Skull, Brain and Cranial Nerves
The Brain
4 Parts



Cerebrum
Diencephalon
Brain Stem



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Pons
Medulla
Midbrain
Cerebellum
Gray matter surrounded by White matter
Meninges: 3 membranes around
brain and spinal cord
Made of Connective tissue
Functions



Cover, Protect CNS
Enclose, protect blood
vessels supplying CNS
Contain CSF
3 Layers

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Dura Mater (external)
Arachnoid Mater (middle)
Pia Mater (internal)
Meninges (continued)
Dura mater

Strongest, 2 Layers, Fibrous Connective Tissue
Periosteal layer (Periosteum): External/superficial layer
 Meningeal layer: Internal/deep layer


Layers fused except around dural sinuses (venous blood
filled internal jugular vein)

Partitions: limit
movement of brain
Falx Cerebri –vertical,
between cerebral
hemispheres
 Falx Cerebelli -vertical,
between cerebellar
hemispheres
 Tentorium Cerebelli –
horizontal, between
cerebrum and cerebellum

Meninges
Arachnoid Mater
Middle layer
 Subarachnoid Space-between arachnoid mater and
pia mater (contains most of CSF, blood vessels)
 Arachnoid Villi- projections of arachnoid mater
through dura into superior sagittal sinus, act as
valves to help CSF pass into dural sinuses

Meninges (continued)
Pia Mater
Innermost layer
 Delicate, highly vascular
 Clings directly to brain tissue, dips into
convolutions

Quiz……
1
2
3
Quiz……
1
1 – Dura Mater
2
3
2 – Arachnoid Mater
3 – Pia Mater
Ventricles
Expansions of brain’s central cavity
Lined with Ependymal Cells
Filled with CSF (cerebrospinal fluid)
Ventricles continuous w/each other + central canal of spinal cord
Ventricles (continued)
Lateral Ventricles (#1+2)


Cerebral Hemisphere
Separated by Septum Pellucidum
Third Ventricle
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Diencephalon
Interventricular Foramen: connects to
lateral ventricle
Fourth Ventricle

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Hindbrain
Cerebral Aqueduct: connects 3rd and 4th
ventricles
Connects to central canal of spinal cord
& medulla
3 openings connect 4th to subarachnoid
space


2 lateral apertures
1 median aperture
4
Cerebrospinal Fluid
Liquid cushion for brain and
spinal cord
Nourishes brain
Removes waste
Conducts chemical signals
between parts of CNS (e.g.
hormones)
Forms as a filtrate of blood
in choroid plexuses
Choroid Plexuses
Choroid Plexuses:
groups of capillaries
surrounded by
ependymal cells
Made of sodium,
chloride ions, proteins,
glucose, O2
Flow of CSF
Formed in Choroid plexuses
Through Ventricles
Into Subarachnoid space &
central canal from 4th
ventricle
Through Arachnoid Villi
into Superior Sagittal Sinus
Into Internal Jugular Vein
Organization of the Brain
Composed of gray and white
matter
Different organization than
in the spinal cord


Cortex: external sheets of gray
matter in cerebrum &
cerebellum
Nuclei: deep masses of gray
matter surrounded by white
matter
Cerebrum
“Executive Suite” of nervous system

Self-awareness, initiate + control voluntary movements,
communicate, remember, understand
Made of Gray matter, White matter, Basal gangli (nuclei)
Most superior region
Covers diencephalon + top of brain stem like mushroom cap
Many small grooves + deep fissures
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Transverse-separates cerebral hemisphere + cerebellum
Longitudinal-separates right + left cerebral hemispheres
Sulci – grooves on surface
Gyri-ridges of brain tissue between sulci
Cerebral Hemispheres
Fissures and Grooves

Fissures – deepest

Transverse cerebral fissure
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Longitudinal fissure

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Separates R and L cerebral
hemispheres
Sulci

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Separates cerebral hemisphere
from cerebellum
Grooves on surface
Gyri

Ridges of brain tissue between the
sulci
Cerebral Hemispheres:
Each hemisphere divided into
5 lobes
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Frontal
Parietal
Occipital
Temporal
Insula
Created by deep sulci
Functional areas: motor,
sensory
Associative areas: integrate
Diencephalon
Surrounded by cerebral
hemispheres
Made of 3 Paired Structures

Thalamus
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
Hypothalamus
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Communicates sensory info of
cerebral cortex
Regulates many body activities
Emotion, sleep, memory, etc.
Pituitary Gland-hormones
Epithalamus

Pineal Gland-hormone
Brainstem:
Medulla Oblongata, Pons, Midbrain
Passage of all signals between spinal cord and brain
Midbrain
Pons
Medulla oblongata
Brainstem: Medulla Oblongata
Regulates several basic physiological
functions
Heartbeat (rate and force)
 Blood pressure (vasoconstriction/dilation of
arteries)
 Breathing (rate and depth)
 Others: speech, coughing, sneezing, salivation,
swallowing, gagging, vomiting, sweating

