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16 The Nervous System: The Brain and Cranial Nerves

PowerPoint® Lecture Presentations prepared by

Steven Bassett

Southeast Community College

Lincoln, Nebraska


Introduction

• The brain is a complex three-dimensional

structure that performs a bewildering

array of functions

• Think of the brain as an organic computer

• However, the brain is far more versatile than a

computer

• The brain is far more complex than the spinal

cord

• The brain consists of roughly 20 billion

neurons


An Introduction to the Organization of the Brain

• Embryology of the brain

• The CNS begins as a neural tube

• The lumen of the tube (neurocoel) is filled with

fluid

• In the fourth week of development, the cephalic

area of the neural tube enlarges to form:

• Prosencephalon

• Mesencephalon

• Rhombencephalon


Table 16.1 Development of the Human Brain



• Embryology of the brain (continued)

• Prosencephalon eventually develops to form:

• Telencephalon: forms the cerebrum

• Diencephalon: forms the epithalamus,

thalamus, and hypothalamus



• Mesencephalon

• Does not subdivide

• Becomes the midbrain

• Rhombencephalon

• Eventually develops to form:

• Metencephalon: forms the pons and cerebellum

• Myelencephalon: forms the medulla oblongata


Figure 16.1 Major Divisions of the Brain

CEREBRUM

DIENCEPHALON

MESENCEPHALON

PONS

MEDULLA OBLONGATA

CEREBELLUM

• Coordinates complex

somatic motor

patterns

• Adjusts output of

other somatic motor

centers in brain and

spinal cord

Spinal

cord

Brain

stem

• Relays sensory information to thalamus and

to other portions of the brain stem

• Autonomic centers for regulation of visceral

function (cardiovascular, respiratory, and

digestive system activities)

• Relays sensory

information to

cerebellum and

thalamus

• Subconscious

somatic and visceral

motor centers

• Processing of visual

and auditory data

• Generation of reflexive

somatic motor

responses

• Maintenance of

consciousness

• Centers controlling

emotions, autonomic

functions, and hormone

production

• Relay and processing

centers for sensory

information

THALAMUS

HYPOTHALAMUS

• Conscious thought processes,

intellectual functions

• Memory storage and processing

• Conscious and subconscious regulation

of skeletal muscle contractions

Left cerebral

hemisphere

Gyri

Sulci

Fissures



• Major Regions and Landmarks of the Brain

• Medulla oblongata

• Pons

• Cerebellum

• Mesencephalon (midbrain)

• Diencephalon

• Cerebrum (telencephalon)


Figure 16.13a Sectional Views of the Brain

Mesencephalon

Pons

Temporal lobe

Mamillary body

Optic chiasm

Anterior

commissure

Frontal lobe

Interventricular

foramen

Septum

pellucidum

Corpus callosum

Precentral gyrus Central sulcus Postcentral gyrus Cingulate gyrus

Fornix

Thalamus

Membranous portion

of epithalamus

Hypothalamus

Pineal gland

Parieto-occipital

sulcus

Superior

colliculus Corpora

quadrigemina Inferior colliculus

Aqueduct

of midbrain

Fourth ventricle

Cerebellum

Medulla

oblongata

A sagittal section through

the brain




• Relays information to the thalamus and brain

stem

• Regulates visceral function

• Pons

• Relays information to the thalamus and

cerebellum

• Regulates subconscious somatic and visceral

motor centers



• Cerebellum

• Coordinates somatic motor function

• Adjusts output of somatic motor centers

resulting in smooth operation

• Mesencephalon (midbrain)

• Processes visual and auditory data

• Maintains consciousness and alertness



• Diencephalon

• Epithalamus

• Contains the pineal gland

• Thalamus

• Relays information to the cerebrum

• Processes sensory information

• Hypothalamus

• Involved in emotions, thirst, some habitual activity



• Telencephalon (cerebrum)

• Conscious thought processes

• Memory storage

• Conscious regulation of skeletal muscle

contractions


Figure 16.1 Major Divisions of the Brain

CEREBRUM

DIENCEPHALON

MESENCEPHALON

PONS

MEDULLA OBLONGATA

CEREBELLUM

• Coordinates complex

somatic motor

patterns

• Adjusts output of

other somatic motor

centers in brain and

spinal cord

Spinal

cord

Brain

stem

• Relays sensory information to thalamus and

to other portions of the brain stem

• Autonomic centers for regulation of visceral

function (cardiovascular, respiratory, and

digestive system activities)

• Relays sensory

information to

cerebellum and

thalamus

• Subconscious

somatic and visceral

motor centers

• Processing of visual

and auditory data

• Generation of reflexive

somatic motor

responses

• Maintenance of

consciousness

• Centers controlling

emotions, autonomic

functions, and hormone

production

• Relay and processing

centers for sensory

information

THALAMUS

HYPOTHALAMUS

• Conscious thought processes,

intellectual functions

• Memory storage and processing

• Conscious and subconscious regulation

of skeletal muscle contractions

Left cerebral

hemisphere

Gyri

Sulci

Fissures



• Gray Matter and White Matter Organization

• The cerebrum consists of:

• Inner region of gray matter

• Surrounded by tracts of white matter

• Gray matter consists of cell bodies



• The Ventricles of the Brain

• Ventricles are fluid-filled cavities

• Filled with cerebrospinal fluid (CSF)

• Fluid transports nutrients to the CNS and transports waste away from the CNS

• CSF also provides protection

• There are four ventricles

• Ventricles 1 and 2 (called lateral ventricles) are in the cerebral hemispheres (separated by a partition called the septum pellucidum)

