks of the brain. – Describe the locations of its gray and white matter. – Describe the embryonic development of the CNS and relate this to adult brain anatomy. 14-4
  5. 5. 14-5 Major Landmarks • Rostral—toward the forehead • Caudal—toward the spinal cord • Brain weighs about 1,600 g (3.5 lb) in men, and 1,450 g in women Figure 14.1b Brainstem Cerebellum Cerebrum Spinal cord Rostral Caudal Central sulcus Lateral sulcus Gyri (b) Lateral view Temporal lobe Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  6. 6. 14-6 Major Landmarks • Three major portions of the brain – Cerebrum is 83% of brain volume; cerebral hemispheres, gyri and sulci, longitudinal fissure, corpus callosum – Cerebellum contains 50% of the neurons; second largest brain region, located in posterior cranial fossa – Brainstem is the portion of the brain that remains if the cerebrum and cerebellum are removed; diencephalon, midbrain, pons, and medulla oblongata Figure 14.1b Brainstem Cerebellum Cerebrum Spinal cord Rostral Caudal Central sulcus Lateral sulcus Gyri (b) Lateral view Temporal lobe Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  7. 7. 14-7 Major Landmarks • Longitudinal fissure—deep groove that separates cerebral hemispheres • Gyri—thick folds • Sulci—shallow grooves • Corpus callosum—thick nerve bundle at bottom of longitudinal fissure that connects hemispheres Figure 14.1a Frontal lobe Occipital lobe Central sulcus Longitudinal fissure Parietal lobe (a) Superior view Cerebral hemispheres Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  8. 8. 14-8 Major Landmarks • Occupies posterior cranial fossa • Marked by gyri, sulci, and fissures • About 10% of brain volume • Contains over 50% of brain neurons Figure 14.1b Brainstem Cerebellum Cerebrum Spinal cord Rostral Caudal Central sulcus Lateral sulcus Gyri (b) Lateral view Temporal lobe Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  9. 9. 14-9 Major Landmarks • Brainstem—what remains of the brain if the cerebrum and cerebellum are removed • Major components – Diencephalon – Midbrain – Pons – Medulla oblongata Figure 14.1b Brainstem Cerebellum Cerebrum Spinal cord Rostral Caudal Central sulcus Lateral sulcus Gyri (b) Lateral view Temporal lobe Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  10. 10. 14-10 Major Landmarks Figure 14.2a Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thalamus Hypothalamus Frontal lobe Corpus callosum Cingulate gyrus Optic chiasm Pituitary gland Mammillary body Midbrain Pons Central sulcus Parietal lobe Parieto–occipital sulcus Occipital lobe Pineal gland Habenula Posterior commissure Cerebral aqueduct Fourth ventricle Cerebellum (a) EpithalamusAnterior commissure Temporal lobe Medulla oblongata
  11. 11. 14-11 Major Landmarks Figure 14.2b Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b: © The McGraw-Hill Companies, Inc./Dennis Strete, photographer Corpus callosum Cingulate gyrus Lateral ventricle Thalamus Hypothalamus Midbrain Cerebellum Fourth ventriclePons (b) Choroid plexus Pineal gland Occipital lobe Medulla oblongata Parieto–occipital sulcus Posterior commissure
  12. 12. 14-12 Gray and White Matter • Gray matter—the seat of neuron cell bodies, dendrites, and synapses – Dull white color when fresh, due to little myelin – Forms surface layer (cortex) over cerebrum and cerebellum – Forms nuclei deep within brain • White matter—bundles of axons – Lies deep to cortical gray matter, opposite relationship in the spinal cord – Pearly white color from myelin around nerve fibers – Composed of tracts, or bundles of axons, that connect one part of the brain to another, and to the spinal cord
  13. 13. 14-13 Embryonic Development • Nervous system develops from ectoderm – Outermost tissue layer of the embryo • Early in third week of development – Neuroectoderm: dorsal streak appears along the length of embryo – Thickens to form neural plate • Destined to give rise to most neurons and all glial cells except microglia, which come from mesoderm • As thickening progresses – Neural plate sinks and its edges thicken • Forming a neural groove with a raised neural fold on each side • Neural folds fuse along the midline – Beginning in the cervical region and progressing rostrally and caudally
  14. 14. 14-14 Embryonic Development • By fourth week, creates a hollow channel—neural tube – Neural tube separates from overlying ectoderm – Sinks deeper – Grows lateral processes that later will form motor nerve fibers – Lumen of neural tube becomes fluid-filled space • Central canal in spinal cord • Ventricles of the brain
  15. 15. 14-15 Embryonic Development Cont. • Neural crest—formed from ectodermal cells that lay along the margins of the groove and separate from the rest forming a longitudinal column on each side – Gives rise to the two inner meninges, most of the peripheral nervous system, and other structures of the skeletal, integumentary, and endocrine systems • By fourth week, the neural tube exhibits three anterior dilations (primary vesicles) – Forebrain (prosencephalon) – Midbrain (mesencephalon) – Hindbrain (rhombencephalon)
  16. 16. 14-16 Embryonic Development • By fifth week, it subdivides into five secondary vesicles – Forebrain divides into two of them • Telencephalon—becomes cerebral hemispheres • Diencephalon—has optic vesicles that become retina of the eye – Midbrain remains undivided • Mesencephalon – Hindbrain divides into two vesicles • Metencephalon • Myelencephalon
  17. 17. Embryonic Development 14-17 Figure 14.3 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (a) 19 days (c) 22 days Ectoderm Notochord Neural groove Neural fold Neural plate (b) 20 days (d) 26 days Somites Neural crest Neural crest Neural crest Neural tube
  18. 18. 14-18 Embryonic Development • Fourth week – Forebrain – Midbrain – Hindbrain • Fifth week – Telencephalon – Diencephalon – Mesencephalon – Metencephalon – Myelencephalon Figure 14.4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Diencephalon Mesencephalon Forebrain Pons Cerebellum Metencephalon Spinal cord Hindbrain Optic vesicle Diencephalon Metencephalon Myelencephalon Spinal cord Rhombencephalon Mesencephalon Prosencephalon (a) 4 weeks (b) 5 weeks (c) Fully developed Midbrain Telencephalon Myelencephalon (medulla oblongata) Telencephalon
  19. 19. Meninges, Ventricles, Cerebrospinal Fluid, and Blood Supply • Expected Learning Outcomes – Describe the meninges of the brain. – Describe the fluid-filled chambers within the brain. – Discuss the production, circulation, and function of the cerebrospinal fluid that fills these chambers. – Explain the significance of the brain barrier system. 14-19
  20. 20. 14-20 Meninges • Meninges—three connective tissue membranes that envelop the brain – Lies between the nervous tissue and bone – As in spinal cord, they are the dura mater, arachnoid mater, and the pia mater – Protect the brain and provide structural framework for its arteries and veins
  21. 21. 14-21 Meninges • Dura mater – In cranial cavity; has two layers • Outer periosteal—equivalent to periosteum of cranial bones • Inner meningeal—continues into vertebral canal and forms dural sac around spinal cord – Cranial dura mater is pressed closely against cranial bones • No epidural space • Not attached to bone except: around foramen magnum, sella turcica, the crista galli, and sutures of the skull • Layers separated by dural sinuses—collect blood circulating through brain
  22. 22. 14-22 Meninges Cont. – Folds inward to extend between parts of the brain • Falx cerebri separates the two cerebral hemispheres • Tentorium cerebelli separates cerebrum from cerebellum • Falx cerebelli separates the right and left halves of cerebellum
  23. 23. 14-23 Meninges • Arachnoid mater and pia mater are similar to those in the spinal cord • Arachnoid mater – Transparent membrane over brain surface – Subarachnoid space separates it from pia mater below – Subdural space separates it from dura mater above in some places • Pia mater – Very thin membrane that follows contours of brain, even dipping into sulci – Not usually visible without a microscope
  24. 24. 14-24 Meninges Figure 14.5 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Subdural space Skull Pia mater Blood vessel Dura mater: Periosteal layer Meningeal layer Arachnoid mater Brain: Gray matter White matter Arachnoid granulation Subarachnoid space Superior sagittal sinus Falx cerebri (in longitudinal fissure only)