Attachment of CN IX, X, XI, XII
Brainstem: The Pons
Contains many tracts carrying signals:
from cerebrum to cerebellum & medulla
 up to thalamus
 between right and left hemispheres of cerebellum
 from brainstem to cerebellum

Attachment of CN V, VI, VII, VIII
Brainstem: Midbrain
Carries signals
Between higher and lower brain centers
 From cerebellum to cerebral cortex

Visual and Auditory reflex centers
Somatic motor
Attachment for CN III, IV
Cerebellum
Smooths + coordinates body
movements directed by other
parts of brain
2 Cerebellar Hemispheres
Functions
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Information on equilibrium
Movement of neck, trunk, limbs
Information from Cerebral cortex
Blood Brain Barrier
Protects brain from bloodborne toxins
(e.g.
urea, food toxins, bacteria)
Endothelium of brain
capillaries are loaded with
tight junction to decrease
permeability
Not complete protection,
some things still have to
get through (e.g. fatsoluble molecules can
pass through)
Blood Supply to Brain
Arteries

External carotid arteries and
branches
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Tissues of head & face, skin,
muscles
Middle meningeal a. = brain

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Internal carotid arteries and branches


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Boxers!
Opthalmic a. = Eye & Orbits
Ant & Middle Cerebral arts =
Cerebrum
Vertebral arteries
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Posterior brain
Vertebrae & Cervical Spinal Cord
Branches form Cerebral Arterial
Circle = Anastomosis
Blood Supply to the Brain
Veins

Dural sinuses
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Internal jugular

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Drains brain
External jugular

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Intracranial-receive blood
from veins in brain, bring
to Internal Jugular
Drains scalp and face
(superficial)
Vertebral

Drains cervical vertebrae,
cervical spinal cord, small
neck muscles
Cranial Nerves
12 Pairs: I-XII
Numbered Anterior to Posterior
Attach to inferior surface of brain
Exit brain through foramina in skull
I + II attach to Forebrain (cerebrum + diencephalon)
III-XII attach to Brainstem (midbrain, pons, medulla)
Only X goes beyond the head-neck
The Cranial Nerves
Number
I
II
Name
Olfactory
Optic
Exit
Cribiform Plate
Optic Foramen
Function
SENSORY: smell
SENSORY: vision
III
Oculomotor
Sup. Orbital Fissure MOTOR:
external muscles of the eye except lateral rectus and superior
oblique: levator palpebrae superioris. PARASYMPATHETIC:
sphincter of pupil and ciliary muscle of lens.
Number
Name
Exit
Function
IV
Trochlear Sup. Orbital Fissure MOTOR:
superior oblique muscle of the eye
V
Trigeminal
V1
Ophthalmic Branch Sup. Orb. Fissure
SENSORY: cornea, nasal mucosa, skin of face
V2
Maxillary Branch
Foramen rotundum
SENSORY: skin of face, oral cavity, anterior two-thirds of
tongue, teeth
V3
Mandibular Branch Foramen ovale MOTOR:
muscles of mastication: SENSORY: Skin of face
Number
Name
Exit
VI
Abducens
Sup. Orb. Fissure
lateral rectus muscle of the eye.
Function
MOTOR:
VII
Facial
Stylomastoid Foramen
PARASYMPATHETIC: lacrimal, submandibular, and sublingual
glands; MOTOR: muscles of facial expression; SENSORY: taste,
anterior two-thirds of tongue
VIII
Vestibulocochlear
VIII 1
Vestibular
VIII 2
Cochlear
Int. auditory meatus
Int. auditory meatus
SENSORY: equilibrium
SENSORY: hearing
Number
Name
Exit
Function
IX
Glossopharyngeal Jugular foramen
MOTOR:
stylopharyngeus muscle; SENSORY: posterior one-third of tongue, taste,
pharynx, branch to the carotid sinus; PARASYMPATHETIC: parotid gland
X
Vagus
Jugular Foramen
SENSORY:
external meatus, pharynx, and larynx; MOTOR: pharynx, and larynx;
PARASYMPATHETIC: thoracic and abdominal viscera
XI
Spinal Accessory Jug. Foramen
trapezius and sternocleidomastoid muscle
MOTOR:
XII
Hypoglossal
Hypoglossal Canal
MOTOR: Muscles of the tongue
Foramina of the Cranial Bones
Foramina
Associated Nerve
Olfactory Foramen
Olfactory N. (I)
Optic Foramen
Optic N. (II)
Superior Orbital Fissure
Oculomotor (III), Trochlear (IV),
Ophthalmic N. (V1), Abducens N. (VI)
Foramen Rotundum
Maxillary N. (V2)
Foramen Ovale
Mandibular N. (V3)
Internal Acoustic Meatus
Facial N. (VII), Acoustic N. (VIII)
Jugular Foramen
Glossopharyngeal N. (IX), Vagus N.
(X), Accessory (XI)
Hypoglossal Canal
Hypoglossal N. (XII)
Stylomastoid Foramen
Facial N. (VII)
Foramen Magnum
Medulla Oblongata, Accessory N. (XI)
Foramina of Facial Bones
Foramina
Supraorbital Foramen
Associated
Nerve
Ophthalmic N. (V1)
Infraorbital Foramen
Maxillary N. (V2)
Mental Foramen
Mandibular N. (V3)
Mandibular Foramen
Mandibular N. (V3)
How to Remember CN I-XII
Oh! Oh! Oh!
To Touch And Feel
Very Good Velvet!
Ah Heaven!
I
Olfactory
(oh)
II
Optic
(oh)
III
Oculomotor
(oh)
IV
Trochlear
(to)
V
Trigeminal (1-3)
(touch)
VI
Abducens
(and)
VII
Facial
(feel)
VIII
Vestibulocochlear
(very)
IX
Glossopharyngeal
(good)
X
Vagus
(velvet)
XI
Accessory
(ah)
XII
Hypoglossal
(heaven)
Motor vs. Sensory Nerves
Sensory = Afferent
Send nervous impulse from sensory receptors to
brain to bring in information
 e.g. pressure, temperature, pain

