The document provides a comprehensive overview of the central nervous system (CNS), detailing its structure and organization, including the brain regions, directional terms, and various types of gray and white matter. It explains the functions of the cerebral cortex, motor and sensory areas, as well as association areas and their roles in processing information. Additionally, it touches on the diencephalon's anatomy and functions, highlighting key components such as the thalamus and hypothalamus.

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Central Nervous System
• Brain
• Spinal Cord

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Directional Terms of the Central Nervous System
• Directional terms unique to the CNS
• Rostral – toward the nose (anterior)
• Caudal – toward the tail (posterior)
• Dorsal – superior
• Ventral - inferior

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Four Main Regions of the Brain
• Cerebral hemispheres
• Diencephalon
• Brain stem:
• midbrain
• Pons
• medulla
• Cerebellum

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Basic Organization of Gray and White Matter in the CNS
Figure 13.5

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Ventricles of the Brain
• Filled with cerebrospinal fluid
• Lined with ependymal cells
• Continuous with each other
• Continuous with the central canal of the spinal
cord

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Lateral Ventricles
Figure 13.6a, b
Lateral ventricles – located in cerebral hemispheres
Horseshoe-shaped

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Third Ventricle
Figure 13.6a, b
Third ventricle – lies in diencephalon
Connected with lateral ventricles by interventricular foramen

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Fourth Ventricle
Figure 13.6a, b
Fourth ventricle – lies in hindbrain
Connects to the central canal of the spinal cord

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Ventricles of the Brain
Figure 13.6a, b
•Cerebral aqueduct – connects 3rd and 4th ventricles

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The Cerebral Hemispheres: Fissures
• Fissures – deep grooves – separate major regions of
the brain
• Transverse fissure – separates cerebrum and
cerebellum
• Longitudinal fissure – separates cerebral
hemispheres

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The Cerebral Hemispheres: Sulci and Gyri
• Sulci – grooves on the surface of the cerebral
hemispheres
• Gyri – twisted ridges between sulci
• Prominent gyri and sulci are similar in all people

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The Cerebral Lobes
• Deeper sulci divide cerebrum into lobes
• Lobes are named for the skull bones overlying
them

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Frontal Lobe
• Anterior/rostral to central sulcus
• Superior to transverse/lateral fissure

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Parietal Lobe
• Posterior to central sulcus
• Superior to lateral fissure
• Anterior to parieto-occipital sulcus

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Temporal Lobe
• Inferior to lateral fissure (sulcus)
• Anterior to occipital lobe

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Occipital Lobe
• Posterior & inferior to parieto-occipital sulcus
• Posterior to temporal lobe

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Top View of the Cerebral Hemispheres
Figure 13.7b, c

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Insula

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Gray and White Matter in the CNS
• Frontal section through forebrain
• Cerebral cortex
• Cerebral white matter
• Deep gray matter of the cerebrum (basal ganglia)

20. Usual pattern of gray/white in CNS
• White exterior to gray
• Gray surrounds hollow
central cavity
• Two regions with additional
gray called “cortex”
• Cerebrum: “cerebral cortex”
• Cerebellum: “cerebellar cortex”
_________________
____________________________
_____________________________

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Frontal Section of Forebrain
Figure 13.8

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The Cerebral Cortex
• Composed of gray matter 2 – 4 mm thick
• Neuronal cell bodies, dendrites, and short axons
• Folds in cortex – triples its size
• Approximately 40% of brain’s mass
• Brodmann areas – 52 structurally distinct areas
(we will not cover these by number, only name)

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Functional and Structural Areas of the Cerebral Cortex
Figure 13.11a

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Functional and Structural Areas of the Cerebral Cortex
Figure 13.11b

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The Cerebral Cortex
• Three kinds of functional areas
• Motor areas
• Sensory areas
• Association areas

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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