  25. 25. 14-25 Meningitis • Meningitis—inflammation of the meninges – Serious disease of infancy and childhood – Especially between 3 months and 2 years of age • Caused by bacterial and virus invasion of the CNS by way of the nose and throat • Pia mater and arachnoid are most often affected • Bacterial meningitis can cause swelling of the brain, enlargment of the ventricles, and hemorrhage • Signs include high fever, stiff neck, drowsiness, and intense headache; may progress to coma then death within hours of onset • Diagnosed by examining the CSF for bacteria – Lumbar puncture (spinal tap) draws fluid from subarachnoid space between two lumbar vertebrae
  26. 26. 14-26 Ventricles and Cerebrospinal Fluid Figure 14.6a,b Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lateral ventricles Central canal Lateral aperture Fourth ventricle Third ventricle Median aperture Lateral ventricle Third ventricle Cerebrum Lateral aperture Fourth ventricle Median aperture (a) Lateral view Caudal Rostral Interventricular foramen Cerebral aqueduct Interventricular foramen Cerebral aqueduct (b) Anterior view
  27. 27. Choroid plexus Thalamus Gyrus Sulcus Caudate nucleus Frontal lobe White matter Lateral ventricle Temporal lobe Third ventricle Lateral sulcus Insula Lateral ventricle Occipital lobe (c) Rostral (anterior) Caudal (posterior) Corpus callosum (anterior part) Septum pellucidum Corpus callosum (posterior part) Longitudinal fissure Gray matter (cortex) Longitudinal fissure 14-27 Ventricles and Cerebrospinal Fluid Figure 14.6c Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. c: © The McGraw-Hill Companies, Inc./Rebecca Gray,photographer/Don Kincaid, dissections
  28. 28. 14-28 Ventricles and Cerebrospinal Fluid • Ventricles—four internal chambers within the brain – Two lateral ventricles: one in each cerebral hemisphere • Interventricular foramen—a tiny pore that connects to third ventricle – Third ventricle: single narrow medial space beneath corpus callosum • Cerebral aqueduct runs through midbrain and connects third to fourth ventricle – Fourth ventricle: small triangular chamber between pons and cerebellum • Connects to central canal, runs down through spinal cord
  29. 29. 14-29 Ventricles and Cerebrospinal Fluid Cont. • Choroid plexus—spongy mass of blood capillaries on the floor of each ventricle • Ependyma—neuroglia that lines the ventricles and covers choroid plexus – Produces cerebrospinal fluid
  30. 30. 14-30 Ventricles and Cerebrospinal Fluid • Cerebrospinal fluid (CSF)—clear, colorless liquid that fills the ventricles and canals of CNS – Bathes its external surface • Brain produces and absorbs 500 mL/day – 100 to 160 mL normally present at one time – 40% formed in subarachnoid space external to brain – 30% by the general ependymal lining of the brain ventricles – 30% by the choroid plexuses • Production begins with the filtration of blood plasma through the capillaries of the brain – Ependymal cells modify the filtrate, so CSF has more sodium and chloride than plasma, but less potassium, calcium, glucose, and very little protein
  31. 31. 14-31 Ventricles and Cerebrospinal Fluid • CSF continually flows through and around the CNS – Driven by its own pressure, beating of ependymal cilia, and pulsations of the brain produced by each heartbeat • CSF secreted in lateral ventricles flows through intervertebral foramina into third ventricle • Then down the cerebral aqueduct into the fourth ventricle • Third and fourth ventricles add more CSF along the way
  32. 32. 14-32 Ventricles and Cerebrospinal Fluid • Small amount of CSF fills the central canal of the spinal cord – All escapes through three pores • Median aperture and two lateral apertures • Leads into subarachnoid space of brain and spinal cord surface • CSF is reabsorbed by arachnoid villi – Cauliflower-shaped extension of the arachnoid meninx – Protrudes through dura mater – Into superior sagittal sinus – CSF penetrates the walls of the villi and mixes with the blood in the sinus
  33. 33. 14-33 Ventricles and Cerebrospinal Fluid • Functions of CSF – Buoyancy • Allows brain to attain considerable size without being impaired by its own weight • If it rested heavily on floor of cranium, the pressure would kill the nervous tissue – Protection • Protects the brain from striking the cranium when the head is jolted • Shaken child syndrome and concussions do occur from severe jolting – Chemical stability • Flow of CSF rinses away metabolic wastes from nervous tissue and homeostatically regulates its chemical environment
  34. 34. 14-34 Ventricles and Cerebrospinal Fluid Figure 14.7 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Arachnoid villus Choroid plexus Third ventricle Lateral aperture Fourth ventricle Median aperture Dura mater Arachnoid mater 1 2 3 4 56 7 7 8 1 2 3 4 5 6 7 8 Superior sagittal sinus Subarachnoid space Cerebral aqueduct Central canal of spinal cord Subarachnoid space of spinal cord CSF is secreted by choroid plexus in each lateral ventricle. CSF flows through interventricular foramina into third ventricle. Choroid plexus in third ventricle adds more CSF. CSF flows down cerebral aqueduct to fourth ventricle. Choroid plexus in fourth ventricle adds more CSF. CSF fills subarachnoid space and bathes external surfaces of brain and spinal cord. At arachnoid villi, CSF is reabsorbed into venous blood of dural venous sinuses. CSF flows out two lateral apertures and one median aperture.
  35. 35. 14-35 Blood Supply and the Brain Barrier System • Brain is only 2% of the adult body weight, and receives 15% of the blood – 750 mL/min. • Neurons have a high demand for ATP, and therefore, oxygen and glucose, so a constant supply of blood is critical to the nervous system – A 10-second interruption of blood flow may cause loss of consciousness – A 1- to 2-minute interruption can cause significant impairment of neural function – Going 4 minutes without blood causes irreversible brain damage
  36. 36. 14-36 Blood Supply and the Brain Barrier System • Blood is also a source of antibodies, macrophages, bacterial toxins, and other harmful agents • Brain barrier system—strictly regulates what substances can get from the bloodstream into the tissue fluid of the brain • Two points of entry must be guarded – Blood capillaries throughout the brain tissue – Capillaries of the choroid plexus
  37. 37. 14-37 Blood Supply and the Brain Barrier System • Blood–brain barrier—protects blood capillaries throughout brain tissue – Consists of tight junctions between endothelial cells that form the capillary walls – Astrocytes reach out and contact capillaries with their perivascular feet – Induce the endothelial cells to form tight junctions that completely seal off gaps between them – Anything leaving the blood must pass through the cells, and not between them – Endothelial cells can exclude harmful substances from passing to the brain tissue while allowing necessary ones to pass
  38. 38. 14-38 Blood Supply and the Brain Barrier System • Blood–CSF barrier—protects the brain at the choroid plexus – Forms tight junctions between the ependymal cells – Tight junctions are absent from ependymal cells elsewhere • Important to allow exchange between brain tissue and CSF • Blood barrier system is highly permeable to water, glucose, and lipid-soluble substances such as oxygen, carbon dioxide, alcohol, caffeine, nicotine, and anesthetics • Slightly permeable to sodium, potassium, chloride, and the waste products urea and creatinine
  39. 39. 14-39 Blood Supply and the Brain Barrier System • Obstacle for delivering medications such as antibiotics and cancer drugs • Trauma and inflammation can damage BBS and allow pathogens to enter brain tissue – Circumventricular organs (CVOs)—places in the third and fourth ventricles where the barrier is absent • Blood has direct access to the brain • Enables the brain to monitor and respond to fluctuations in blood glucose, pH, osmolarity, and other variables • CVOs afford a route for invasion by the human immunodeficiency virus (HIV)
  40. 40. The Hindbrain and Midbrain • Expected Learning Outcomes – List the components of the hindbrain and midbrain and their functions. – Describe the location and functions of the reticular formation. 14-40
  41. 41. 14-41 The Medulla Oblongata • Embryonic myelencephalon becomes medulla oblongata • Begins at foramen magnum of the skull • Extends for about 3 cm rostrally and ends at a groove between the medulla and pons • Slightly wider than spinal cord • Pyramids—pair of external ridges on anterior surface – Resembles side-by-side baseball bats Figure 14.2a Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thalamus Hypothalamus Frontal lobe Corpus callosum Cingulate gyrus Optic chiasm Pituitary gland Mammillary body Midbrain Pons Central sulcus Parietal lobe Parieto–occipital sulcus Occipital lobe Pineal gland Habenula Posterior commissure Cerebral aqueduct Fourth ventricle Cerebellum (a) EpithalamusAnterior commissure Temporal lobe Medulla oblongata
