NEUROANATOMY

AND

NEUROPHYSIOLOGY

STUDY GUIDE

Neuroanatomy Learning Objectives

THE SPINAL CORD

The Gross Structure of the Spinal Cord in Situ

Lies within vertebral canal formed by foramina of vertebral column.

Extends from medulla oblongata (lower half of brainstem).

Spinal cord begins at occipital bone and ends between 1st and 2nd lumbar vertebrae.

The diameter of the spinal cord varies as follows (thickest to thinnest):

1. Cervical. The cervical enlargement extends from C3-T2. It corresponds with the brachial plexus nerves,

which innervate upper limb and 6th pair of cervical nerves.

2. Thoracic

3. Lumbar (note lumbar cord basically consists of the lumbar enlargement, which is thicker than thoracic

cord). It extends from T11-L1, below which it tapers rapidly into conus medullaris. It corresponds to

lumbosacral plexus nerves, which innervate lower limb.

The enlargements are where sensory and motor neurons enter and exit.

The spinal cord is divided into segments (31 spinal segments based on origins of spinal nerves):

1. There are 33 spinal cord nerve segments. Axons in CNS are grouped into tracts (not nuclei).

a. Cervical (C3-C8):

8 segments 8 pairs of cervical nerves (excluding C1 and C2. C1 spinal nerves exit column

between occiput and C1 vertebra. C2 nerves exit between posterior arch of C1 vertebra and

lamina of C2 vertebra).

b. Thoracic (T1-T12):

12 segments 12 pairs of thoracic nerves.

c. Lumbar (L1-L5):

5 segments 5 pairs of lumbar nerves.

d. Sacral (S1-S5):

5 segments 5 pairs of cranial nerves.

e. Coccygeal:

3 segments 3 segments join to form 1 segment 1 pair of nerves (exit through sacral

hiatus).

2. Motor nerve rootlets branch out of R. and L. ventro-lateral sulci.

3. Sensory nerve rootlets branch out of R. and L. dorsal lateral sulci.

4. Rootlets form nerve roots and are part of peripheral nervous system.

2 Ventral (motor) + 2 dorsal (sensory) roots= spinal nerve (one on each side of cord).

Spinal nerves (except C1 and C2) form inside and exit through inter-vertebral foramen below corresponding

vertebra.

Spinal nerves:

1. Upper part of vertebral column: Spinal nerves exit directly from cord.

2. Lower part of vertebral column: Spinal nerves pass further down column before exiting.

Terminal portion of cord is called conus medullaris. The pia mater continues as an extension called the filum

terminale, which anchors cord to the coccyx.

The cauda equina is a dangling collection of nerve roots in the vertebral column that continue to travel through

the vertebral column below the conus medullaris.

The cauda equina forms because the spinal cord stops growing in length at ~4yo, even though the

vertebral column continues to lengthen until adulthood. This results in the fact that sacral spinal

nerves actually originate in upper lumbar region.

Ganglia and Roots:

Each segment of the spinal cord is associated with a pair of ganglia, called dorsal root ganglia, which are situated

just outside spinal cord.

Dorsal root ganglia contain cell bodies of sensory neurons. Axons of these sensory neurons travel

into the spinal cord via the dorsal roots.

Ventral roots consist of axons from motor neurons, which bring information to periphery from cell

bodies in CNS.

Grey and White Matter of the Spinal Cord

The Gross Structure of the Vasculature of the Spinal Cord

Three arteries run longitudinally along the spinal cord:

1. One anterior (ventral) artery

2. Two posterior (dorsal) arteries

Spinal arteries arise from the segmental or root (radicular) arteries that follow dorsal and ventral spinal

roots. They interconnect in the pial plexus which then supplies the deep tissue of the spinal cord.

The other connections to the spinal arterial supply are:

1. Vertebral artery (cervical region)

2. Intercostal arteries (thoracic region)

3. Lumbar arteries (lumbar region)

4. Lateral sacral artery (sacral region)

Venous drainage of the spinal cord occurs from veins running parallel with the dorsal and ventral spinal

arteries and then into the large and complex epidural venous network.

The Internal Structure of the Spinal Cord

Internally, the spinal cord consists of: 1. White matter: Tracts of myelinated nerve fibres.

Lies around outside of grey matter.

Is divided into dorsal (posterior), lateral and ventral (anterior) funiculi.