• Ventricle 3 is in the diencephalon

• Ventricle 4 lies between the pons and the cerebellum



• Lateral ventricles (ventricles 1 and 2)

• Main portion of the ventricle lies in the parietal lobes

• Each has an anterior horn extending into the frontal

lobe

• Each has a posterior horn extending into the occipital

lobe

• Each has an inferior horn extending into the temporal

lobe

• Each communicates with the third ventricle

• Through the interventricular foramen


Figure 16.2a Ventricles of the Brain

Orientation and extent of the ventricles as

seen in a lateral view of a transparent brain

Anterior horns of lateral ventricles

Cerebral hemispheres

Pons

Medulla oblongata

Central canal

Spinal cord

Lateral ventricles

Interventricular foramen

Third ventricle

Posterior horns of lateral ventricles

Inferior horns of lateral ventricles

Aqueduct of midbrain

Fourth ventricle

Cerebellum



• Third ventricle

• Communicates with the fourth ventricle

• Through the aqueduct of the midbrain

• Fourth ventricle

• Communicates with the central canal of the

spinal cord


Figure 16.2a Ventricles of the Brain

Orientation and extent of the ventricles as

seen in a lateral view of a transparent brain

Anterior horns of lateral ventricles

Cerebral hemispheres

Pons

Medulla oblongata

Central canal

Spinal cord

Lateral ventricles


Third ventricle

Posterior horns of lateral ventricles



Fourth ventricle

Cerebellum


Figure 16.2b Ventricles of the Brain

Lateral view of a plastic cast of the

ventricles


Posterior horn of lateral ventricle

Anterior horn of lateral ventricle

Lateral ventricle

(left)


Third ventricle


Fourth ventricle


Figure 16.2c Ventricles of the Brain

Anterior view of the ventricles as if

seen through a transparent brain

Third ventricle


Fourth ventricle

Cerebellum

Central canal

Medulla oblongata

Pons


Longitudinal fissure

Lateral ventricles in cerebral hemispheres



Figure 16.2d Ventricles of the Brain

Diagrammatic coronal section showing the

interconnections between the ventricles

Lateral ventricles


Third ventricle

Inferior horn of lateral ventricle


Fourth ventricle

Septum pellucidum

Central canal


Protection and Support of the Brain

• Protection involves:

• Bones of the skull

• Parietal, frontal, occipital, and temporal bones

• Cranial meninges

• Dura mater, arachnoid mater, and pia mater

• Cerebrospinal fluid

• Blood–brain barrier



• Cranial Meninges: The Dura Mater

• Consists of two layers

• Endosteal layer

• This is the layer felt within the anterior fontanel of a baby

• Meningeal layer

• Space between the two layers is called the dural sinus

• The meningeal layer forms folds called:

• falx cerebri

• tentorium cerebelli

• falx cerebelli

• diaphragma sellae



• Folds of the Dura Mater

• Falx cerebri

• Meningeal layer that extends into the longitudinal

fissure

• Inferior/anterior portion attaches to the crista galli

• Inferior/posterior portion attaches to the internal occipital

crest and the tentorium cerebelli

• Tentorium cerebelli

• Separates the cerebellar hemispheres from the

cerebral hemispheres

• Extends across the cranium at right angles to the falx

cerebri



• Folds of the Dura Mater (continued)

• Falx cerebelli

• Extends from the tentorium cerebelli to separate the

cerebellar hemispheres

• Diaphragma sellae

• Lines the sella turcica of the sphenoid bone

• It anchors the dura mater to the sphenoid bone

• It encases the pituitary gland


Figure 16.3a Relationships among the Brain, Cranium, and Meninges

Lateral view of the brain

showing its position in the

cranium and the organization

of the meningeal coverings

Spinal cord

Medulla oblongata

Cerebellum

Cerebral

cortex

Cerebral

cortex

Pia

mater Subarachnoid

space

Cranium Dura mater

(endosteal layer)

Dural sinus

Dura mater

(meningeal layer)

Subdural space

Arachnoid

mater


Figure 16.3b Relationships among the Brain, Cranium, and Meninges

A corresponding view of the cranial cavity with the

brain removed showing the orientation and extent

of the falx cerebri and tentorium cerebelli

Diaphragma sellae

Pituitary gland

Sella turcica

of sphenoid

Inferior sagittal sinus

Dura mater

Superior sagittal sinus

Cranium

Falx cerebri

Tentorium

cerebelli

Transverse

sinus

Falx cerebelli


Figure 16.5a The Cranial Meninges, Part II

Coronal section

This view shows the organization and relationship

of the cranial meninges to the brain.

Arachnoid

mater

Arachnoid

trabeculae

Pia mater

Dura mater

Cerebral cortex

Falx cerebri

Subarachnoid

space

Arachnoid

granulation

Subdural

space

Superior sagittal

sinus



• Cranial Meninges: The Arachnoid Mater

• Consists of projections called arachnoid

granulations

• CSF flows through these to enter into blood

circulation

• Consists of weblike material underlining the

arachnoid layer

• These collagenous fibers help anchor cerebral blood

vessels


Figure 16.5b The Cranial Meninges, Part II

Coronal section

A detailed view of the arachnoid membrane, the

subarachnoid space, and the pia mater. Note the

relationship between the cerebral vein and the

subarachnoid space.