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Motor Areas – Corticospinal Tract (Pyramidal Tract)
• Corticospinal tracts descend through brainstem
and spinal cord
• Axons signal motor neurons to control fine skilled
movements
• Contralateral – pyramidal axons cross over to
opposite side of the brain

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Corticospinal Tract

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Primary Motor Cortex Organization
• Specific pyramidal cells control specific areas of
the body
• Face and hand muscles – controlled by many
pyramidal cells for fine control
• Motor homunculus – body map of the motor
cortex
• Somatotopy – body is represented spatially in
many parts of the CNS

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Motor Homunculus
Figure 13.10

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Motor Areas – Premotor Cortex
• Located anterior to the precentral
gyrus
• Controls more complex movements
• Involved in the planning of
movements

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Motor Areas – Frontal Eye Field
• Lies anterior to the premotor cortex
• Controls voluntary movement of the eyes
• Especially when moving eyes to follow a moving
target

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Motor Areas – Broca’s Area
• Located in left cerebral hemisphere
• Manages speech production
• Corresponding region in the right cerebral
hemisphere
• Controls emotional overtones to spoken words

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Sensory Areas
• Cortical areas involved in conscious awareness of
sensation
• Distinct area for each of the major senses

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Sensory Areas – Primary Somatosensory Cortex
• Located along the postcentral
gyrus or parietal lobe
• Involved with conscious
awareness of general somatic
senses

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Sensory Areas – Primary Somatosensory Cortex
• Projection is contralateral
• Cerebral hemispheres
• Receive sensory input from the opposite side of the
body
• Sensory homunculus – a body map of the sensory
cortex

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Sensory Areas – Sensory Homunculus
Figure 13.10

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Sensory Areas – Somatosensory Association Area
• Lies posterior to the primary
somatosensory cortex
• Integrates different sensory
inputs
• Touch, pressure, and others
• Draws upon stored memories
of past sensory experiences

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Sensory Areas – Primary Visual Cortex
• Primary visual cortex
• Located deep within the
calcarine sulcus
• On the posterior and medial
part of the occipital lobe
• Receives visual information
that originates on the retina
• First of a series of areas that
interprets visual input

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Sensory Areas – Visual Association Areas
• Visual association area
• Surrounds the primary visual
area
• Continues the processing of
visual information
• Complex visual processing
extends into:
• Temporal and parietal lobes

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Visual Association Areas continued
• Approximately 30 cortical areas have been
identified
• Visual information proceeds in two streams

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Sensory Areas – Ventral and Dorsal Streams
• Ventral stream – into inferior part of the temporal
lobe
• Responsible for recognizing objects, words, and
faces = “What”
• Dorsal stream – extends to the postcentral gyrus
• Perceives spatial relationships = “Where”

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Sensory Areas – Primary Auditory Cortex
• Primary auditory cortex
• Function – conscious awareness of sound
• Location – superior edge of the temporal lobe

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Sensory Areas – Auditory Association Areas
• Auditory association area
• Lies posterior to the
primary auditory cortex
• Permits evaluation of
different sounds

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Sensory Areas – Gustatory Cortex
• Involved in the conscious
awareness of taste stimuli
• Located on the “roof” of the
lateral sulcus

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Sensory Areas – Vestibular Cortex
• Located in the posterior
part of the insula
• Deep to the lateral
sulcus

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Sensory Areas – Olfactory Cortex
• Lies on the medial aspect
of the cerebrum
• Located in a region called
the piriform lobe
• Olfactory nerves transmit
impulses to the olfactory
cortex
• Provides conscious
awareness of smells

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Sensory Areas – Olfactory Cortex
• Connects the brain to the limbic system
• Explains why smells trigger emotions
• Orbitofrontal cortex
• Involved with consciously identifying and recalling
specific smells

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Association Areas
• Make associations between different types of
sensory information
• Associate new sensory input with memories of
past experiences
• New name for association areas – higher order
processing areas

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Association Areas – Prefrontal Cortex
• Large region of the frontal lobe anterior to motor
areas

