THE CENTRAL NERVOUS
SYSTEM
Human Anatomy
Sonya Schuh-Huerta, Ph.D.
The Central Nervous System
• Central nervous system
– The brain & spinal cord
• Directional terms unique to the CNS
– Rostral  toward the nose
– Caudal  toward the tail
The Spinal Cord
• Functions of the spinal cord
– Spinal nerves attach to it
– Provides 2-way conduction pathway
– Major center for reflexes
• Location of the spinal cord
– Runs through the vertebral canal
– Extends from the foramen magnum to the
level of vertebra L1 or L2
The Spinal Cord
• Conus medullaris
– The inferior end of the spinal cord
• Filum terminale
– Long filament of connective tissue
– Attaches to the coccyx inferiorly
• Cervical & lumbar enlargements
– Where nerves for upper & lower limbs arise
• Cauda equina
– Collection of spinal nerve roots
The Spinal Cord
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
(a) 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.
The Spinal Cord
• Spinal cord segments
– Indicate the region of the spinal cord from
which spinal nerves emerge
– Designated by the spinal nerve that issues
from it
• T1 is the region where the first thoracic nerve
emerges
Spinal Cord Segments
Dorsal (posterior)
Ventral (anterior)
Spinal cord
segment C1
Spinal nerve C1
Spinal cord
segment T1
Spinous
process T1
Spinal cord
segment T5
Spinal nerve C8
Spinal nerve T1
Spinal nerve T5
Spinal cord
segment L1
Spinal nerve L1
Spinal nerve S1
The Spinal Cord
• 2 deep grooves run the length of the cord
– Dorsal median sulcus
– Ventral median fissure
– Remember seeing these in lab on the spinal
cord cross section?....
White Matter of the Spinal Cord
• White matter
– Outer region of the spinal cord
– Composed of myelinated & unmyelinated
axons
• Allow communication between spinal cord & brain
– Fibers classified by type
• Ascending fibers
• Descending fibers
• Commissural fibers
Gray Matter of the Spinal Cord
& Spinal Roots
• Shaped like butterfly!
– Gray commissure  contains the central
canal
• Dorsal horns
– Consist of interneurons
• Ventral & lateral horns
– Contain cell bodies of motor neurons
Anatomy of the Spinal Cord
Epidural space
(contains fat)
Subdural space
Pia mater
Arachnoid mater
Dura mater
Spinal
meninges
Subarachnoid
space
(contains CSF)
Dorsal
root
ganglion
Body of
vertebra
(a) Cross section of spinal cord and vertebra
Anatomy of the Spinal Cord
Dorsal median sulcus
Dorsal funiculus
White
matter
Ventral funiculus
Lateral funiculus
Gray commissure
Dorsal horn
Ventral horn
Lateral horn
Gray
matter
Dorsal root
ganglion
Spinal nerve
Dorsal root (fans
out into dorsal
rootlets)
Ventral root
(derived from several
ventral rootlets)
Central canal
Ventral median
fissure
Pia mater
Arachnoid mater
Spinal dura mater
(b) The spinal cord and its meningeal coverings
Organization of the Gray Matter
of the Spinal Cord
• Gray matter
– Divided according to somatic & visceral
regions
•
•
•
•
SS  somatic sensory
VS  visceral sensory
VM  visceral motor
SM  somatic motor
Gray Matter of the Spinal Cord &
Spinal Roots
Dorsal root
(sensory)
Dorsal horn (interneurons)
Dorsal root
ganglion
SS
Somatic sensory
neuron
Visceral
sensory neuron
Visceral
motor
neuron
Somatic motor
neuron
VS
VM
SM
Spinal nerve
Ventral root
(motor)
Ventral horn
(motor neurons)
Interneurons receiving input from somatic sensory neurons
Interneurons receiving input from visceral sensory neurons
Visceral motor (autonomic) neurons
Somatic motor neurons
Protection of the Spinal Cord
• Protected by vertebrae, meninges, & CSF
– Meninges
• Dura mater  a single layer surrounding spinal
cord
• Arachnoid mater  lies deep to the dura mater
• Pia mater  innermost layer
– Delicate layer of connective tissue
– Extends to the coccyx
– Denticulate ligaments  lateral extensions of pia mater
Cerebrospinal Fluid
• Fills the hollow cavities of brain & spinal cord
• Provides a liquid cushion for spinal cord &
brain
• Other functions:
– Nourishes brain & spinal cord
– Removes wastes
– Carries chemical signals between parts of CNS
Diagram of Lumbar Puncture
T12
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
The Brain
• Performs the most complex
neural functions:
–
–
–
–
–
Intelligence
Consciousness
Memory
Sensory-motor integration
Involved in innervation of the head
• Brain also controls:
– Heart rate, respiratory rate, blood pressure
– Autonomic nervous system (ANS)
– Endocrine system
Embryonic Development of the
Brain
• Brain arises from rostral part of the?...
