ar - houston community college

© 2012 Pearson Education, Inc.

PowerPoint® Lecture Presentations prepared by

Jason LaPres

Lone Star College—North Harris

14 The Brain and Cranial Nerves

© 2012 Pearson Education, Inc. Picture adapted from MRC Centre for Synaptic Plasticity

AMP

AR NMD

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Glutam

ate

Synapse • In the pre-synaptic neuron, an

electrical signal comes in, opens up

to voltage-gated channels, and

signals the vesicles containing

neurotransmitters (chemical signal) to

be released into the synaptic cleft.

• Receptors on the post-synaptic

neuron bind to the neurotransmitter

signaling it to open its gate and let

ions flow through.

• The flow of ions will generate a

current that changes the resting

membrane potential. If the membrane

potential passes the threshold, then

an action potential is produced.

• The action potential is then

propagated to the next neuron, and

the communication continues from

neuron to neuron.

Pre-synaptic

neuron

Post-synaptic

neuron

Synaptic cleft


An Introduction to the Brain and Cranial Nerves

• The Adult Human Brain

• Ranges from 750 cc to 2100 cc

• Contains almost 97% of the body’s neural tissue

• Average weight about 1.4 kg (3 lb)


Brain Summary • Important component of the CNS.

• Site for coordination and integration of sensations, emotions,

memory, and behavior.

• Divided into 6 regions (cerebrum, cerebellum, diencephalon,

mesencephalon, pons, and medulla oblongata)

• Protected by 3 connective tissue meninges: dura mater,

arachnoid, and the pia mater—just like the spinal cord.

• Large blood vessels called dural sinuses can be found

between 2 layers of dura mater.

• The subarachnoid space is filled with CSF

• Cranial nerves emerge from various parts of the brain

• The brain contains both gray matter and white matter

• Gray = interneurons and neuroglia

• White = fiber tracts


14-1 The Brain

• Six Regions of the Brain

1. Cerebrum

2. Cerebellum

3. Diencephalon

4. Mesencephalon (midbrain)

5. Pons

6. Medulla oblongata

Brain Stem


14-1 The Brain

• Cerebrum

• Largest part of brain

• Controls higher mental functions

• Divided into left and right cerebral hemispheres

• Surface layer of gray matter (neural cortex)


14-1 The Brain

• Cerebrum

• Neural cortex

• Also called cerebral cortex

• Folded surface increases surface area

• Elevated ridges (gyri)

• Shallow depressions (sulci)

• Deep grooves (fissures)


14-1 The Brain

• Cerebellum

• Second largest part of brain

• Coordinates repetitive body movements

• Two hemispheres

• Covered with cerebellar cortex


Figure 14-1 An Introduction to Brain Structures and Functions

CEREBRUM

• Conscious thought processes,

• Memory storage and processing • Conscious and subconscious regulation

of skeletal muscle contractions

intellectual functions

CEREBELLUM

• Coordinates complex somatic motor patterns

other somatic motor centers in brain and spinal cord

Fissures

Sulci

Gyri

Left cerebral

hemisphere

• Adjusts output of

Spinal cord


14-1 The Brain

• Diencephalon

• Located under cerebrum and cerebellum

• Links cerebrum with brain stem

• Three divisions of the diencephalon

1. Epithalamus

2. thalamus

3. Hypothalamus


14-1 The Brain

• Diencephalon

• Thalamus

• Relays and processes sensory information

• Hypothalamus

• Hormone production

• Emotion

• Autonomic function


14-1 The Brain

• Diencephalon

• Pituitary gland

• Major endocrine gland

• Connected to hypothalamus


14-1 The Brain

• The Brain Stem

• Processes information between:

• Spinal cord and cerebrum or cerebellum

• Includes:

• Midbrain

• Pons

• Medulla oblongata


14-1 The Brain

• Midbrain

• Also called mesencephalon

• Processes sight, sound, and associated reflexes

• Maintains consciousness

• Pons

• Connects cerebellum to brain stem

• Is involved in somatic and visceral motor control


14-1 The Brain

• Medulla Oblongata

• Connects brain to spinal cord

• Relays information

• Regulates autonomic functions

• Heart rate, blood pressure, and digestion


Figure 14-1 An Introduction to Brain Structures and Functions

DIENCEPHALON

THALAMUS

• Relay and processing centers for sensory

information

• Centers controlling

HYPOTHALAMUS

emotions, autonomic

functions, and

hormone production

MIDBRAIN

• Generation of reflexive

and auditory data

somatic motor responses

consciousness

PONS

MEDULLA OBLONGATA

function (cardiovascular, respiratory, and

digestive system activities)

• Relays sensory information to thalamus and to other portions of the brain stem

• Autonomic centers for regulation of visceral

Brain stem • Processing of visual

• Maintenance of

• Relays sensory information to cerebellum and thalamus • Subconscious somatic and visceral motor centers


14-1 The Brain

• Ventricles of the Brain

• Within the brain are 4 spaces called ventricles

• 2 lateral ventricles

• Third ventricle

• Fourth ventricle

• Connects with third ventricle via narrow canal in

midbrain called the cerebral aqueduct


Figure 14-2a Ventricles of the Brain

Cerebral hemispheres

Pons

Medulla oblongata

Spinal cord Central canal

Ventricular system, lateral view

Lateral ventricles

Third ventricle

Fourth ventricle

Ventricles of the Brain

Cerebral aqueduct


Figure 14-2b Ventricles of the Brain

Lateral ventricles

Third ventricle

Fourth ventricle

Ventricles of the Brain

Cerebral hemispheres

Central canal Cerebellum

Ventricular system, anterior view


14-1 The Brain

• The Brain

• The brain is a large, delicate mass of neural tissue

• Containing internal passageways and chambers filled

with cerebrospinal fluid

• Each of the six major brain regions has specific

functions

• Ascending from the medulla oblongata to the cerebrum,

brain functions become more complex and variable

• Conscious thought and intelligence

• Are produced in the neural cortex of the cerebral

hemispheres


14-2 Brain Protection and Support

• Physical Protection of the Brain

• Bones of the cranium

• Cranial meninges

• Cerebrospinal fluid

• Biochemical Isolation

• Blood–brain barrier



• The Cranial Meninges

• Have three layers

1. Dura mater

2. Arachnoid mater

3. Pia mater

• Are continuous with spinal meninges

• Protect the brain from cranial trauma



• The Cranial Meninges

• Dura mater

• Inner fibrous layer

• Arachnoid mater

• Covers brain

• Contacts epithelial layer of dura mater

• Subarachnoid space between arachnoid mater and pia mater

• Pia mater

• Attached to brain surface by astrocytes



• Dural Folds

• Folded inner layer of dura mater

• Extend into cranial cavity

• Stabilize and support brain

• Contain collecting veins (dural sinuses)


Figure 14-3a The Relationship among the Brain, Cranium, and Meninges

Cranium (skull)

Cerebellum

Medulla oblongata

Spinal cord

A lateral view of the brain, showing its

position in the cranium and the organization

of the meninges

Cerebral cortex

Dura mater (endosteal layer)

Dural sinus

Dura mater (meningeal layer)

Subdural space

Arachnoid mater

Subarachnoid space

Arachnoid trabeculae

Pia mater

Cerebral cortex



• Cerebrospinal Fluid (CSF) – subarachnoid

space is filled with CSF

• Surrounds all exposed surfaces of CNS

• Interchanges with interstitial fluid of brain

• Functions of CSF

• Cushions delicate neural structures

• Supports brain

• Transports nutrients, chemical messengers, and waste

products



• Cerebrospinal Fluid (CSF)

• Choroid plexus—site of CSF production

• Specialized ependymal cells and capillaries

• Secrete CSF into ventricles

• Remove waste products from CSF

• Adjust composition of CSF

• Produces about 500 mL of CSF/day



• Cerebrospinal Fluid (CSF)

• CSF circulates:

• From choroid plexus

• Through ventricles

• To central canal of spinal cord

• Into subarachnoid space via two lateral apertures and

one median aperture around the brain, spinal cord,

and cauda equina



• Blood Supply to the Brain

• Supplies nutrients and oxygen to brain

• Delivered by internal carotid arteries and vertebral

arteries

• Removed from dural sinuses by internal jugular veins


Figure 21–24a Arteries of the Brain


Figure 21–29a Major Veins of the Head, Neck, and Brain



• Blood–Brain Barrier (BBB)

• Isolates CNS neural tissue from general circulation

• Formed by network of tight junctions

• Between endothelial cells of CNS capillaries

• Lipid-soluble compounds (O2, CO2) and steroids

• Diffuse into interstitial fluid of brain and spinal cord

• Astrocytes control blood–brain barrier by:

• Releasing chemicals that control permeability of endothelium



• Blood–CSF Barrier

• Formed by special ependymal cells

• Surrounds capillaries of choroid plexus

• Limits movement of compounds transferred

• Allows chemical composition of blood and CSF to

differ



• Protection and Support

• Meninges stabilize brain in cranial cavity

• Cerebrospinal fluid protects against sudden

movement

• CSF provides nutrients and removes wastes

• Blood–brain barrier and blood–CSF barrier

• Selectively isolate brain from chemicals in blood that

might disrupt neural function


14-3 The Medulla Oblongata

• The Medulla Oblongata

• Allows brain and spinal cord to communicate

• Coordinates complex autonomic reflexes

• Controls visceral functions

• Sensory and Motor Nuclei of the Medulla

Oblongata

• Associated with 5 of 12 cranial nerves (VIII, IX, X,

XI, XII)


Figure 14-5a The Diencephalon and Brain Stem

Cerebral peduncle

Diencephalon

Optic tract

Lateral geniculate nucleus

Midbrain

Cerebellar peduncles

Medial geniculate nucleus

Superior colliculus

Inferior colliculus

Inferior cerebellar peduncle

Middle cerebellar peduncle

Superior cerebellar peduncle

Cranial nerves

Medulla

oblongata

Thalamus

N II

N IV

N V

N VI N VII

N VIII N IX N X N XI

Pons

Spinal cord

Spinal

nerve C1

Spinal

nerve C2

Lateral view

N III

N XII


Medulla Oblongata Summary

• The pathway from spinal cord to brain

through which all ascending (sensory) and

descending (motor) fibers pass. Many of the

nuclei involved in basic survival processes

such as coughing, sneezing, sweating, and

chewing are found here as well as nuclei that

control the heart rate, respiratory rate, and

blood pressure.


14-4 The Pons

• The Pons

• Sensory and motor nuclei of cranial nerves (V, VI, VII, VIII)

• “the bridge” contains fiber tracts that connect the medulla and

midbrain as well as transverse tracks between left and right

cerebellar hemispheres.


Figure 14-6c The Medulla Oblongata and Pons

Tracts

Ascending tracts Descending tracts

Transverse fibers

Respiratory Centers

Pneumotaxic center

Apneustic center

Cerebellum

Fourth ventricle

Reticular formation

Medulla oblongata

Olivary nucleus

Lateral view

Midbrain

Pons

Medulla

oblongata

Spinal cord


14-5 The Cerebellum • Summary

• Located in the posterior part of the brain, it plays an important role in

motor control, interpreting textures of objects, some spatial perception,

understanding some aspects of speech, and time keeping.

• It is the second largest part of the brain and externally exhibits gyri and

folia

• Functions of the Cerebellum

1. Adjusts postural muscles

2. Fine-tunes conscious and subconscious movements


Figure 14-7a The Cerebellum

Anterior

lobe

Vermis

Primary

fissure

Right Hemisphere

of Cerebellum

Left Hemisphere

of Cerebellum

The posterior, superior surface of the cerebellum, showing

major anatomical landmarks and regions

Posterior

lobe Folia


Figure 14-7b The Cerebellum

Midbrain

Anterior lobe

Pons Cerebellar Peduncles

Superior cerebellar

peduncle

Middle cerebellar

peduncle

Inferior cerebellar

peduncle

Medulla oblongata Flocculonodular lobe

Choroid plexus of

the fourth ventricle

Posterior

lobe

Cerebellar

cortex

Cerebellar

nucleus

Arbor

vitae

A sectional view of the cerebellum, showing the arrangement of gray matter and white matter