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Association Areas – Prefrontal Cortex
• Performs cognitive functions
• All aspects of thinking and perceiving
• Remembering and recalling information
• Problem solving
• Also related to mood
• Has close links to the limbic part of the forebrain

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Association Areas – General Interpretation Area
• Function is currently under
investigation
• Located at the interface of:
• The visual, auditory, and
somatosensory association
areas
• Newer studies show most of
this region is involved in the
visual processing of spatial
relationships

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Association Areas – Language Area
• Five parts have been identified
• Broca’s area – speech production
• Wernicke’s area – speech comprehension
• Lateral prefrontal cortex – conceptual analysis of spoken words
• Most of the lateral and inferior temporal lobe
• Coordination of auditory and visual aspects of language
• Parts of the insula
• Initiation of word articulation
• Recognition of rhymes and sound sequences

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Language Areas of the Cortex

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Association Areas – Insula
• Functions of its cortex – not well understood
• Some parts function in language and the sense of
balance
• Other parts – visceral function
• Conscious perception of:
• Upset stomach
• Full bladder
• Some aspects of the sense of smell

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Lateralization of Cortical Functioning
• The two hemispheres control opposite sides of the
body
• Hemispheres are specialized for different
cognitive functions

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Lateralization of Cortical Functioning
• Left cerebral hemisphere – more control over:
• Language abilities, math, and logic
• Right cerebral hemisphere – more involved with:
• Visual-spatial skills
• Reading facial expressions
• Intuition, emotion, artistic and musical skills

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Cerebral White Matter
• Different areas of the cerebral cortex
communicate:
• With each other
• With the brainstem and spinal cord
• Fibers are usually myelinated and bundled into
tracts

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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

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Corpus Callosum

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Cerebral White Matter
Figure 13.13a

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Cerebral White Matter
• Types of tracts (continued)
• Projection fibers – run vertically
• Descend from the cerebral cortex
• Ascend to the cortex from lower regions

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Cerebral White Matter
Figure 13.13b

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White Matter: MRI

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White Matter: Horizontal Section

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Deep Gray Matter of the Cerebrum
• Consists of:
• Basal forebrain nuclei – associated with memory
• Basal ganglia – invovled in motor control
• Claustrum – a nucleus of unknown function
• Amygdala – located in cerebrum but is considered
part of the of the limbic system

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Basal Ganglia
• A group of nuclei deep within the cerebral white
matter
• Caudate nucleus – arches over the thalamus
• Lentiform nucleus – “lens shaped”
• Together, these nuclei are called the corpus
striatum

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Basal Ganglia
• Lentiform nucleus
• Divided into two parts
• Globus pallidus
• Putamen

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Basal Ganglia
Figure 13.13b

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Basal Ganglia
• Corpus striatum – combination of the lentiform
and caudate nuclei

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Basal Ganglia
• Cooperate with the cerebral cortex in controlling
movements
• Receive input from many cortical areas
• Evidence shows that they:
• Start, stop, and regulate intensity of voluntary
movements
• In some way estimate the passage of time

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The Diencephalon
• Forms the center core of the forebrain
• Surrounded by the cerebral hemispheres
• Composed of three paired structures:
• Thalamus, hypothalamus, and epithalamus
• Border the third ventricle
• Primarily composed of gray matter

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The Diencephalon and Brainstem: Sagittal Section
Figure 13.15

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The Diencephalon: Lateral View
Figure 13.16a

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The Diencephalon: Coronal Section
Figure 13.16b

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The Diencephalon – The Thalamus
• Makes up 80% of the diencephalon
• Contains approximately a dozen major nuclei
• Send axons to regions of the cerebral cortex
• Nuclei act as relay stations for incoming sensory
messages

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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 and amplify or tone down signals