neural tube
• 3 primary brain vesicles in 4-week-old
embryo
– Prosencephalon  the forebrain
– Mesencephalon  the midbrain
– Rhombencephalon  the hindbrain
Embryonic Development of the
Brain
• Structures of the adult brain
– Develop from secondary brain vesicles
• Telencephalon  the cerebral hemispheres
• Diencephalon  thalamus, hypothalamus, &
epithalamus
• Metencephalon  pons & cerebellum
• Myelencephalon  medulla oblongata
Embryonic Development of the
Brain
• Brain stem includes:
– The midbrain, pons, & medulla oblongata
• Ventricles
– Central cavity of the neural tube enlarges
Embryonic Development of the Brain
(a) Neural
tube
Anterior
(rostral)
(b) Primary brain vesicles
Week 4
Prosencephalon
(forebrain)
Mesencephalon
(midbrain)
Rhombencephalon
(hindbrain)
(c) Secondary brain vesicles
Week 5
(e) Adult neural
canal
regions
Telencephalon
Cerebrum: cerebral
hemispheres (cortex,
white matter, basal nuclei)
Lateral ventricles
Diencephalon
(thalamus, hypothalamus,
epithalamus), retina
Third ventricle
Diencephalon
Mesencephalon
Brain stem: midbrain
Metencephalon
Brain stem: pons
Cerebellum
Myelencephalon
Posterior
(caudal)
(d) Adult brain
structures
Cerebral
aqueduct
Fourth ventricle
Brain stem: medulla
oblongata
Spinal cord
Central canal
Embryonic Development of the
Brain
• Brain grows rapidly
• Changes occur in the relative position of its
parts
– Cerebral hemispheres envelop the diencephalon
& midbrain
– Wrinkling of the cerebral hemispheres
• Fit many more neurons within the limited space!
Brain Development from Week 5 - Birth
Anterior (rostral)
Metencephalon
Mesencephalon
Diencephalon
Telencephalon
Myelencephalon
Posterior (caudal)
Midbrain
Cervical
Cerebral
hemisphere
Flexures
Cerebellum
Pons
Medulla
oblongata
Spinal cord
(a) Week 5
Cerebral
hemisphere
(c) Week 26
Outline of
diencephalon
Spinal cord
Cerebrum
Midbrain
Cerebellum
Diencephalon
Pons
Cerebellum
Medulla
oblongata
Spinal cord
(b) Week 13
(d) Birth
Brain stem
Midbrain
Pons
Medulla
oblongata
Basic Parts & Organization of
the Brain
• Divided into 4 regions:
– Cerebral hemispheres
– Diencephalon
– Brain stem:
• Midbrain, pons, & medulla oblongata
– Cerebellum
Basic Parts & Organization of
the Brain
• Organization
– Centrally located gray matter
– Externally located white matter
– Additional layer of gray matter external to
white matter
• Due to groups of neurons migrating externally
– Cortex  outer layer of gray matter
• Formed from neuronal cell bodies
• Located in cerebrum & cerebellum
Basic Parts & Organization of the Brain
Cortex of
gray matter
Central cavity
Migratory
pattern of
neurons
Inner gray
matter
Outer white
matter
Cerebrum
Cerebellum
Region of cerebellum
Gray matter
Central
cavity
Inner gray
matter
Outer white
matter
Brain stem
Gray matter
Central
cavity
Outer white
matter
Spinal cord
Inner gray
matter
Ventricles of the Brain
•
•
•
•
•
Expansions of the brain’s central cavity
Filled with cerebrospinal fluid
Lined with ependymal cells
Continuous with each other
Continuous with the central canal of spinal
cord
Ventricles of the Brain
• Lateral ventricles  located in cerebral
hemispheres
– Horseshoe-shaped from bending of the
cerebral hemispheres
• Third ventricle  lies in diencephalon
– Connected with lateral ventricles by
interventricular foramen
Ventricles of the Brain
• Cerebral aqueduct  connects 3rd & 4th
ventricles
• Fourth ventricle  lies in hindbrain
– Connects to the central canal of spinal cord
Ventricles of the Brain
Lateral ventricle
Septum
pellucidum
Anterior horn
Posterior
horn
Interventricular
foramen
Inferior
horn
Third ventricle
Inferior
horn
Cerebral aqueduct
Lateral
aperture
(a) Anterior view
Fourth ventricle
Median
aperture
Central canal
Lateral
aperture
(b) Left lateral view
The Brain Stem
• Several general functions:
– Produces automatic behaviors necessary for
survival
– Passageway for all fiber tracts running
between cerebrum & spinal cord
– Heavily involved with the innervation of the
face & head
• 10 of the 12 pairs of cranial nerves attach to it
Ventral View of the Human Brain