14-6 The Midbrain

• Structures of the Midbrain

• Two pairs of sensory nuclei (corpora quadrigemina)

• Superior colliculus (visual)

• Inferior colliculus (auditory)

• Summary

• The corpora quadrigemina control reflexes of the eye

and ear. Fiber tracts extend between the pons and

cerebrum and between the midbrain and the

cerebellum. Contains nuclei of cranial nerves III and

IV.


Figure 14-8a The Midbrain

Thalamus

Cerebral peduncle

Pineal gland

Red nucleus

Substantia nigra

Corpora quadrigemina

Superior colliculus

Inferior colliculus

Reticular formation

A posterior view. The underlying nuclei are colored only on the right.


14-7 The Diencephalon

• The Diencephalon

• Integrates sensory information and motor commands

• Thalamus, epithalamus, and hypothalamus


14-7 The Diencephalon

• Thalamus: site of some aspects of emotion and memory; relay and filter to

the cerebrum for the special senses and motor activity

• Hypothalamus: Inferior to the thalamus. The major controller of the

autonomic nervous system and the link between the nervous system and

much of the endocrine system via its connection with the pituitary gland. It is

also involved in memory, thermoregulation, satiety, thirst, sleep, and

emotion.

• Epithalamus: contains the pineal gland (endocrine in function) and a relay

from the limbic system to the midbrain.


14-9 The Cerebrum

• The Cerebrum

• Is the largest part of the brain

• Controls all conscious thoughts and intellectual

functions

• Processes somatic sensory and motor information


14-9 The Cerebrum

• The Cerebrum Summary

• Forms the bulk of the brain, is folded superficially to form

ridges (gyri) and grooves (sulci).

• A longitudinal fissure divides the cerebrum into 2 cerebral

hemispheres. Each hemisphere is further subdivided into

5 lobes: frontal, parietal, temporal, insula, and occipital.


Figure 14-12a The Brain in Lateral View

Lateral sulcus

Pons

Medulla oblongata

FRONTAL

LOBE

Central sulcus

TEMPORAL LOBE

Lateral view, cadaver brain

Cerebellum

OCCIPITAL

LOBE

PARIETAL LOBE


Figure 14-12b The Brain in Lateral View

FRONTAL

LOBE

Precentral

gyrus

Central

sulcus

Postcentral

gyrus

Lateral sulcus

Pons

PARIETAL LOBE

OCCIPITAL

LOBE

TEMPORAL

LOBE

Cerebellum

Medulla oblongata

Lateral view


Figure 14-12c The Brain in Lateral View

Insula

Retractors along the lateral sulcus showing the insula


Figure 14-12d The Brain in Lateral View

Central sulcus Postcentral gyrus

PARIETAL LOBE

OCCIPITAL

LOBE

Parieto-

occipital sulcus

Cerebellum Pons

Medulla oblongata

Midsagittal section

TEMPORAL LOBE

FRONTAL

LOBE

Precentral gyrus

Cingulate

gyrus


14-9 The Cerebrum

• The Cerebrum Summary

• The cerebrum receives sensory information from both internal and

external stimuli. Within the cerebral gray matter, this information is

evaluated in conjunction with memory and is used to coordinate motor

output .

• The fiber tracts (white matter) of the brain serve to receive or send

information to the rest of the body (projection tracts), cross from one

cerebral hemisphere to the other (commissural tracts such as the corpus

collosum), or connect different regions within one hemisphere

(association tracts).

• Deep pockets of gray matter called the basal nuclei are involved in motor

control.