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The Thalamus
Figure 13.17a

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The Diencephalon – The Hypothalamus
• Lies between the optic chiasm and the mammillary
bodies
• Pituitary gland projects inferiorly
• Anterior pituitary
• Posterior pituitary
• Contains approximately a dozen nuclei
• Main visceral control center of the body

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The Diencephalon – The Hypothalamus
• Functions include the following:
• Control of the autonomic nervous system
• Control of emotional responses
• Regulation of body temperature
• Regulation of hunger and thirst sensations
• Control of behavior
• Regulation of sleep-wake cycles
• Neural communication with endocrine system
• Formation of memory

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Nuclei of the Hypothalamus
Figure 13.18

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The Diencephalon – The Epithalamus
• Forms part of the “roof”
of the third ventricle
• Consists of a tiny group of
nuclei
• Includes the pineal gland
(pineal body)
• Secretes the hormone
melatonin
• Under influence of the
hypothalamus

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The Brain Stem
• Includes the midbrain, pons, and medulla
oblongata

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Ventral View of the Brain – Brain Stem and Diencephalon
Figure 13.19

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The Brain Stem: General Functions
• Produces automatic behaviors necessary for
survival
• Passageway for all fiber tracts running between the
cerebrum and spinal cord
• Heavily involved with the innervation of the face
and head
• 10 of the 12 pairs of cranial nerves attach to it

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The Brain Stem – The Midbrain
• Lies between the diencephalon
and the pons
• Central cavity – the cerebral
aqueduct
• Cerebral peduncles located on
the ventral surface of the brain
• Contain pyramidal
(corticospinal) tracts
• Superior cerebellar peduncles
• Connect midbrain to the
cerebellum

88. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.21a
The Brain Stem – The Midbrain
• Periaqueductal gray
matter surrounds the
cerebral aqueduct
• Involved in two
related functions
• Fright-and-flight
reaction
• Mediates response
to visceral pain

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The Brain Stem – The Midbrain
• Corpora quadrigemina – the largest nuclei
• Divided into the superior and inferior colliculi
• Superior colliculi – nuclei that act in visual reflexes
• Inferior colliculi – nuclei that act in reflexive
response to sound

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The Brain Stem – The Midbrain
• Imbedded in the white matter
of the midbrain
• Two pigmented nuclei
• Substantia nigra – neuronal
cell bodies contain melanin
• Functionally linked to the
basal nuclei
• Red nucleus – lies deep to the
substantia nigra
• Largest nucleus of the
reticular formation

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The Brain Stem – The Pons
• Located between the
midbrain and medulla
oblongata
• Contains the nuclei of
cranial nerves V, VI,
and VII

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The Brain Stem – The Medulla Oblongata
• Most caudal level of
the brain stem
• Continuous with the
spinal cord

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The Brain Stem – The Medulla Oblongata
• Choroid plexus lies in the
roof of the fourth ventricle
• Pyramids of the medulla –
lie on its ventral surface
• Decussation of the
pyramids – crossing over
of motor tracts
• Cranial nerves VIII–XII
attach to the medulla

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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, and
coughing

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The Cerebellum
• Located dorsal to the pons and medulla
• Smoothes and coordinates body movements
• Helps maintain equilibrium

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The Cerebellum
• Consists of two cerebellar hemispheres
• Surface folded into ridges called folia
• Separated by fissures
• Hemispheres each subdivided into:
• Anterior lobe
• Posterior lobe
• Flocculonodular lobe

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Cerebellum

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Cerebellum: Posterior View

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The Cerebellum: Frontal Section
• Composed of three regions
• Cortex – gray matter
• Internal white matter
• Deep cerebellar nuclei – deeply situated gray
matter

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Cerebellum: Sagittal Section

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The Cerebellum
• Cerebellum must receive information
• On equilibrium
• On current movements of limbs, neck, and trunk
• From the cerebral cortex

