AP-Ch13 by EVE ROAKE

Chapter

13 The Brain and Cranial Nerves PowerPoint® Lecture Slides prepared by Jason LaPres Lone Star College - North Harris

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)

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)

The Brain   Cerebrum   Neural cortex   Also called cerebral cortex   Folded surface increases surface area   Elevated ridges (gyri)   Shallow depressions (sulci)   Deep grooves (fissures)

The Brain   Cerebellum   Second largest part of brain   Coordinates repetitive body movements   Two hemispheres   Covered with cerebellar cortex

The Brain   Diencephalon   Located under cerebrum and cerebellum   Links cerebrum with brain stem   Three divisions   Left thalamus   Right thalamus   Hypothalamus

The Brain   Diencephalon   Thalamus   Relays and processes sensory information

  Hypothalamus   Hormone production   Emotion   Autonomic function

  Pituitary gland       

Major endocrine gland Connected to hypothalamus Via infundibulum (stalk) Interfaces nervous and endocrine systems

The Brain   The Brain Stem   Processes information between   Spinal cord and cerebrum or cerebellum

  Includes   Mesencephalon   Pons   Medulla oblongata

The Brain   The Brain Stem   Mesencephalon   Also called midbrain   Processes sight, sound, and associated reflexes   Maintains consciousness

The Brain   The Brain Stem   Medulla oblongata   Connects brain to spinal cord   Relays information   Regulates autonomic functions: –  heart rate, blood pressure, and digestion

The Brain

The Brain   Embryological Development   Determines organization of brain structures   Neural tube   Origin of brain   Enlarges into three primary brain vesicles – prosencephalon – mesencephalon – rhombencephalon Copyright © 2010 Pearson Education, Inc.

The Brain   Five Secondary Brain Vesicles   Telencephalon   Diencephalon   Mesencephalon   Metencephalon   Myelencephalon

The Brain   Origins of Brain Structures   Diencephalon and mesencephalon persist   Telencephalon:   Becomes cerebrum

  Metencephalon   Forms cerebellum and pons

The Brain

The Brain   Ventricles of the Brain   Origins of ventricles   Neural tube encloses neurocoel   Neurocoel expands to form chambers (ventricles) lined with ependymal cells

  Each cerebral hemisphere contains one large lateral ventricle   Separated by a thin medial partition (septum pellucidum)

The Brain   Ventricles of the Brain   Third ventricle   Ventricle of the diencephalon   Lateral ventricles communicate with third ventricle: –  via interventricular foramen (foramen of Monro)

The Brain   Ventricles of the Brain   Fourth ventricle   Extends into medulla oblongata   Becomes continuous with central canal of the spinal cord   Connects with third ventricle: –  via narrow canal in mesencephalon –  aqueduct of midbrain Copyright © 2010 Pearson Education, Inc.

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 Copyright © 2010 Pearson Education, Inc.

Brain Protection and Support   Physical protection   Bones of the cranium   Cranial meninges   Cerebrospinal fluid

  Biochemical isolation   Blood–brain barrier

Brain Protection and Support   The Cranial Meninges   Have three layers:   Dura mater   Arachnoid mater   Pia mater

  Are continuous with spinal meninges   Protect the brain from cranial trauma

Brain Protection and Support   The Cranial Meninges   Dura mater   Inner fibrous layer (meningeal layer)   Outer fibrous layer (endosteal layer) fused to periosteum   Venous sinuses between two layers

  Arachnoid mater   Covers brain   Contacts epithelial layer of dura mater   Subarachnoid space: between arachnoid mater and pia mater

Brain Protection and Support   Dural Folds   Folded inner layer of dura mater   Extend into cranial cavity   Stabilize and support brain   Contain collecting veins (dural sinuses)   Falx cerebri, tentorium cerebelli, and falx cerebelli

Brain Protection and Support   Dural Folds   Falx cerebri   Projects between the cerebral hemispheres   Contains superior sagittal sinus and inferior sagittal sinus

  Tentorium cerebelli   Separates cerebellum and cerebrum   Contains transverse sinus

Brain Protection and Support

Brain Protection and Support   Cerebrospinal Fluid (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 Copyright © 2010 Pearson Education, Inc.

Brain Protection and Support   Cerebrospinal Fluid (CSF)   Choroid plexus   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

Brain Protection and Support   Cerebrospinal Fluid (CSF)   CSF circulates   From choroid plexus   Through ventricles   To central canal of spinal cord   Into subarachnoid space around the brain, spinal cord, and cauda equina

Brain Protection and Support   Cerebrospinal Fluid (CSF)   CSF in subarachnoid space   Arachnoid villi: –  extensions of subarachnoid space –  extend through dura mater to superior sagittal sinus

  Arachnoid granulations: –  large clusters of villi –  absorb CSF into venous circulation

Brain Protection and Support

Figure 13–4 The Formation and Circulation of Cerebrospinal Fluid.

