Anatomy Chapter 15 Brain and Crainial Nerves

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Gyri

The outer surface of an adult brain exhibits folds called gyri (sing. gyrus).

Sulci

Shallow depressions between gyri is called sulci (sing. sulcus)

Anterior

Directional term
Refers to Rostal (toward the nose)

Posterior

Directional term
Refers to Caudal (toward the tail)

Primary Brain Vesicles

By the fourth week of development, the three primary brain vesicles have formed. These eventually give rise to all the different regions of the adult brain.
Prosencephalon
Mesencephalon
Rhombencephalon

Prosencephalon

Forebrain

Mesencephalon

Midbrain

Rhombencephalon

Hindbrain

Five secondary brain vesicles

Five weeks of development
Three primary vesicles gives rise to five secondary vesicles.
Telencephalon
Diencephalon
Mesencephalon
Metencephalon
Myelencephalon

Telencephalon

Arises from the prosencephalon and eventually forms the cerebrum.

Diencephalon

Arises from the prosencephalon and eventually forms the thalamus, hypothalamus, and epithalamus.

Mesencephalon

The only primary vesicle that does not form a new secondary vesicle.

Metencephalon

Arises from the rhombencephalon and eventually forms the pons and cerebellum.

Myelencephalon

Derives from the rhombencephalon, and it eventually forms the medulla oblongata.

13 weeks development

26 weeks development

Gray Matter

Houses motor neuron and interneuron cell bodies, dendrites, telodendria, and unmyelinated axons.
Forms the cortex that covers the surface of most of the adult brain.

White Matter

Derives its color from the myelin in the myelinated axons.
Lies below (deep) to the gray matter of the cortex.

Cerebral Cortex

The external layer of gray matter
Covers the surface of most of the adult brain

Cerebral nuclei

Within the masses of white matter, the brain also contains discrete internal clusters of gray matter called cerebral nuclei, which are oval, spherical, or sometimes irregularly shaped clusters of neuron cell bodies.

Ganglion

Cluster of neuron cell bodies within the PNS

Center

Group of CNS neuron cell bodies with a common function.

Nucleus

Center in the CNS that displays discrete anatomic boundaries.

Nerve

Axon bundles extending through the PNS

Nerve Plexus

Network of nerves in PNS

Tract

CNS axon bundle in which the axons have a similar function and share a common origin and destination.

Funiculus

Group of tracts in a specific area of the spinal cord

Pathway

Centers and tracts that connect the CNS with body organs and systems.

Cortex

Outer layer of gray matter in cerebrum and cerebellum; consists of densely packed neuron cell bodies.

Cerebral hemisphere

Either of two symmetrical halves of the cerebrum, separated by the longitudinal fissure.

Cranial Meninges

Three CT layers that separate the soft tissues of the brain from the bones of the cranium, enclose and protect blood vessels that supply the brain, and contain and circulate cerebrospinal fluid.
Forms some of the veins that drain blood from the brain.
Deep (closest to the brain): pia mater
Middle: arachnoid mater
Superficial (farthest away from the brain): dura mater

Pia Mater

Innermost layer
Thin layer of areolar CT
Highly vascularized
Tightly adheres to the brain

Arachnoid Mater

Lies external to the pia mater
Composed of delicate web of collagen and elastic fibers, termed arachnoid trabeculae.

Subarachnoid Space

Immediately deep to the arachnoid mater
Arachnoid trabeculae extend through this space from the arachnoid mater to the underlying pia mater.

Subdural Space

Between the arachnoid mater and the overlying dura mater is a potential space called subdural space.
Becomes an actual space if blood or fluid accumulates there, a condition called subdural hematoma.

Dura Mater

External tough, dense irregular CT layer composed of two fibrous layers.
Meningeal layer lies deep to the periosteal layer.
Periosteal layer is the most superficial layer, forms the periosteum on the internal surface of the cranial bones.

Dural venous sinuses

The meningeal layer is usually fused to the periosteal layer, except in specific areas where the two layers separate to form large, blood-filled spaces called dural venous sinuses.
Typically triangular in cross-section, they do not have valves to regulate venous blood flow.
They are large veins that drain blood from the brain and transport to the internal jugular veins that help drain blood circulation of the head.