Arachnoid mater

Arachnoid

trabecula

Cerebral

vein

Perivascular

space

Pia mater

Cerebral

cortex



• Cranial Meninges: The Pia Mater

• Attached to the surface of the brain

• Follows the sulci and gyri of the brain

• Helps to anchor the larger blood vessels

of the cerebrum


Figure 16.4 The Cranial Meninges, Part I

ANTERIOR

POSTERIOR

Cranium

Dura mater

Subarachnoid

space

Arachnoid

mater

Cerebral

cortex

covered

by pia mater

Loose

connective

tissue and

periosteum

of cranium

Epicranial

aponeurosis

Scalp



• Cerebrospinal Fluid (CSF)

• Provides protection of the brain and spinal cord

• Provides support

• Transports nutrients to the CNS tissue

• Transports waste away from the CNS



• Formation of CSF

• Produced by the ependymal cells of the

choroid plexus

• They actively transport nutrients, vitamins, and

ions into the CSF

• They actively remove waste from the CSF


Figure 16.6 The Choroid Plexus and Blood–Brain Barrier

INTERSTITIAL FLUID IN THALAMUS

The location of the choroid plexus in

each of the four ventricles of the brain

The structure and function of the

choroid plexus. The ependymal

cells are a selective barrier, actively

transporting nutrients, vitamins,

and ions into the CSF. When

necessary, these cells also actively

remove ions or compounds from

the CSF to stabilize its composition. CEREBROSPINAL FLUID IN THIRD VENTRICLE

CHOROID PLEXUS

Tight junction

Ions

(Na, K, Cl, HCO3, Ca2, Mg2)

Vitamins

Organic nutrients

Oxygen

Waste products

Ions

Amino acids

(when necessary)

Choroid plexus cells

Capillary

CO2

Waste products

Tight

junction Astrocyte Neuron

Blood–brain

barrier

Capillary

Endothelial cell

Ependymal

cells

Nutrients

(especially glucose)

Oxygen



• Circulation of CSF

• CSF from the choroid plexus of the lateral ventricles

• Flows through the interventricular foramen

• Flows into the third ventricle

• Flows into the aqueduct of the midbrain

• Flows into the fourth ventricle

• Through the lateral aperture and median aperture and

central canal of the spinal cord

• Flows into the subarachnoid space

• Flows around the brain and spinal cord eventually

enters circulation via the arachnoid granulations


Figure 16.7 Circulation of Cerebrospinal Fluid

Dura mater

Filum

terminale

Spinal

cord

Central

canal

Subarachnoid space

Arachnoid mater

Median aperture

Choroid plexus of

fourth ventricle

Lateral aperture

Aqueduct

of midbrain

Choroid plexus

of third ventricle

Extension of choroid

plexus into

lateral ventricle

Arachnoid

granulations

Superior

sagittal

sinus

Pia

mater

Subarachnoid

space

Cerebral

cortex

Superior

sagittal sinus Cranium Dura mater

(endosteal

layer)

Arachnoid

granulation

Fluid

movement

Arachnoid

trabecula

Dura mater

(meningeal

layer)

Subdural

space

Arachnoid

mater



• Blood–Brain Barrier

• The lining of the blood vessels consists of

endothelial cells that are highly interconnected

by tight junctions

• Due to this tight connection, only lipid-soluble

material can pass from the blood to the cells of the

brain and spinal cord

• Water-soluble material can only pass via the action

of transport mechanisms

• The transport mechanisms are very specific


The Medulla Oblongata


• Continuous with the spinal cord to the brain

stem

• All communication between the brain and spinal

cord passes through the medulla oblongata

• Nuclei in the medulla oblongata are:

• Relay stations for sensory or motor pathways

• Associated with cranial nerves connected to the

medulla oblongata

• Associated with the autonomic control of visceral

organs



• Relay stations

• Nucleus gracilis and nucleus cuneatus

• Pass sensory information to the thalamus

• Olivary nuclei

• Pass information to the cerebrum, diencephalon, and

brain stem



• Nuclei of cranial nerves

• Contains sensory and motor nuclei of cranial

nerves:

• VIII, IX, X, XI, and XII

• Autonomic nuclei

• Major centers include:

• Cardiovascular centers (cardiac and vasomotor)

• Respiratory centers (rhythmic breathing)


Figure 16.8a The Medulla Oblongata

Anterior view

Pyramids

Olive

Medulla oblongata

Pons

Spinal cord

Olivary nucleus

Cardiovascular centers

Solitary nucleus

Nucleus cuneatus

Nucleus gracilis

Reticular formation

Lateral white column


Figure 16.8b The Medulla Oblongata

Pyramids

Olive

Pons

Posterolateral view

Spinal cord

Olivary nucleus

Cardiovascular centers

Respiratory rhythmicity center

Solitary nucleus

Nucleus cuneatus

Nucleus gracilis

Reticular formation

Lateral white column

Attachment to membranous roof of fourth ventricle

Posterior median sulcus

Posterior white columns


The Pons

• The pons is a prominent bulge superior to

the medulla oblongata and consists of:

• Sensory and motor nuclei for cranial nerves:

• V, VI, VII, and VIII

• Nuclei involved with involuntary control of

breathing:

• Consist of apneustic center and pneumotaxic center

• Nuclei that relay cerebellar commands:

• Consist of cerebellar peduncles

• Ascending, descending, and transverse tracts


Figure 16.9 The Pons

Olivary nucleus

Medulla oblongata

Transverse fibers

Ascending tracts

Pons

Descending tracts

Pneumotaxic center

Apneustic center

Cerebellum

Fourth ventricle

Reticular formation


The Mesencephalon

• Mesencephalon (also called the midbrain)

• Consists of two pairs of nuclei collectively called

corpora quadrigemina

• Responsible for processing auditory and visual

stimuli

• Auditory processing occurs in the inferior colliculus

• Visual processing occurs in the superior colliculus

• Consists of nuclei of the reticular formation

• Involved in maintaining alertness


The Mesencephalon

• Mesencephalon (continued)

• Consists of:

• Red nucleus: integrates information between the

cerebrum and cerebellum

• Substantia nigra: regulates motor output of the

basal nuclei

• Cerebral peduncles: have ascending fibers that

synapse in the thalamus and descending fibers of the

corticospinal pathway


Figure 16.10b The Mesencephalon

Diagrammatic and posterior views of the diencephalon

and brain stem. The diagrammatic view is drawn, as if

transparent, to show the positions of important nuclei.

