cortex - Dr. Par Mohammadian

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Transcript cortex - Dr. Par Mohammadian

PowerPoint® Lecture Slides
prepared by
Barbara Heard,
Atlantic Cape Community
Ninth Edition
College
Human Anatomy & Physiology
CHAPTER
12
The Central Nervous
System: Revised by Dr.
Par Mohammadian
© Annie Leibovitz/Contact Press Images
© 2013 Pearson Education, Inc.
Central Nervous System (CNS)
• CNS:
– Brain
– spinal cord
• Cephalization
– Evolutionary development of rostral (anterior)
portion of CNS
– Increased number of neurons in head
– Highest level reached in human brain
Regions and Organization
•
Adult brain regions
1.
2.
3.
4.
Cerebral hemispheres
Diencephalon (thalamus, hypothalamus)
Brain stem (midbrain, pons, and medulla)
Cerebellum
Cerebral
hemisphere
Diencephalon
Cerebellum
Brain stem
• Midbrain
• Pons
• Medulla oblongata
Birth: Shows adult pattern of structures and convolutions.
Organization of the CNS
• Brain
– Central cavity surrounded by gray
matter (mostly cell bodies); External
white matter composed of
myelinated fiber tracts
– Cerebral hemispheres and
cerebellum
• Outer gray matter called cortex
– Cortex disappears in brain stem
• Spinal cord
– Same patterns
Ventricles of the Brain
Hollow ventricular chamber filled with cerebrospinal fluid (CSF)
• Lateral ventricles – 2x in each hemisphere
• Third ventricle - in diencephalon
• Fourth ventricle - between brain stem & cerebellum
Lateral
ventricle
Anterior
horn
Interventricular
foramen
Septum
pellucidum
Inferior
horn
Posterior
horn
Third
ventricle
Inferior
horn
Median
aperture
Cerebral aqueduct
Lateral
aperture
Fourth ventricle
Lateral
aperture
Central canal
Anterior view
Left lateral view
Cerebral Hemispheres
– Ridges (gyri), shallow grooves (sulci), and
deep grooves (fissures)
– Longitudinal fissure: Separates two
hemispheres
– Transverse cerebral fissure: Separates
cerebrum and cerebellum
Cerebral Hemispheres
Ridges (gyri), shallow grooves (sulci)
Deep grooves (fissures)
Longitudinal fissure:
Separates two
Precentral
gyrus
Frontal lobe
hemispheres
Transverse cerebral
fissure: Separates
cerebrum and
cerebellum
Fissure
(a deep
sulcus)
Central
sulcus
Postcentral
gyrus
Parietal lobe
Parieto-occipital sulcus
(on medial surface
of hemisphere)
Lateral sulcus
Occipital lobe
Temporal lobe
Transverse
cerebral fissure
Cerebellum
Pons
Medulla oblongata
Spinal cord
Gyrus
Cortex (gray matter)
Sulcus
White matter
Lobes and sulci of the cerebrum
Cerebral Hemispheres
• Deep sulci divide the hemispheres into five
lobes
– Frontal
Frontal lobe
Parietal lobe
– Parietal
– Temporal
Occipital lobe
Temporal lobe
– Occipital
– Insula
Lobes and sulci of the cerebrum
Frontal lobe
Central
sulcus
Gyri of insula
Temporal lobe
(pulled down)
Location of the insula lobe
Cerebral Hemispheres
• Central sulcus
– Separates precentral
gyrus of frontal lobe
and postcentral
gyrus of parietal lobe
Lateral
sulcus
Precentral
gyrus
Frontal lobe
Central
sulcus
Postcentral
gyrus
Parieto-occipital
sulcus
(on medial surface
of hemisphere)
Occipital lobe
Temporal lobe
• Parieto-occipital
sulcus
– Separates occipital
and parietal lobes
Cerebellum
Pons
Medulla oblongata
Spinal cord
• Lateral sulcus outlines
temporal lobes
Lobes and sulci of the cerebrum
Cerebral Hemispheres
• Three basic regions
– Cerebral cortex of gray matter superficially
– White matter internally
– Basal nuclei deep within white matter
Figure 12.4a Lobes, sulci, and fissures of the cerebral hemispheres.
Anterior
Longitudinal
fissure
Frontal lobe
Cerebral veins
and arteries
covered by
arachnoid
mater
Parietal lobe
Left cerebral
hemisphere
Right cerebral
hemisphere
Occipital
lobe
Posterior
Superior view
Figure 12.4b Lobes, sulci, and fissures of the cerebral hemispheres.
Left cerebral
hemisphere
Brain stem
Transverse
cerebral
fissure
Cerebellum
Left lateral view
Cerebral Cortex
• 40% mass of brain
• Site of conscious mind: awareness, sensory
perception, voluntary motor initiation, communication,
memory storage, understanding
• Each hemisphere acts contralaterally (controls the
opposite side of the body)
• Hemispheres are not equal in function
• No functional area acts alone; conscious behavior
involves the entire cortex
General Considerations of Cerebral Cortex
Three types of functional areas
– Motor areas—control voluntary movement
– Sensory areas—conscious awareness of
sensation
– Association areas—integrate diverse information
Figure 12.5 Functional neuroimaging (fMRI) of the cerebral cortex.