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
The Brain Stem – The Medulla
Oblongata
• Cranial nerves VIII–XII attach to the
medulla
– VIII  vestibulocochlear
– IX  glossopharyngeal nerve
– X  vagus nerve
– XI  accessory nerve
– XII  hypoglossal nerve
The Brain Stem – Medulla Oblongata
& Cranial Nerves
View
(a)
Diencephalon
Thalamus
Hypothalamus
View
(c)
Optic chiasma
Optic nerve (II)
View
(b)
Optic tract
Mammillary body
Oculomotor nerve (III)
Crus cerebri of cerebral
peduncles (midbrain)
Trochlear nerve (IV)
Trigeminal nerve (V)
Pons
Facial nerve (VII)
Middle cerebellar
peduncle
Abducens nerve (VI)
Vestibulocochlear
nerve (VIII)
Glossopharyngeal nerve (IX)
Hypoglossal nerve (XII)
Pyramid
Vagus nerve (X)
Ventral root of first
cervical nerve
Accessory
nerve (XI)
Decussation of
pyramids
Spinal cord
(a) Ventral view
Thalamus
Hypothalamus
Midbrain
Pons
Medulla
oblongata
Diencephalon
Brainstem
The Brain Stem – The Medulla
Oblongata
• The core of the medulla contains
– Much of the reticular formation
• Nuclei influence autonomic functions
– Visceral centers of the reticular formation
include
•
•
•
•
Cardiac center
Vasomotor center
The medullary respiratory center
Centers for hiccupping, sneezing, swallowing, &
coughing
Brain Stem – The Medulla Oblongata
View
Diencephalon
Pineal gland
Anterior wall of
fourth ventricle
Choroid plexus
(fourth ventricle)
Dorsal median sulcus
Thalamus
(a)
Midbrain
Superior
colliculus Corpora
Inferior
quadrigemina
colliculus
View
(c)
View
(b)
Trochlear nerve (IV)
Superior cerebellar peduncle
Pons
Middle cerebellar peduncle
Medulla oblongata
Inferior cerebellar peduncle
Facial nerve (VII)
Vestibulocochlear nerve (VIII)
Glossopharyngeal nerve (IX)
Vagus nerve (X)
Accessory nerve (XI)
Thalamus
Dorsal root of
first cervical nerve
(c) Dorsal view
Hypothalamus
Diencephalon
Midbrain
Pons
Medulla
oblongata
Brainstem
The Brain Stem – The Pons
• A “bridge” between the midbrain & medulla
oblongata
• Pons contains the nuclei of cranial nerves:
– V  trigeminal nerve
– VI  abducens nerve
– VII  facial nerve
The Brain Stem – The Pons
• The pons contains:
– Motor tracts coming from the cerebral cortex
– Pontine nuclei
• Connect portions of the cerebral cortex &
cerebellum
• Send axons to cerebellum through the middle
cerebellar peduncles
The Brain Stem – The Pons
Superior cerebellar
peduncle
Fourth
ventricle
Trigeminal
main sensory
nucleus
Reticular
formation
Trigeminal
motor
nucleus
Middle
cerebellar
peduncle
Trigeminal
nerve (V)
Medial lemniscus
Pontine
nuclei
Fibers of
pyramidal tract
The Brain Stem – The Midbrain
• Lies between the diencephalon & the pons
• Cerebral aqueduct
– The central cavity of the midbrain
• Cerebral peduncles located on the ventral
surface of the brain
– Contain pyramidal (corticospinal) tracts
• Superior cerebellar peduncles
– Connect midbrain to the cerebellum; dorsal surface
The Brain Stem – The Midbrain
• Periaqueductal gray matter surrounds
the cerebral aqueduct
– Involved in 2 related functions
• Fight-or-flight reaction
• Mediates response to visceral pain
The Brain Stem – The Midbrain
• Corpora quadrigemina
– The largest nuclei
• Divided into the superior & inferior colliculi
– Superior colliculi  nuclei that act in visual
reflexes
– Inferior colliculi  nuclei that act in reflexive
response to sound
The Brain Stem – Dorsal View
Diencephalon
Pineal gland
Anterior wall of
fourth ventricle
Choroid plexus
(fourth ventricle)
Dorsal median sulcus
Thalamus
Midbrain
Superior
colliculus
Inferior
colliculus
View
(a)
Corpora
quadrigemina
of tectum
View
(c)
View
(b)
Trochlear nerve (IV)
Superior cerebellar peduncle
Pons
Middle cerebellar peduncle
Medulla oblongata
Inferior cerebellar peduncle
Facial nerve (VII)
Vestibulocochlear nerve (VIII)
Glossopharyngeal nerve (IX)
Vagus nerve (X)
Accessory nerve (XI)
Thalamus
Hypothalamus
Dorsal root of
first cervical nerve
Midbrain
Pons
Medulla
oblongata
(c) Dorsal view
Diencephalon
Brainstem
The Brain Stem – The Midbrain
• Imbedded in the white matter of the
midbrain
– 2 pigmented nuclei:
• Substantia nigra  neuronal cell bodies contain