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The Cerebellum – Cerebellar Peduncles
• Thick tracts connecting the
cerebellum to the brain stem
• Superior cerebellar peduncles
• Middle cerebellar peduncles
• Inferior cerebellar peduncles
• Fibers to and from the
cerebellum are ipsilateral
• Run to and from the same
side of the body

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Decussation of Superior Cerebellar Peduncle
1. Decussation of superior cerebellar peduncles 2. Superior cerebellar
peduncle 3. Superior medullary velum 4. Fastigial nucleus 5. Globose nuclei
6. Emboliform nucleus 7. White matter of vermis 8. Dentate nucleus

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Functional Brain Systems
• Networks of neurons functioning together
• The limbic system – spread widely in the forebrain
• The reticular formation – spans the brain stem

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Functional Brain Systems – The Limbic System
• Location
• Medial aspect of cerebral hemispheres
• Also within the diencephalon
• Composed of:
• Septal nuclei, cingulate gyrus, and hippocampal
formation
• Part of the amygdala
• The fornix and other tracts link the limbic system
together

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Functional Brain Systems – The Limbic System
Figure 13.23

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Functional Brain Systems – The Limbic System
• The “emotional brain”
• Cingulate gyrus
• Allows us to shift between thoughts
• Interprets pain as unpleasant
• Hippocampal formation
• Hippocampus and the parahippocampal gyrus

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Functional Brain Systems – The Reticular Formation
• Runs through the central core of the medulla,
pons, and midbrain
• Forms three columns
• Midline raphe nuclei
• Medial nuclear group
• Lateral nuclear group

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Functional Brain Systems – The Reticular Formation
Figure 13.21c

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Functional Brain Systems – The Reticular Formation
• Widespread connections
• Ideal for arousal of the brain as a whole
• Reticular activating system (RAS)
• Maintains consciousness and alertness
• Functions in sleep and arousal from sleep

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Functional Brain Systems – The Reticular Formation
Figure 13.24

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Protection of the Brain
• The brain is protected from injury by
• The skull
• Meninges
• Cerebrospinal fluid
• Blood-brain barrier

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Protection of the Brain – Meninges
• Three meninges
• Dura mater
• Arachnoid mater
• Pia mater
• Cover and protect the CNS
• Enclose and protect the vessels that supply the
CNS
• Contain the cerebrospinal fluid

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The Dura Mater
• Strongest of the meninges
• Composed of two layers
• Periosteal layer
• Meningeal layer
• Two layers are fused except to enclose the dural
sinuses

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The Dura Mater
Figure 13.25a
Periosteal dura
Meningeal dura
Superior sagittal
sinus

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Dura mater

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The Dura Mater
• Largest sinus – the
superior sagittal sinus
• Dura mater extends
inward to subdivide
the cranial cavity
Figure 13.26

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Falx Cerebri
1. falx cerebri
2. location of inferior sagittal sinus
3. location of superior sagittal sinus
4. location of straight sinus
5. tentorium cerebelli

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The Arachnoid Mater
• Located beneath the dura mater
• Subdural space
• Potential space between dura and arachnoid mater
• Subarachnoid space
• Filled with CSF
• Contains the blood vessels that supply the brain
• Arachnoid villi
• Allow CSF to pass into the dural blood sinuses

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Arachnoid Mater
Arachnoid mater
Arachnoid villus
Subdural space
Subarachnoid
space

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Arachnoid mater

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The Pia Mater
• Delicate connective tissue
• Clings tightly to the surface of the brain
• Follows all convolutions of the cortex

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The Pia Mater
Figure 13.25a

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Protection of the Brain – Cerebrospinal Fluid (CSF)
• Provides a liquid cushion for the brain and spinal
cord
• The brain “floats” in CSF
• Formed in choroid plexuses in the brain
ventricles

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Choroid Plexus
Choroid plexus

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Choroid Plexus and Production of CSF
Figure 13.27a

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Circulation of Cerebrospinal Fluid (CSF)
Figure 13.27b