Longitudinal
fissure
© 2013 Pearson Education, Inc.
Left frontal
lobe
Left temporal
lobe
Central sulcus
Areas active
in speech and
hearing (fMRI)
Motor Areas of Cerebral Cortex
• In frontal lobe; control voluntary movement
• Primary (somatic) motor cortex in precentral
gyrus
• Premotor cortex anterior to precentral gyrus
• Broca's area anterior to inferior premotor area
• Frontal eye field within and anterior to premotor
cortex; superior to Broca's area
Motor areas
Central sulcus
Primary motor cortex
Premotor cortex
Frontal
eye field
Broca's area
(outlined by dashes)
Sensory areas and related
association areas
Primary somatosensory
cortex
Somatic
Somatosensory
sensation
association cortex
Gustatory cortex
(in insula)
Prefrontal cortex
Working memory
for spatial tasks
Executive area for
task management
Working memory for
object-recall tasks
Solving complex,
multitask problems
Wernicke's area
(outlined by dashes)
Primary visual
cortex
Visual
association
area
Auditory
association area
Primary
auditory cortex
Lateral view, left cerebral hemisphere
Primary motor
cortex
Taste
Motor association
cortex
Primary sensory
cortex
Sensory
association cortex
Vision
Hearing
Multimodal association
cortex
Primary Motor Cortex
• Large pyramidal cells of precentral gyri
• Long axons  pyramidal (corticospinal)
tracts of spinal cord
• Allows conscious control of precise,
skilled, skeletal muscle movements
• Motor homunculi - upside-down
caricatures represent contralateral motor
innervation of body regions
Figure 12.7 Body maps in the primary motor cortex and somatosensory cortex of the cerebrum.
Posterior
Motor
Sensory
Anterior
Hip
Trunk
Neck
Motor map in
precentral gyrus
Sensory map in
postcentral gyrus
Foot
Knee
Toes
Genitals
Jaw
Tongue
Swallowing
Primary motor
cortex
(precentral gyrus)
Primary somatosensory cortex
(postcentral gyrus)
Intraabdominal
Premotor Cortex
• Helps plan movements; staging area for skilled motor activities
• Controls learned, repetitious, or patterned motor skills (e.g.,
playing an instrument or typing)
Broca's Area
• Present in one hemisphere (usually the left)
• Motor speech area that directs muscles of speech production
• Active in planning speech and voluntary motor activities
Frontal Eye Field
• Controls voluntary eye movements
Sensory Areas of Cerebral Cortex
• Conscious awareness of sensation
• Occur in parietal, insular, temporal, and occipital lobes
• Primary
somatosensory cortex
• Somatosensory
association cortex
• Visual areas
• Auditory areas
•
•
•
•
Vestibular cortex
Olfactory cortex
Gustatory cortex
Visceral sensory
area
Motor areas
Central sulcus
Primary motor cortex
Sensory areas and related
association areas
Primary somatosensory cortex
Somatic
Somatosensory
sensation
association cortex
Premotor cortex
Frontal
eye field
Broca's area
(outlined by dashes)
Gustatory cortex
(in insula)
Prefrontal cortex
Working memory
for spatial tasks
Executive area for
task management
Working memory for
object-recall tasks
Solving complex,
multitask problems
Wernicke's area
(outlined by dashes)
Primary visual
cortex
Visual
association
area
Auditory
association area
Primary
auditory cortex
Lateral view, left cerebral hemisphere
Primary motor
cortex
Taste
Motor association
cortex
Primary sensory
cortex
Sensory
association cortex
Vision
Hearing
Multimodal association
cortex
Premotor
cortex
Cingulate Primary
gyrus
motor cortex
Corpus
callosum
Central sulcus
Primary somatosensory
cortex
Frontal eye field
Parietal lobe
Somatosensory
association cortex
Parieto-occipital
sulcus
Prefrontal
cortex
Occipital
lobe
Processes emotions
related to personal
and social interactions
Visual association
area
Orbitofrontal
cortex
Olfactory bulb
Olfactory tract
Fornix
Temporal
lobe
Primary
olfactory
cortex
Parasagittal view, right cerebral hemisphere
Primary motor
cortex
Motor association
cortex
Primary sensory
cortex
Uncus
Calcarine
sulcus
Parahippocampal
gyrus
Sensory
association cortex
Primary
visual cortex
Multimodal association
cortex
Primary Somatosensory Cortex
• In postcentral gyri of parietal lobe
• Receives general sensory information from skin,
and proprioceptors of skeletal muscle, joints,
and tendons
• Capable of spatial discrimination: identification
of body region being stimulated
• Somatosensory homunculus upside-down
caricatures represent contralateral sensory input
from body regions
Figure 12.7b Body maps in the primary motor cortex and somatosensory cortex of the cerebrum.
Posterior
Sensory
Neck
Hip
Trunk
Anterior
Sensory map in
postcentral gyrus
Foot
Genitals
Primary somatosensory cortex
(postcentral gyrus)
Intraabdominal
Somatosensory Association Cortex
• Posterior to primary somatosensory cortex
• Integrates sensory input from primary somatosensory
cortex for understanding of object
• Determines size, texture, and relationship of parts of
objects being felt
Motor areas
Central sulcus
Primary motor cortex
Sensory areas and related
association areas
Primary somatosensory cortex
Somatic
Somatosensory
sensation
association cortex
Premotor cortex
Frontal
eye field
Broca's area
(outlined by dashes)
Gustatory cortex
(in insula)
Prefrontal cortex
Working memory
for spatial tasks
Taste
Wernicke's area
(outlined by dashes)
Executive area for
task management
For example, put
your hand in your
pocket and you will
know what is in
there.