Superior colliculi

Inferior colliculi

Corpora quadrigemina

Trochlear nerve (N IV)

Cerebral peduncle

Superior cerebellar peduncle

Reticular formation in floor of

fourth ventricle

Fourth ventricle

Pineal gland

Superior colliculus

Cerebral peduncle

Thalamus

Red nucleus

Substantia nigra

Inferior colliculus

Reticular formation


The Diencephalon

• The diencephalon consists of:

• Epithalamus

• Thalamus

• Hypothalamus


Figure 16.12a The Hypothalamus

Midsagittal section through the brain. This view shows the major features

of the diencephalon and adjacent portions of the brain stem.

Optic

nerve

Infundibulum

(cut)

Tuberal

area Mamillary

body

Corpus

callosum

Septum

pellucidum

Fornix

Anterior

cerebral artery

Frontal lobe

Anterior

commissure

Optic chiasm

Parietal

lobe

Choroid plexus

in epithalamus

Thalamus

(surrounds

third ventricle)

Pineal gland

Aqueduct of

midbrain

Hypothalamus

Cerebellum

Fourth

ventricle


The Diencephalon

• The epithalamus

• Forms the roof of the third ventricle

• Contains the pineal gland

• Produces the hormone melatonin

• Regulates our day/night cycles


The Diencephalon

• The thalamus

• Forms the walls of the third ventricle

• There is a right and a left thalamus

• Thalamic nuclei are egg-shaped

• Each thalamic nucleus is divided into: • Anterior group: part of the limbic system

• Medial group: relays information to the frontal lobe

• Ventral group: relays information to the parietal lobes

• Posterior group: relays information to the occipital lobe

• Lateral group: adjusts activity in the cingulate gyrus


Figure 16.11a The Thalamus

Lateral view of the brain showing the

positions of the major thalamic

structures. Functional areas of

cerebral cortex are also indicated,

with colors corresponding to those of

the associated thalamic nuclei.

Occipital

lobe

Parietal lobe Frontal

lobe


Figure 16.11b The Thalamus

Enlarged view of the thalamic nuclei of the left side. The color of

each nucleus or group of nuclei matches the color of the associated

cortical region. The boxes either provide examples of the types of

sensory input relayed to the basal nuclei and cerebral cortex or

indicate the existence of important feedback loops involved with

emotional states, learning, and memory.

Cerebellum

Basal

nuclei

General

sensory

input

Visual

input

Auditory

input

Limbic

system

Frontal

lobes

Parietal lobe and

cingulate gyrus

Association areas

of cerebral cortex

Lateral geniculate nucleus

Medial geniculate nucleus

Pulvinar

Medial group

Lateral group

Anterior group

Posterior group

V e n t r a l g r o u p


Table 16.5 The Thalamus


The Diencephalon

• The hypothalamus

• Forms the floor of the third ventricle

• Consists of numerous nuclei

• Consists of an infundibulum, which connects

to the pituitary gland

• Consists of the mamillary body on the

posterior wall of the hypothalamus


The Diencephalon

• The hypothalamus (continued)

• Consists of nuclei to control:

• Subconscious control of skeletal muscles

• Heart rate, blood pressure, respiration, and digestive

functions

• Secretion of antidiuretic hormone and oxytocin

• Emotional and behavioral drives and thirst drives

• Coordination between voluntary and autonomic

functions

• Body temperature

• Circadian rhythm


Figure 16.12a The Hypothalamus

Midsagittal section through the brain. This view shows the major features

of the diencephalon and adjacent portions of the brain stem.

Optic

nerve

Infundibulum

(cut)

Tuberal

area Mamillary

body

Corpus

callosum

Septum

pellucidum

Fornix

Anterior

cerebral artery

Frontal lobe

Anterior

commissure

Optic chiasm

Parietal

lobe

Choroid plexus

in epithalamus

Thalamus

(surrounds

third ventricle)

Pineal gland

Aqueduct of

midbrain

Hypothalamus

Cerebellum

Fourth

ventricle


Figure 16.12b The Hypothalamus

Enlarged view of the hypothalamus showing the locations of major nuclei and

centers. Functions for these centers are summarized in Table 16.6.

Thalamus

Hypothalamus

Pons

Tuberal

area Mamillary

body

Posterior lobe of pituitary gland (pars nervosa)

Autonomic centers (sympathetic)

Paraventricular nucleus

Preoptic area

Autonomic centers (parasympathetic)

Suprachiasmatic nucleus

Anterior lobe of

pituitary gland

Supraoptic nucleus

Tuberal nuclei

Optic chiasm

Infundibulum

Pars distalis

Pars intermedia


The Cerebellum

• The cerebellum consists of:

• Two hemispheres

• Folia (folds similar to gyri of the cerebrum)

• Anterior and posterior lobes

• Vermis (separates the hemispheres)

• Flocculonodular lobes

• Arbor vitae

• Cerebellar peduncles


Figure 16.15b The Cerebellum

Dendrites projecting

into the gray matter

of the cerebellum

Axons of Purkinje cells

projecting into the white

matter of the cerebellum Purkinje cells LM 120

Cell body of Purkinje cell

Sagittal view of the cerebellum showing the arrangement of gray matter

and white matter. Purkinje cells are seen in the photomicrograph; these

large neurons are found in the cerebellar cortex.