Epidural Space

The dura mater and the bones of the skull may be separated by the potential epidural space, which contains the arteries and veins that nourish the meninges and bones of the cranium. Under healthy conditions, not a space, but can fill with fluid if needed.

Cranial Dural Septa

The meningeal layer of the dura mater extends as flat partitions (septa) into the cranial cavity at four locations.
Collectively, these double layers of dura mater are called cranial dural septa.
They separate parts of the brain and provide additional stabilization and support to the entire brain.
Four: The falx cerebri, tentorium cerebelli, falx cerebelli, and diaphragma sellae.

Falx cerebri

Largest of the four dural septa
Sickle shape, vertical fold of dura mater
Located in midsagittal plane, projects into the longitudinal fissure between the left and right cerebral hemispheres.
Running within the margins of this dural septa are two dural venous sinuses: superior sagittal sinus and the inferior sagittal sinus.

Tentorium cerebelli

Horizontally oriented fold of dura mater that separates the occipital and temporal lobes of the cerebrum from the cerebellum.
Transverse sinuses run within its posterior border.
Tentorial notch- gap in anterior surface, allows for passage of brainstem.

Falx cerebelli

Extending into the midsagittal line inferior to the tentorium cerebelli is the falx cerebelli, a sickle-shaped vertical partition that divides the left and right cerebral hemispheres. A tiny occipital sinus runs in its posterior vertical border.

Diaphragma sellae

Smallest of the dural septa
Forms a "roof" over the sella turcica of the sphenoid bone.
A small opening within it allows for the passage of a thin stalk, called the infundibulum, that attaches the pituitary gland to the base of the hypothalamus.

Brain Ventricles

Cavities or expansions within the brain that are derived from the lumen (openings) of the embryonic neural tube.
They are continuous with one another as well as with the central canal of the spinal cord.
Contains CSF

Lateral ventricles

Two
In the cerebrum
Separated by a thin medial partition called the septum pellucidum.
Communicates with the third ventricle via an opening called interventricular foramen.
Contains CSF

Third Ventricle

Within the diencephalon is a smaller ventricle called third ventricle.
Lateral ventricles communicate with this ventricle via an opening called interventricular foramen.
Communicates with fourth ventricle via a narrow canal called the cerebral aqueduct, which passes through the mesencephalon.
Contains CSF

Fourth ventricle

Located between the pons/medulla and the cerebellum.
Narrows at its inferior end before it merges with the slender central canal in the spinal cord.
Contains CSF

Cerebral Spinal Fluid (CSF)

A clear, colorless liquid that circulates in the ventricles and subarachnoid space.
Bathes the exposed areas of the CNS and completely surrounds the brain and spinal Cord.
Functions:
Buoyancy- without CSF, the brain would sink through the foramen magnum.
Protection- Cushions, asks as a "movement buffer"
Environmental stability- Transports nutrients and chemicals to the brain and removes waste products from the brain.

CSF Formation

Formed by choroid plexus in each ventricle
Choroid plexus is composed of a layer of ependymal cells and the capillaries that lie within the pia mater.
Produced by secretion of a fluid from the ependymal cells that originates from the blood plasma.
Similar to blood plasma, although certain ion concentrations differ between the two types of fluid.

CSF Circulation

1. CSF is produced by choroid plexus in each ventricle
2. CSF flows from lateral ventricles and 3rd ventricle through the cerebral aqueduct into the 4th ventricle.
3. CSF in 4th flows into subarachnoid space by passing through openings in the roof of the 4th ventricle. These openings are the paired lateral apertures and the single median aperture. CSF also fills the central canal of the spinal cord.
4. As it travels through the subarachnoid space, CSF removes waste products and provides buoyancy for the brain and spinal cord.
5.CSF accumulates w/i the suarachnoid space, it exerts pressure w/i the arachnoid villi. This pressure exceeds the pressure in the venous sinuses. Thus, the arachnoid villi extending into the dural venous sinuses provide a conduit for a one-way flow of excess CSF to be returned into the blood within the dural venous sinuses.