melanin (degenerates in people with Parkinson’s)
– Functionally linked to the basal nuclei
• Red nucleus  lies deep to the substantia nigra
– Largest nucleus of the reticular formation
The Cerebellum
• Located dorsal to the pons & medulla
• Looks like “mini-brain” behind the real brain
– Smoothes & coordinates body movements
– Helps maintain equilibrium
– Involved in motor learning &
motor memories
The Cerebellum
• Consists of 2 cerebellar hemispheres
• Surface folded into ridges called folia
– Separated by fissures
• Hemispheres each subdivided into
– Anterior lobe
– Posterior lobe
– Flocculonodular lobe (tiny)
The Cerebellum
Anterior lobe
Cerebellar cortex
Arbor
vitae
Anterior lobe
Arbor vitae
Cerebellar
cortex
Folia
Cerebellar
peduncles
Superior
Middle
Inferior
Medulla
oblongata
Pons
Fourth
ventricle
Medulla
oblongata
(a) Midsagittal section
Posterior
lobe
Flocculonodular
lobe
Choroid
plexus of
fourth
ventricle
Posterior
lobe
Flocculonodular lobe
Choroid plexus
(b) Illustration of parasagittal section
The Cerebellum
• Composed of 3 regions:
– Cortex  gray matter
– Arbor vitae
• Internal white matter
– Deep cerebellar nuclei  deeply situated gray
matter
The Cerebellum
• To coordinate body movements, the
cerebellar cortex receives 3 types of
information:
– On equilibrium
– On current movements of the limbs, neck, &
trunk
– From the cerebral cortex
The Cerebellum
•
Coordinating movement
1. The Cerebellum receives info on movement
from the motor cortex of the cerebrum
2. The cerebellum compares intended
movement with body position
3. The cerebellum sends instructions back to
the cerebral cortex to continuously adjust &
fine tune motor commands
The Cerebellum
• Higher cognitive functions of the
cerebellum
– Learning a new motor skill
– Participates in cognition
• Language, problem-solving, task planning
The Cerebellum – Cerebellar
Peduncles
• Thick tracts connecting the cerebellum to
the brain stem are:
– Superior cerebellar peduncles
– Middle cerebellar peduncles
– Inferior cerebellar peduncles
• Fibers to & from the cerebellum are
ipsilateral
The Cerebellum
Anterior lobe
Cerebellar cortex
Arbor
vitae
Anterior lobe
Arbor vitae
Cerebellar
cortex
Folia
Cerebellar
peduncles
Superior
Middle
Inferior
Medulla
oblongata
Pons
Fourth
ventricle
Medulla
oblongata
(a) Midsagittal section
Posterior
lobe
Flocculonodular
lobe
Choroid
plexus of
fourth
ventricle
Posterior
lobe
Flocculonodular lobe
Choroid plexus
(b) Illustration of parasagittal section
The Diencephalon
• Forms the center core of the forebrain
• Surrounded by the cerebral hemispheres
• Composed of 3 paired structures:
– Thalamus
– Hypothalamus
– Epithalamus
• Border the 3rd ventricle
• Primarily composed of gray matter
The Diencephalon & Brainstem
Cerebral hemisphere
Septum pellucidum
Interthalamic
adhesion
(massa intermedia)
Interventricular
foramen
Anterior
commissure
Hypothalamus
Optic chiasma
Pituitary gland
Mammillary body
Pons
Medulla oblongata
Spinal cord
Corpus callosum
Fornix
Choroid plexus
Thalamus
(encloses third ventricle)
Posterior commissure
Pineal gland
(part of epithalamus)
Corpora
quadrigemina
Cerebral
aqueduct
Midbrain
Arbor vitae (of cerebellum)
Fourth ventricle
Choroid plexus
Cerebellum
The Diencephalon – The Thalamus
• Makes up 80% of diencephalon
• Contains approximately a dozen major
nuclei
– Act as relay stations for incoming sensory
messages
– Every part of brain communicating with
cerebral cortex relays signals through
thalamic nuclei!!!
• Send axons to regions of the cerebral
cortex
The Diencephalon – The Thalamus
• Afferent impulses converge on the
thalamus
– Synapse in at least one of its nuclei
• Is the “gateway” to the cerebral cortex
• Nuclei organize & amplify or tone down
signals
The Thalamus (Nuclei)
Dorsal nuclei
Medial Lateral Lateral
dorsal posterior
Anterior
nuclear
group
Pulvinar
Medial
geniculate
body
Reticular
nucleus
Ventral
Ventral Ventral posteroanterior lateral lateral
Ventral nuclei
(a) The main thalamic nuclei. (The reticular
nuclei that “cap” the thalamus laterally are
depicted as curving translucent structures.)