The white matter is located outside of the grey matter and consists of myelinated motor

and sensory axons. Columns of white matter carry information up or down the cord.

2. Grey matter: Nerve cell bodies and their neuropil.

Lies centrally in the spinal cord.

In cross section looks like an H or a butterfly.

Contains a central canal which is continuous with ventricular system of brain.

The grey matter consists of interneurons and motor neurons. It also consists of

neuroglia cells and unmyelinated axons. Projections of the grey matter (wings) are

called horns. The grey horns and grey commissure form the “grey H.”

Neurons of the Spinal Cord

The Dorsal Roots of the Spinal Cord

Bear the dorsal root ganglia (sensory).

The Ventral Roots of the Spinal Cord:

1. Somatic motor fibres arise from final motor neurons in ventral horns striated muscle.

2. Autonomic preganglionic fibres arise from spinal preganglionic neurons. They are in the

intermediolateral columns (below) and project to final motor neurons in peripheral autonomic

ganglia:

a. Thoracic and upper lumbar cord (sympathetic).

b. Sacral cord (parasympathetic).

3. Paravertebral sympathetic chain ganglia are linked to the ventral roots by communicating

rami.

Lateral Horn

The lateral horn is found at thoracic, upper lumbar and sacral levels, which contain autonomic

preganglionic neurons.

Descending [upper] motor tracts of the WHITE MATTER (all end in various regions of ventral horns)

1. Cortico-spinal (pyramidal) Tract

a. Crossed = lateral funiculus.

b. Uncrossed = ventral funiculus.

2. Extra-pyramidal Tracts

a. Rubrospinal = descends in lateral funiculus

Small and rudimentary. Responsible for large muscle movement and fine motor

control.

b. Medullary Reticulospinal = descends in ventral/lateral funiculus

Excites anti-gravity extensor muscles.

The fibres of this tract arise from caudal pontine reticular nucleus and the oral

pontine reticular nucleus.

Fibres of this tract project to interneurons of lamina VII and VIII of cord.

c. Pontine (lateral) reticulospinal = descends in ventral funiculus

Inhibits excitatory axial extensor muscles of movement.

The fibres of this tract arise from the medullary reticular formation, mostly from the

gigantocellular nucleus, and descend the length of the cord in the anterior part of the

lateral column.

This tract terminates in the grey spinal laminae.

d. Vestibulospinal = descends in ventral funiculus

Maintain balance and posture of body and head based on information from the inner

ear (via vestibulocochlear nerve).

The fibres of this tract arise from the lateral vestibular nucleus.

This tract terminates at the interneurons of lamina VII and VIII.

Ascending [lower] sensory tracts of the WHITE MATTER (via the dorsal horns)

1. Fasciculus gracilis (carries information from below T6) = Ascends in medial part of dorsal funiculus

Bundle of axon fibres in posterior column of cord.

Carries proprioceptive information from middle thoracic and lower limbs of the body to the brain

stem.

Also carries deep touch, vibrational and visceral pain sensations to the brain stem.

2. Fasciculus cuneatus (carries information from T6 and up) = Ascends in lateral part of dorsal funiculus

Nerves running in posterior column of cord.

Sensation from spinal nerves in C1 and T6 dermatomes.

Carries fine touch, fine pressure, vibration and proprioceptive information.

Carries sensation to the brain stem.

3. Spinothalamic tract = Ascends in ventral and lateral funiculi

Transmits pain, temperature, itch and crude touch information to thalamus.

This pathway decussates at spinal cord level, not the brainstem.

There are two main parts of this tract:

a. Lateral tract: Pain and temperature.

b. Anterior (ventral) tract: Crude touch.

4. Dorsal spinocerebellar tract = Ascends in dorsal part of lateral funiculus

Transmits proprioceptive information from muscles to cerebellum.

This tract runs in parallel with ventral tract.

Transmits information from ipsilateral caudal aspect of the body and legs.

5. Ventral spinocereballar tract = Ascends in ventral part of lateral funiculus

Transmits proprioceptive information from muscles to cerebellum.

Transmits information from ipsilateral caudal aspect of body and legs.

The Relative Sizes of the Spinal Fibre Tract Varies with Spinal Level

Spinal Level Grey Matter White Matter

Sacral Dorsal horn prominent.

Lateral horn prominent.