Blood-Brain Barrier (BBB)

Nervous tissue is protected from the general circulation by the BBB, which strictly regulates what substances can enter the interstitial fluid of the brain.
Keeps the neurons in the brain from being exposed to drugs, waste products in the blood,and variations in levels of normal substances (e.g. ions, hormones) that could adversely affect brain function.
Astrocytes contribute to the BBB by using their perivascular feet to cover and wrap around the capillaries in the brain. Controlling what goes in and out of them.
BBB is reduced or missing in the choroid plexus, hypothalamus, and the pineal gland due to permeability and hormones.

Cerebrum

The location of conscious thought processes and the origin of all complex intellectual functions. It is identified as the two large hemispheres.
Center of your intelligence, reasoning, sensory perception, thought, memory, and judgement, as well as your voluntary motor, visual, and auditory activities.
Formed from the telecephalon.

Fissures

Deeper grooves in the brain.

Cerebral Hemispheres

Left and right
Separated by the longitudinal fissure that extends along the midsagittal plane.
Separated from one another, except at a few locations where bundles of axons called tracts form white matter regions that allow for communication between them. The largest one is the corpus callosum. This provides the main communications like between these hemispheres.

Hemispheric Lateralization

The two hemispheres appear as anatomic mirror images, but they display some functional differences.
Ex. the portions of the brain that are responsible for controlling speech and understanding verbalizarion are frequently located in the left hemisphere.

Frontal Lobe

Primary motor cortex (located within precentral gyrus)
Premotor cortex
Motor speech area (Broca area) (usually found only on the left frontal lobe)
Frontal eye fields
Functions:
Higher intellectual functions (concentration, decision making, planning); personality; verbal communication; voluntary motor control of skeletal muscles.
Central sulcus separates frontal from parietal lobes
Lateral sulcus separates frontal and parietal lobes from the temporal lobe

Parietal Lobe

Primary somatosensory cortex (located within postcentral gyrus)
Somatosensory association area
Pert of Wernicke area
Part of gnostic area
Functions:
Sensory interpretation of textures and shapes; understanding speech and formulating words to express thoughts and emotions.
Terminates at the central sulcus- anteriorly
Terminates at the parieto-occipital sulcus- posteriorly

Temporal Lobe

Primary auditory cortex
Primary olfactory cortex
Auditory association area
Olfactory association area
Part of Wernicke area
Part of gnostic area
Functions:
Interpretation of auditory and olfactory sensations; storage of auditory and olfactory experiences; understanding speech.

Occipital Lobe

Primary visual cortex
Visual association areas
Functions:
Conscious perception of visual stimuli; integration of eye-focusing movements; correlation of visual images with previous visual experiences.

Insula

Primary gustatory cortex
Functions:
Interpretation of taste; memory
Located deep to the lateral sulcus

Motor Areas of Cerebrum

Housed in the frontal lobe
Primary motor cortex: located within the precental gyrus of frontal lobe.
Controls skeletal muscle activity.
Left controls the right skeletal muscles and vice versa.

Motor homunculus

Reflects the amount of cortex dedicated to the motor activity of each body part.

Motor Speech area

(Broca area)
Located within the inferolateral portion of the left frontal love.
Responsible for controlling the muscular movements necessary for vocalization.

Frontal eye field

Superior surface of the middle frontal gyrus, which is immediately anterior to the premotor cortex in the frontal lobe.

Primary Somatosensory cortex

Housed within the postcentral gyrus of the parietal lobes. Neurons in this cortex receive general somatic sensory information from touch, pressure, pain, and temperature receptors.

Sensory Homunulus

May be traced on the postcentral gyrus surface.