Working memory for
object-recall tasks
Primary visual
cortex
Solving complex,
multitask problems
Visual
association
area
Vision
Auditory
association area
Primary
auditory cortex
Hearing
Lateral view, left cerebral hemisphere
Primary motor
cortex
Motor association
cortex
Primary sensory
cortex
Sensory
association cortex
Multimodal association
cortex
Visual Areas
• Primary visual (striate) cortex
– Extreme posterior tip of occipital lobe
– Receives visual information from retinas
• Visual association area
– Surrounds primary visual cortex
– Uses past visual experiences to interpret visual
stimuli (e.g., color, form, and movement) e.g., ability to
recognize faces
Auditory Areas
Motor areas
Central sulcus
• Primary auditory cortex
Primary motor cortex
Sensory areas and related
association areas
Premotor cortex
Frontal
eye field
Broca's area
(outlined by dashes)
Primary somatosensory cortex
Somatic
Somatosensory
sensation
association cortex
– Superior margin of temporal lobes
– Interprets information from inner ear as pitch,
loudness, and location
Gustatory cortex
(in insula)
Prefrontal cortex
Working memory
for spatial tasks
Executive area for
task management
Working memory for
object-recall tasks
Solving complex,
multitask problems
Taste
Wernicke's area
(outlined by dashes)
• Auditory association area
Primary visual
cortex
Visual
association
area
Vision
– Located posterior to primary auditory cortex
– Stores memories of sounds and permits
perception of sound stimulus
Auditory
association area
Primary
auditory cortex
Lateral view, left cerebral hemisphere
Primary motor
cortex
Motor association
cortex
Primary sensory
cortex
Sensory
association cortex
Hearing
Multimodal association
cortex
Figure 12.6b Functional and structural areas of the cerebral cortex.
Premotor
cortex
Cingulate Primary
gyrus
motor cortex
Corpus
callosum
Central sulcus
Primary somatosensory
cortex
Frontal eye field
Parietal lobe
Somatosensory
association cortex
Parieto-occipital
sulcus
Prefrontal
cortex
Occipital
lobe
Processes emotions
related to personal
and social interactions
Visual association
area
Orbitofrontal
cortex
Olfactory bulb
Olfactory tract
Fornix
Temporal
lobe
Primary
olfactory
cortex
Parasagittal view, right cerebral hemisphere
Primary motor
cortex
Motor association
cortex
Primary sensory
cortex
Uncus
Calcarine
sulcus
Parahippocampal
gyrus
Sensory
association cortex
Primary
visual cortex
Multimodal association
cortex
Multimodal Association Areas
• Receive inputs from multiple sensory areas
• Send outputs to multiple areas, including premotor cortex
• Allows meaning to information received, store in memory,
tying to previous experience, and deciding on actions
• Sensations, thoughts, emotions become conscious – makes
us who we are
Crashing a bottle of acid on the lab floor - pain, noise, skin
burning, panic …
• Three broad parts:
– Anterior association area (prefrontal cortex)
– Posterior association area
– Limbic association area
Anterior Association Area (Prefrontal Cortex)
Prefrontal cortex
• Most complicated cortical region
• Involved with intellect, cognition, recall, and
personality
• Contains working memory needed for abstract
ideas, judgment, reasoning, persistence, and
planning
• DEVELOPS SLOWLY IN CHILDREN =>
Development depends on feedback from social
environment
Posterior Association Area
Prefrontal cortex
• Large region in temporal,
parietal, and occipital lobes
• Plays role in recognizing
patterns and faces and
localizing us in space
• Involved in understanding
written and spoken language
(Wernicke's area)
Limbic Association Area
• Part of limbic system (discussed later)
• Involves cingulate gyrus, parahippocampal
gyrus, and hippocampus
• Provides emotional impact that makes
scene important and helps establish
memories
Lateralization of Cortical Function
• Hemispheres almost identical
• Lateralization - division of labor between hemispheres;
hemispheres don’t share the same abilities
• Cerebral dominance - hemisphere dominant for
language (left hemisphere - 90% people)
• Left hemisphere
– Controls language, math, and logic
• Right hemisphere
– Visual-spatial skills, intuition, emotion, and artistic and
musical skills
• Hemispheres communicate almost instantaneously via
fiber tracts and functional integration
Cerebral White Matter
• Myelinated fibers and tracts
• Communication between cerebral areas, and between
cortex and lower CNS
– Association fibers— horizontal; connect different
parts of same hemisphere
– Commissural fibers— horizontal; connect gray
matter of two hemispheres
– Projection fibers— vertical; connect hemispheres
with lower brain or spinal cord
Figure 12.8a White fiber tracts of the cerebral hemispheres.
