Download 12 - Chemistry

The Central Nervous System
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(d) Adult brain
structures
(e) Adult
neural canal
regions
Telencephalon
Cerebrum: cerebral
hemispheres (cortex,
white matter, basal nuclei)
Lateral
ventricles
Diencephalon
Diencephalon
(thalamus, hypothalamus,
epithalamus), retina
Third ventricle
Mesencephalon
Brain stem: midbrain
Cerebral
aqueduct
Metencephalon
Brain stem: pons
(c) Secondary brain
vesicles
Cerebellum
Myelencephalon
Brain stem: medulla
oblongata
Spinal cord
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Fourth
ventricle
Central canal
Regions and Organization of the CNS
•
Adult brain regions
1. Cerebral hemispheres
2. Diencephalon
3. Brain stem (midbrain, pons, and medulla)
4. Cerebellum
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Cerebral
hemisphere
Diencephalon
(d) Birth
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Cerebellum
Brain stem
• Midbrain
• Pons
• Medulla
oblongata
Figure 12.3d
Ventricles of the Brain
• Connected to one another and to the central
canal of the spinal cord
• Lined by ependymal cells
• Hold and transport CSF
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Lateral ventricle
Septum pellucidum
Anterior horn
Inferior
horn
Lateral
aperture
Interventricular
foramen
Third ventricle
Inferior horn
Cerebral aqueduct
Fourth ventricle
Central canal
(a) Anterior view
(b) Left lateral
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Posterior
horn
Median
aperture
Lateral
aperture
view
Figure 12.5
Cerebral Hemispheres
• Surface markings
• Ridges (gyri), shallow grooves (sulci), and
deep grooves (fissures)
• Five lobes
• Frontal
• Parietal
• Temporal
• Occipital
• Insula
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Cerebral Hemispheres
• Surface markings
• Central sulcus
• Separates the precentral gyrus of the frontal lobe
and the postcentral gyrus of the parietal lobe
• Longitudinal fissure
• Separates the two hemispheres
• Transverse cerebral fissure
• Separates the cerebrum and the cerebellum
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Precentral
gyrus
Frontal
lobe
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
Fissure
(a deep
sulcus)
Gyrus
Cortex (gray matter)
Sulcus
White matter
(a)
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Figure 12.6a
Cerebral Cortex
• Thin (2–4 mm) superficial layer of gray
matter
• 40% of the mass of the brain
• Site of conscious mind: awareness,
sensory perception, voluntary motor
initiation, communication, memory storage,
understanding
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Functional Areas of the Cerebral Cortex
• The three types of functional areas are:
• Motor areas—control voluntary movement
• Sensory areas—conscious awareness of
sensation
• Association areas—integrate diverse
information
• Conscious behavior involves the entire cortex
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Motor Areas
• Primary (somatic) motor cortex
• Premotor cortex
• Broca’s area
• Frontal eye field
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Motor areas
Central sulcus
Primary motor cortex
Premotor cortex
Frontal eye field
Broca’s area
(outlined by dashes)
Prefrontal cortex
Working memory
for spatial tasks
Executive area for
task management
Working memory for
object-recall tasks
Solving complex,
multitask problems
(a) Lateral view, left cerebral hemisphere
Sensory areas and related
association areas
Primary somatosensory
cortex
Somatic
Somatosensory
sensation
association cortex
Gustatory cortex
(in insula)
Taste
Wernicke’s area
(outlined by dashes)
Primary visual
cortex
Visual
association
area
Auditory
association area
Primary
auditory cortex
Vision
Hearing
Motor association cortex
Primary sensory cortex
Primary motor cortex
Sensory association cortex
Multimodal association cortex
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Figure 12.8a
Primary Motor Cortex
• Large pyramidal cells of the precentral gyri
• Allows conscious control of precise, skilled,
voluntary movements
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Posterior
Motor
Motor map in
precentral gyrus
Anterior
Toes
Jaw
Tongue
Swallowing
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Primary motor
cortex
(precentral gyrus)
Figure 12.9
Premotor Cortex
• Anterior to the precentral gyrus
• Controls learned, repetitious, or patterned
motor skills
• Coordinates simultaneous or sequential
actions
• Involved in the planning of movements that
depend on sensory feedback
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Broca’s Area
• Anterior to the inferior region of the premotor
area
• Present in one hemisphere (usually the left)
• A motor speech area that directs muscles of
the tongue
• Is active as one prepares to speak
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Frontal Eye Field