Cerebellar peduncles

Superior

Middle

Inferior

Medulla oblongata

Pons

Anterior lobe

Arbor vitae

Cerebellar nucleus

Cerebellar cortex

Posterior lobe

Flocculonodular lobe

Choroid plexus of the fourth ventricle

Medulla oblongata

Fourth ventricle

Mamillary body

Pons

Superior colliculus


Inferior colliculus

Anterior lobe

Arbor vitae

Cerebellar cortex

Cerebellar nucleus

Posterior lobe


Mesencephalon


Figure 16.15a The Cerebellum

Superior surface of the cerebellum. This view

shows major anatomical landmarks and regions.

Left hemisphere

of cerebellum

Right hemisphere

of cerebellum

Folia

Folia

Vermis Vermis

Cerebellum

Anterior lobe

Primary fissure

Posterior lobe


The Cerebellum

• The cerebellum

• Cerebellar cortex: subconscious coordination

of movements

• Arbor vitae: connects cerebellar cortex with

cerebellar peduncles

• Cerebellar peduncles

• Superior: connect cerebellum with mesencephalon,

diencephalon, and cerebrum

• Middle: communicate between cerebellum and pons

• Inferior: connect cerebellum with the medulla

oblongata


Figure 16.15b The Cerebellum

Dendrites projecting

into the gray matter

of the cerebellum

Axons of Purkinje cells

projecting into the white

matter of the cerebellum Purkinje cells LM 120

Cell body of Purkinje cell

Sagittal view of the cerebellum showing the arrangement of gray matter

and white matter. Purkinje cells are seen in the photomicrograph; these

large neurons are found in the cerebellar cortex.

Cerebellar peduncles

Superior

Middle

Inferior

Medulla oblongata

Pons

Anterior lobe

Arbor vitae

Cerebellar nucleus

Cerebellar cortex

Posterior lobe


Choroid plexus of the fourth ventricle

Medulla oblongata

Fourth ventricle

Mamillary body

Pons

Superior colliculus


Inferior colliculus

Anterior lobe

Arbor vitae

Cerebellar cortex

Cerebellar nucleus

Posterior lobe


Mesencephalon


The Cerebrum

• The cerebrum consists of:

• Two hemispheres

• Several lobes

• Frontal, parietal, occipital, and temporal

• Gyri and sulci

• Longitudinal fissure

• Corpus callosum

• Basal nuclei

• Limbic system


The Cerebrum

• The Cerebral Hemispheres

• The hemispheres consist of:

• Gyri and sulci

• Central sulcus

• Longitudinal fissure

• Cerebral lobes


Figure 16.16a The Cerebral Hemispheres, Part I

Superior view

POSTERIOR

ANTERIOR

Right cerebral hemisphere

Cerebral veins and arteries covered by arachnoid mater

Central sulcus

Parieto-occipital sulcus

Cerebellum

Left cerebral hemisphere



The Cerebrum

• The Cerebral Hemispheres

• The Cerebral Lobes

• Frontal lobe: conscious control of skeletal muscles

• Occipital lobe: perception of visual stimuli

• Parietal lobe: conscious perception of touch,

pressure, vibration, pain, temperature, and taste

• Temporal lobe: conscious perception of auditory and

olfactory stimuli


Figure 16.17a The Cerebral Hemispheres, Part II

Lateral view of intact brain after removal of the

dura mater and arachnoid mater showing

superficial surface anatomy of the left hemisphere

Precentral gyrus

Central sulcus

Lateral sulcus

FRONTAL LOBE

of left cerebral

hemisphere

Branches of middle

cerebral artery emerging

from lateral sulcus

TEMPORAL LOBE

Medulla oblongata

Pons

Cerebellum

OCCIPITAL LOBE

PARIETAL

LOBE

Postcentral

gyrus


The Cerebrum

• Motor and Sensory Areas of the Cerebral Cortex

• Precentral gyrus

• Anterior to the central gyrus

• Neurons direct voluntary movements by controlling somatic motor neurons in the brain stem and spinal cord

• Postcentral gyrus

• Posterior to the central gyrus

• Neurons receive somatic sensory information for touch, pressure, pain, taste, and temperature from the dorsal columns and spinothalamic tracts


Figure 16.13a Sectional Views of the Brain

Mesencephalon

Pons

Temporal lobe

Mamillary body

Optic chiasm

Anterior

commissure

Frontal lobe

Interventricular

foramen

Septum

pellucidum

Corpus callosum

Precentral gyrus Central sulcus Postcentral gyrus Cingulate gyrus

Fornix

Thalamus

Membranous portion

of epithalamus

Hypothalamus

Pineal gland

Parieto-occipital

sulcus

Superior

colliculus Corpora

quadrigemina Inferior colliculus

Aqueduct

of midbrain

Fourth ventricle

Cerebellum

Medulla

oblongata

A sagittal section through

the brain


The Cerebrum

• Hemispheric Specialization

• Left hemisphere

• Speech center, writing, language, mathematics

• Right hemisphere

• Analysis by touch, spatial visualization


Figure 16.18 Hemispheric Specialization

LEFT HAND

Prefrontal cortex

Speech center

Writing

Auditory cortex (right ear)