  42. 42. 14-42 The Medulla Oblongata • Olive—a prominent bulge lateral to each pyramid • Posteriorly, gracile and cuneate fasciculi of the spinal cord continue as two pair of ridges on the medulla • All nerve fibers connecting the brain to the spinal cord pass through the medulla • Four pairs of cranial nerves begin or end in medulla—IX, X, XI, XII Figure 14.2a Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thalamus Hypothalamus Frontal lobe Corpus callosum Cingulate gyrus Optic chiasm Pituitary gland Mammillary body Midbrain Pons Central sulcus Parietal lobe Parieto–occipital sulcus Occipital lobe Pineal gland Habenula Posterior commissure Cerebral aqueduct Fourth ventricle Cerebellum (a) EpithalamusAnterior commissure Temporal lobe Medulla oblongata
  43. 43. 14-43 The Medulla Oblongata • Cardiac center – Adjusts rate and force of heart • Vasomotor center – Adjusts blood vessel diameter • Respiratory centers – Control rate and depth of breathing • Reflex centers – For coughing, sneezing, gagging, swallowing, vomiting, salivation, sweating, movements of tongue and head
  44. 44. 14-44 The Medulla Oblongata • Pyramids contain descending fibers called corticospinal tracts – Carry motor signals to skeletal muscles • Inferior olivary nucleus—relay center for signals to cerebellum • Reticular formation—loose network of nuclei extending throughout the medulla, pons, and midbrain – Contains cardiac, vasomotor, and respiratory centers Figure 14.9c Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hypoglossal nerve Medial lemniscus Tectospinal tract Nucleus Tract Gracile nucleus Cuneate nucleus Olive Pyramids of medullaCorticospinal tract Trigeminal nerve: Fourth ventricle Reticular formation (a) Midbrain (c) Medulla oblongata (c) Medulla (b) Pons Nucleus of hypoglossal nerve Dorsal spinocerebellar tract Nucleus of vagus nerve Inferior olivary nucleus
  45. 45. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Diencephalon: Midbrain: Thalamus Optic tract Cranial nerves: Oculomotor nerve (III) Optic nerve (II) Trochlear nerve (IV) Trigeminal nerve (V) Abducens nerve (VI) Facial nerve (VII) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Vagus nerve (X) Accessory nerve (XI) Hypoglossal nerve (XII) Spinal nerves Infundibulum Mammillary body Cerebral peduncle Pyramid Anterior median fissure Pyramidal decussation Spinal cord (a) Ventral view Pons Medulla oblongata: Regions of the brainstem Midbrain Diencephalon Pons Medulla oblongata 14-45 The Medulla Oblongata Figure 14.8a
  46. 46. 14-46 The Pons Figure 14.8b Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Diencephalon: Midbrain: Thalamus Pineal gland Superior colliculus Inferior colliculus Spinal cord Pons Olive Cerebral peduncle Medial geniculate body Lateral geniculate body Optic tract Fourth ventricle Cuneate fasciculus Gracile fasciculus (b) Dorsolateral view Regions of the brainstem Midbrain Diencephalon Pons Medulla oblongata Medulla oblongata Superior cerebellar peduncle Middle cerebellar peduncle Inferior cerebellar peduncle
  47. 47. Thalamus Hypothalamus Frontal lobe Corpus callosum Cingulate gyrus Optic chiasm Pituitary gland Mammillary body Midbrain Pons Central sulcus Parietal lobe Parieto–occipital sulcus Occipital lobe Pineal gland Habenula Posterior commissure Cerebral aqueduct Fourth ventricle Cerebellum (a) EpithalamusAnterior commissure Temporal lobe Medulla oblongata 14-47 The Pons Figure 14.2a • Metencephalon—develops into the pons and cerebellum • Pons—anterior bulge in brainstem, rostral to medulla • Cerebral peduncles—connect cerebellum to pons and midbrain Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  48. 48. 14-48 The Pons • Ascending sensory tracts • Descending motor tracts • Pathways in and out of cerebellum • Cranial nerves V, VI, VII, and VIII – Sensory roles: hearing, equilibrium, taste, facial sensations – Motor roles: eye movement, facial expressions, chewing, swallowing, urination, and secretion of saliva and tears • Reticular formation in pons contains additional nuclei concerned with sleep, respiration, posture
  49. 49. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Reticular formation Trigeminal nerve Trigeminal nerve nuclei Vermis of cerebellum Medial lemniscus Tectospinal tract Anterolateral system Transverse fascicles Longitudinal fascicles Fourth ventricle (a) Midbrain (c) Medulla (b) Pons (b) Pons Superior cerebellar peduncle Sensory root of trigeminal nerve Ventral spinocerebellar tract Middle cerebellar peduncle 14-49 The Pons Figure 14.9b
  50. 50. 14-50 The Midbrain • Mesencephalon becomes one mature brain structure, the midbrain – Short segment of brainstem that connects the hindbrain to the forebrain – Contains cerebral aqueduct – Contains continuations of the medial lemniscus and reticular formation – Contains the motor nuclei of two cranial nerves that control eye movements: CN III (oculomotor) and CN IV (trochlear)
  51. 51. 14-51 The Midbrain • Mesencephalon (cont.) – Tectum: rooflike part of the midbrain posterior to cerebral aqueduct • Exhibits four bulges, the corpora quadrigemina • Upper pair, the superior colliculi, function in visual attention, tracking moving objects, and some reflexes • Lower pair, the inferior colliculi, receives signals from the inner ear – Relays them to other parts of the brain, especially the thalamus
  52. 52. 14-52 The Midbrain Cont. – Cerebral peduncles: two stalks that anchor the cerebrum to the brainstem anterior to the cerebral aqueduct • Cerebral peduncles—three main components – Tegmentum • Dominated by the red nucleus • Pink color due to high density of blood vessels • Connections go to and from cerebellum • Collaborates with cerebellum for fine motor control
  53. 53. 14-53 The Midbrain – Substantia nigra • Dark gray to black nucleus pigmented with melanin • Motor center that relays inhibitory signals to thalamus and basal nuclei preventing unwanted body movement • Degeneration of neurons leads to tremors of Parkinson disease – Cerebral crus • Bundle of nerve fibers that connect the cerebrum to the pons • Carries corticospinal tracts
  54. 54. 14-54 The Midbrain Figure 14.9a Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tegmentum Cerebral peduncle: Cerebral crus Tectum Superior colliculus Cerebral aqueduct Medial geniculate nucleus Reticular formation Central gray matter Oculomotor nucleus Medial lemniscus Red nucleus Substantia nigra Oculomotor nerve (III) Posterior Anterior (a) Midbrain (a) Midbrain (c) Medulla (b) Pons
  55. 55. 14-55 The Reticular Formation • Loosely organized web of gray matter that runs vertically through all levels of the brainstem • Clusters of gray matter scattered throughout pons, midbrain, and medulla • Occupies space between white fiber tracts and brainstem nuclei • Has connections with many areas of cerebrum – More than 100 small neural networks without distinct boundaries Figure 14.10 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Reticular formation Auditory input Thalamus Visual input Ascending general sensory fibers Descending motor fibers to spinal cord Radiations to cerebral cortex
  56. 56. 14-56 The Reticular Formation • Networks – Somatic motor control • Adjust muscle tension to maintain tone, balance, and posture • Especially during body movements • Relays signals from eyes and ears to the cerebellum • Integrates visual, auditory, and balance and motion stimuli into motor coordination • Gaze center—allows eyes to track and fixate on objects • Central pattern generators—neural pools that produce rhythmic signals to the muscles of breathing and swallowing
  57. 57. 14-57 The Reticular Formation Cont. – Cardiovascular control • Includes cardiac and vasomotor centers of medulla oblongata – Pain modulation • One route by which pain signals from the lower body reach the cerebral cortex • Origin of descending analgesic pathways—fibers act in the spinal cord to block transmission of pain signals to the brain
  58. 58. 14-58 The Reticular Formation – Sleep and consciousness • Plays central role in states of consciousness, such as alertness and sleep • Injury to reticular formation can result in irreversible coma – Habituation • Process in which the brain learns to ignore repetitive, inconsequential stimuli while remaining sensitive to others