• Anterior to the premotor cortex and superior to
Broca’s area
• Controls voluntary eye movements
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Sensory Areas
• Primary somatosensory
cortex
• Somatosensory
association cortex
• Visual areas
• Auditory areas
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• Olfactory cortex
• Gustatory cortex
• Visceral sensory area
• Vestibular cortex
Motor areas
Central sulcus
Primary motor cortex
Premotor cortex
Frontal eye field
Broca’s area
(outlined by dashes)
Prefrontal cortex
Working memory
for spatial tasks
Executive area for
task management
Working memory for
object-recall tasks
Solving complex,
multitask problems
(a) Lateral view, left cerebral hemisphere
Sensory areas and related
association areas
Primary somatosensory
cortex
Somatic
Somatosensory
sensation
association cortex
Gustatory cortex
(in insula)
Taste
Wernicke’s area
(outlined by dashes)
Primary visual
cortex
Visual
association
area
Auditory
association area
Primary
auditory cortex
Vision
Hearing
Motor association cortex
Primary sensory cortex
Primary motor cortex
Sensory association cortex
Multimodal association cortex
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Figure 12.8a
Primary Somatosensory Cortex
• In the postcentral gyri
• Receives sensory information from the skin,
skeletal muscles, and joints
• Capable of spatial discrimination: identification
of body region being stimulated
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Posterior
Sensory
Anterior
Sensory map in
postcentral gyrus
Genitals
Primary somatosensory cortex
(postcentral gyrus)
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Intraabdominal
Figure 12.9
Somatosensory Association Cortex
• Posterior to the primary somatosensory cortex
• Integrates sensory input from primary
somatosensory cortex
• Determines size, texture, and relationship of
parts of objects being felt
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Visual Areas
• Primary visual (striate) cortex
• Extreme posterior tip of the occipital lobe
• Receives visual information from the retinas
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Auditory Areas
• Primary auditory cortex
• Superior margin of the temporal lobes
• Interprets information from inner ear as pitch,
loudness, and location
• Auditory association area
• Stores memories of sounds and permits
perception of sounds
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OIfactory Cortex
• Medial aspect of temporal lobes
• Region of conscious awareness of odors
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Gustatory Cortex
• In the insula
• Involved in the perception of taste
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Visceral Sensory Area
• Posterior to gustatory cortex
• Conscious perception of visceral sensations,
e.g., upset stomach or full bladder
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Vestibular Cortex
• Posterior part of the insula and adjacent
parietal cortex
• Responsible for conscious awareness of
balance (position of the head in space)
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Multimodal Association Areas
• Receive inputs from multiple sensory areas
• Send outputs to multiple areas
• Allow us to give meaning to information
received, store it as memory, compare it to
previous experience, and decide on action to
take
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Multimodal Association Areas
• Three parts
• Anterior association area (prefrontal cortex)
• Posterior association area
• Limbic association area
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Anterior Association Area (Prefrontal
Cortex)
• Most complicated cortical region
• Involved with intellect, cognition, recall, and
personality
• Contains working memory needed for
judgment, reasoning, persistence, and
conscience
• Development depends on feedback from
social environment
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Posterior Association Area
• Large region in temporal, parietal, and
occipital lobes
• Plays a role in recognizing patterns and faces
and localizing us in space
• Involved in understanding written and spoken
language (Wernicke’s area)
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Limbic Association Area
• Part of the limbic system
• Provides emotional impact that helps
establish memories
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Lateralization of Cortical Function
• Lateralization
• Division of labor between hemispheres
• Cerebral dominance
• Designates the hemisphere dominant for
language (left hemisphere in 90% of people)
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Lateralization of Cortical Function
• Left hemisphere
• Controls language, math, and logic
• Right hemisphere