General interpretive center (language

and mathematical calculation)

Visual cortex (right visual field)

LEFT HEMISPHERE

RIGHT HEMISPHERE

C O R P U S

C A L L O S U M

RIGHT HAND

Prefrontal cortex

Anterior commissure

Auditory cortex (left ear)

Analysis by touch

Spatial visualization and analysis

Visual cortex (left visual field)


The Cerebrum

• The Central White Matter

• Consists of bundles called:

• Association fibers: tracts that interconnect areas of

neural cortex within a hemisphere (arcuate fibers

and longitudinal fasciculi)

• Commissural fibers: tracts that connect the two

hemispheres (anterior commissure and corpus

callosum)

• Projection fibers: tracts that link the cerebrum with

other regions of the brain and spinal cord


Figure 16.19a The Central White Matter

Lateral aspect of the brain showing arcuate fibers and longitudinal fasciculi

Arcuate fibers

Longitudinal fasciculi


Figure 16.19b The Central White Matter

Anterior view of the brain showing orientation of the commissural and projection fibers

Anterior commissure

Projection fibers of internal capsule

Corpus callosum



The Cerebrum

• The Basal Nuclei

• These are masses of gray matter embedded in

the white matter inferior to the lateral ventricles

• Consist of:

• Caudate nucleus

• Amygdaloid body

• Claustrum

• Putamen

• Globus pallidus


The Cerebrum

• The Basal Nuclei

• Caudate nucleus, putamen, and globus

pallidus

• Control the cycles of arm and leg movements when

walking

• Claustrum

• Plays a role in subconscious processing of visual

information

• Amygdaloid body

• Component of the limbic system


Figure 16.20c The Basal Nuclei

Frontal section

Head of caudate nucleus

Lateral ventricle

Claustrum

Insula

Putamen

Lentiform nucleus

Globus pallidus

Amygdaloid body

Corpus callosum

Septum pellucidum

Internal capsule

Lateral sulcus

Anterior commissure

Tip of inferior horn of lateral ventricle


The Cerebrum

• The Limbic System

• Located between the cerebrum and the

diencephalon just superior to the corpus

callosum

• Functions:

• Establishes emotional states

• Links the conscious functions with the unconscious

autonomic functions

• Facilitates memory storage and retrieval


Figure 16.21a The Limbic System

Sagittal section through the cerebrum showing the cortical

areas associated with the limbic system. The parahippocampal

and dentate gyri are shown as if transparent so that deeper

limbic components can be seen.

Thalamus

Hypothalamus

Temporal lobe

Parahippocampal

gyrus (limbic lobe) Hippocampus

(within dentate gyrus) Mamillary

body

Corpus

callosum

Interthalamic

adhesion

Central

sulcus Cingulate gyrus

(limbic lobe)

Fornix

Pineal gland


The Cerebrum

• The limbic system consists of: • Cingulate gyrus

• Dentate gyrus

• Parahippocampal gyrus

• Hippocampus


Figure 16.21b The Limbic System

Additional details concerning the three-

dimensional structure of the limbic system

Anterior nucleus

of thalamus

Hypothalamic

nuclei

Olfactory

tract

Amygdaloid

body

Mamillary

body Hippocampus

(within dentate gyrus)

Parahippocampal

gyrus

Cingulate

gyrus

Corpus

callosum Fornix


Figure 16.21a The Limbic System

Sagittal section through the cerebrum showing the cortical

areas associated with the limbic system. The parahippocampal

and dentate gyri are shown as if transparent so that deeper

limbic components can be seen.

Thalamus

Hypothalamus

Temporal lobe

Parahippocampal

gyrus (limbic lobe) Hippocampus

(within dentate gyrus) Mamillary

body

Corpus

callosum

Interthalamic

adhesion

Central

sulcus Cingulate gyrus

(limbic lobe)

Fornix

Pineal gland


The Cerebrum

• The Limbic System

• The fornix

• Tract of white matter connecting the hippocampus

with the hypothalamus

• Many fornix fibers extend to the mamillary bodies

• Mamillary bodies control reflex movements

associated with eating


The Cranial Nerves

• There are 12 pairs of cranial nerves

• These nerves innervate the periphery emerging

from the brain (not the spinal cord)

• These nerves are on the ventrolateral surface of

the brain

• They are numbered beginning at the anterior

aspect of the brain

• They are numbered CN I to CN XII


Figure 16.22b Origins of the Cranial Nerves

Diagrammatic inferior view of the human

brain. Compare view with part (a).

Olfactory bulb, termination

of olfactory nerve (N I)

Olfactory tract

Optic chiasm

Optic nerve (N II)

Infundibulum

Oculomotor nerve (N III)


Trigeminal nerve (N V)

Abducens nerve (N VI)

Facial nerve (N VII)

Vestibulocochlear

nerve (N VIII)

Glossopharyngeal

nerve (N IX)

Vagus nerve (N X)

Hypoglossal nerve (N XII)

Accessory nerve (N XI)


Figure 16.22a Origins of the Cranial Nerves

The inferior surface of the brain as it appears on

gross dissection. The roots of the cranial nerves

are clearly visible.