  59. 59. 14-59 The Cerebellum • The largest part of the hindbrain and the second largest part of the brain as a whole • Consists of right and left cerebellar hemispheres connected by vermis • Cortex of gray matter with folds (folia) and four deep nuclei in each hemisphere • Contains more than half of all brain neurons—about 100 billion – Granule cells and Purkinje cells synapse on deep nuclei • White matter branching pattern is called arbor vitae Figure 14.11b (b) Superior view Folia Anterior Posterior Anterior lobe Vermis Posterior lobe Cerebellar hemisphere Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  60. 60. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Superior colliculus Posterior commissure Pineal glandInferior colliculus Mammillary body Midbrain Cerebral aqueduct Oculomotor nerve Pons Fourth ventricle Medulla oblongata Gray matter (a) Median section White matter (arbor vitae) 14-60 The Cerebellum • Cerebellar peduncles—three pairs of stalks that connect the cerebellum to the brainstem – Inferior peduncles: connected to medulla oblongata • Most spinal input enters the cerebellum through inferior peduncle – Middle peduncles: connected to the pons • Most input from the rest of the brain enters by way of middle peduncle – Superior peduncles: connected to the midbrain • Carries cerebellar output • Consist of thick bundles of nerve fibers that carry signals to and from the cerebellum Figure 14.11a
  61. 61. 14-61 The Cerebellum • Monitors muscle contractions and aids in motor coordination • Evaluation of sensory input – Comparing textures without looking at them – Spatial perception and comprehension of different views of three- dimensional objects belonging to the same object • Timekeeping center – Predicting movement of objects – Helps predict how much the eyes must move in order to compensate for head movements and remain fixed on an object
  62. 62. 14-62 The Cerebellum Cont. • Hearing – Distinguish pitch and similar-sounding words • Planning and scheduling tasks • Lesions may result in emotional overreactions and trouble with impulse control
  63. 63. The Forebrain • Expected Learning Outcomes – Name the three major components of the diencephalon and describe their locations and functions. – Identify the five lobes of the cerebrum and their functions. – Identify the three types of tracts in the cerebral white matter. – Describe the distinctive cell types and histological arrangement of the cerebral cortex. – Describe the location and functions of the basal nuclei and limbic system. 14-63
  64. 64. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Diencephalon Mesencephalon Forebrain Pons Cerebellum Metencephalon Spinal cord Hindbrain (c) Fully developed Midbrain Myelencephalon (medulla oblongata) Telencephalon 14-64 The Forebrain • Forebrain consists of two parts – Diencephalon • Encloses the third ventricle • Most rostral part of the brainstem • Has three major embryonic derivatives – Thalamus – Hypothalamus – Epithalamus – Telencephalon • Develops chiefly into the cerebrum Figure 14.4c
  65. 65. 14-65 The Diencephalon: Thalamus • Thalamus—ovoid mass on each side of the brain perched at the superior end of the brainstem beneath the cerebral hemispheres – Constitutes about four-fifths of the diencephalon – Two thalami are joined medially by a narrow intermediate mass – Composed of at least 23 nuclei; to consider five major functional groups Figure 14.12a Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Part of limbic system; memory and emotion Emotional output to prefrontal cortex; awareness of emotions Somesthetic output to postcentral gyrus; signals from cerebellum and basal nuclei to motor areas of cortex Somesthetic output to association areas of cortex; contributes to emotional function of limbic system Relay of visual signals to occipital lobe (via lateral geniculate nucleus) and auditory signals to temporal lobe (via medial geniculate nucleus) (a) Thalamus Medial geniculate nucleus Lateral geniculate nucleus Thalamic Nuclei Anterior group Medial group Ventral group Lateral group Posterior group
  66. 66. The Diencephalon: Thalamus Cont. – “Gateway to the cerebral cortex”: nearly all input to the cerebrum passes by way of synapses in the thalamic nuclei, filters information on its way to cerebral cortex – Plays key role in motor control by relaying signals from cerebellum to cerebrum and providing feedback loops between the cerebral cortex and the basal nuclei – Involved in the memory and emotional functions of the limbic system: a complex of structures that include some cerebral cortex of the temporal and frontal lobes and some of the anterior thalamic nuclei 14-66
  67. 67. 14-67 • Hypothalamus—forms part of the walls and floor of the third ventricle • Extends anteriorly to optic chiasm and posteriorly to the paired mammillary bodies • Each mammillary body contains three or four mammillary nuclei – Relay signals from the limbic system to the thalamus The Diencephalon: Hypothalamus Figure 14.2a Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thalamus Hypothalamus Frontal lobe Corpus callosum Cingulate gyrus Optic chiasm Pituitary gland Mammillary body Midbrain Pons Central sulcus Parietal lobe Parieto–occipital sulcus Occipital lobe Pineal gland Habenula Posterior commissure Cerebral aqueduct Fourth ventricle Cerebellum (a) EpithalamusAnterior commissure Temporal lobe Medulla oblongata
  68. 68. The Diencephalon: Hypothalamus • Infundibulum—a stalk that attaches the pituitary gland to the hypothalamus • Major control center of autonomic nervous system and endocrine system – Plays essential role in homeostatic regulation of all body systems • Functions of hypothalamic nuclei – Hormone secretion • Controls anterior pituitary • Regulates growth, metabolism, reproduction, and stress responses 14-68
  69. 69. The Diencephalon: Hypothalamus Cont. – Hormone secretion • Controls anterior pituitary • Regulates growth, metabolism, reproduction, and stress responses – Autonomic effects • Major integrating center for autonomic nervous system • Influences heart rate, blood pressure, gastrointestinal secretions, motility, etc. – Thermoregulation • Hypothalamic thermostat monitors body temperature • Activates heat-loss center when temp is too high • Activates heat-promoting center when temp is too low 14-69
  70. 70. The Diencephalon: Hypothalamus Cont. – Food and water intake • Hunger and satiety centers monitor blood glucose and amino acid levels – Produce sensations of hunger and satiety • Thirst center monitors osmolarity of the blood – Rhythm of sleep and waking • Controls 24-hour (circadian) rhythm of activity – Memory • Mammillary nuclei receive signals from hippocampus – Emotional behavior • Anger, aggression, fear, pleasure, and contentment 14-70
  71. 71. The Diencephalon: Epithalamus • Epithalamus—very small mass of tissue composed of: – Pineal gland: endocrine gland – Habenula: relay from the limbic system to the midbrain – Thin roof over the third ventricle 14-71 Figure 14.2a Thalamus Hypothalamus Frontal lobe Corpus callosum Cingulate gyrus Optic chiasm Pituitary gland Mammillary body Midbrain Pons Central sulcus Parietal lobe Parieto–occipital sulcus Occipital lobe Pineal gland Habenula Posterior commissure Cerebral aqueduct Fourth ventricle Cerebellum (a) EpithalamusAnterior commissure Temporal lobe Medulla oblongata Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  72. 72. The Telencephalon: Cerebrum • Cerebrum—largest and most conspicuous part of the human brain – Seat of sensory perception, memory, thought, judgment, and voluntary motor actions 14-72 Figure 14.2a Thalamus Hypothalamus Frontal lobe Corpus callosum Cingulate gyrus Optic chiasm Pituitary gland Mammillary body Midbrain Pons Central sulcus Parietal lobe Parieto–occipital sulcus Occipital lobe Pineal gland Habenula Posterior commissure Cerebral aqueduct Fourth ventricle Cerebellum (a) EpithalamusAnterior commissure Temporal lobe Medulla oblongata Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  73. 73. Brainstem Cerebellum Cerebrum Spinal cord Rostral Caudal Central sulcus Lateral sulcus Gyri (b) Lateral view Temporal lobe Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 14-73 The Cerebrum • Two cerebral hemispheres divided by longitudinal fissure – Connected by white fibrous tract, the corpus callosum – Gyri and sulci: increase amount of cortex in the cranial cavity – Gyri increases surface area for information-processing capability – Some sulci divide each hemisphere into five lobes named for the cranial bones overlying them Figure 14.1a,b Frontal lobe Occipital lobe Central sulcus Longitudinal fissure Parietal lobe (a) Superior view Cerebral hemispheres