Longitudinal fissure
Lateral
ventricle
Basal nuclei
• Caudate
• Putamen
• Globus
pallidus
Thalamus
Third
ventricle
Superior
Association fibers
(within hemisphere)
Commissural fibers
(between hemispheres)
• Corpus callosum
Projection fibers
(cerebral cortex
to lower area)
• Corona
radiata
• Internal
capsule
Gray matter
White matter
Pons
Medulla oblongata
Frontal section
Decussation
(cross-over)
of pyramids
Figure 12.8b White fiber tracts of the cerebral hemispheres.
Association fibers
Commissural fibers
• Corpus callosum
Projection fibers
• Corona radiata
• Internal capsule
Parasagittal section and dissection
Gray
matter
Basal Nuclei (Ganglia)
• Subcortical nuclei
– Caudate nucleus
– Putamen
– Globus pallidus
• Caudate nucleus + putamen = striatum
• Putamen + globus pallidus = lentiform nucleus
• Associated with subthalamic nuclei (diencephalon) and substantia
nigra (midbrain)
Striatum
Caudate
nucleus
Putamen
Thalamus
Tail of caudate
nucleus
Figure 12.9b Basal nuclei.
Anterior
Cerebral cortex
Cerebral white matter
Corpus callosum
Anterior horn
of lateral ventricle
Head of caudate nucleus
Putamen
Globus
pallidus
Thalamus
Tail of caudate nucleus
Third ventricle
Inferior horn
of lateral ventricle
Posterior
Functions of Basal Nuclei
• Functions thought to be
– Influence muscle movements
– Role in cognition and emotion
– Regulate intensity of slow or stereotyped movements
e.g. involved in starting, monitoring, and stopping a
movement (arm-swinging while walking);
– Inhibit antagonistic/unnecessary movements
Disorders of basal nuclei:
Parkinson’s Dz: too little movement
Huntington’s Dz: too much movement
Diencephalon
• Three paired structures
– Thalamus
– Hypothalamus
– Epithalamus
• Encloses third ventricle
Cerebral hemisphere
Corpus callosum
Fornix
Choroid plexus
Septum pellucidum
Interthalamic
adhesion
(intermediate
mass of thalamus)
Thalamus
(encloses third ventricle)
Posterior
commissure
Pineal gland
Interventricular
foramen
Anterior
commissure
Hypothalamus
Optic chiasma
Epithalamus
Corpora
quadrigemina Midbrain
Cerebral
aqueduct
Pituitary gland
Mammillary
body
Pons
Medulla
oblongata
Spinal cord
Arbor vitae (of cerebellum)
Fourth ventricle
Choroid plexus
Cerebellum
Thalamus (“inner room”)
•80% of diencephalon
•Superolateral walls of third ventricle
Functions:
•Relay station for information coming into the cerebral cortex
•Sorts, edits, and relays ascending input
– Impulses from hypothalamus for regulation of emotion
and visceral function
– Impulses from cerebellum and basal nuclei to help direct
motor cortices
– Impulses for memory or sensory integration
•Mediates sensation, motor activities, cortical arousal,
learning, and memory
Hypothalamus
• Contains many nuclei
– Example: mammillary bodies
• Paired anterior nuclei
• Olfactory relay stations
• Infundibulum—stalk that connects to pituitary gland
Paraventricular
nucleus
Anterior
commissure
Preoptic
nucleus
Anterior
hypothalamic
nucleus
Supraoptic
nucleus
Suprachiasmatic
nucleus
Optic
chiasma
Infundibulum
(stalk of the
pituitary gland)
Fornix
Arcuate
nucleus
Pituitary
gland
The main hypothalamic nuclei.
Dorsomedial
nucleus
Posterior
hypothalamic
nucleus
Lateral
hypothalamic
area
Ventromedial
nucleus
Mammillary
body
Hypothalamic Function
• Controls autonomic nervous system (e.g., blood pressure,
rate and force of heartbeat, digestive tract motility, pupil size)
• Physical responses to emotions (limbic system)
– Perception of pleasure, fear, and rage, and in biological
rhythms and drives
• Regulates body temperature – sweating/shivering
• Regulates hunger and satiety in response to nutrient blood
levels or hormones
• Regulates water balance and thirst
Epithalamus
• Most dorsal portion of diencephalon; forms
roof of third ventricle
• Pineal gland (body)—extends from
posterior border and secretes melatonin
– Melatonin—helps regulate sleep-wake cycle
Brain Stem
• Three regions
– Midbrain
– Pons
– Medulla oblongata
Cerebral hemisphere
Corpus callosum
Fornix
Choroid plexus
Septum pellucidum
Interthalamic
adhesion
(intermediate
mass of thalamus)
Thalamus
(encloses third ventricle)
Posterior
commissure
Pineal gland
Interventricular
foramen
Anterior
commissure
Hypothalamus
Optic chiasma
Epithalamus
Corpora
quadrigemina Midbrain
Cerebral
aqueduct
Pituitary gland
Mammillary
body
Pons
Medulla
oblongata
Spinal cord
Arbor vitae (of cerebellum)
Fourth ventricle
Choroid plexus
Cerebellum
Corpus callosum
Fornix
Thalamus
Lateral ventricle
(covered by septum
pellucidum)
Posterior
commissure
Pineal gland
Third ventricle
Epithalamus
Corpora
quadrigemina
Cerebral
aqueduct
Anterior
commissure
Hypothalamus
Arbor vitae
Fourth ventricle
Optic chiasma
Cerebellum
Mammillary body
Pons
Medulla oblongata
Midbrain
Brain Stem
• Similar structure to spinal cord
• Controls automatic behaviors necessary
for survival
• Contains fiber tracts connecting higher
and lower neural centers
• Nuclei associated with 10 of the 12 pairs
of cranial nerves
Figure 12.13c Three views of the brain stem (green) and the diencephalon (purple).