Medulla oblongata

Spinal cord

Cerebellum

Vertebral

artery

Basilar

artery

Mamillary

body

Pons

Olfactory bulb, termination

of olfactory nerve (N I)

Olfactory tract

Optic chiasm

Optic nerve (N II)

Infundibulum

Oculomotor nerve (N III)



Abducens nerve (N VI)

Facial nerve (N VII)

Vestibulocochlear

nerve (N VIII)

Glossopharyngeal

nerve (N IX)

Vagus nerve (N X)

Hypoglossal nerve (N XII)

Accessory nerve (N XI)


The Cranial Nerves

• CN I: The Olfactory Nerve

• Function: sensory (smell)

• Origin: olfactory epithelium

• Foramen: olfactory foramina

• Destination: olfactory bulbs


Figure 16.23 The Olfactory Nerve

Olfactory

nerve fibers

Olfactory epithelium

Cribriform plate

of ethmoid

OLFACTORY

NERVE (N I)

Olfactory tract

(to olfactory cortex

of cerebrum)

Left olfactory bulb

(termination of

olfactory nerve)


The Cranial Nerves

• CN II: The Optic Nerve

• Function: sensory (vision)

• Origin: retina

• Foramen: optic canal

• Destination: diencephalon, then to occipital

lobe


Figure 16.24 The Optic Nerve

OPTIC NERVE

(N II)

Mesencephalon

(cut)

Optic chiasm

Optic tract

Eye

Visual cortex

(in occipital lobes)

Optic

projection

fibers

Lateral

geniculate

nucleus

(in thalamus)

Pituitary

gland

Olfactory tract

Olfactory bulb


The Cranial Nerves

• CN III: The Oculomotor Nerve

• Function: controls extra-ocular eye muscles

• Motor function

• Superior, inferior, and medial rectus

• Inferior oblique

• Levator palpebrae superioris

• Origin: mesencephalon

• Foramen: superior orbital fissure

• Destination: extra-ocular eye muscles


Figure 16.25 Cranial Nerves Controlling the Extra–Ocular Muscles

Trigeminal

nerve (N V), cut

Vestibulocochlear

nerve (N VIII), cut

Facial nerve

(N VII), cut

ABDUCENS

NERVE (N VI)

Lateral

rectus

muscle

(cut)

Medial

rectus

muscle

Inferior

rectus

muscle

Ciliary

ganglion

OPTIC

NERVE (N II)

Optic

chiasm

OCULOMOTOR

NERVE (N III)

TROCHLEAR

NERVE (N IV)

Superior

rectus

muscle Superior

oblique

muscle

Trochlea

Levator

palpebrae

superioris

muscle

Inferior

oblique

muscle


The Cranial Nerves

• CN IV: The Trochlear Nerve

• Function: controls extra-ocular eye muscles

• Motor function

• Superior oblique

• Origin: mesencephalon


• Destination: extra-ocular eye muscles



Trigeminal

nerve (N V), cut

Vestibulocochlear

nerve (N VIII), cut

Facial nerve

(N VII), cut

ABDUCENS

NERVE (N VI)

Lateral

rectus

muscle

(cut)

Medial

rectus

muscle

Inferior

rectus

muscle

Ciliary

ganglion

OPTIC

NERVE (N II)

Optic

chiasm

OCULOMOTOR

NERVE (N III)

TROCHLEAR

NERVE (N IV)

Superior

rectus

muscle Superior

oblique

muscle

Trochlea

Levator

palpebrae

superioris

muscle

Inferior

oblique

muscle


The Cranial Nerves

• CN V: The Trigeminal Nerve

• Function:

• Mixed (sensory and motor) function

• Ophthalmic: sensations from the forehead, eyelids,

and nose

• Maxillary: sensations from lower eyelid, upper lip, and

cheek

• Mandibular: controls mastication

• Origin: ophthalmic, maxillary, and mandibular

nerves


The Cranial Nerves

• CN V: The Trigeminal Nerve (continued)

• Foramen:

• Ophthalmic: superior orbital fissure

• Maxillary: foramen rotundum

• Mandibular: foramen ovale

• Destination:

• Ophthalmic and maxillary: Pons

• Mandibular: mandibular muscles


Figure 16.26 The Trigeminal Nerve

TRIGEMINAL NERVE (N V)

Maxillary branch

Foramen ovale

Pons

Otic ganglion

Mandibular branch

Pterygopalatine ganglion

Ophthalmic branch

Semilunar ganglion

Superior orbital fissure

Supraorbital nerves

Ciliary ganglion

Foramen rotundum

Infra-orbital nerve

Lingual nerve

Submandibular ganglion

Mental nerve


The Cranial Nerves

• CN VI: The Abducens Nerve

• Function: controls eye movements

• Motor function

• Origin: pons


• Destination: innervates the lateral rectus eye

muscle



Trigeminal

nerve (N V), cut

Vestibulocochlear

nerve (N VIII), cut

Facial nerve

(N VII), cut

ABDUCENS

NERVE (N VI)

Lateral

rectus

muscle

(cut)

Medial

rectus

muscle

Inferior

rectus

muscle

Ciliary

ganglion

OPTIC

NERVE (N II)

Optic

chiasm

OCULOMOTOR

NERVE (N III)

TROCHLEAR

NERVE (N IV)

Superior

rectus

muscle Superior

oblique

muscle

Trochlea

Levator

palpebrae

superioris

muscle

Inferior

oblique

muscle


The Cranial Nerves

• CN VII: The Facial Nerve • Function: Mixed (sensory and motor)

• Sensory: sensations from the face / taste

• Motor: controls muscles of the face

• Origin:

• Sensory: taste buds

• Motor: pons

• Foramen: internal acoustic meatus

• Destination:

• Sensory: pons

• Motor: muscles of the face


Figure 16.27a The Facial Nerve

Origin and branches of the facial

nerve

Posterior auricular

branch

Stylomastoid

foramen

Chorda tympani nerve

(with mandibular

branch of N V)