  74. 74. 14-74 • Frontal lobe – Voluntary motor functions – Motivation, foresight, planning, memory, mood, emotion, social judgment, and aggression • Parietal lobe – Receives and integrates general sensory information, taste, and some visual processing • Occipital lobe – Primary visual center of brain • Temporal lobe – Areas for hearing, smell, learning, memory, and some aspects of vision and emotion • Insula (hidden by other regions) – Understanding spoken language, taste and sensory information from visceral receptors The Cerebrum Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Postcentral gyrus Occipital lobe Temporal lobe Lateral sulcus Frontal lobe Parietal lobe Insula Rostral Caudal Precentral gyrus Central sulcus
  75. 75. 14-75 Tracts of Cerebral White Matter Figure 14.14 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Projection tracts Parietal lobe Occipital lobe Commissural tracts Lateral ventricle Third ventricle Mammillary body Pons Pyramid Medulla oblongata Thalamus Association tracts Frontal lobe Temporal lobe Corpus callosum Longitudinal fissure Corpus callosum Basal nuclei Cerebral peduncle Projection tracts Decussation in pyramids (b) Frontal section (a) Sagittal section
  76. 76. 14-76 The Cerebral White Matter • Most of the volume of cerebrum is white matter – Glia and myelinated nerve fibers transmitting signals from one region of the cerebrum to another and between cerebrum and lower brain centers
  77. 77. 14-77 The Cerebral White Matter • Three types of tracts – Projection tracts • Extends vertically between higher and lower brain and spinal cord centers • Carries information between cerebrum and rest of the body – Commissural tracts • Cross from one cerebral hemisphere through bridges called commissures – Most pass through corpus callosum – Anterior and posterior commissures – Enables the two sides of the cerebrum to communicate with each other
  78. 78. 14-78 The Cerebral White Matter Cont. – Association tracts • Connect different regions within the same cerebral hemisphere • Long association fibers—connect different lobes of a hemisphere to each other • Short association fibers—connect different gyri within a single lobe
  79. 79. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. I II III IV V VI Cortical surface Stellate cells Small pyramidal cells Large pyramidal cells White matter 14-79 The Cerebral Cortex • Neural integration is carried out in the gray matter of the cerebrum • Cerebral gray matter found in three places – Cerebral cortex – Basal nuclei – Limbic system Figure 14.15
  80. 80. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. I II III IV V VI Cortical surface Stellate cells Small pyramidal cells Large pyramidal cells White matter 14-80 The Cerebral Cortex • Cerebral cortex—layer covering the surface of the hemispheres – Only 2 to 3 mm thick – Cortex constitutes about 40% of brain mass – Contains 14 to 16 billion neurons Figure 14.15
  81. 81. The Cerebral Cortex • Contains two principal types of neurons – Stellate cells • Have spheroid somas with dendrites projecting in all directions • Receive sensory input and process information on a local level – Pyramidal cells • Tall, and conical, with apex toward the brain surface • A thick dendrite with many branches with small, knobby dendritic spines • Include the output neurons of the cerebrum • Only neurons that leave the cortex and connect with other parts of the CNS. 14-81
  82. 82. The Cerebral Cortex • Neocortex—six-layered tissue that constitutes about 90% of the human cerebral cortex – Relatively recent in evolutionary origin 14-82
  83. 83. 14-83 The Basal Nuclei • Basal nuclei—masses of cerebral gray matter buried deep in the white matter, lateral to the thalamus – Receives input from the substantia nigra of the midbrain and the motor areas of the cortex – Send signals back to both these locations – Involved in motor control Figure 14.16 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cerebrum Corpus callosum Lateral ventricle Thalamus Insula Optic tract Hypothalamus Third ventricle Pituitary gland Internal capsule Caudate nucleus Putamen Subthalamic nucleus Globus pallidus Corpus striatumLentiform nucleus
  84. 84. The Basal Nuclei • At least three brain centers form basal nuclei – Caudate nucleus – Putamen – Globus pallidus • Lentiform nucleus—putamen and globus pallidus collectively • Corpus striatum—putamen and caudate nucleus collectively 14-84
  85. 85. 14-85 The Limbic System • Limbic system—important center of emotion and learning • Most anatomically prominent components are: – Cingulate gyrus: arches over the top of the corpus callosum in the frontal and parietal lobes – Hippocampus: in the medial temporal lobe; memory – Amygdala: immediately rostral to the hippocampus; emotion Figure 14.17 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Basal nuclei Amygdala Fornix Hippocampus Medial prefrontal cortex Corpus callosum Cingulate gyrus Orbitofrontal cortex Temporal lobe Thalamic nuclei Mammillary body
  86. 86. 14-86 The Limbic System • Limbic system components are connected through a complex loop of fiber tracts allowing for somewhat circular patterns of feedback • Limbic system structures have centers for both gratification and aversion – Gratification: sensations of pleasure or reward – Aversion: sensations of fear or sorrow Figure 14.17 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Basal nuclei Amygdala Fornix Hippocampus Medial prefrontal cortex Corpus callosum Cingulate gyrus Orbitofrontal cortex Temporal lobe Thalamic nuclei Mammillary body
  87. 87. Integrative Functions of the Brain • Expected Learning Outcomes – List the types of brain waves and discuss their relationship to mental states. – Describe the stages of sleep, their relationship to the brain waves, and the neural mechanisms of sleep. – Identify the brain regions concerned with consciousness and thought, memory, emotion, sensation, motor control, and language. – Discuss the functional differences between the right and left cerebral hemispheres. 14-87
  88. 88. 14-88 Integrative Functions of the Brain • Higher brain functions—sleep, memory, cognition, emotion, sensation, motor control, and language • Involve interactions between cerebral cortex and basal nuclei, brainstem, and cerebellum • Functions of the brain do not have easily defined anatomical boundaries • Integrative functions of the brain focus mainly on the cerebrum, but involve combined action of multiple brain levels
  89. 89. 14-89 The Electroencephalogram • Alpha waves 8 to 13 Hz – Awake and resting with eyes closed and mind wandering – Suppressed when eyes open or performing a mental task • Beta waves 14 to 30 Hz – Eyes open and performing mental tasks – Accentuated during mental activity and sensory stimulation • Theta waves 4 to 7 Hz – Drowsy or sleeping adults – If awake and under emotional stress • Delta waves (high amplitude) <3.5 Hz – Deep sleep in adults
  90. 90. 14-90 The Electroencephalogram • Electroencephalogram (EEG)—monitors surface electrical activity of the brain waves – Useful for studying normal brain functions as sleep and consciousness – In diagnosis of degenerative brain diseases, metabolic abnormalities, brain tumors, etc. Figure 14.18a Figure 14.18b Delta (δ) (b) 1 second Alpha (α) Theta (θ) Beta (β) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  91. 91. The Electroencephalogram Cont. • Brain waves—rhythmic voltage changes resulting from synchronized postsynaptic potentials at the superficial layer of the cerebral cortex – Four types distinguished by amplitude (mV) and frequency (Hz) • Persistent absence of brain waves is common clinical and legal criterion of brain death 14-91
  92. 92. 14-92 Sleep • Sleep occurs in cycles called circadian rhythms – Events that reoccur at intervals of about 24 hours • Sleep—temporary state of unconsciousness from which one can awaken when stimulated – Characterized by stereotyped posture • Lying down with eyes closed – Sleep paralysis: inhibition of muscular activity – Resembles unconsciousness but can be aroused by sensory stimulation – Coma or hibernation: states of prolonged unconsciousness where individuals cannot be aroused by sensory stimulation
  93. 93. 14-93 Sleep Cont. • Restorative effect – Brain glycogen and ATP levels increase in non-REM sleep – Memories strengthened in REM sleep • Synaptic connections reinforced • Four stages of sleep – Stage 1 • Feel drowsy, close eyes, begin to relax • Often feel drifting sensation, easily awakened if stimulated • Alpha waves dominate EEG
  94. 94. 14-94 Sleep Cont. – Stage 2 • Pass into light sleep • EEG declines in frequency but increases in amplitude • Exhibits sleep spindles—high spikes resulting from interactions between neurons of the thalamus and cerebral cortex – Stage 3 • Moderate to deep sleep • About 20 minutes after stage 1 • Theta and delta waves appear • Muscles relax and vital signs fall (body temperature, blood pressure, heart and respiratory rates)