Lateral
geniculate
body
The Diencephalon – The
Hypothalamus
• Lies between the optic chiasm & the
mammillary bodies
• Pituitary gland projects inferiorly
• Contains approximately a dozen nuclei
• Main visceral control center of the body
– The master gland’s master!!
The Diencephalon – The
Hypothalamus
• Functions include:
– Control of the ANS
– Control of emotional responses
– Regulation of body temperature
– Regulation of hunger & thirst sensations
– Control of behavior
– Regulation of sleep-wake cycles
– Control of the endocrine & reproductive sys
– Formation of memory
Nuclei of the Hypothalamus
Paraventricular
nucleus
Anterior
commissure
Preoptic
nucleus
Anterior
hypothalamic
nucleus
Supraoptic
nucleus
Suprachiasmatic
nucleus
Optic
chiasma
Infundibulum
(stalk of the
pituitary gland)
Fornix
Dorsomedial
nucleus
Arcuate
nucleus
Posterior
hypothalamic
nucleus
Lateral
hypothalamic
area
Ventromedial
nucleus
Mammillary
body
Pituitary
gland
The Diencephalon – The
Epithalamus
• Forms part of “roof” (top) of the 3rd ventricle
• Consists of a tiny group of nuclei
• Includes the pineal gland (pineal body)
– Secretes the hormone melatonin
– Under influence of the hypothalamus
– Aids in control of circadian rhythms
The Cerebral Hemispheres
• Account for ~83% of brain mass!!!
– Fissures  deep grooves, which separate
major regions of brain
• Transverse fissure  separates cerebrum &
cerebellum
• Longitudinal fissure  separates cerebral
hemispheres
transverse
fissure
The Cerebral Hemispheres
• Sulci
– Grooves on the surface of the cerebral
hemispheres
• Gyri
– Twisted ridges between sulci
• Prominent gyri & sulci are similar in all
people
The Cerebral Hemispheres
• Deeper sulci divide cerebrum into lobes
• Lobes are named for the skull bones
overlying them
• Central sulcus separates frontal & parietal
lobes
– Bordered by 2 gyri:
• Precentral gyrus
• Postcentral gyrus
The Cerebral Hemispheres
Precentral
gyrus
Frontal lobe
Central
sulcus
Postcentral
gyrus
Parietal lobe
Parieto-occipital sulcus
(on medial surface
of hemisphere)
Lateral fissure
Occipital lobe
Temporal lobe
Transverse
cerebral fissure
Cerebellum
Pons
Medulla oblongata
Spinal cord
Fissure
(a deep
sulcus)
Gyrus
Cortex (gray matter)
Sulcus
White matter
(c) Lobes and sulci of the cerebrum
The Cerebral Hemispheres
• Parieto-occipital sulcus
– Separates the occipital from the parietal lobe
• Lateral fissure/sulcus
– Separates temporal lobe from parietal &
frontal lobes
• Insula  deep within the lateral sulcus
The Cerebral Hemispheres
Frontal lobe
Gyri of insula
Temporal lobe
(pulled down)
(d) Location of the insula lobe
Central sulcus
The Cerebral Hemispheres
• Frontal section through forebrain
– Cerebral cortex
– Cerebral white matter
– Deep gray matter of the cerebrum (basal
ganglia)
The Cerebral Cortex
• Home of our conscious mind
• Enables us to:
– Be aware of ourselves & our sensations
– Initiate & control voluntary movements
– Communicate,
remember, &
understand
– Process info on both
conscious &
unconscious levels
The Human Mind
• To prove to you that your brain is
constantly processing information, that you
are not always aware of, and also
selecting your attention to specific things, I
have a set of activities….
The McGurk Effect
(McGurk & MacDonald, 1976)
Attention Experiment
(Neisser & Becklen, 1975)
Stroop Effect
(Stroop, 1935)
Visual illusions – The Power &
Stubborness of the Mind
The Human Mind
• All of these illustrate how powerful the
unconscious processing of our mind is – based
on experience & memory our minds create
biases that actually shape how we view the
world around us, other people, & other things.
They shape our “reality.” These unconscious
biases are also at the root of prejudice &
discrimination.
• But we can be aware of this fact – & truly keep
an open mind!
The Cerebral Cortex
• Is composed of gray matter
– Neuronal cell bodies, dendrites, & short axons
• Folds in cortex  triples its size!!!