14-9 The Cerebrum

• Three Functional Principles of the Cerebrum

1. Each cerebral hemisphere receives sensory

information from, and sends motor commands to,

the opposite side of the body

2. The two hemispheres have different functions,

although their structures are alike

3. Correspondence between a specific function and a

specific region of cerebral cortex is not precise


Figure 14-13b Fibers of the White Matter of the Cerebrum

Longitudinal

fissure

Corpus

callosum

Projection

fibers of

internal

capsule

Anterior

commissure

Anterior view


• Motor and Sensory Areas of the Cortex


Figure 14-15a Motor and Sensory Regions of the Cerebral Cortex

Major anatomical landmarks on the surface of

the left cerebral hemisphere. The lateral sulcus

has been pulled apart to expose the insula.

FRONTAL LOBE

Prefrontal cortex

Gustatory cortex

Insula

Lateral sulcus

Olfactory cortex

Somatic motor association area (premotor cortex)

Primary motor cortex (precentral gyrus)

Central sulcus Primary sensory cortex (postcentral gyrus)

PARIETAL LOBE

TEMPORAL LOBE

OCCIPITAL LOBE

Somatic sensory association area

Visual association area

Visual cortex

Auditory cortex

Auditory association area


14-9 The Cerebrum

• Hemispheric Lateralization

• Functional differences between left and right

hemispheres

• Each cerebral hemisphere performs certain functions

that are not ordinarily performed by the opposite

hemisphere


14-9 The Cerebrum

• The Left Hemisphere

• In most people, left brain (dominant hemisphere) controls:

• Reading, writing, and math

• Decision making

• Speech and language

• The Right Hemisphere

• Right cerebral hemisphere relates to:

• Senses (touch, smell, sight, taste, feel)

• Recognition (faces, voice inflections)


Figure 14-16 Hemispheric Lateralization

Left Cerebral Hemisphere

LEFT HAND

Prefrontal

cortex

Speech center

Writing

Auditory cortex

General interpretive center

(language and mathematical

calculation)

Visual cortex

(right visual field)

C O R P U S

C A L L O S U M


Figure 14-16 Hemispheric Lateralization

Right Cerebral Hemisphere

RIGHT HAND

Prefrontal

cortex

Anterior commissure

Analysis by touch

Auditory cortex

Spatial visualization

and analysis

Visual cortex

(left visual field)

C O R P U S

C A L L O S U M


14-10 Cranial Nerves

• Cranial Nerves

• 12 pairs connected to brain

• Four Classifications of Cranial Nerves

1. Sensory nerves carry somatic sensory information, including

touch, pressure, vibration, temperature, and pain

2. Special sensory nerves carry sensations such as smell, sight,

hearing, balance

3. Motor nerves: axons of somatic motor neurons

4. Mixed nerves: mixture of motor and sensory fibers


14-10 Cranial Nerves

• Cranial Nerves

• Are classified by primary functions

• May also have important secondary functions

• Distributing autonomic fibers to peripheral ganglia

• The 12 cranial nerve groups are identified by:

• Primary function

• Origin

• Pathway

• Destination


Cranial Nerve Nerve Type Major Functions

I: Olfactory sensory smell

II: Optic sensory vision

III: Oculomotor primarily motor eyeball and eyelid movement; lens shape

IV: Trochlear primarily motor eyeball movement; proprioception (superior oblique

muscle)

V: Trigeminal: sensory

sensations of touch and pain from facial skin, nose,

mouth, teeth, and tongue; proprioception motor control of

chewing

VI: Abducens primarily motor eyeball movement; proprioception (lateral rectus muscle)

VII: Facial mixed movement of facial muscles; tear and saliva secretion;

sense of taste and proprioception

VIII: Vestibulocochlear: cochlear branch sensory hearing

VIII: Vestibulocochle-ar: vestibular branch sensory sense of equilibrium

IX: Glosso-phayrngeal mixed

sensations of taste, touch, and pain from tongue and

pharynx; chemoreceptors (that monitor O2and CO2);

blood pressure receptors; movement of tongue and

swallowing; secretion of saliva

X: Vagus mixed

parasympathetic sensation and motor control of smooth

muscles associated with heart, lungs, viscera; secretion

of digestive enzymes

XI: Accessory primarily motor head movement; swallowing; proprioception

XII: Hypoglossal primarily motor tongue movement, speech, and swallowing;

proprioception


Figure 14-18 Origins of the Cranial Nerves

Olfactory bulb: termination

of olfactory nerve (I)