Thalamus
Hypothalamus
Diencephalon
Midbrain
Pons
View (a)
View (c)
Brain stem
Medulla
oblongata
View (b)
Thalamus
Diencephalon
Pineal gland
Floor of
fourth ventricle
Facial nerve (VII)
Choroid plexus
(fourth ventricle)
Dorsal median sulcus
Dorsal root of
first cervical nerve
Dorsal view
Midbrain
• Superior
colliculus
• Inferior
colliculus
Corpora
quadrigemina
of tectum
• Trochlear nerve (IV)
• Superior cerebellar peduncle
Pons
• Middle cerebellar peduncle
Medulla oblongata
• Inferior cerebellar peduncle
• Vestibulocochlear nerve (VIII)
• Glossopharyngeal nerve (IX)
• Vagus nerve (X)
• Accessory nerve (XI)
Midbrain
• Between diencephalon and pons
– Contain pyramidal motor tracts
• Hollow cerebral aqueduct
– Channel connecting third and fourth ventricles
Lateral
ventricle
Anterior
horn
Interventricular
foramen
Septum
pellucidum
Inferior
horn
Posterior
horn
Third
ventricle
Inferior
horn
Median
aperture
Cerebral aqueduct
Lateral
aperture
Fourth ventricle
Lateral
aperture
Central canal
Anterior view
Left lateral view
Midbrain Nuclei
• Periaqueductal gray matter
– Pain suppression; links amygdaloid body and ANS;
controls cranial nerves III (oculomotor) and IV (trochlear)
• Corpora quadrigemina— dorsal protrusions
– Superior colliculi—visual reflex centers
– Inferior colliculi—auditory relay centers
• Substantia nigra—functionally linked to basal
nuclei (dark area; high conc of melanin; produces
dopamine – degeneration: Parkinson’s Dz)
• Red nucleus—relay nuclei for some descending
motor pathways; part of reticular formation
Figure 12.14a Cross sections through different regions of the brain stem.
Tectum
Periaqueductal gray
matter
Oculomotor
nucleus (III)
Medial
lemniscus
Red
nucleus
Substantia
nigra
Fibers of
pyramidal tract
Dorsal
Cerebral aqueduct
Reticular formation
Ventral
Midbrain
© 2013 Pearson Education, Inc.
Superior
colliculus
Crus cerebri of
cerebral peduncle
Pons
• Fourth ventricle seperates pons and cerebellum
• Fibers of pons
– Connect higher brain centers and spinal cord
– Relay impulses between motor cortex and cerebellum
• Origin of cranial nerves V (trigeminal), VI
(abducens), and VII (facial)
• Some nuclei of reticular formation
• Nuclei help maintain normal rhythm of breathing
Medulla Oblongata (Medulla)
• Joins spinal cord at foramen magnum
• Forms part of ventral wall of fourth ventricle
• Contains choroid plexus of fourth ventricle
Pons
Medulla
oblongata
Spinal cord
Corpora
quadrigemina
Midbrain
Cerebral
aqueduct
Arbor vitae (of cerebellum)
Fourth ventricle
Choroid plexus
Cerebellum
Medulla Oblongata
• Inferior olivary nuclei—relay sensory
information from muscles and joints to
cerebellum
• Cranial nerves VIII, IX, X, and XII are associated
with medulla
• Vestibular nuclei (pons and medulla)—mediate
responses that maintain equilibrium
• Several nuclei (e.g., nucleus cuneatus and
nucleus gracilis) relay sensory information
Reticular formation
Figure 12.14c Cross sections through different regions of the brain stem.
Hypoglossal nucleus (XII)
Dorsal motor nucleus
of vagus (X)
Inferior cerebellar
peduncle
Lateral
nuclear
group
Medial
nuclear
group
Raphe
nucleus
Medial lemniscus
Fourth ventricle
Choroid
plexus
Medulla oblongata
Solitary
nucleus
Vestibular
nuclei
(VIII)
Cochlear
nuclei
(VIII)
Nucleus
ambiguus
Inferior
olivary
nucleus
Pyramid
Medulla Oblongata: Functions
• Autonomic reflex center
– Functions overlap with hypothalamus
• Hypothalamus relays instructions via medulla
• Cardiovascular center
– Cardiac center adjusts force and rate of heart contraction
– Vasomotor center adjusts blood vessel diameter for blood
pressure regulation
• Respiratory centers
– Generate respiratory rhythm
– Control rate and depth of breathing (with pontine centers)
Medulla Oblongata
• Additional centers regulate
– Vomiting
– Hiccuping
– Swallowing
– Coughing
– Sneezing
Cerebellum
• 11% of brain mass
• Dorsal to pons and medulla
• Input from cortex, brain stem and sensory
receptors
• Allows smooth, coordinated movements
Anatomy of Cerebellum
• Cerebellar hemispheres connected by vermis
• Folia—transversely oriented gyri
• Each hemisphere has three lobes
– Anterior, posterior, and flocculonodular
• Arbor vitae—treelike pattern of cerebellar
white matter
Anterior
lobe
Primary
fissure
Posterior
lobe
Horizontal
fissure
Vermis
Vermis
Figure 12.15a Cerebellum.