  95. 95. 14-95 Sleep Cont. – Stage 4 • Called slow-wave sleep (SWS)—EEG dominated by low- frequency, high-amplitude delta waves • Muscles now very relaxed, vital signs at their lowest, and more difficult to awaken • About five times a night, a sleeper backtracks from stage 3 or 4 to stage 2 – Exhibits bouts of rapid eye movement (REM) sleep, eyes oscillate back and forth – Also called paradoxical sleep, because EEG resembles the waking state, but sleeper is harder to arouse than any other stage
  96. 96. 14-96 Sleep Cont. – Vital signs increase, brain uses more oxygen than when awake – Sleep paralysis stronger to prevent sleeper from acting out dreams • Dreams occur in both REM and non-REM sleep – REM tends to be longer and more vivid • Parasympathetic nervous system active during REM sleep – Causing constriction of the pupils – Erection of the penis and clitoris
  97. 97. 14-97 Sleep • Rhythm of sleep is controlled by a complex interaction between the cerebral cortex, thalamus, hypothalamus, and reticular formation – Arousal induced in the upper reticular formation, near junction of pons and midbrain – Sleep induced by nuclei below pons, and in ventrolateral preoptic nucleus in the hypothalamus
  98. 98. 14-98 Sleep • Suprachiasmatic nucleus (SCN)—another important control center for sleep – Above optic chiasma in anterior hypothalamus – Input from eye allows SCN to synchronize multiple body rhythms with external rhythms of night and day • Sleep, body temperature, urine production, secretion, and other functions
  99. 99. 14-99 Sleep • Sleep has a restorative effect, and sleep deprivation can be fatal to experimental animals – Bed rest alone does not have the restorative effect of sleep— why must we lose consciousness? – Sleep may be the time to replenish such energy sources as glycogen and ATP – REM sleep may consolidate and strengthen memories by reinforcing some synapses, and eliminating others
  100. 100. 14-100 Sleep Stages and Brain Activity Figure 14.19 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 0 0 1 2 3 4 5 6 7 8 10 Awake Stage 1 Stage 2 Stage 3 Stage 4 EEGstages 20 30 40 (a) One sleep cycle Stage 50 60 70 REM REM REMREMREM Sleep spindles Stage 1 Drowsy Stage 2 Light sleep Stage 3 Moderate to deep sleep Stage 4 Deepest sleep REM sleep Time (min.) Awake (b) Typical 8-hour sleep period Time (hours)
  101. 101. 14-101 Cognition • Cognition—the range of mental processes by which we acquire and use knowledge – Such as sensory perception, thought, reasoning, judgment, memory, imagination, and intuition • Association areas of cerebral cortex have above functions – Constitute about 75% of all brain tissue
  102. 102. 14-102 Cognition • Studies of patients with brain lesions, cancer, stroke, and trauma yield information on cognition – Parietal lobe association area: perceiving stimuli • Contralateral neglect syndrome—unaware of objects on opposite side of the body – Temporal lobe association area: identifying stimuli • Agnosia—inability to recognize, identify, and name familiar objects • Prosopagnosia—person cannot remember familiar faces – Frontal lobe association area: planning our responses and personality; inability to execute appropriate behavior
  103. 103. 14-103 Memory • Information management entails: – Learning: acquiring new information – Memory: information storage and retrieval – Forgetting: eliminating trivial information; as important as remembering • Amnesia—defects in declarative memory: inability to describe past events • Procedural memory—ability to tie one’s shoes – Anterograde amnesia: unable to store new information – Retrograde amnesia: person cannot recall things known before the injury
  104. 104. 14-104 Memory • Hippocampus—important memory-forming center – Does not store memories – Organizes sensory and cognitive information into a unified long-term memory – Memory consolidation: the process of “teaching the cerebral cortex” until a long-term memory is established – Long-term memories are stored in various areas of the cerebral cortex
  105. 105. 14-105 Memory Cont. – Vocabulary and memory of familiar faces stored in superior temporal lobe – Memories of one’s plans and social roles stored in the prefrontal cortex • Cerebellum—helps learn motor skills • Amygdala—emotional memory
  106. 106. 14-106 Accidental Lobotomy • Phineas Gage—railroad construction worker; severe injury with metal rod • Injury to the ventromedial region of both frontal lobes • Extreme personality change – Fitful, irreverent, grossly profane – Opposite of previous personality • Prefrontal cortex functions – Planning, moral judgment, and emotional control Figure 14.20
  107. 107. 14-107 Emotion • Emotional feelings and memories are interactions between prefrontal cortex and diencephalon • Prefrontal cortex—seat of judgment, intent, and control over expression of emotions • Feelings come from hypothalamus and amygdala – Nuclei generate feelings of fear or love
  108. 108. 14-108 Emotion • Amygdala receives input from sensory systems – Role in food intake, sexual behavior, and drawing attention to novel stimuli – One output goes to hypothalamus influencing somatic and visceral motor systems • Heart races, raises blood pressure, makes hair stand on end, induces vomiting – Other output to prefrontal cortex important in controlling expression of emotions • Ability to express love, control anger, or overcome fear • Behavior shaped by learned associations between stimuli, our responses to them, and the reward or punishment that results
  109. 109. 14-109 Sensation • Primary sensory cortex—sites where sensory input is first received and one becomes conscious of the stimulus • Association areas nearby to sensory areas that process and interpret that sensory information – Primary visual cortex is bordered by visual association area: interprets and makes cognitive sense of visual stimuli – Multimodal association areas: receive input from multiple senses and integrate this into an overall perception of our surroundings Figure 14.22a Anterior Posterior (a) Precentral gyrus Central sulcus Postcentral gyrus Occipital lobe Parietal lobe Frontal lobe Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  110. 110. 14-110 The Special Senses • Special senses—limited to the head and employ relatively complex sense organs • Primary cortices and association areas listed below • Vision – Visual primary cortex in far posterior region of occipital lobe – Visual association area: anterior, and occupies all the remaining occipital lobe • Much of inferior temporal lobe deals with facial recognition and other familiar objects • Hearing – Primary auditory cortex in the superior region of the temporal lobe and insula – Auditory association area: temporal lobe deep and inferior to primary auditory cortex • Recognizes spoken words, a familiar piece of music, or a voice on the phone
  111. 111. 14-111 The Special Senses • Equilibrium – Signals for balance and sense of motion project mainly to the cerebellum and several brainstem nuclei concerned with head and eye movements and visceral functions – Association cortex in the roof of the lateral sulcus near the lower end of the central sulcus • Seat of consciousness of our body movements and orientation in space • Taste and smell – Gustatory (taste) signals received by primary gustatory cortex in inferior end of the postcentral gyrus of the parietal lobe and anterior region of insula – Olfactory (smell) signals received by the primary olfactory cortex in the medial surface of the temporal lobe and inferior surface of the frontal lobe
  112. 112. 14-112 The General Senses • General (somesthetic, somatosensory, or somatic) senses—distributed over the entire body and employ relatively simple receptors – Senses of touch, pressure, stretch, movement, heat, cold, and pain • Several cranial nerves carry general sensations from head • Ascending tracts bring general sensory information from the rest of the body – Thalamus processes the input – Selectively relays signals to the postcentral gyrus • Fold of the cerebrum that lies immediately caudal to the central sulcus and forms the rostral border of the parietal lobe – Primary somesthetic cortex is the cortex of the postcentral gyrus – Somesthetic association area: caudal to the gyrus and in the roof of the lateral sulcus
  113. 113. 14-113 The General Senses • Awareness of stimulation occurs in primary somesthetic cortex • Making cognitive sense of the stimulation occurs in the somesthetic association area • Because of decussation, the right postcentral gyrus receives input from the left side of the body and vice versa • Sensory homunculus—upside-down sensory map of the contralateral side of the body • Somatotopy—point-for-point correspondence between an area of the body and an area of the CNS