Primary Visual Cortex

Located in the occipital lobe
Receives and processes incoming visual information

Primary auditory cortex

Located in temporal lobe
Receives and processes incoming visual information

Primary Gustatory Cortex

Located in the insula
Involved in processing taste information

Primary Olfactory cortex

Located in temporal lobe
Provides conscious awareness of smells

Association Areas

Either process and interpret incoming data or coordinate a motor response.
Integrate new sensory inputs with memories of past experiences

Premotor Cortex

Located in the frontal lobe
Permits us to process motor information and is primarily responsible for coordinating learned, skilled motor activities, such as moving the eyes in a coordinated fashion.

Somatosensory Association area

Located in the parietal lobe
interprets sensory information and is responsible for integrating and interpreting sensations to determine the texture, temperature, pressure, and shape of objects.
Allows us to identify objects with our eyes closed.

Auditory Association area

Located within the temporal lobe
interpret the characteristics of sound and store memories of sounds heard in the past.

Visual Association area

Located in the occipital lobe and surrounds the primary visual area
Enables us to process visual information by analyzing color, movement, and form, and to use this information to identify things we see.

Wernicke Area

Functional Brain region
Typically located in the left hemisphere
involved in recognizing, understanding, and comprehending spoken and written language.

Gnostic Area

Functional Brain Region
Located in regions of the parietal, occipital, and temporal lobes
Integrates all sensory, visual, and auditory information being processed by the association areas within these lobes.

Higher-Order Processing Centers

These centers process information from several different association areas.
Ultimately direct either extremely complex motor activity or complicated analytical functions.
Involve functions such as speech, cognition, understanding spatial relationships, and general interpretation.
Housed in both cerebral hemispheres.
Primary -> Association -> Higher Order

Central White Matter

Lies deep to the gray matter of the cerebral cortex and is composed primarily of myelinated axons.
Most of the axons are grouped into bundles called tracts, or projection tracts.

Association tracts

Connect different regions of the cerebral cortex within the same hemisphere.
Short association tracts are composed of arcuate fibers; they connect neighboring gyri within the same lobe.
Longer association tracts are composed of longitudinal fasciculi; connect gyri in different lobes of the same hemisphere.

Commissural Tracts

Extend between the cerebral hemispheres through axonal bridges called commissures.
The prominent commissural tracts that link the left and right cerebral hemispheres include the large, C-Shaped corpus callosum and the smaller anterior and posterior commissures.

Projection Tracts

Link the cerebral cortex to the inferior brain regions and the spinal cord.
The packed group of axons in these tracts passing to and from the cortex between the cerebral nuclei is called internal capsule.

Cerebral Nuclei

Paired, irregular masses of gray matter buried deep within the central white matter in the basal region of the cerebral hemispheres inferior to the floor of the lateral ventricle.
Components:
Caudate Nucleus- C-shaped. when one walks, the neurons in this nucleus stimulate the appropriate muscles to produce pattern and rhythm of arm and leg movements associated with walking.
Amygdaloid Body-Participates in the expression of emotions, control of behavioral activities, and development of moods.
Putamen and globus pallidus- combine to form a larger body, the lentiform nucleus. Functions in controlling muscular movement at the subconscious level.
Claustrum- Processes visual information at a subconscious level.

Epithalamus

Forms the posterior roof of the diencephalon and covers the 3rd ventricle.
Posterior portion houses the pineal gland and the habenular nuclei.

Pineal Gland

Endocrine gland
Part of epithalamus
Secretes hormone melatonin- which appears to help regulate day-night cycles known as circadian rhythm.

Habenular nuclei

Part of epithalamus
Help relay signals from the limbic system to the mesencephalon and are involved in visceral and emotional responses to odors.

Thalamus

Refers to paired oval masses of gray matter that lie on each side of the 3rd ventricle.
Located between the anterior commissure and the pineal gland (midsagittal view)
interthalamic adhesion: a small, midline mass of gray matter that connects the right and left thalamic bodies.
The principle and final relay point for sensory information that will be processed and projected to the primary somatosensory cortex.
Responsible for filtering out the sounds and sights in a busy dorm cafeteria when you are trying to study.

Thalamic nuclei

Each part of the thalamus is a gray matter mass composed of about a dozen major thalamic nuclei that are organized into groups; axons from these nuclei project to particular regions of the cerebral cortex.
Sensory impulses from all the conscious senses except olfaction converge on the thalamus and synapse in at least one of its nuclei.