Ventral horn large.

Small

Lumbar Dorsal horn prominent.

Lateral horn small/absent.

Ventral horn large.

Large

Thoracic Dorsal horn slender.

Lateral horn small.

Ventral horn modest.

Large

Cervical Dorsal horn slender.

Lateral horn absent.

Ventral horn large.

Large (especially lateral and dorsal)

The various sizes in the table above vary in accordance with the number of nerves that coverage on that area.

????????????????????????????????????????????????????????????????????????????????????????????

The Gross Structure of the Meninges

The meninges consists of three principal layers and enclose a space containing the CSF (superficial to deep):

1. Dura

2. Arachnoid

3. Pia

The epidural space is external to the dura and carries the epidural veins of the spinal cord.

The CSF itself is in the subarachnoid space.

The spinal cord is suspended in the dural sheath by the denticulate ligaments that run from the inner surface of

the dura between the dorsal and ventral rootlets.

Other Aspects of the Spinal Cord

Be able to identify:

Dorsal sulcus

Ventral Medial Fissure

Conus Medullaris (tapering caudal end of spinal cord)

Filum Terminale (pial extension beyond spinal cord)

Cauda Equina (spinal nerves arising caudal to L2)

THE BRAIN

The Major Divisions of the Brain

Major functions of the brain have different embryological origins and different levels of function.

The brain (excepting the cerebral cortex, which is highly homogenous) can be divided into a series of major

division, each of which has a characteristic set of functions. Be able to identify:

PRIMARY DIVISION SECONDARY DIVISION MAIN STRUCTURE

Prosencephalon (forebrain) Telencephalon

Diencephalon

Cerebral hemisphere

Thalamus, hypothalamus

Mesencephalon (midbrain) Mesencephalon Midbrain

Rhombencephalon (hindbrain) Metencephalon

Myelencephalon

Pons, cerebellum

Medulla oblongata

The midbrain + hindbrain = brain stem

The Cortex

You can identify parts of the cortex by anatomical or functional criteria.

The major anatomical areas of the cortex are known as loves, the names of which reflect their location.

Be able to identify:

Frontal lobe

Temporal lobe

Parietal lobe

Occipital lobe

The two hemispheres of the brain are joined by a vast tract of nerve fibres, most of which are myelinated, known

as the corpus callosum. You can see it in sagittal sections.

The Landmarks of the Cortex

The surface of the cortex is folded into ridges (gyri) and fissures (sulci) that are more or less constant between

individuals.

STRUCTURE 1 SEPARATION STRUCTURE 2

Frontal lobe Lateral fissure (or sulcus) Temporal lobe

Frontal lobe Central sulcus Parietal lobe

Parietal lobes Separated on medial side of cerebral hemispheres by parieto-occipital fissure (or sulcus)

Occipital lobe

Be able to identify on whole brains, sagittal sections, cross-sections (real brains, CT and MRI):

Deep within the lateral fissure is a region of the cortex known as the insula

Cingulate gyrus

Corpus callosum

Parahippocampal gyrus

Precentral gyrus

Postcentral gyrus

Superior, middle and inferior gyri of frontal lobe

Superior, middle and inferior gyri of temporal lobe

Lobules of parietal lobe (superior and inferior lobe, divided by intraparietal sulcus)

The Diencephalic part of the Forebrain- the Thalamus (inner room) and Hypothalamus

Thalamus + hypothalamus = lateral wall of 3rd ventricle inferior to corpus callosum.

Pineal gland (circadian rhythms).

Thalamic nuclei have connections with cerebral cortex, cerebellum and spinal cord. There is a topographic

relationship between the thalamus and cerebral cortex.

Y-shaped internal medullary lamina divides thalamus into lateral, anterior and medial nuclear groups.

All sensory input (except olfaction) to the cortex is first relayed through thalamus.

Lateral geniculate body (visual system).

Medial geniculate body (auditory system).

Hypothalamus (immediately superior to optic chiasm).

Hypothalamic motor outputs to posterior and anterior pituitary.

Links to brainstem.

Links to cortical structures: amygdala, anterior cingulate and insula (visceral function, emotion, reward etc.)

The Midbrain

Tectum (dorsal surface).

Tegmentum (ventral surface).

Cerebral aqueduct.

Periaqueductal grey (autonomic function and sensory processing).