  114. 114. Thigh Shoulder Arm V (b) Insula Lateral sulcus Genitalia Leg Hip Trunk Eye Nose Face Upper lip Lower lip Thum b (I) Hand Forearm Neck Elbow II III IV Fingers I II III IVV Lateral Medial Tongue Teeth, gums W rist Toes Viscerosensory area Abdominal viscera Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The General Senses Figure 14.22b • Sensory homunculus— diagram of the primary somesthetic cortex which resembles an upside-down sensory map of the contralateral side of the body • Shows receptors in the lower limbs projecting to the superior and medial parts of the gyrus • Shows receptors from the face projecting to the inferior and lateral parts • Somatotopy—point-to-point correspondence between an area of the body and an area of the CNS 14-114
  115. 115. 14-115 Functional Regions of the Cerebral Cortex Figure 14.21 Wernicke area Broca area Primary motor cortex Motor association area Prefrontal cortex Olfactory association area Primary somatosensory cortex Somatosensory association area Primary gustatory cortex Visual association area Primary visual cortex Primary auditory cortex Auditory association area Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  116. 116. 14-116 Motor Control • The intention to contract a muscle begins in motor association (premotor) area of frontal lobes – Where we plan our behavior – Where neurons compile a program for degree and sequence of muscle contraction required for an action – Program transmitted to neurons of the precentral gyrus (primary motor area) • Most posterior gyrus of the frontal lobe
  117. 117. 14-117 Motor Control • Premotor area (cont.) – Neurons send signals to the brainstem and spinal cord – Ultimately resulting in muscle contraction – Precentral gyrus also exhibits somatotopy • Neurons for toe movement are deep in the longitudinal fissure of the medial side of the gyrus • The summit of the gyrus controls the trunk, shoulder, and arm • The inferolateral region controls the facial muscles – Motor homunculus has a distorted look because the amount of cortex devoted to a given body region is proportional to the number of muscles and motor units in that body region
  118. 118. 14-118 Motor Control • Pyramidal cells of the precentral gyrus are called upper motor neurons – Their fibers project caudally – About 19 million fibers ending in nuclei of the brainstem – About 1 million forming the corticospinal tracts – Most fibers decussate in lower medulla oblongata – Form lateral corticospinal tracts on each side of the spinal cord • In the brainstem or spinal cord, the fibers from upper motor neurons synapse with lower motor neurons whose axons innervate the skeletal muscles • Basal nuclei and cerebellum are also important in muscle control
  119. 119. 14-119 Motor Control• Basal nuclei – Determines the onset and cessation of intentional movements • Repetitive hip and shoulder movements in walking – Highly practiced, learned behaviors that one carries out with little thought • Writing, typing, driving a car – Lies in a feedback circuit from the cerebrum, to the basal nuclei, to the thalamus, and back to the cerebrum – Dyskinesias: movement disorders caused by lesions in the basal nuclei • Cerebellum – Highly important in motor coordination – Aids in learning motor skills – Maintains muscle tone and posture – Smoothes muscle contraction – Coordinates eye and body movements – Coordinates the motions of different joints with each other – Ataxia: clumsy, awkward gait
  120. 120. Fingers Eye and eyelid Tongue Ankle Lips Face Jaw Pharynx Salivation Mastication Swallowing Neck Brow V H andW rist Elbow Shoulder Trunk Knee Hip IV III II Thumb (I) I II III IV V (b) Lateral Medial Vocalization Toes 14-120 Motor Homunculus Figure 14.23b Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  121. 121. 14-121 Motor Pathways Involving the Cerebellum Figure 14.24 Cerebrum Cerebrum Motor cortex Cerebellum Cerebellum Brainstem Brainstem Inner ear Eye Reticular formation Muscle and joint proprioceptors (a) Input to cerebellum (b) Output from cerebellum Spinocerebellar tracts of spinal cord Reticulospinal and vestibulospinal tracts of spinal cord Limb and postural muscles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  122. 122. 14-122 Language • Language include several abilities: reading, writing, speaking, and understanding words assigned to different regions of the cerebral cortex • Wernicke area – Permits recognition of spoken and written language and creates plan of speech – When we intend to speak, Wernicke area formulates phrases according to learned rules of grammar – Transmits plan of speech to Broca area • Broca area – Generates motor program for the muscles of the larynx, tongue, cheeks, and lips – Transmits program to primary motor cortex for commands to the lower motor neurons that supply relevant muscles • Affective language area lesions produce aprosody—flat emotionless speech
  123. 123. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Precentral gyrus Anterior Posterior Speech center of primary motor cortex Primary auditory cortex (in lateral sulcus) Broca area Postcentral gyrus Angular gyrus Primary visual cortex Wernicke area 14-123 Language Centers of the Left Hemisphere Figure 14.25
  124. 124. 14-124 Aphasia • Aphasia—any language deficit from lesions in same hemisphere (usually left) containing the Wernicke and Broca areas • Nonfluent (Broca) aphasia – Lesion in Broca area – Slow speech, difficulty in choosing words, using words that only approximate the correct word • Fluent (Wernicke) aphasia – Lesion in Wernicke area – Speech normal and excessive, but uses senseless jargon – Cannot comprehend written and spoken words • Anomic aphasia – Can speak normally and understand speech, but cannot identify written words or pictures
  125. 125. 14-125 Cerebral Lateralization Figure 14.26 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Olfaction, left nasal cavity Memory for shapes Left hand motor control Musical ability Intuitive, nonverbal thought Speech Olfaction, right nasal cavity Left hemisphere Right hemisphere Posterior Anterior Verbal memory Right hand motor control Feeling shapes with right hand Hearing vocal sounds (right ear advantage) Rational, symbolic thought Superior language comprehension Vision, right field (Limited language comprehension, mute) Feeling shapes with left hand Hearing nonvocal sounds (left ear advantage) Superior recognition of faces and spatial relationships Vision, left field
  126. 126. 14-126 Cerebral Lateralization • Cerebral lateralization—the difference in the structure and function of the cerebral hemispheres • Left hemisphere—categorical hemisphere – Specialized for spoken and written language – Sequential and analytical reasoning (math and science) – Breaks information into fragments and analyzes it in a linear way • Right hemisphere—representational hemisphere – Perceives information in a more integrated holistic way – Seat of imagination and insight – Musical and artistic skill – Perception of patterns and spatial relationships – Comparison of sights, sounds, smells, and taste
  127. 127. 14-127 Cerebral Lateralization • Highly correlated with handedness – Left hemisphere is the categorical one in 96% of right-handed people • Right hemisphere in 4% – Left-handed people: right hemisphere is categorical in 15% and left in 70% • Lateralization develops with age – Males exhibit more lateralization than females and suffer more functional loss when one hemisphere is damaged
  128. 128. The Cranial Nerves • Expected Learning Outcomes – List the 12 cranial nerves by name and number. – Identify where each cranial nerve originates and terminates. – State the functions of each cranial nerve. 14-128
  129. 129. 14-129 The Cranial Nerves • Brain must communicate with rest of body – Most of the input and output travels by way of the spinal cord – 12 pairs of cranial nerves arise from the base of the brain – Exit the cranium through foramina – Lead to muscles and sense organs located mainly in the head and neck
  130. 130. 14-130 Cranial Nerve Pathways • Most motor fibers of the cranial nerves begin in nuclei of brainstem and lead to glands and muscles • Sensory fibers begin in receptors located mainly in head and neck and lead mainly to the brainstem – Sensory fibers for proprioception may travel to brain in a different nerve from motor nerve