Anterior lobe
Arbor vitae
Cerebellar
cortex
Pons
Fourth
ventricle
Medulla
oblongata
© 2013 Pearson Education, Inc.
Posterior
lobe
Flocculonodular lobe
Choroid plexus
Figure 12.15b Cerebellum.
Anterior lobe
Cerebellar cortex
Arbor
vitae
Cerebellar
peduncles
• Superior
• Middle
• Inferior
Medulla
oblongata
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Posterior
lobe
Flocculonodular
lobe
Choroid
plexus of
fourth
ventricle
Cerebellar Processing of Motor Activity
• Cerebellum receives impulses from cerebral
cortex of intent to initiate voluntary muscle
contraction
• Signals from proprioceptors and visual and
equilibrium pathways continuously "inform"
cerebellum of body's position and momentum
• Cerebellar cortex calculates the best way to
smoothly coordinate muscle contraction
• "Blueprint" of coordinated movement sent to
cerebral motor cortex and brain stem nuclei
Cognitive Function of Cerebellum
• Role in thinking, language, and emotion
• May compare actual with expected output
and adjust accordingly
Functional Brain Systems
• Networks of neurons that work together
but span wide areas of brain
– Limbic system
– Reticular formation
Limbic System
• Structures on medial aspects of cerebral hemispheres and
diencephalon
• Includes parts of diencephalon and some cerebral structures
that encircle brain stem
Septum pellucidum
Diencephalic
structures of the
limbic system
Corpus callosum
Fiber tracts connecting
limbic system structures
Fornix
Anterior commissure
Anterior thalamic
nuclei (flanking
3rd ventricle)
Cerebral structures
of the limbic system
Hypothalamus
Cingulate gyrus
Septal nuclei
Amygdaloid body
Mammillary
body
Hippocampus
• Dentate gyrus
Olfactory bulb
• Parahippocampal
gyrus
Limbic System
• Emotional or affective brain
– Amygdaloid body—recognizes angry or
fearful facial expressions, assesses danger,
and elicits fear response
– Cingulate gyrus—role in expressing
emotions via gestures, and resolves mental
conflict
• Puts emotional responses to odors
– Example: skunks smell bad
• Most output relayed via hypothalamus
Psychosomatic illnesses
Limbic System: Emotion and Cognition
• Limbic system interacts with prefrontal
lobes
– React emotionally to things we consciously
understand to be happening
– Consciously aware of emotional richness in
our lives
• Hippocampus and amygdaloid body—
play a role in memory
Reticular Formation
• Three broad columns run length of brain
stem
– Raphe nuclei
– Medial (large cell) group of nuclei
– Lateral (small cell) group of nuclei
• Has far-flung axonal connections with
hypothalamus, thalamus, cerebral cortex,
cerebellum, and spinal cord  can govern
brain arousal
Figure 12.17 The reticular formation.
Radiations
to cerebral
cortex
Visual
impulses
Auditory
impulses
Reticular formation
Ascending general
sensory tracts
(touch, pain, temperature)
Descending
motor projections
to spinal cord
Reticular Formation: RAS and Motor Function
• Reticular activating system (RAS)
– Sends impulses to cerebral cortex to keep it conscious and alert
– Filters out repetitive, familiar, or weak stimuli (~99% of all stimuli!)
– Inhibited by sleep centers, alcohol, drugs
– Severe injury results in permanent unconsciousness (coma)
• Motor function
– Helps control coarse limb movements via reticulospinal tracts
– Reticular autonomic centers regulate visceral motor functions
• Vasomotor centers
• Cardiac center
• Respiratory centers
Protection of the Brain
•
•
•
•
Bone (skull)
Membranes (meninges)
Watery cushion (cerebrospinal fluid)
Blood brain barrier
Meninges
Cover and protect CNS
Protect blood vessels and enclose venous sinuses
Contain cerebrospinal fluid (CSF)
Form partitions in skull
• Three layers
– Dura mater
– Arachnoid mater
– Pia mater
• Meningitis
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medications linked to an unprecedented fungal
meningitis outbreak faced mounting scrutiny on
Saturday over whether it illegally sold drugs to
medical facilities, as the death toll from the
disease grew to 15. 10/13/12
– Inflammation of meninges
Figure 12.22 Meninges: dura mater, arachnoid mater, and pia mater.
Skin of scalp
Periosteum
Superior sagittal
sinus
Subdural
space
Subarachnoid
space
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Bone of skull
Dura mater
• Periosteal layer
• Meningeal layer
Arachnoid mater
Pia mater
Arachnoid villus
Blood vessel
Falx cerebri
(in longitudinal
fissure only)
•
•
•
Dura Mater
Strongest meninx
Two layers of fibrous connective tissue (around brain) separate to form dural venous
sinuses
Dural septa limit excessive movement of brain
– Falx cerebri—in longitudinal fissure; attached to crista galli
– Falx cerebelli—along vermis of cerebellum
– Tentorium cerebelli—horizontal dural fold over cerebellum and in transverse
Superior
fissure
sagittal sinus
Falx cerebri
Straight
sinus
Crista galli of
the ethmoid
bone
Pituitary
gland
Midsagittal view
Tentorium
cerebelli
Falx
cerebelli
Figure 12.23b Dural septa and dural venous sinuses.