• Insight, visual-spatial skills, intuition, and
artistic skills
• Left and right hemispheres communicate via
fiber tracts in the cerebral white matter
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Basal Nuclei (Ganglia)
• Caudate nucleus
• Lentiform nucleus (putamen + globus pallidus)
• Functionally associated with the subthalamic
nuclei (diencephalon) and the substantia nigra
(midbrain)
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Fibers of
corona radiata
Caudate
nucleus
Lentiform
Corpus
nucleus
striatum • Putamen
• Globus pallidus
(deep to putamen)
Projection fibers
run deep to
lentiform nucleus
(a)
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Thalamus
Tail of
caudate
nucleus
Figure 12.11a
Anterior
(b)
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Posterior
Cerebral cortex
Cerebral white matter
Corpus callosum
Anterior horn
of lateral ventricle
Caudate nucleus
Putamen
Lentiform
Globus
nucleus
pallidus
Thalamus
Tail of caudate nucleus
Third ventricle
Inferior horn
of lateral ventricle
Figure 12.11b (1 of 2)
Cerebral cortex
Cerebral white matter
Corpus callosum
Anterior horn
of lateral ventricle
Caudate nucleus
Lentiform nucleus
Thalamus
Third ventricle
Inferior horn
of lateral ventricle
(b)
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Figure 12.11b (2 of 2)
Functions of Basal Nuclei
• Thought to be functions of basal nuclei
• Influence muscular control
• Help regulate attention and cognition
• Regulate intensity of slow or stereotyped
movements
• Inhibit antagonistic and unnecessary
movements
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Diencephalon
• Three paired structures
• Thalamus
• Hypothalamus
• Epithalamus
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Cerebral hemisphere
Septum pellucidum
Interthalamic
adhesion
(intermediate
mass of
thalamus)
Interventricular
foramen
Anterior
commissure
Hypothalamus
Optic chiasma
Pituitary gland
Mammillary body
Pons
Medulla oblongata
Corpus callosum
Fornix
Choroid plexus
Thalamus
(encloses third
ventricle)
Posterior commissure
Pineal gland
(part of epithalamus)
Corpora
quadrigemina MidCerebral
brain
aqueduct
Arbor vitae (of
cerebellum)
Fourth ventricle
Choroid plexus
Cerebellum
Spinal cord
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Figure 12.12
Thalamus
• 80% of diencephalon
• Contains several nuclei, named for their
location
• Nuclei project and receive fibers from the
cerebral cortex
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Dorsal nuclei
Medial Lateral Lateral
dorsal posterior
Pulvinar
Anterior
nuclear
group
Reticular
nucleus
Ventral
Ventral Ventral posteroanterior lateral lateral
Medial
geniculate
body
Lateral
geniculate
body
Ventral nuclei
(a) The main thalamic nuclei. (The reticular nuclei that “cap” the
thalamus laterally are depicted as curving translucent structures.)
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Figure 12.13a
Thalamic Function
• Gateway to the cerebral cortex
• Sorts, edits, and relays information
• Afferent impulses from all senses and all parts of the
body
• Impulses from the hypothalamus for regulation of
emotion and visceral function
• Impulses from the cerebellum and basal nuclei to help
direct the motor cortices
• Mediates sensation, motor activities, cortical arousal,
learning, and memory
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Hypothalamus
• Contains many nuclei
• Example: mammillary bodies
• Paired anterior nuclei
• Olfactory relay stations
• Infundibulum—stalk that connects to the
pituitary gland
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Paraventricular
nucleus
Anterior
commissure
Preoptic
nucleus
Anterior
hypothalamic
nucleus
Supraoptic
nucleus
Suprachiasmatic
nucleus
Fornix
Arcuate
nucleus
Pituitary
gland
Optic
chiasma
Infundibulum
(stalk of the
pituitary gland)
(b) The main hypothalamic nuclei.
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Dorsomedial
nucleus
Posterior
hypothalamic
nucleus
Lateral
hypothalamic
area
Ventromedial
nucleus
Mammillary
body
Figure 12.13b
Hypothalamic Function
• Autonomic control center for many visceral
functions (e.g., blood pressure, rate and force
of heartbeat, digestive tract motility)
• Center for emotional response: Involved in
perception of pleasure, fear, and rage and in
biological rhythms and drives
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Hypothalamic Function
• Regulates body temperature, food intake,
water balance, and thirst
• Regulates sleep and the sleep cycle
• Controls release of hormones by the anterior
pituitary
• Produces posterior pituitary hormones
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Epithalamus
• Most dorsal portion of the diencephalon;
forms roof of the third ventricle
• Pineal gland—extends from the posterior
border and secretes melatonin