• Approximately 40% of brain’s mass
• “Brodmann areas”
– 47 structurally distinct areas
The Cerebral Cortex
• Functional regions
– Traditionally studied in brain-injured people &
animals
• Many new discoveries  by PET & fMRI
– Regions of the cerebral cortex
• Perform distinct motor & sensory functions
– Memory & language spread over wide area
The Cerebral Cortex
• 3 general kinds of functional areas
– Sensory areas
– Association areas
– Motor areas
The Cerebral Cortex
• There is a sensory area for each of the
major senses
– A “primary sensory cortex”
• Each primary sensory cortex
– Has an association area that processes
sensory information
• Sensory association areas
Functional & Structural Areas of Cerebral
Cortex
Motor areas
Central sulcus
Primary motor cortex
Premotor cortex
Frontal
eye field
Sensory areas & related
association areas
Primary somatosensory
cortex
Somatosensory
association cortex
Broca’s area
(outlined by dashes)
Gustatory cortex
(in insula)
Prefrontal cortex
Working memory
for spatial tasks
Somatic
sensation
Taste
Wernicke’s area
(recognizing & understanding
speech)
Executive area for
task management
Primary visual
cortex
Working memory for
object-recall tasks
Solving complex,
multitask problems
Visual
association
area
Auditory
association area
Primary
auditory cortex
Primary motor cortex
Motor association cortex
Primary sensory cortex
Sensory association cortex
Multimodal association cortex
(a) Lateral view, left cerebral hemisphere
Vision
Hearing
Sensory Areas
• Cortical areas involved in conscious
awareness of sensation
– Located in:
• Parietal lobes
• Temporal lobes
• Occipital lobes
• Distinct regions of each lobe interpret each
of the major senses
Sensory Areas – Primary
Somatosensory Cortex
• Located along the postcentral gyrus
• Involved with conscious awareness of general
somatic senses
• Spatial discrimination
– Precisely locates a stimulus
– Certain regions are more adept at distinguishing
precise stimuli
Sensory Areas – Primary
Somatosensory Cortex
• Projection is contralateral
– Cerebral hemispheres:
• Receive sensory input from the opposite side of
the body!!!
• Sensory homunculus – somatotopy (map)
– A body map of the sensory cortex
Sensory Areas – Primary Somatosensory
Cortex
Posterior
Sensory
Anterior
Hip
Trunk
Motor map in
precentral gyrus
Motor
Foot
Toes
Genitals
Jaw
Tongue
Swallowing
Primary
motor
cortex
(precentral
gyrus)
Primary
somatosensory
cortex
(postcentral
gyrus)
Sensory map in
postcentral gyrus
Sensory Areas – Somatosensory
Association Cortex
• Lies posterior to the primary somatosensory
cortex
• Integrates different sensory inputs
– Touch
– Pressure
• Draws upon stored memories of past sensory
experiences
– You are able to recognize keys or coins in your
pocket without looking at them
Sensory Areas – Visual Areas
• Primary visual cortex
– Location is deep within the calcarine sulcus
• On medial part of the occipital lobe
– Largest of all sensory areas
• Receives visual information that originates on the
retina
• Exhibits contralateral function
– First of a series of areas processing visual
input
Sensory Areas – Visual Areas
• Visual association areas
– Approximately 30 cortical areas have been
identified
– Visual information proceeds in two streams
The Ventral & Dorsal Streams
Central sulcus
Post central gyrus
Parietal lobe
Dorsal stream
(“where” pathway)
Visual
association
area
Primary
visual
cortex
Ventral stream
(“what” pathway)
Frontal lobe
Temporal lobe
Sensory Areas – Auditory Areas
• Primary auditory cortex
– Function
• Conscious awareness of sound
• Sound waves excite receptors in the inner ear
– Impulses transmitted to primary auditory cortex
– Location
• Superior edge of the temporal lobe
Sensory Areas – Auditory Pathways
Central sulcus
Posterolateral
(“where” pathway)
Parietal lobe
Prefrontal
cortex
Primary
auditory
cortex
Anterolateral
(“what” pathway)
Temporal lobe
Auditory
association
area
Sensory Areas – Vestibular
Cortex
• Responsible for
– Conscious awareness of sense of balance
• Located in the posterior part of the insula
– Deep to the lateral sulcus
Sensory Areas – Gustatory Cortex
• Function
– Involved in the conscious awareness of taste
stimuli
• Location
– On the “roof” of the lateral sulcus – insula
Sensory Areas – Olfactory Cortex
• Lies on the medial aspect of the cerebrum
– Located in the piriform lobe
• Olfactory nerves transmit impulses to the