Motor = Efferent
Send nervous impulses from brain to body to
accomplish an action
 e.g. movement of a muscle, activation of a gland

Sensory Nerves
Sensory = Afferent

Visceral Sensory (sensory innervation of viscera)
stretch, pain, temp., chemical changes, irritation in viscera
 Special: taste


Somatic Sensory (sensory innervation of outer part body)
touch, pain, pressure, vibration, temp. in skin, body wall, limbs
 Special: hearing, equilibrium, vision, smell

Motor Nerves
Motor Nerves

Visceral Motor (motor innervation muscle in viscera + glands)


Branchial Motor (motor innervation of pharyngeal arch m.)


innervation smooth + cardiac muscle, glands
facial expression, pharyngeal constrictors, suprahyoid,
sternocleidomastoid, trapezius
Somatic Motor (motor innervation of skeletal muscle)

innervation of skeletal muscles (except pharyngeal arch m.)
Mnemonic for CN Function
Some
Say
Marry
Money
But
My
Brother
Says
Big
Brains
Matter
Most!
(CN I)
(CN II)
(CN III)
(CN IV)
(CN V)
(CN VI)
(CN VII)
(CN VIII)
(CN IX)
(CN X)
(CN XI)
(CN XII)
S = Sensory function
M = Motor function
B = BOTH (Sensory and Motor function)
Cranial Nerve Function
I
Olfactory--------Sensory--smell
II
Optic-------------Sensory--vision
III
Oculomotor----Motor----extrinsic eye muscles
IV
Trochlear-------Motor----extrinsic eye muscles
V
Trigeminal
V1
Opthalmic-----Sensory-cornea, nasal mucosa, face skin
V2
Maxillary------Sensory-skin of face, oral cavity, teeth
V3
Mandibular---Motor-muscles of mastication
---Sensory-face skin, teeth, tongue (general)
Distribution of sensory innervation
to skin of face from CN V
CN V = Trigeminal
V1 = Opthalmic
V2 = Maxillary
V3 = Mandibular
Cranial Nerves (continued)
VI
Abducens--------------Motor-----eye abduction muscles
VII
Facial-------------------Sensory---part of tongue (taste)
-------------------Motor------muscles of facial expression
VIII
Vestibulocochlear---Sensory----hearing, equilibrium
IX
Glossopharyngeal----Motor------stylopharyngeus muscle
----Sensory----tongue (gen & taste), pharynx
X
Vagus------------------Motor-------pharynx, larynx
-------------------Sensory----pharynx, larynx, abd. organs
XI
Accessory-------------Motor------trapezius, sternocleidomastoid
XII
Hypoglossal----------Motor-------tongue muscles
Summary of Functional Groups
Purely Sensory = I, II, VIII
Primarily Motor = III, IV, VI, XI, XII
Mixed = V, VII, IX, X
Parasympathetic Fibers = III, VII, IX, X
(Division of Autonomic NS = Visceral Motor)
Parasympathetic Fibers
CN III = Oculomotor
Contracts Iris (controls pupil)
 Contracts Ciliary Muscle (controls lens)

CN VII = Facial
Innervates Salivary glands (mandibular & sublingual)
 Innervates Lacrimal gland

CN IX = Glossopharyngeal

Innervates Parotid Salivary gland
CN X = Vagus

Innervates thoracic & abdominal viscera
The Autonomic Nervous System