  131. 131. 14-131 Cranial Nerve Pathways • Most cranial nerves carry fibers between brainstem and ipsilateral receptors and effectors – Lesion in left brainstem causes sensory or motor deficit on same side • Exceptions: optic nerve where half the fibers decussate, and trochlear nerve where all efferent fibers lead to a muscle of the contralateral eye
  132. 132. 14-132 Cranial Nerve Classification • Some cranial nerves are classified as motor, some sensory, others mixed – Sensory (I, II, and VIII) – Motor (III, IV, VI, XI, and XII) • Stimulate muscle but also contain fibers of proprioception – Mixed (V, VII, IX, X) • Sensory functions may be quite unrelated to their motor function – Facial nerve (VII) has sensory role in taste and motor role in facial expression
  133. 133. 14-133 The Cranial Nerves Figure 14.27a,b Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b: © The McGraw-Hill Companies, Inc./Rebecca Gray, photographer/DonKincaid, dissections Cranial nerves: Optic nerve (II) Trochlear nerve (IV) Trigeminal nerve (V) Abducens nerve (VI) Facial nerve (VII) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Accessory nerve (XI) Hypoglossal nerve (XII) Oculomotor nerve (III) Frontal lobe Frontal lobe Cerebellum Cerebellum Olfactory tract Temporal lobe Infundibulum Pons Medulla Optic chiasm Optic chiasm Olfactory tract Pons Spinal cordSpinal cord (a) (b) Longitudinal fissure Medulla oblongata Olfactory bulb (from olfactory nerve, I) Vagus nerve (X) Temporal lobe
  134. 134. 14-134 The Olfactory Nerve (I) • Sense of smell • Damage causes impaired sense of smell Figure 14.28 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Olfactory bulb Olfactory tract Nasal mucosa Cribriform plate of ethmoid bone Fascicles of olfactory nerve (I)
  135. 135. 14-135 The Optic Nerve (II) • Provides vision • Damage causes blindness in part or all of visual field Figure 14.29 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Eyeball Optic nerve (II) Optic chiasm Optic tract Pituitary gland
  136. 136. 14-136 The Oculomotor Nerve (III) • Controls muscles that turn the eyeball up, down, and medially, as well as controlling the iris, lens, and upper eyelid • Damage causes drooping eyelid, dilated pupil, double vision, difficulty focusing, and inability to move eye in certain directions Figure 14.30 Oculomotor nerve (III): Superior orbital fissure Superior branch Inferior branch Ciliary ganglion Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  137. 137. 14-137 The Trochlear Nerve (IV) • Eye movement (superior oblique muscle) • Damage causes double vision and inability to rotate eye inferolaterally Figure 14.31 Superior orbital fissure Superior oblique muscle Trochlear nerve (IV) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  138. 138. 14-138 The Trigeminal Nerve (V) • Largest of the cranial nerves • Most important sensory nerve of the face • Forks into three divisions – Ophthalmic division (V1): sensory – Maxillary division (V2): sensory – Mandibular division (V3): mixed Figure 14.32 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lingual nerve V1 V3 V2 Superior orbital fissure Foramen ovale Foramen rotundum Temporalis muscle Medial pterygoid muscle Masseter muscle Lateral pterygoid muscle Infraorbital nerve Superior alveolar nerves Inferior alveolar nerve Ophthalmic division (V1) Trigeminal ganglion Trigeminal nerve (V) Maxillary division (V2) Mandibular division (V3) Anterior trunk of V3 to chewing muscles Anterior belly of digastric muscle Motor branches of the mandibular division (V3) Distribution of sensory fibers of each division
  139. 139. 14-139 The Abducens Nerve (VI) • Provides eye movement (lateral rectus m.) • Damage results in inability to rotate eye laterally and at rest eye rotates medially Figure 14.33 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Abducens nerve (VI) Superior orbital fissure Lateral rectus muscle
  140. 140. 14-140 The Facial Nerve (VII) • Motor—major motor nerve of facial muscles: facial expressions; salivary glands and tear, nasal, and palatine glands • Sensory—taste on anterior two-thirds of tongue • Damage produces sagging facial muscles and disturbed sense of taste (no sweet and salty) Figure 14.34a Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Geniculate ganglion Pterygopalatine ganglion Lacrimal (tear) gland Submandibular gland Stylomastoid foramen Sublingual gland Internal acoustic meatus Facial nerve (VII) (a) Parasympathetic fibers Submandibular ganglion Chorda tympani branch (taste and salivation) Motor branch to muscles of facial expression
  141. 141. 14-141 Five Branches of Facial Nerve Clinical test: test anterior two-thirds of tongue with substances such as sugar, salt, vinegar, and quinine; test response of tear glands to ammonia fumes; test motor functions by asking subject to close eyes, smile, whistle, frown, raise eyebrows, etc. Figure 14.34b,c Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Temporal Zygomatic Buccal Mandibular Cervical (c) c: © The McGraw-Hill Companies, Inc./Joe DeGrandis, photographer Zygomatic Buccal Mandibular Cervical (b) Temporal
  142. 142. Cochlear nerve Cochlea Semicircular ducts Vestibular ganglia Vestibular nerve Vestibulocochlear nerve (VIII) Internal acoustic meatus Vestibule Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 14-142 The Vestibulocochlear Nerve (VIII) • Nerve of hearing and equilibrium • Damage produces deafness, dizziness, nausea, loss of balance, and nystagmus (involuntary rhythmic oscillation of the eyes from side to side) Figure 14.35
  143. 143. 14-143 The Glossopharyngeal Nerve (IX) • Swallowing, salivation, gagging, control of BP and respiration • Sensations from posterior one-third of tongue • Damage results in loss of bitter and sour taste and impaired swallowing Figure 14.36 Glossopharyngeal nerve (IX) Parotid salivary gland Jugular foramen Superior ganglion Inferior ganglion Otic ganglion Carotid sinus Pharyngeal muscles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  144. 144. 14-144 The Vagus Nerve (X) • Most extensive distribution of any cranial nerve • Major role in the control of cardiac, pulmonary, digestive, and urinary function • Swallowing, speech, regulation of viscera • Damage causes hoarseness or loss of voice, impaired swallowing, and fatal if both are cut Figure 14.37 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Heart Lung Liver Spleen Small intestine Stomach Kidney Carotid sinus Laryngeal nerve Pharyngeal nerve Jugular foramen Vagus nerve (X) Colon (proximal portion)
  145. 145. 14-145 The Accessory Nerve (XI) • Swallowing; head, neck, and shoulder movement – Damage causes impaired head, neck, shoulder movement; head turns toward injured side Figure 14.38 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Accessory nerve (XI) Posterior view Jugular foramen Foramen magnum Spinal nerves C3 and C4 Sternocleidomastoid muscle Vagus nerve Trapezius muscle
  146. 146. 14-146 The Hypoglossal Nerve (XII) • Tongue movements for speech, food manipulation, and swallowing – If both are damaged: cannot protrude tongue – If one side is damaged: tongue deviates toward injured side; see ipsilateral atrophy Figure 14.39 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hypoglossal canal Hypoglossal nerve (XII) Intrinsic muscles of the tongue Extrinsic muscles of the tongue
  147. 147. 14-147 Cranial Nerve Disorders • Trigeminal neuralgia (tic douloureux) – Recurring episodes of intense stabbing pain in trigeminal nerve area (near mouth or nose) – Pain triggered by touch, drinking, washing face – Treatment may require cutting nerve • Bell palsy – Degenerative disorder of facial nerve causes paralysis of facial muscles on one side – May appear abruptly with full recovery within 3 to 5 weeks
  148. 148. 14-148 Images of the Mind • Positron emission tomography (PET) and MRI visualize increases in blood flow when brain areas are active – Injection of radioactively labeled glucose • Busy areas of brain “light up” • Functional magnetic resonance imaging (fMRI) looks at increase in blood flow to an area (additional glucose is needed in active area)—magnetic properties of hemoglobin depend on how much oxygen is bound to it (additional oxygen is there due to additional blood flow) – Quick, safe, and accurate method to see brain function
  149. 149. 14-149 Images of the Mind Figure 14.40 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Broca area Primary motor cortexPremotor areaPrimary auditory cortex 1 2 3 4 Rostral Caudal Wernicke area conceives of the verb drive to go with it. Broca area compiles a motor program to speak the word drive. The primary motor cortex executes the program and the word is spoken. Wernicke areaVisual cortex The word car is seen in the visual cortex.
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