Superior and inferior colliculi on dorsal surface (visual and auditory processing respectively).

Corticospinal fibre tract (main motor output from cortex to spinal cord and fine motor control).

Corticobulbar fibre tract (motor cortex to brainstem areas involved in movement, balance and orientation).

Corticopontine fibres, which terminate in pontine nuclei (in pons) that in turn project to cerebellum.

Deep to fibre tracts is the substantia nigra.

Deep to substantia nigra is the red nucleus (source of rubrospinal tract).

Be able to identify all these structure on whole brains on in brain sections.

The Hindbrain- pons and medulla oblongata)

Main external feature of pons are cerebellar peduncles (superior, middle and inferior pairs) on dorsum.

Peduncles connect brainstem and cerebellum.

Dorsal pons forms floor of 4th ventricle.

Motor nuclei of abducens, facial and trigeminal nerves beneath floor of 4th ventricle.

Most of pons is fibres connecting with cerebellum.

Fasciculus gracilis -- sensory information gracilis nucleus.

Fasciculus cuneatus -- sensory information cuneatus nucleus.

Trigeminal sensory nucleus.

Pyramids, which contain corticospinal (pyramidal) tract.

Decussation of pyramidal tract.

The Olive contains inferior olivary nucleus (connects to cerebellum).

At the level of the Olive:

Lateral and medial vestibular nuclei

Nucleus tractus solitaries

Dorsal motor nucleus of vagus

Hypoglossal nucleus

Cerebellum

Involved with balance, coordination and learning.

Vermis (muscle tone and position).

Two lobes/hemispheres (coordination of muscle movement, trajectory, speed and force).

Surface of the cerebellum folia (cerebellar gyri)

Primary fissure separates anterior and posterior lobe.

Deep surface of primary fissure flocculus and node (together form flocculonodular lobe) balance.

Cerebellum connected to brain stem and midbrain by cerebellar peduncles.

The Cranial Nerves

Refer to attached document.

The Meninges (out to in)

1. Dura mater tough outer covering

2. Arachnoid mater soft translucent membrane underlying dura

3. Pia mater thin vascular membrane adherent to brain surface

The arachnoid and pia is the subarachnoid space, which is filled with CSF.

Subarachnoid cisterns (enlargement of subarachnoid space):

Cisterna magna

Interpeduncular cistern

Two reflections of the dura partially divide cranial cavity and provide paths for major cerebral sinuses:

Falx cerebri (between cerebral hemispheres) superior sagittal sinus

Tentorium cerebelli (between cerebral hemispheres and cerebellum) transverse sinus

Be able to identify:

Meninges on brains and sagittal heads

Subarachnoid space and main cisterns

Relation between dura and bones of skull

What happens to dura and the points where cranial nerves exit/enter skull

The Ventricles and CSF

CSF flows through:

Subarachnoid space

Ventricular system

CSF is made by choroid plexus.

Choroid plexus lines parts of:

Lateral ventricle

Third ventricle

Fourth ventricle

CSF is returned to circulation via arachnoid villi (lines superior sagittal sinus).

There are four ventricles:

1. Right lateral ventricle

2. Left lateral ventricle

3. Third ventricle

4. Fourth ventricle

The ventricles:

Are interconnected

Connect with the central canal of spinal cord

Connect with subarachnoid space (via foramina in 4th ventricle)

Foramina of the 4th ventricle:

1. Median aperture (foramen of Magendie) Cisterna magna

2. 2x lateral apertures (foramina of Luschka) Cerebellopontine angle

Be able to identify on models and sagittal sections:

Ventricles and interconnections

Relations of ventricles to subarachnoid spaces and cisterns

Relations of ventricles to major structures of the brain

Choroid plexus

Getting Blood to and from the Brain

Internal carotid and vertebral arteries supply blood to brain.

A small amount of blood gets to meninges via middle meningeal artery, which is the 3rd branch of the 1st part of

the maxillary artery, which is a branch of the external carotid artery.

The internal carotid feeds into anterior and middle cerebral arteries, which supply major areas of the brain.

The internal carotid and middle cerebral arteries also feed into:

ARTERY BRANCHES SUPPLIES

Hypophyseal artery Branch of internal carotid

Superior

Inferior

Pars tuberalis, infundibulum of pituitary and median eminence. Posterior pituitary.