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Protection of the Brain – Blood-Brain Barrier
• Prevents most blood-borne toxins from entering
the brain
• Impermeable capillaries
• Not an absolute barrier
• Nutrients such as oxygen pass through
• Allows alcohol, nicotine, and anesthetics through

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Blood-Brain Barrier

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The Spinal Cord
• Runs through the
vertebral canal
• Extends from the
foramen magnum to the
level of the vertebra L1 or
L2

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Spinal Cord: Cervical, Thoracic, Lumbar, and Sacral

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The Spinal Cord Meninges
• Protected by bone,
meninges, and CSF
• Dura mater of the spinal
cord
• The spinal dural sheath –
only one layer

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Spinal Cord Meninges
Dura mater
Arachnoid mater

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Cervical and Lumbar Enlargements
Where nerves for upper and lower
limbs arise

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The Spinal Cord
• Conus medullaris – the inferior end of the spinal
cord
• Filum terminale – long filament of connective
tissue
• Attaches to the coccyx inferiorly
• Cauda equina – collection of nerve roots

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The Spinal Cord
Figure 13.29a

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The Spinal Cord
• Denticulate ligaments –
anchor spinal cord to
vertebrae
• Two deep grooves run the
length of the cord
• Posterior median sulcus
• Anterior median fissure
• (not shown (ventral))

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Cross-section of the Spinal Cord/Vertebra
Figure 13.30a

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Anatomy of the Spinal Cord
Figure 13.30b

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Gray Matter of the Spinal Cord and Spinal Roots
• Shaped like the letter H
• Gray commissure – contains the central canal
• Anterior horns – contain cell bodies of motor
neurons
• Posterior horns – consist of interneurons
• Gray matter – divided according to somatic and
visceral regions

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Gray Matter of the Spinal Cord and Spinal Roots
Figure 13.32

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White Matter of the Spinal Cord
• Composed of myelinated and unmyelinated axons
• Three types of fibers
• Ascending
• Descending
• Commissural

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White Matter of the Spinal Cord
Figure 13.33

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Sensory and Motor Pathways
• Most motor pathways:
• Decussate at some point along their course
• Consist of a chain of two or three neurons
• Exhibit somatotopy
• Tracts arranged according to the body region they
supply
• All pathways are paired
• One of each on each side of the body

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Ascending (Sensory) Pathways
• Conduct general somatic sensory impulses
• Chains of neurons composed of:
• First-, second-, and third-order neurons
• Four main ascending pathways
• Dorsal column pathway
• Spinothalamic pathway
• Posterior spinocerebellar pathway
• Anterior spinocerebellar pathway

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Ascending Pathways
Figure 13.34a

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Ascending Pathways
Figure 13.34b

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Descending (Motor) Pathways
• Deliver motor instructions from the brain to the
spinal cord
• Divided into two groups
• Pyramidal, or corticospinal, tracts
• Other motor pathways
• Tectospinal tracts
• Vestibulospinal tract
• Rubrospinal tract
• Reticulospinal tract

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Descending Motor Pathways
Figure 13.35a

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Descending Motor Pathways
Figure 13.35b

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Disorders of the Central Nervous System: Trauma
• Traumatic brain injuries
• Concussion – brain injury is slight
• Contusion – marked destruction of brain tissue

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Disorders of the Central Nervous System: Stroke
Cerebrovascular accident (stroke)
• Hemorrhagic
• Ischemic
• Blockage or interruption of blood flow to a brain region

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Disorders of the Central Nervous System
• 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 the spinal cord in the
cervical region
• Paralysis of all four limbs

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The Central Nervous System Throughout Life
• Congenital malformations
• Hydrocephalus
• Neural tube defects
• Anencephaly – cerebrum and cerebellum are absent
• Spina bifida – absence of vertebral lamina
• Cerebral palsy – voluntary muscles are poorly
controlled
• Results from damage to the motor cortex

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Hydrocephalus

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Anencephaly

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Spina bifida