olfactory cortex
– Provides conscious awareness of smells
Sensory Areas – Olfactory Cortex
• Part of the rhinencephalon  “nose
brain”
• Includes:
– The piriform lobe, olfactory tracts, &
olfactory bulbs
• Connects the brain to the limbic system
– Explains why smells trigger emotions
• Involved with consciously identifying &
recalling specific smells
Visceral Sensory Areas
• Location
– Within the lateral sulcus
– On the insula lobe
• Receives general sensory input
– Pain
– Pressure
– Hunger
Multimodal Association Areas
• Large areas of the cerebral cortex
– Receive sensory input from
• Multiple sensory modalities
• Sensory association areas
– Make associations between different kinds of
sensory information
Posterior Association Area
A type of Multimodal Assoc Area
• Multiple language areas in left cerebral
cortex
– Wernicke’s area functions in:
• Speech comprehension
• Coordination of auditory & visual aspects of
language
• Initiation of word articulation
• Recognition of sound sequences
Functional Neuroimaging (fMRI)
Central sulcus
Longitudinal
fissure
Left frontal
lobe
Left temporal
lobe
Areas active
in speech & hearing
Anterior Association Areas
• Prefrontal Cortex
• More complex functions
include all aspects of
– Thinking, perceiving,
intentionally remembering
– Processing abstract ideas, reasoning,
judgment
– Impulse control, mental flexibility, social skills
– Humor, empathy, conscience
– Has 3 working memory areas
Limbic Association Areas
• Located on medial side of frontal lobe
– Involved with memory & emotions
– Integrates sensory & motor behaviors
– Aids in the formation of memory
– Processes emotions
Motor Areas
• Cortical areas controlling motor function
– Premotor cortex
– Primary motor cortex
– Frontal eye field
– Broca’s area
• All localized in posterior frontal lobe
• Motor cortex
– Plans & initiates voluntary motor functions
Motor Areas – Primary Motor
Cortex
• Controls motor functions
– Primary motor cortex (somatic motor area)
– Located in precentral gyrus
• Pyramidal cells
– Large neurons of primary motor cortex
Motor Areas – Primary Motor
Cortex
• Corticospinal tracts descend through
brain stem & spinal cord
– Axons signal motor neurons to control skilled
movements
– Contralateral
• Pyramidal axons cross over to opposite side of
brain
Motor Areas
• Specific pyramidal cells control specific
areas of the body
– Face & hand muscles are controlled by many
pyramidal cells
• Somatotopy
– Body is represented spatially in the primary
motor cortex (just like somatosensory cortex)
– Humunculus of motor cortex
Motor Areas
Posterior
Motor map in
precentral gyrus
Motor
Anterior
Foot
Toes
Genitals
Jaw
Tongue
Swallowing
Primary
motor
cortex
(precentral
gyrus)
Motor Areas – Broca’s Area
• Located in left cerebral hemisphere
– Manages speech production
– Connected to language comprehension areas
in posterior association area
• A corresponding region in the right
cerebral hemisphere controls emotional
overtones to spoken words
Lateralization of Cortical
Functioning
• The 2 hemispheres control opposite sides
of the body
– Contralateral = opposite side
• Hemispheres are specialized for different
cognitive functions
Lateralization of Cortical
Functioning
• Left cerebral hemisphere  control over:
– Language abilities, math, logic
• Right cerebral hemisphere  involved
with:
– Visual-spatial skills
– Reading facial expressions
– Intuition, emotion, artistic, & musical skills
– Where the terms “left-” & “right-brained” come from
Cerebral White Matter
• Types of tracts
– Commissures  composed of commissural
fibers
• Allows communication between cerebral
hemispheres
• Corpus callosum  the largest commissure!
– Association fibers
• Connect different parts of the same hemisphere
– Parts of Wernike’s & Broca’s areas are connected by
association fibers
Cerebral White Matter
Longitudinal fissure
Lateral
ventricle
Basal ganglia
Caudate
Putamen
Globus
pallidus
Thalamus
Third
ventricle
Pons
Medulla oblongata
(a) Frontal section
Superior
Association fibers
Commissural fibers
(corpus callosum)
Corona
radiata
Fornix
Internal
capsule
Gray matter
White matter
Projection
fibers
Decussation
of pyramids
Deep Gray Matter of Cerebrum
• Consists of:
– Basal ganglia
• Involved in motor control
• Dysfunction in Parkinson’s
– Basal forebrain nuclei
• Associated with memory
• Amygdala
– Located in cerebrum, but is considered
part of the of limbic system!