Lingual branch

(with lingual nerve

of N V)

Submandibular

ganglion

Pons

Pterygopalatine

ganglion

Greater

petrosal

nerve

Geniculate

ganglion

FACIAL

NERVE (N VII)

Temporal

branch

Zygomatic

branches

Buccal

branch

Mandibular

branch

Cervical

branch


The Cranial Nerves

• CN VIII: The Vestibulocochlear Nerve

• Function:

• Sensory: balance and hearing

• Origin: receptors of the vestibule and cochlea

• Foramen: internal acoustic meatus

• Destination: pons


Figure 16.28 The Vestibulocochlear Nerve

Tympanic cavity

(middle ear)

Semicircular canals

Vestibular branch (N VIII)

Facial nerve

(N VII), cut

Internal acoustic

canal VESTIBULOCOCHLEAR

NERVE (N VIII)

Pons

N V

N VI N VII

N IX

N XII N X

N XI

Medulla oblongata

Cochlear branch (N VIII)

Cochlea Auditory tube

Tympanic membrane


The Cranial Nerves

• CN IX: The Glossopharyngeal Nerve

• Function: Mixed (sensory and motor)

• Sensory function: tongue pain

• Motor function: swallowing

• Origin:

• Sensory: posterior 1/3 of the tongue

• Motor: salivary gland


The Cranial Nerves

• CN IX: The Glossopharyngeal Nerve

(continued)

• Foramen: jugular foramen

• Destination:

• Sensory: pons

• Visceral motor: parotid salivary gland

• Somatic motor: pharyngeal muscles for swallowing


Figure 16.29 The Glossopharyngeal Nerve

Common carotid artery

Carotid sinus

Carotid body

Lingual branch

Otic ganglion

Inferior (petrosal) ganglion

GLOSSOPHARYNGEAL NERVE (N IX)

Superior (jugular) ganglion

Pharyngeal branches

Carotid sinus branch

Parotid salivary gland

Medulla oblongata

Pons

N VII

N VI

N V

N VIII


The Cranial Nerves

• CN X: The Vagus Nerve

• Function:

• Sensory: information from organs

• Motor: sends information to the organs

• Origin:

• Sensory: from the organs

• Motor: medulla oblongata


The Cranial Nerves

• CN X: The Vagus Nerve (continued)


• Destination:

• Sensory: autonomic centers of the medulla oblongata

• Somatic motor: muscles of the palate and pharynx

• Visceral motor: respiratory, cardiovascular, and

digestive organs


Figure 16.30 The Vagus Nerve

Superior pharyngeal

branch

Superior laryngeal nerve

Recurrent laryngeal nerve

Internal branch

External branch

VAGUS NERVE (N X)

Inferior ganglion of

vagus nerve

Cardiac branches

Cardiac plexus

Anterior vagal trunk

Left lung Right lung

Liver

Stomach

Colon

Pancreas

Spleen

Small intestine

Celiac plexus

Hypogastric plexus

Medulla oblongata

Auricular branch to external ear

Superior ganglion of vagus nerve

Pharyngeal branch

Superior laryngeal nerve


The Cranial Nerves

• CN XI: The Accessory Nerve

• Function:

• Motor: controls the sternocleidomastoid, trapezius,

palate, pharynx, and larynx muscles

• Origin: spinal cord and medulla oblongata


• Destination:

• Internal branch: muscles of the palate, pharynx, and

larynx

• External branch: sternocleidomastoid and trapezius

muscles


Figure 16.31 The Accessory and Hypoglossal Nerves

HYPOGLOSSAL NERVE (N XII)

ACCESSORY NERVE (N XI)

Internal branch: to palatal, pharyngeal, and laryngeal muscles with vagus nerve

Intrinsic muscles of tongue

Styloglossus muscle

Genioglossus muscle

Geniohyoid muscle

Hyoglossus muscle

Hyoid bone

Thyrohyoid muscle

Sternohyoid muscle

Sternothyroid muscle

Omohyoid muscle

Sternocleidomastoid muscle

Trapezius muscle

Ansa cervicalis (cervical plexus)

Spinal cord

External branch of N XI

Spinal root of N XI

Cranial root of N XI


Medulla oblongata


The Cranial Nerves

• CN XII: The Hypoglossal Nerve

• Function:

• Motor: controls tongue movement

• Origin: medulla oblongata

• Foramen: hypoglossal canal

• Destination: tongue muscles


Figure 16.31 The Accessory and Hypoglossal Nerves

HYPOGLOSSAL NERVE (N XII)

ACCESSORY NERVE (N XI)

Internal branch: to palatal, pharyngeal, and laryngeal muscles with vagus nerve

Intrinsic muscles of tongue

Styloglossus muscle

Genioglossus muscle

Geniohyoid muscle

Hyoglossus muscle

Hyoid bone

Thyrohyoid muscle

Sternohyoid muscle

Sternothyroid muscle

Omohyoid muscle

Sternocleidomastoid muscle

Trapezius muscle

Ansa cervicalis (cervical plexus)

Spinal cord

External branch of N XI

Spinal root of N XI

Cranial root of N XI


Medulla oblongata


The Cranial Nerves

• Summary of Cranial Nerve Branches and

Functions

• Mnemonic aid

• Oh, Once One Takes The Anatomy Final, Very Good

Vacations Are Heavenly


Table 16.12 The Cranial Nerves (Part 1 of 2)


Table 16.12 The Cranial Nerves (Part 2 of 2)

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