Olfactory tract

Optic nerve (II)

Infundibulum

Oculomotor nerve (III)

Pons

Basilar artery

Vertebral artery

Cerebellum

Medulla oblongata

Spinal cord


Figure 14-18 Origins of the Cranial Nerves

Optic chiasm

Optic tract

Mamillary body

Trochlear nerve (IV)

Trigeminal nerve (V)

Abducens nerve (VI)

Vestibulocochlear

nerve (VIII)

Facial nerve (VII)

Glossopharyngeal

nerve (IX)

Vagus nerve (X)

Hypoglossal nerve (XII)

Accessory nerve (XI)


Figure 14-21 Cranial Nerves Controlling the Extra-Ocular Muscles

Superior

oblique

muscle

Trochlea

Superior

rectus

muscle

Levator

palpebrae

superioris

muscle

Inferior

rectus

muscle

Ciliary

ganglion

Lateral rectus

muscle (cut)

ABDUCENS

NERVE (N VI)

OPTIC

NERVE (N II) Optic

chiasm

OCULOMOTOR

NERVE (N III)

TROCHLEAR

NERVE (N IV)

Trigeminal

nerve (N V), cut

Vestibulocochlear

nerve (N VIII), cut

Facial nerve

(N VII), cut Medial

rectus

muscle

Inferior

oblique

muscle


Figure 14-22 The Trigeminal Nerve

Supra-orbital

nerves

Ciliary ganglion

Foramen

rotundum

Infra-orbital

nerve

Lingual nerve

Submandibular

ganglion

Mental nerve

Pterygopalatine

ganglion

Mandibular

branch

Otic ganglion

Foramen ovale

Maxillary

branch

Pons

TRIGEMINAL

NERVE (N V)

Semilunar

ganglion

Ophthalmic

branch

Superior orbital fissure


Figure 14-23a The Facial Nerve

Pterygopalatine

ganglion

Greater petrosal

nerve

Geniculate

ganglion

Pons

FACIAL

NERVE (N VII)

Posterior

auricular

branch

Stylomastoid

foramen

Chorda tympani nerve

(with mandibular

branch of N V)

Lingual branch

(with lingual nerve

of N V)

Submandibular

ganglion

Temporal

branch

Zygomatic

branches

Buccal

branch

Mandibular

branch

Cervical

branch

The origin and branches of the facial nerve


Figure 14-24 The Vestibulocochlear Nerve

Tympanic cavity

(middle ear)

Semicircular

canals

Vestibular

branch (N VIII)

Facial nerve

(N VII),

cut

Internal

acoustic

meatus

VESTIBULOCOCHLEAR

NERVE (N VIII)

N V

Pons

N VI

N VII

N XII

N IX

N X

N XI

Medulla

oblongata

Cochlear branch (N VIII) Cochlea Auditory tube Tympanic membrane


Figure 14-25 The Glossopharyngeal Nerve

Otic ganglion

Inferior

(petrosal)

ganglion

Lingual

branch

Carotid body

Carotid sinus

Common carotid artery

Carotid sinus branch

Pharyngeal branches

Parotid salivary gland

Superior (jugular)

ganglion

Medulla oblongata

GLOSSOPHARYNGEAL

NERVE (N IX)

Pons

N VII

N VI

N V

N VIII


Figure 14-26 The Vagus Nerve

Superior

pharyngeal

branch

VAGUS

NERVE (N X)

Pons

Superior

laryngeal nerve

Internal branch

External branch

Inferior

ganglion

of vagus

nerve

Medulla oblongata

Auricular branch

to external ear

Superior ganglion

of vagus nerve

Pharyngeal branch

Superior laryngeal nerve


Figure 14-27 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

Trigeminal nerve (N V)

Medulla oblongata

Cranial root of N XI

Spinal

root of N XI

External

branch of N XI

Spinal cord

Omohyoid muscle

Sternocleidomastoid

muscle

Ansa cervicalis

(cervical plexus)

Trapezius muscle

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