Superior
sagittal sinus
Falx cerebri
Parietal
bone
Scalp
Occipital lobe
Tentorium
cerebelli
Falx
cerebelli
Cerebellum
Arachnoid
mater over
medulla oblongata
Posterior dissection
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Dura mater
Transverse
sinus
Temporal
bone
Arachnoid Mater
•
•
•
•
Middle layer with weblike extensions
Separated from dura mater by subdural space
Subarachnoid space contains CSF and largest blood vessels of brain
Arachnoid villi protrude into superior sagittal sinus and permit CSF
reabsorption
Skin of scalp
Periosteum
Superior sagittal
sinus
Subdural
space
Subarachnoid
space
Bone of skull
Dura mater
• Periosteal layer
• Meningeal layer
Arachnoid mater
Pia mater
Arachnoid villus
Blood vessel
Falx cerebri
(in longitudinal
fissure only)
Pia Mater
• Delicate vascularized connective tissue
that clings tightly to brain
Cerebrospinal Fluid (CSF)
• Composition
– Watery solution formed from blood plasma
• Less protein and different ion concentrations than plasma
– Constant volume
• Functions
– Gives buoyancy (tendency or capacity to remain afloat in a liquid or rise in air)
to CNS structures
• Reduces weight by 97%
– Protects CNS from blows and other trauma
– Nourishes brain and carries chemical signals
Figure 12.24a Formation, location, and circulation of CSF.
Slide 1
4
Superior
sagittal sinus
Arachnoid villus
Choroid plexus
Subarachnoid space
Arachnoid mater
Meningeal dura mater
Periosteal dura mater
1
Interventricular
foramen
Third ventricle
Right lateral ventricle
(deep to cut)
3
Cerebral aqueduct
Lateral aperture
Fourth ventricle
Median aperture
Central canal
of spinal cord
(a) CSF circulation
Choroid plexus
of fourth ventricle
2
1 The choroid plexus of each
Ventricle produces CSF.
2 CSF flows through the ventricles
and into the subarachnoid space via
the median and lateral apertures.
3 CSF flows through the
subarachnoid space.
4 CSF is absorbed into the dural
venous sinuses via the arachnoid villi.
Choroid Plexuses
• Hang from roof of each ventricle; produce CSF at constant rate; keep in
motion - Clusters of capillaries enclosed by pia mater and layer of
ependymal cells
• Ependymal cells use ion pumps to control composition of CSF and help
cleanse CSF by removing wastes - Normal volume ~ 150 ml; replaced
every 8 hours
Ependymal
cells
Capillary
Section
of choroid
plexus
Connective
tissue of
pia mater
Wastes and
unnecessary
solutes absorbed
Cavity of
ventricle
CSF formation by choroid plexuses
CSF forms as a filtrate
containing glucose, oxygen,
vitamins, and ions
(Na+, Cl–, Mg2+, etc.)- more than blood
Hydrocephalus – water in the brain
• Obstruction (e.g. a tumor) blocks CSF circulation or
drainage
• Unfused skull bones of newborn allow enlargement of
head
• Brain damage in adult due to rigid adult skull
• Treated by draining with ventricular shunt to abdominal
cavity
Blood Brain Barrier BBB
• Helps maintain stable environment for brain
• Separates neurons from some bloodborne substances
• Composition
– Continuous endothelium of capillary walls
– Thick basal lamina around capillaries
– Feet of astrocytes
• Provide signal to endothelium for formation of tight
junctions
• BBB is selective – glucose, essential amino acids and
some electrolytes move passively –
• Bloodborne metabolic wastes, proteins, certain toxins,
and most drugs can pass
• Small nonessential amino acids and K actively pumped
out!!
Figure 11.3a Neuroglia.
Capillary
Neuron
Astrocyte
Astrocytes are the most abundant CNS neuroglia.
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Spinal Cord: Gross Anatomy and Protection
• Location
– Begins at the foramen magnum
– Ends at L1 or L2 vertebra
• Functions
– Provides two-way communication to and from
brain
– Contains spinal reflex centers
Spinal Cord: Gross Anatomy and Protection
• Bone, meninges, and CSF
• Epidural space
– Cushion of fat and network of veins in space
between vertebrae and spinal dura mater
• CSF in subarachnoid space
• Dural and arachnoid membranes extend to
sacrum, beyond end of cord at L1 or L2
– Site of lumbar puncture or tap
Spinal Cord: Gross Anatomy and Protection
T12
•
•
•
Terminates in conus
medullaris
Filum terminale
extends to coccyx
– Fibrous extension
of conus covered
with pia mater
– Anchors spinal
cord
Denticulate
ligaments
– Extensions of pia
mater that secure
cord to dura mater
L5
Ligamentum
flavum
Lumbar puncture
needle entering
subarachnoid
space
L4
Supraspinous
ligament
Filum
terminale
L5
S1
Intervertebral
disc
Arachnoid
mater
Dura
mater
Cauda equina
in subarachnoid
space
Figure 12.26a Gross structure of the spinal cord, dorsal view.