Ophthalmic artery Branch of internal carotid artery

Internal carotid orbit

Central retinal

Lacrimal

Posterior ciliary

Muscular branches

Supraorbital

Ethmoidal

Medial palpebral

Terminal

Inner layers of retina. Lacrimal gland, eyelids. Posterior uveal tract. Extraocular muscles. Muscles and skin of forehead. Meninges. Eyelids. Forehead and nose.

Anterior choroidal artery Branch of internal carotid artery

None. Telecephalon, diencephalon and mesencephalon.

Posterior communicating artery Connections to internal carotid via middle cerebral artery and anterior cerebral artery. Posteriorly communicates with posterior cerebral artery.

None. Part of structure of Circle of Willis.

Vertebral arteries:

ARTERY BRANCHES SUPPLIES

Posterior inferior cerebellar Anterior medullary segment

Lateral medullary segment

Supratonsillar segment

Posteronferior cerebellum

Anterior inferior cerebellar Internal auditory

Lateral branch

Medial branch

Anteroinferior cerebellum

Labyrinthine (aka. auditory artery) Anterior vestibular

Common cochlear proper & vestibulochochlear

Ear

Superior cerebellar Perforating branches

Lateral (marginal) branch

Hemispheric branches

Superior vermian

Superior cerebellum

Posterior cerebral Posterior communicating

Medial posterior choroidal

Lateral posterior choroidal

Perforators

Temporal branches

Lateral occipital

Medial occipital

Splenial

Occipital lobes and posteromedial temporal lobes

Be able to identify all branches and aspects of the Circle of Willis.

What is the advantage in having a vascular circle at the base of the brain?

One advantage to a circle is that there are redundancies in circulation. If one vessel is blocked, the brain is

still perfused.

At the base of the brain, the circle has the greatest and most immediate access to the most parts of the

brain.

Dural venous sinuses:

SINUS DRAINS TO

Inferior sagittal Straight sinus

Superior sagittal Becomes right transverse

Straight Becomes left transverse

Transverse Sigmoid

Sigmoid Internal jugular

Cavernous Superior and inferior petrosal Internal jugular vein

Dural venous sinuses are venous channels found between layers of dura mater. They:

Receive blood from internal and external veins of the brain.

Receive CSF from subarachnoid space.

Ultimately empty into internal jugular vein.

Clinical relevance of sinuses:

Damage to dura mater may cause a thrombosis in dural sinuses haemorrhagic infarction

Cavernous sinus is:

Traversed by internal carotid artery

Surrounded by CN 3, 4, 5 and 6

Important because: Thrombosis in cavernous sinus can affect CN 3, 4, 5 and 6 resulting in symptoms

related to those nerves.

Dural venous sinus:

Drain into extracranial veins via emissary veins.

Emissary veins have no valves, so pus can flow into skull through them and they are therefore a possible

route for extracranial infection to enter the skull.

One emissary vein communicates from outside skull through sphenoidal emissary foramen inferior to the

zygomatic arch with the cavernous sinus on the inside of the skull. This is an important route for spread of

infection because CN 2, 4, V1, V2 and 6 and internal carotid pass through cavernous sinus. Infection or

inflammation in the cavernous sinus can damage any of the cranial nerves that pass through it, or

meningitis. Rupture of the emissary veins will result in subdural haematoma.

THE BRAIN II

The Major Areas of the Cortex Involved in Motor Activity

FUNCTIONAL REGION ANATOMICAL STRUCTURE

Primary motor cortex Precentral gyrus

Supplementary motor cortex Superior gyrus of frontal lobe, rostral to precentral gyrus

Premotor cortex Middle gyrus of frontal lobe, rostral to precentral gyrus

Broca’s area (speech motor area) Caudal part of inferior gyrus of frontal lobe, adjacent to lateral fissure

Frontal eye field (eye movements) Middle region of middle gyrus of frontal lobe

Somatosensory cortex - Awareness of body position, joint angles, muscle force and touch etc.

Postcentral gyrus

Parietal association cortex - Awareness of contralateral body, knowledge

of object shapes, personal space etc.

Superior parietal lobe

Hippocampus - Memory, spatial/temporal maps, emotional

aspect of behaviour

Medial aspect of temporal lobe, deep to Parahippocampal gyrus

The Basal Ganglia and Corpus Striatum

Be able to identify all parts of the basal ganglia, corpus striatum and amygdala.