Brain Protection and Support

Figure 13–4a The Formation and Circulation of Cerebrospinal Fluid.

Brain Protection and Support

Figure 13–4b The Formation and Circulation of Cerebrospinal Fluid.

Brain Protection and Support   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

Brain Protection and Support

Brain Protection and Support   Cerebrovascular Disease   Disorders interfere with blood circulation to brain   Stroke or cerebrovascular accident (CVA)   Shuts off blood to portion of brain   Neurons die

Brain Protection and Support   Blood–Brain Barrier   Isolates CNS neural tissue from general circulation   Formed by network of tight junctions   Between endothelial cells of CNS capillaries   Lipid-soluble compounds (O2, CO2), steroids, and prostaglandins diffuse into interstitial fluid of brain and spinal cord   Astrocytes control blood–brain barrier by releasing chemicals that control permeability of endothelium Copyright © 2010 Pearson Education, Inc.

Brain Protection and Support   Blood–CSF Barrier   Formed by special ependymal cells   Surround capillaries of choroid plexus   Limits movement of compounds transferred   Allows chemical composition of blood and CSF to differ

Brain Protection and Support   Four Breaks in the BBB   Portions of hypothalamus   Secrete hypothalamic hormones

  Posterior lobe of pituitary gland   Secretes hormones ADH and oxytocin

  Pineal glands   Pineal secretions

Brain 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

The Medulla Oblongata   The Medulla Oblongata   Allows brain and spinal cord to communicate   Coordinates complex autonomic reflexes   Controls visceral functions   Nuclei in the Medulla   Autonomic nuclei: control visceral activities   Sensory and motor nuclei: of cranial nerves   Relay stations: along sensory and motor pathways Copyright © 2010 Pearson Education, Inc.

The Medulla Oblongata

The Medulla Oblongata   The Medulla Oblongata   Includes three groups of nuclei   Autonomic nuclei   Sensory and motor nuclei of cranial nerves   Relay stations along sensory and motor pathways

The Medulla Oblongata   Autonomic Nuclei of the Medulla Oblongata   Reticular formation   Gray matter with embedded nuclei   Regulates autonomic functions

  Reflex centers   Control peripheral systems: –  cardiovascular centers: »  cardiac center »  control blood flow through peripheral tissues –  respiratory rhythmicity centers sets pace for respiratory movements Copyright © 2010 Pearson Education, Inc.

The Medulla Oblongata   Sensory and Motor Nuclei of the Medulla Oblongata  Associated with 5 of 12 cranial nerves (VIII, IX, X, XI, XII)

The Medulla Oblongata   Relay Stations of the Medulla Oblongata   Nucleus gracilis and nucleus cuneatus   Pass somatic sensory information to thalamus

  Solitary nucleus   Receives visceral sensory information

  Olivary nuclei (olives)   Relay information about somatic motor commands

The Medulla Oblongata

The Pons   The Pons   Links cerebellum with mesencephalon, diencephalon, cerebrum, and spinal cord   Sensory and motor nuclei of cranial nerves V, VI, VII, VIII

The Pons   The Pons   Nuclei involved with respiration   Apneustic center and pneumotaxic center: –  modify respiratory rhythmicity center activity

  Nuclei and tracts   Process and relay information to and from cerebellum   Ascending, descending, and transverse tracts: –  transverse fibers (axons): »  link nuclei of pons with opposite cerebellar hemisphere Copyright © 2010 Pearson Education, Inc.

The Pons

The Cerebellum   Functions of the Cerebellum   Adjusts postural muscles   Fine-tunes conscious and subconscious movements

The Cerebellum   Structures of the Cerebellum   Folia   Surface of cerebellum   Highly folded neural cortex

  Anterior and posterior lobes   Separated by primary fissure

  Cerebellar hemispheres:   Separated at midline by vermis

  Vermis   Narrow band of cortex

The Cerebellum   Structures of the Cerebellum   Purkinje cells   Large, branched cells   Found in cerebellar cortex   Receive input from up to 200,000 synapses

The Cerebellum   Structures of the Cerebellum   The peduncles   Tracts link cerebellum with brain stem, cerebrum, and spinal cord: –  superior cerebellar peduncles –  middle cerebellar peduncles –  inferior cerebellar peduncles

The Cerebellum   Disorders of the Cerebellum   Ataxia   Damage from trauma or stroke   Intoxication (temporary impairment)   Disturbs muscle coordination

The Cerebellum

The Mesencephalon   Structures of the Mesencephalon   Tectum   Two pairs of sensory nuclei (corpora quadrigemina): –  superior colliculus (visual) –  inferior colliculus (auditory)