Anterior Group

Thalamic Nuclei
Changes motor cortex excitability and modifies mood

Lateral Group

Controls sensory flow to parietal loves and emotional information to cingulate gyrus.

Medial Group

Sends signals about conscious awareness of emotional states to frontal lobe.

Posterior Group

Lateral geniculate nuclei: Relay visual information from optic tract to visual cortex and midbrain.
Medial geniculate nuclei: Relay auditory information from inner ear to auditory cortex
Pulvinar Nuclei: Integrate and relay sensory information for projection to association areas of cerebral cortex.

Ventral Group

Ventral anterior nuclei: Relay somatic motor information from cerebral nuclei and cerebellum to primary motor cortex and premotor cortex of frontal lobe.
Ventral lateral nuclei: Same as ventral anterior nuclei
Ventral posterior nuclei: Relay sensory information to primary somatosensory cortex of parietal lobe

Hypothalamus

Anterionferior region of the diencephalon
A thin, stalklike infundibulum extends inferiorly from the hypothalamus to attach the pituitary gland.

Functions of Hypothalamus

-Master control of autonomic nervous system (influences heart rate, blood pressure, digestive activities, and respiration)
-Master control of the endocrine system (secretes hormones that control secretory activities in the anterior pituitary gland)
-Regulation of body temperature (shivering and sweating)
-Control of emotional behavior (Pleasure, aggression, fear, rage, contentment, and the sex drive)
-Control of food intake (Monitors nutrients and produces sensations of hunger)
-Control of water intake (Monitor blood solute concentrations)
-Regulation of sleep-wake (circadian) rhythms

Anterior Nucleus

Hypothalamic Nuclei
"Thirst Center" (stimulates fluid intake); autonomic control center

Arcuate Nucleus

Hypothalamic Nuclei
Regulates appetite, release of gonadotropin-releasing hormone, release of growth hormone-releasing hormone, and release of prolactin-inhibiting hormone

Mammillary Body

Hypothalamic Nuclei
Processes sensations related to smelling

Paraventricular Nucleus

Hypothalamic Nuclei
Produces oxytocin and antidiuretic hormone (ADH)

Preoptic Area

Hypothalamic Nuceli
"Thermostat" (regulates body temperature)

Suprachiasmatic Nucleus

Hypothalamic Nuclei
Regulates sleep-wake (circadian) rhythm

Supraoptic Nucleus

Hypothalamic Nuclei
Produces oxytocin and antidiuretic hormone (ADH)

Ventromedial nucleus

Hypothalamic Nuclei
"Satiety center" (produces hunger sensations)

Brainstem

Connects the prosencephalon and cerebellum to the spinal cord.
Three regions: superiorly placed mesencephalon, the pons, and the inferiorly placed medulla oblongata.
It is a bidirectional passageway for all tracts extending between the cerebrum and the spinal cord.

Cerebral aqueduct

Part of the brainstem/mesencephalon
Extends through the mesencephalon, which connects the 3rd and 4th ventricles; it is surrounded by a region called the periaqueductal gray matter.

Cerebral Puduncles

Part of brainstem/mesencephalon
Located on the anterolateral surfaces of the mesencephalon.
Somatic motor axons descend from the primary motor cortex, through these peduncles, to the spinal cord.

Superior Cerebellar Peduncles

The mesencephalon is the final destination of the superior cerebellar peduncles connecting the cerebellum to the mesencephalon.

Tegmentum

Part of brainstem/mesencephalon
Contains pigmented red nuclei and the reticular formation.
The reddish color of the nuclei is due to both blood vessel density and iron pigmentation in the neuronal cell bodies.
Integrates information from the cerebrum and cerebellum and issues voluntary motor commands to the erector spinae muscles of the back to help maintain posture while standing, bending the waist, or walking.