Inter-hemispheric Connections

On sagittal sections be able to identify:

Corpus callosum

Anterior commissure (information between temporal lobes)

Association fibres connect various ipsilateral regions of the cortex. Be able to identify:

Superior longitudinal fasciculus

Inferior longitudinal fasciculus

Cingulum (“girdle”)

Connections between Cortex and Subcortical Structures

These connections are known as projection fibres.

Are input/output between cortex and thalamus, striatum, brainstem and spinal cord etc.

These projection fibres are divided into:

Corticospinal tract

Corticobulbar tract These fibres are distributed radially as corona radiata,

Thalamocortical tract which converge towards brainstem.

As fibres of corona radiate converge towards brain stem, they form the internal capsule.

The anterior limb of internal capsule contains connections between thalamus and prefrontal cortex.

The posterior limb of internal capsule contains:

Corticobulbar motor tracts

Corticospinal motor tracts

Thalamus and somatosensory cortex connections

Thalamus and motor areas of frontal lobe connections

THE SKULL

Gross Anatomy of the Skull

Looking at the base of skull you can see three main areas:

Anterior fossae

Middle fossae

Posterior cranial fossae

The floor of each fossa is traversed by foramina transmitting cranial nerves and/or blood vessels. Be able to

identify:

THE ANTERIOR CRANIAL FOSSA OF THE SKULL

FORAMINA CRANIAL NERVE/S BLOOD VESSLES

Cribriform plate Olfactory nerves

THE MIDDLE CRANIAL FOSSA OF THE SKULL

FORAMINA CRANIAL NERVE/S BLOOD VESSLES

Optic canal Optic nerve

Superior orbital fissure Oculomotor nerve

Trochlear nerve

Abducens nerve

Ophthalmic division of trigeminal nerve

Foramen rotundum Maxillary division of trigeminal nerve

Foramen ovale Mandibular division of trigeminal nerve

Foramen lacerum Internal carotid on floor

Foramen spinosum Middle meningeal Note hypophyseal fossa in which pituitary lies.

THE POSTERIOR CRANIAL FOSSA OF THE SKULL

FORAMINA CRANIAL NERVE/S BLOOD VESSLES

Foramen magnum Spinal root of accessory nerve

Spinal cord

Vertebral arteries

Hypoglossal canal Hypoglossal nerve

Jugular foramen Glossopharyngeal nerve

Vagus nerve

Accessory nerve

Internal jugular vein

Internal auditory meatus Vestibulocochlear nerve

Facial nerve

OTHER

Extraocular eye muscles.

The Auditory System

The Cranial Nerves

The cranial nerves emerge directly

from the brain, in contrast to spinal

nerves, which emerge from

segments of the spinal cord. In

humans, there are TWELVE

PAIRS of cranial nerves. The

FIRST AND SECOND emerge

from the cerebrum, the

REMAINING TEN PAIRS

emerge from the brainstem.

Mnemonic for the nerves

Oh, Oh, Oh, To Touch And Feel

Vagina, God Vaginas Are Hot.

Mnemonic for the type of nerve

S= Sensory, M= Motor and B= Both (sensory + motor)

Some Say Money Matters, But My Brother Says Big Boobs Matter More.

Mnemonic for the foramina

C= Cribriform plate (Olfactory), O= Optic canal, S= Superior orbital fissure (Oculomotor), S= superior orbital fissure

(Trochlear), S= Superior orbital fissure (Trigeminal – Ophthalmic), R= Foramen Rotundum (Trigeminal – Maxillary),

O= Foramen Ovale (Trigminal – Mandibular), S= Superior orbital fissure (Abducens), I= Internal acoustic meatus (Facial),

I= Internal acoustic meatus (Vestibulocochlear), J= Jugular foramen (Glossopharyngeal), J= Jugular foramen (Vagus),

J= Jugular foramen (Accessory), H= Hypoglossal canal (Hypoglossal).

Carl Only Swims South. Silly Roger Only Swims In Incredible Jacuzzis. Jane Just Hitchhikes.

Figure 1 The Cranial Nerves and their Distributions.

Cranial

Nerve

Foramen Branches Type of

Impulse

Nucleus

Name

Nucleus

Location

Symptom/Signs of

Damage

Function

Olfactory (CNI)

Telencephalon

Skull: Cribriform

Plate

Olfactory

Filaments

Special Sensory

(afferent)

Anterior

olfactory

Olfactory

tract

Anosmia Smell and nasal

mucosa.