  Tegmentum   Red nucleus (many blood vessels)   Substantia nigra (pigmented gray matter)

The Mesencephalon   Structures of the Mesencephalon   Cerebral peduncles   Nerve fiber bundles on ventrolateral surfaces   Contain: –  descending fibers to cerebellum –  motor command fibers

The Mesencephalon

The Diencephalon   Integrates sensory information and motor commands   Thalamus, epithalamus, and hypothalamus   The pineal gland   Found in posterior epithalamus   Secretes hormone melatonin

The Diencephalon   The Thalamus   Filters ascending sensory information for primary sensory cortex   Relays information between basal nuclei and cerebral cortex   The third ventricle   Separates left thalamus and right thalamus   Interthalamic adhesion (or intermediate mass): –  projection of gray matter –  extends into ventricle from each side Copyright © 2010 Pearson Education, Inc.

The Diencephalon   The Thalamus   Thalamic nuclei   Are rounded masses that form thalamus   Relay sensory information to basal nuclei and cerebral cortex

The Diencephalon   Five Groups of Thalamic Nuclei   Anterior group   Anterior nuclei   Part of limbic system (emotions)

  Medial group   Provides awareness of emotional states

The Diencephalon   Five Groups of Thalamic Nuclei   Posterior group   Pulvinar nucleus (sensory)   Lateral geniculate nucleus (visual)   Medial geniculate nucleus (auditory)

The Diencephalon

The Diencephalon   The Hypothalamus   Mamillary bodies   Process olfactory and other sensory information   Control reflex eating movements

  Infundibulum   A narrow stalk   Connects hypothalamus to pituitary gland

  Tuberal area   Located between the infundibulum and mamillary bodies   Helps control pituitary gland function

The Diencephalon

The Diencephalon   Eight Functions of the Hypothalamus   Provides subconscious control of skeletal muscle   Controls autonomic function   Coordinates activities of nervous and endocrine systems   Secretes hormones   Antidiuretic hormone (ADH) by supraoptic nucleus   Oxytocin (OT; OXT) by paraventricular nucleus

The Diencephalon   Eight Functions of the Hypothalamus   Produces emotions and behavioral drives   The feeding center (hunger)   The thirst center (thirst)

  Coordinates voluntary and autonomic functions   Regulates body temperature   Preoptic area of hypothalamus

The Diencephalon

The Limbic System   The Limbic System   Is a functional grouping that   Establishes emotional states   Links conscious functions of cerebral cortex with autonomic functions of brain stem   Facilitates memory storage and retrieval

The Limbic System   Components of the Limbic System   Amygdaloid body   Acts as interface between the limbic system, the cerebrum, and various sensory systems

The Limbic System   Components of the Limbic System   Fornix   Tract of white matter   Connects hippocampus with hypothalamus

  Anterior nucleus of the thalamus   Relays information from mamillary body to cingulate gyrus

The Limbic System

The Cerebrum   The Cerebrum   Is the largest part of the brain   Controls all conscious thoughts and intellectual functions   Processes somatic sensory and motor information

The Cerebrum   Gray matter   In cerebral cortex and basal nuclei

  White matter   Deep to basal cortex   Around basal nuclei

The Cerebrum   Structures of the Cerebrum   Gyri of neural cortex   Increase surface area (number of cortical neurons)

  Insula (island) of cortex   Lies medial to lateral sulcus

  Longitudinal fissure   Separates cerebral hemispheres

The Cerebrum   Structures of the Cerebrum   Central sulcus divides   Anterior frontal lobe from posterior parietal lobe

  Lateral sulcus divides   Frontal lobe from temporal lobe

  Parieto-occipital sulcus divides   Parietal lobe from occipital lobe

The Cerebrum

The Cerebrum   Three Functional Principles of the Cerebrum   Each cerebral hemisphere receives sensory information from, and sends motor commands to, the opposite side of the body   The two hemispheres have different functions, although their structures are alike   Correspondence between a specific function and a specific region of cerebral cortex is not precise Copyright © 2010 Pearson Education, Inc.

The Cerebrum   White Matter of the Cerebrum   Association fibers   Commissural fibers   Projection fibers

The Cerebrum   White Matter of the Cerebrum   Association fibers   Connections within one hemisphere: –  arcuate fibers: »  are short fibers »  connect one gyrus to another

–  longitudinal fasciculi: »  are longer bundles »  connect frontal lobe to other lobes in same hemisphere

The Cerebrum   White Matter of the Cerebrum   Commissural fibers  Bands of fibers connecting two hemispheres: – corpus callosum – anterior commissure

The Cerebrum   White Matter of the Cerebrum   Projection fibers   Pass through diencephalon   Link cerebral cortex with: –  diencephalon, brain stem, cerebellum, and spinal cord