Cervical
enlargement
Dura and
arachnoid
mater
Lumbar
enlargement
Conus
medullaris
Cauda
equina
Filum
terminale
Cervical
spinal
nerves
Thoracic
spinal nerves
Lumbar
spinal nerves
Sacral
spinal nerves
The spinal cord and its nerve roots, with the bony
vertebral arches removed. The dura mater and
arachnoid mater are cut open and reflected laterally.
Spinal Cord
• Spinal nerves (Part of PNS)
– 31 pairs
• Cervical and lumbosacral enlargements
– Nerves serving upper and lower limbs emerge
here
• Cauda equina
– Collection of nerve roots at inferior end of
vertebral canal
Cross-sectional Anatomy
• Two lengthwise grooves partially divide cord into right
and left halves
– Ventral (anterior) median fissure
– Dorsal (posterior) median sulcus
• Gray commissure—connects masses of gray matter;
encloses central canal
Epidural space
(contains fat)
Subdural space
Subarachnoid
space
(contains CSF)
Pia mater
Arachnoid mater
Dura mater
Spinal meninges
Bone of
vertebra
Dorsal root
ganglion
Body
of vertebra
Cross section of spinal cord and vertebra
Gray Matter
•
•
•
•
•
Dorsal horns - interneurons that receive somatic and visceral sensory input
Ventral horns - some interneurons; somatic motor neurons; axons exit cord via
ventral roots
Lateral horns (only in thoracic and superior lumbar regions) - sympathetic neurons
Dorsal roots – sensory input to cord
Dorsal root (spinal) ganglia—cell bodies of sensory neurons
Dorsal median sulcus
Dorsal funiculus
White
columns
Ventral funiculus
Lateral funiculus
Gray commissure
Dorsal horn
Gray
Ventral horn
matter
Lateral horn
Dorsal root
ganglion
Spinal nerve
Dorsal root
(fans out into
dorsal rootlets)
Central canal
Ventral median fissure
Pia mater
Ventral root
(derived from several
ventral rootlets)
Arachnoid mater
Spinal dura mater
The spinal cord and its meningeal coverings
Zones of Spinal Gray Matter
• Per relative involvement in innervating somatic and visceral regions
of body
• Somatic sensory (SS)
• Visceral sensory (VS)
• Visceral (autonomic) motor (VM)
• Somatic motor (SM)
Dorsal root
(sensory)
Dorsal horn (interneurons)
Dorsal root
ganglion
SS
VS
Somatic sensory neuron
VM
Visceral sensory
neuron
SM
Visceral motor
neuron
Somatic motor neuron
Spinal nerve
Ventral horn
(motor neurons)
Ventral root
(motor)
SS
Interneurons receiving input from somatic sensory neurons
VS
Interneurons receiving input from visceral sensory neurons
VM
Visceral motor (autonomic) neurons
SM
Somatic motor neurons
Nonspecific Ascending Pathway
• Nonspecific
pathway for pain,
temperature, and
crude touch within
the lateral
spinothalamic
tract
Figure 12.33b
The Direct (Pyramidal) System
• Direct pathways originate with the
pyramidal neurons in the
precentral gyri
• Impulses are sent through the
corticospinal tracts and synapse
in the anterior horn
• Stimulation of anterior horn
neurons activates skeletal
muscles
• Parts of the direct pathway, called
corticobulbar tracts, innervate
cranial nerve nuclei
• The direct pathway regulates fast
and fine (skilled) movements
Indirect (Extrapyramidal) System
• Includes the brain stem, motor
nuclei, and all motor pathways not
part of the pyramidal system
• This system includes the
rubrospinal, vestibulospinal,
reticulospinal, and tectospinal
tracts
• These motor pathways are complex
and multisynaptic, and regulate:
– Axial muscles that maintain
balance and posture
– Muscles controlling coarse
movements of the proximal
portions of limbs
– Head, neck, and eye movement
Spinal Cord Trauma: Paralysis
• Paralysis – loss of motor function
• Flaccid paralysis – severe damage to the ventral root
or anterior horn cells
– Lower motor neurons are damaged and impulses do
not reach muscles
– There is no voluntary or involuntary control of
muscles
• Spastic paralysis – only upper motor neurons of the
primary motor cortex are damaged
– Spinal neurons remain intact and muscles are
stimulated irregularly
– There is no voluntary control of muscles
Spinal Cord Trauma: Transection
• Cross sectioning of the spinal cord at any level results
in total motor and sensory loss in regions inferior to the
cut
• Paraplegia – transection between T1 and L1
• Quadriplegia – transection in the cervical region
Poliomyelitis
• Destruction of the anterior horn motor neurons by
the poliovirus
• Early symptoms – fever, headache, muscle pain
and weakness, and loss of somatic reflexes
• Vaccines are available and can prevent infection
Amyotrophic Lateral Sclerosis (ALS)
• Lou Gehrig’s disease – neuromuscular condition
involving destruction of anterior horn motor neurons
and fibers of the pyramidal tract
• Symptoms – loss of the ability to speak, swallow, and
breathe
• Death occurs within five years
• Linked to malfunctioning genes for glutamate
transporter and/or superoxide dismutase