• Melatonin—helps regulate sleep-wake cycles
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Cerebral hemisphere
Septum pellucidum
Interthalamic
adhesion
(intermediate
mass of
thalamus)
Interventricular
foramen
Anterior
commissure
Hypothalamus
Optic chiasma
Pituitary gland
Mammillary body
Pons
Medulla oblongata
Corpus callosum
Fornix
Choroid plexus
Thalamus
(encloses third
ventricle)
Posterior commissure
Pineal gland
(part of epithalamus)
Corpora
quadrigemina MidCerebral
brain
aqueduct
Arbor vitae (of
cerebellum)
Fourth ventricle
Choroid plexus
Cerebellum
Spinal cord
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Figure 12.12
Brain Stem
• Three regions
• Midbrain
• Pons
• Medulla oblongata
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Brain Stem
• Controls automatic behaviors necessary for
survival
• Associated with 10 of the 12 pairs of cranial
nerves
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Frontal lobe
Olfactory bulb
(synapse point of
cranial nerve I)
Optic chiasma
Optic nerve (II)
Optic tract
Mammillary body
Midbrain
Pons
Temporal lobe
Medulla
oblongata
Cerebellum
Spinal cord
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Figure 12.14
View (a)
Optic chiasma
Optic nerve (II)
Crus cerebri of
cerebral peduncles
(midbrain)
Diencephalon
• Thalamus
• Hypothalamus
Mammillary body
Thalamus
Hypothalamus
Diencephalon
Midbrain
Oculomotor nerve (III)
Trochlear nerve (IV)
Pons
Brainstem
Medulla
oblongata
Trigeminal nerve (V)
Pons
Facial nerve (VII)
Middle cerebellar
peduncle
Abducens nerve (VI)
Vestibulocochlear
nerve (VIII)
Pyramid
Glossopharyngeal nerve (IX)
Hypoglossal nerve (XII)
Vagus nerve (X)
Ventral root of first
cervical nerve
Decussation of pyramids
Accessory nerve (XI)
Spinal cord
(a) Ventral view
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Figure 12.15a
Crus cerebri of
cerebral peduncles
(midbrain)
Thalamus
View (b)
Infundibulum
Pituitary gland
Superior colliculus
Inferior colliculus
Trochlear nerve (IV)
Trigeminal nerve (V)
Pons
Superior cerebellar peduncle
Middle cerebellar peduncle
Facial nerve (VII)
Abducens nerve (VI)
Glossopharyngeal nerve (IX)
Hypoglossal nerve (XII)
Inferior cerebellar peduncle
Vestibulocochlear nerve (VIII)
Olive
Thalamus
Vagus nerve (X)
Hypothalamus
Diencephalon
Midbrain
Accessory nerve (XI)
Pons
Brainstem
Medulla
oblongata
(b) Left lateral view
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Figure 12.15b
Midbrain Nuclei
• Nuclei that control cranial nerves III (oculomotor) and
IV (trochlear)
• Visual reflex centers
• Auditory relay centers
• Substantia nigra—functionally linked to basal nuclei
• Red nucleus—relay nuclei for some descending
motor pathways and part of reticular formation
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Tectum
Periaqueductal gray
matter
Oculomotor
nucleus (III)
Medial
lemniscus
Red
nucleus
Substantia
nigra
Fibers of
pyramidal tract
(a) Midbrain
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Dorsal
Superior
colliculus
Cerebral aqueduct
Reticular formation
Ventral
Crus cerebri of
cerebral peduncle
Figure 12.16a
Pons
• Forms part of the anterior wall of the fourth ventricle
• Connect higher brain centers and the spinal cord
• Relay impulses between the motor cortex and the
cerebellum
• Origin of cranial nerves V (trigeminal), VI (abducens),
and VII (facial)
• Nuclei that help maintain normal rhythm of breathing
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Fourth
ventricle
Superior cerebellar
peduncle
Trigeminal main
sensory nucleus
Trigeminal
motor nucleus
Middle
cerebellar
peduncle
Trigeminal
nerve (V)
Medial lemniscus
(b) Pons
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Reticular
formation
Pontine
nuclei
Fibers of
pyramidal
tract
Figure 12.16b
Medulla Oblongata
• Joins spinal cord at foramen magnum
• Contains a choroid plexus of the fourth
ventricle
• Relay sensory information from muscles and
joints to cerebellum
• Cranial nerves VIII, X, and XII are associated
with the medulla
• Mediates responses that maintain equilibrium
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Medulla Oblongata
• Autonomic reflex centers
• 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
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Medulla Oblongata
• Additional centers regulate
• Vomiting
• Hiccuping
• Swallowing
• Coughing
• Sneezing
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Reticular formation
Fourth ventricle
Choroid
Hypoglossal nucleus (XII)
plexus
Dorsal motor nucleus
of vagus (X)
Inferior cerebellar
peduncle
Lateral
nuclear
group
Medial
nuclear
group
Raphe
nucleus
Medial lemniscus
(c) Medulla oblongata
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Solitary
nucleus
Vestibular nuclear
complex (VIII)
Cochlear
nuclei (VIII)
Nucleus
ambiguus
Inferior olivary
nucleus
Pyramid
Figure 12.16c