Tectum

Part of brainstem/mesencephalon
Contains pairs of sensory nuclei, the superior and inferior colliculi, which are called the tectal plate. They are relay stations in the processing pathway of visual and auditory sensations.
Superior colliculi: "visual reflex centers" help visually track moving objects and control reflexes such as turning the eye and head in response to a visual stimulus.
Inferior colliculi: "Auditory reflex centers" control reflexive turning of the head and eyes in the direction of sound.

Substantia nigra

Part of brainstem/mesencephalon
Almost black in appearance, due to melanin
Houses clusters of neurons that produce the neurotransmitter dopamine, which affects the brain processes that control movement, emotional response, and ability to experience pleasure and pain.

Pons

Forms part of the mesencephalon
Housed within the Pons are the sensory and motor tracts that connect to the brain and spinal cord.
The middle cerebellar peduncles are transverse groups of fibers that connect the pons to the cerebellum.
Houses CN V, CN VI, CN VII, some of CN VIII

Autonomic respiratory centers

In the pons
Pseumotaxic center
Apneustic center
They regulate the rate and depth of breathing, and both of them influence and modify the activity of the respiratory center in the medulla oblongata.

Superior Olivary Complex

In the pons
located in the inferior pons
Receives auditory input and is involved in the pathway for sound localization

Medulla Oblongata

Part of brainstem
Formed from the myelencephalon
Continuous with the spinal cord
All communication b/w the brain and the spinal cord involves tracts that ascend or descend through the medulla oblongata.
Associated with CN VIII, CN IX, CN X, CN XI, CN XII

Pyramids

medulla oblongata
House the motor projection tracts called the corticospinal tracts

Decussarion pyramids

Medulla oblongata
In the posterior region of the medulla, most of these axons cross to the opposite side of the brain at a point called the decussation of the pyramids.
As a result of the crossover, each cerebral hemisphere controls the voluntary movements of the opposite side of the body.

Olive

Medulla oblongata
Contains a large fold of gray matter called the inferior olivary nucleus.
Relay ascending sensory impulses, especially prorioceptive information, to the cerebellum.

Nucleus cuneatus and Nucleus gracilis

Medulla oblongata
Relay somatic sensory information to the thalamus
Nucleus cuneatus: Receives posterior root fibers corresponding to sensory innervation from the arm and hand of the same side.
Nucleus gracilis: Receives posterior root fibers carrying sensory information from the leg and lower limbs of the same side.

Medial Lemniscus

Medulla oblongata
Projects through the brainstem to the ventral posterior nucleus of the thalamus

Autonomic Centers of the medulla oblongata

Cardiac center: Heart rate and strength of contracrion
Vasomotor center: Blood pressure
Respiratory Center: Respiratory rate
Other nuclei: coughing, sneezing, salivating, swallowing, gagging, and vomiting.

Cerebellum

Second largest part of the brain
Develops from the metencephalon
Folds of the cerebellar cortex are called folia.
Composed of left and right cerebellar hemispheres.
Each hemisphere has a anterior and posterior lobe, which are separated by the primary fissure.
Three regions: outer gray matter layer of cortex, an internal region of white matter (arbor vitae), and the deepest gray matter layer, which is composed of cerebellar nuclei.
Coordinates and "fine tunes" skeletal muscle movements and ensures that skeletal muscle contraction follows the correct pattern leading to smooth muscle, coordinated movements.

Vermis

Part of Cerebellum
Separates the left and right cerebellar hemispheres
Receives sensory input reporting torso position and balance.
Its output to the vestibular nucleus helps maintain balance.

Flocculonodular lobes

Life anterior and inferior to each cerebellar hemisphere

Cerebellar Peduncles

Three thick tracts, called peduncles, link the cerebellum with the brainstem.
Superior cerebellar peduncles connect the cerebellum to the mesencephalon.
Middle cerebellar peduncles connect the pons to the cerebellum.
Inferior cerebellar peduncles connect the cerebellum to the medulla oblongata.

Limbic System

The limbic system and reticular formation, a loosely organized gray matter core in the brainstem.
Composed of multiple cerebral and diencephalic structures that collaboratively process and experience emotions.
It is a collective name for the human brain structures that are involved in motivation, emotion, and memory with an emotional association.
Affects memory formation by integrating past memories of physical sensations with emotional states.
Forms a ring around the diencephalon.