Optic (CNII)

Diencephalon

Skull: Optic

Foramen

None Special Sensory

(afferent)

Lateral

geniculate

nucleus

Thalamus Blindness Vision and retina.

Oculomotor

(CNIII)

Anterior Aspect

of Midbrain

Skull: Superior

Orbital Fissure

Superior and

Inferior

Divisions

General Motor

(efferent)

Parasympathetic

Motor

Oculomotor

Edinger-

Westphal

Midbrain

Midbrain

Eye deviates down & out

Loss of

pupillary/accommodation

reflexes

Eye movement

(elevation and

adduction)

Trochlear

(CNIV)

Dorsal Aspect of

Midbrain

Skull: Superior

Orbital Fissure

Muscular

Branches

Motor (efferent) Trochlear Midbrain Diplopia, lateral

deviation of eye

Eye movement

(Superior oblique

muscle

depression of

adducted eye)

Cranial

Nerve

Foramen Branches Type of

Impulse

Nucleus

Name

Nucleus

Location

Symptom/Signs of

Damage

Function

Trigeminal

(CNV)

Pons

Skull: Superior

Orbital Fissure

Meningeal,

Frontal, Lacrimal

and Nasocilliary

General Motor

(efferent)

General Sensory

(afferent)

Principal

Spinal

Mesencephalic

Motor

Pons

Medulla

Pons/midbrain

Pons

Facial aneasthesia

Loss of pain sensation

Insignificant

Weakness/loss of mastication

Sensation from dura,

nasal mucosa and

beneath eye, side of

nose, cheek, lip, upper

teeth, hard palate and

mastication

Ophthalmic

(CNV1)

Skull: Superior

Orbital Fissure

Other: Supraorbital

Foramen, Anterior

and Posterior

Ethmoidal

Foramina

Meningeal,

Frontal, Lacrimal

and Nasocilliary

General Sensory

(afferent)

Maxillary

(CNV2)

Skull: Foramen

Rotundum

Other: Inferior

Orbital Fissure,

Infraorbital

Foramen

Meningeal,

Infraorbital,

Posterior and

Anterior Superior

Alveolar Branches,

Zygmoatic, Sensory

Roots to

Pterygopalantine

Ganglion and

Greater and Lesser

Palantine

General Sensory

(afferent)

Mandibular

(CNV3)

Skull: Foramen

Ovale

Other: Mandibular

Foramen

Meningeal,

Auriculotemporal,

Buccal, Lingual

and Inferior

Alveolar

General Sensory

(afferent)

General Motor

(efferent)

Figure 2 Sensory branches of Trigeminal nerve.

Cranial

Nerve

Foramen Branches Type of

Impulse

Nucleus

Name

Nucleus

Location

Symptom/Signs

of Damage

Function

Abducens

(CNVI)

Anterior Margin

of Pons

Skull: Superior

Orbital Fissure

Muscular

Branches

General Motor

(efferent)

Abducens Pons Medial eye deviation

(lateral rectus)

Eye movement

(Abduction)

Facial (CNVII)

Pons

(cerebellopontine

angle) above olive

Skull: Internal

Auditory Meatus

Other: Facial Canal,

Hiatus of Facial

Canal, Stylomastoid

Foramen

Internal acoustic

canal facial canal

stylomastoid

foramen.

Greater Petrosal

Nerve, Chorda

Tympani

(Auricular

Branch), Facial

Branches and

Cervical

Branches

Special and

General Sensory

(afferent)

General and

Parasympathetic

Motor (efferent)

Motor

Solitary

Superior

salivatory

Pons

Pons

Pons

Paralysis of facial

nerve muscles

Loss of taste

(anterior 2/3rds of

tongue)

Dry mouth, loss of

lacrimation

Facial expresssion

Taste

Salivation, lacrimation

Vestibulocochlear

(CN VIII)

Lateral to CNVII

(cerebellopontine

angle)

Skull: Internal

Auditory Meatus via

internal acoustic

canal.