Basal Ganglia
• A group of nuclei deep within the cerebral
white matter
• Formed from
– Caudate nucleus
– Putamen
– Globus pallidus
Basal Ganglia
• Complex neural calculators
– Cooperate with the cerebral cortex in controlling
movement
• Receive input from many cortical areas
• Substantia nigra also influences basal
ganglia (this degenerates in Parkinson’s Disease)
Basal Ganglia
Striatum
Caudate
nucleus
Thalamus
Putamen
Tail of
caudate
nucleus
Substantia nigra
of midbrain
Basal Ganglia
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
Posterior horn
of lateral ventricle
(b)
Posterior
Basal Ganglia
• Evidence shows that they:
– Start, stop, & regulate intensity of voluntary
movements
– Select appropriate muscles for a task & inhibit
others
– In some way estimate the passage of time
Structures & Functions of the Cerebrum
Structures & Functions of the Cerebrum
Structures & Functions of the Cerebrum
Functional Brain Systems
• Networks of neurons functioning together
– Limbic system
• Spread widely in the forebrain
– The reticular formation
• Spans the brain stem
Functional Brain Systems –
The Limbic System
• Location
– Medial aspect of cerebral hemispheres
– Also within the diencephalon
• Composed of:
– Septal nuclei, cingulate gyrus, hippocampus,
olfactory bulb & tracts
– Part of the amygdala
• The fornix & other tracts link the limbic
system together
Functional Brain Systems –
The Limbic System
Functional Brain Systems – The
Limbic System
• The “emotional brain”
– Cingulate gyrus
• Allows us to shift between thoughts
• Interprets pain as unpleasant
• Hippocampal formation (memory)
– Hippocampus & the parahippocampal gyrus
Functional Brain Systems – The Limbic
System
Septum pellucidum
Diencephalic structures
of the limbic system
Anterior thalamic
nuclei (flanking
3rd ventricle)
Corpus callosum
Fiber tracts connecting
limbic system structures
Fornix
Anterior commissure
Cerebral structures
of the limbic system
Hypothalamus
Mammillary body
Cingulate gyrus
Septal nuclei
Amygdala
Hippocampus
Dentate gyrus
Parahippocampal
gyrus
Olfactory bulb
Protection of the Brain
• The brain is protected from injury by
– The skull
– Meninges
– Cerebrospinal fluid
– Blood-brain barrier
Protection of the Brain –
Meninges
• Functions of meninges
– Cover & protect the CNS
– Enclose & protect the vessels that supply the
CNS
– Contain the CSF
• Between pia & arachnoid maters
The Meninges
Skin of scalp
Periosteum
Bone of skull
Superior sagittal
sinus
Subdural space
Subarachnoid
space
Periosteal Dura
mater
Meningeal
Arachnoid mater
Pia mater
Arachnoid villus
Blood vessel
Falx cerebri
(in longitudinal
fissure only)
Protection of the Brain –
Cerebrospinal Fluid (CSF)
• Formed in choroid plexuses in the brain
ventricles
– Choroid plexus is
• Located in all 4 ventricles
• Composed of ependymal cells & capillaries
• Arises from blood
– 500 ml/day
Protection of the Brain – BloodBrain Barrier
• Prevents most blood-borne toxins from
entering the brain
– Impermeable capillaries!
• Not an absolute barrier
– Nutrients such as glucose & oxygen pass
through
– Allows alcohol, nicotine, & anesthetics
through
Disorders of the CNS
• Spinal cord damage
– Paralysis  loss of motor function
– Parasthesia  loss of sensation
– Paraplegia  injury to the spinal cord is
between T1 and L2
• Paralysis of the lower limbs
– Quadriplegia  injury to
spinal cord in cervical region
• Paralysis of all 4 limbs!
Disorders of the CNS
• Brain disorders
• Schizophrenia
• Autism (Austism spectrum disorder)
Disorders of the CNS
• Brain dysfunction
– Degenerative brain diseases
• Cerebrovascular accident (= stroke)
– Blockage or interruption of blood flow to a brain region
• Alzheimer’s disease
– Progressive degenerative disease leading to dementia &
memory loss (characterized by abnormal accumulations
of proteins in the brain)
• Parkinson’s Disease
– Progressive degenerative disease leading to impaired
motor skills, speech & other functions (loss of normal
functioning of basal ganglia & substantia nigra – where
are these?)
Disorders of the CNS
• Congenital malformations
– Hydrocephalus – “water on the brain”
– Neural tube defects
• Anencephaly  cerebrum & cerebellum absent
• Spina bifida  incomplete closing of neural tube
during development (some vertebrae not surrounding
spinal cord - exposed)
– Cerebral palsy  voluntary muscles are
poorly controlled
• Results from damage to motor cortex of brain
• Common in multiple-baby pregnancies!
Hydrocephalus
Baby with hydrocephalus
AJ Rizzo, 6 years old
Born with hydrocephalus
(Now doing very good!)
Postnatal Changes in the Brain
• Brain structures complete development at
different times
– Critical periods in learning
• Language
– Some development occurs into early 20s!
– Decline with age attributed to changes in:
• Neural circuitry
• Amount of neurotransmitters being released
Remember – in general, no regeneration
of neurons throughout life! Exercise your
brain! “Use it or lose it.”
Questions…?
What’s Next?
Lab: Brain, & other models
Mon Lecture: CNS / PNS & ANS
Mon Lab: Sheep Brain Dissection!
Additional images