Brain structures associated with the Limbic System

1. Cingulate Gyrus: receives input from the other components of the limbic system. Focuses attention on emotionally significant events and appears to bring them into consciousness.
2. Parahippocampal gyrus: Associated with the hippocampus
3. Hippocampus: Essential in storing memories and forming long-term memory.
4. Amygdaloid body: Involved in several aspects of emotion, especially fear. Can help store and code memories based on how a person emotionally perceives them- ex. as related to feat, extreme happiness, or sadness.
5. Olfactory bulbs, olfactory tracts, olfactory cortex: emotions with odors.
6. Fornix: connects hippocampus with diencephalon
7. Anterior thalamic nuclei, habenular nuclei, septal nuclei, and mammillary bodies: contribute to overall function of limbic system.

Cranial Nerves

Are part of the PNS and originate on the inferior surface of the brain.
12 of them

CN I

Olfactory
Sensory Function: Olfaction (smell)
Somatic Motor Function: NONE
Parasympathetic Motor (autonomic) Function: NONE

CN II

Optic
Sensory Function: Vision
Somatic Motor Function: NONE
Parasympathetic Motor (autonomic) Function: NONE

CN III

Oculomotor
Sensory Function: NONE
Somatic Motor Function: Four extrinsic eye muscles (medial rectus, superior rectus, inferior rectus, inferior oblique)
Levator palpebrae superioris muscle (elevates eyelid)
Parasympathetic Motor (autonomic) Function: Innervates sphincter pupillae muscle in eye to make pupil constrict; contracts ciliary muscles to make lens of eye more rounded (as needed for near vision)

CN IV

Trochlear
Sensory Function: NONE
Somatic Motor Function: Superior oblique eye muscle
Parasympathetic Motor (autonomic) Function: NONE

CN V

Trigeminal
Sensory Function: General sensory from anterior scalp, nasal cavity, entire face, most of oral cavity, teeth, anterior two-thirds of tongue; part of auricle of ear.
Somatic Motor Function: Muscles of mastication, mylohyoid, digastric (anterior belly), tensor tympani, tensor veli palatini
Parasympathetic Motor (autonomic) Function: NONE

CN VI

Abducens
Sensory Function: NONE
Somatic Motor Function: Lateral rectus eye muscle
Parasympathetic Motor (autonomic) Function: NONE

CN VII

Facial
Sensory Function: Taste from anterior two-thirds of tongue
Somatic Motor Function: Muscles of facial expression, digastric (posterior belly), stylohyoid, Stapedius
Parasympathetic Motor (autonomic) Function: Increases secretion from lacrimal gland of eye, submandibular and sublingual salivary glands.

CN VIII

Vestibulocochlear
Sensory Function: Hearing (cochlear branch); equilibrium (vestibular branch)
Somatic Motor Function: NONE
Parasympathetic Motor (autonomic) Function: NONE

CN IX

Glossopharyngeal
Sensory Function: Touch and taste of posterior one-third of tongue, visceral sensory from carotid bodies
Somatic Motor Function: Stylopharyngeus
Parasympathetic Motor (autonomic) Function: Increases secretion from parotid salivary gland

CN X

Vagus
Sensory Function: Visceral sensory information from pharynx, larynx, coratid bodies, heart, lungs, and most abdominal organs.
General sensory information from external acoustic meatus, eardrum, and pharynx
Somatic Motor Function: Most pharyngeal muscles; laryngeal muscles
Parasympathetic Motor (autonomic) Function: Innervates smooth muscle and glands of heart, lungs, larynx, trachea, most abdominal organs.

CN XI

Accessory
Sensory Function: NONE
Somatic Motor Function: Trapezius muscle, sternocleidomastoid muscle
Parasympathetic Motor (autonomic) Function: NONE

CN XII

Hypoglossal
Sensory Function: NONE
Somatic Motor Function: Intrinsic tongue muscles and extrinsic tongue muslces
Parasympathetic Motor (autonomic) Function: NONE

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