None General Sensory

(afferent)

Vestibular

Cochlear

Medulla

Medulla

Dysequilibrium,

Nystagmus

Hearing

Balance

Hearing

Glossopharyngeal

(CN IX)

Medulla

Skull: Jugular

Foramen

Muscular

Branches,

Auricular Branch,

Lingual Branch,

Branch to Carotid

Body and Sinus,

Tympanic Branch

and Lesser

Petrosal

General and

Special Sensory

(afferent)

General and

Parasympathetic

Motor (efferent)

Nucleus

ambiguus

Inferior

salivary

Solitary

Medulla

Medulla

Medulla

Loss of taste

(posterior 1/3rd

)

Insignificant

Loss of gag reflex

Taste

Salivation

Innervation of pharynx,

sensation from carotid

and aortic bodies and

carotid and aortic

sinuses.

Cranial

Nerve

Foramen Branches Type of

Impulse

Nucleus

Name

Nucleus

Location

Symptom/Signs

of Damage

Function

Vagus (X)

Posterolateral

Sulcus of Medulla

Skull: Jugular

Foramen

Palatopharyngeal

Branch, Superior

Laryngeal

Branch,

Recurrent

Laryngeal

Branch, Carotid

Sinus Nerve,

Cardiac,

Pulmonary,

Gastric, Renal,

Hepatic,

Pancreatic, Small

Intestine and

Large Intestine

Branches

Sensory

(afferent)

Motor (efferent)

Nucleus

ambiguus

Dorsal motor

vagal

Solitary

Medulla

Medulla

Medulla

Dysphagia &

hoarseness of voice

Insignificant

Loss of cough reflex

(larynx/pharynx),

loss of taste (hard

palate)

Swallowing & talking

(palatoglossus)

Cardiac, GI tract,

Respiration, taste,

sensation from carotid

and aortic bodies and

carotid and aortic

sinuses.

Cranial

Accessory (XI)

Spinal accessory

Cranial and

Spinal Roots

Skull: Jugular

Foramen

Other: Foramen

Magnum

Muscular

Branches

Motor (efferent) Nucleus

ambiguus

Spinal

accessory

Medulla

Cervical cord

Insignificant

Head

turning/shoulder

shrugging weakness

Pharynx/larynx muscles.

Cranial branch overlaps

with vagal functions.

Neck & shoulder

movement

Hypoglossal

(XII)

Medulla

Skull: Hypoglossal

Foramen via

hypoglossal canal

Muscular

Branches

General Motor

(efferent)

Hypoglossal Medulla Atrophy of tongue

muscles, deviation

on protrusion,

fasciculaations

Tongue movement,

except palatoglossus.

Trigeminal, glossopharyngeal and vagus derive from 1st, 2

nd, 3

rd and 4

th branchial arches.

Parasympathetic preganglionic pathways run with ciliary, glossopharyngeal and vagus nerves. In the head, the ganglia are associated with

branches of the trigeminal nerve.

GANGLION PREGANGLIONIC PATH LOCATION

Ciliary Oculomotor Ophthalmic branch of trigeminal

Pteryogopalatine Facial Maxillary branch of trigeminal

Submandibular Facial Mandibular branch of trigeminal

Otic Glossopharyngeal Mandibular branch of trigeminal

Vagal Vagus Associated with target organs

Anatomy of the Cranial Nerves

Figure 3 Olfactory Nerve (CN I) passing through

cribriform plate of ethmoid bone Figure 4 Optic Nerve (CN II). Figure 5 Oculomotor Nerve (CN III).

Figure 6 Trochlear Nerve (CN IV).

Figure 7 Trigeminal

Nerve and its branches

(CN V).

Anatomy of the Cranial Nerves

Figure 8 Abducens Nerve (CNVI). Figure 9 Facial Nerve (CNVII).

Figure 10 Vestibulocochlear Nerve (CN VIII)

Anatomy of the Cranial Nerves

Figure 11 Glossopharyngeal Nerve and branches (CN IX)

Figure 12 Vagus Nerve (CN X).

Anatomy of the Cranial Nerves

Figure 13 Accessory Nerve with Cranial (joins Vagus) and Spinal

branches. The cranial branch is often considered part of the

vagus, while the spinal branch is considered the accessory nerve

(CN XI) proper.

Figure 14 Hypoglossal Nerve (CN XII).

Anatomy of the Cranial Nerves

Anatomy of the Cranial Nerves (Inferior View)

LOCALISING

STROKE

LESIONS