  Internal capsule: –  all ascending and descending projection fibers

The Cerebrum

The Cerebrum   The Basal Nuclei   Also called cerebral nuclei   Are masses of gray matter   Are embedded in white matter of cerebrum   Direct subconscious activities

The Cerebrum   Structures of Basal Nuclei   Caudate nucleus   Curving, slender tail

  Lentiform nucleus   Globus pallidus   Putamen

The Cerebrum

The Cerebrum   Functions of Basal Nuclei   Involved with   The subconscious control of skeletal muscle tone   The coordination of learned movement patterns (walking, lifting)

The Cerebrum   Motor and Sensory Areas of the Cortex   Central sulcus separates motor and sensory areas   Motor areas   Precentral gyrus of frontal lobe: –  directs voluntary movements

  Primary motor cortex: –  is the surface of precentral gyrus

The Cerebrum   Motor and Sensory Areas of the Cortex   Sensory areas   Postcentral gyrus of parietal lobe: –  receives somatic sensory information (touch, pressure, pain, vibration, taste, and temperature)

  Primary sensory cortex: –  surface of postcentral gyrus

The Cerebrum   Special Sensory Cortexes   Visual cortex   Information from sight receptors

  Auditory cortex   Information from sound receptors

  Olfactory cortex   Information from odor receptors

The Cerebrum

The Cerebrum   Association Areas   Sensory association areas   Monitor and interpret arriving information at sensory areas of cortex

  Somatic motor association area (premotor cortex)   Coordinates motor responses (learned movements)

The Cerebrum   Sensory Association Areas   Somatic sensory association area   Interprets input to primary sensory cortex (e.g., recognizes and responds to touch)

  Visual association area   Interprets activity in visual cortex

  Auditory association area   Monitors auditory cortex

The Cerebrum   Integrative Centers   Are located in lobes and cortical areas of both cerebral hemispheres   Receive information from association areas   Direct complex motor or analytical activities

The Cerebrum   General Interpretive Area   Also called Wernicke area   Present in only one hemisphere   Receives information from all sensory association areas   Coordinates access to complex visual and auditory memories

The Cerebrum   Other Integrative Areas   Speech center   Is associated with general interpretive area   Coordinates all vocalization functions

  Prefrontal cortex of frontal lobe   Integrates information from sensory association areas   Performs abstract intellectual activities (e.g., predicting consequences of actions) Copyright © 2010 Pearson Education, Inc.

The Cerebrum

The Cerebrum   Interpretive Areas of Cortex   Brodmann areas   Patterns of cellular organization in cerebral cortex

The Cerebrum

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

The Cerebrum   The Left Hemisphere   In most people, left brain (dominant hemisphere) controls   Reading, writing, and math   Decision making   Speech and language

The Cerebrum

The Cerebrum   Monitoring Brain Activity   Brain activity is assessed by an electroencephalogram (EEG)   Electrodes are placed on the skull   Patterns of electrical activity (brain waves) are printed out

The Cerebrum   Four Categories of Brain Waves   Alpha waves   Found in healthy, awake adults at rest with eyes closed

  Beta waves   Higher frequency   Found in adults concentrating or mentally stressed

  Theta waves   Found in children   Found in intensely frustrated adults   May indicate brain disorder in adults

The Cerebrum

The Cerebrum   Synchronization   A pacemaker mechanism   Synchronizes electrical activity between hemispheres

  Brain damage can cause desynchronization

Cranial Nerves   12 pairs connected to brain   Four Classifications of Cranial Nerves   Sensory nerves: carry somatic sensory information, including touch, pressure, vibration, temperature, and pain   Special sensory nerves: carry sensations such as smell, sight, hearing, balance   Motor nerves: axons of somatic motor neurons   Mixed nerves: mixture of motor and sensory fibers Copyright © 2010 Pearson Education, Inc.

Cranial Nerves   Cranial nerves are classified by primary functions   May also have important secondary functions   Distributing autonomic fibers to peripheral ganglia

Cranial Nerves

Cranial Nerves   Olfactory Nerves (I)   Primary function   Special sensory (smell)

  Origin   Receptors of olfactory epithelium

  Pathway   Olfactory foramina in cribriform plate of ethmoid

  Destination   Olfactory bulbs

Cranial Nerves   Olfactory Nerve Structures   Olfactory bulbs   Located on either side of crista galli

  Olfactory tracts   Axons of postsynaptic neurons   Leading to cerebrum

Cranial Nerves

Cranial Nerves   Optic Nerves (II)   Primary function   Special sensory (vision)

  Origin   Retina of eye

  Pathway   Optic canals of sphenoid

  Destination   Diencephalon via optic chiasm

Cranial Nerves   Optic Nerve Structures   Optic chiasm   Where sensory fibers converge   And cross to opposite side of brain

  Optic tracts   Reorganized axons   Leading to lateral geniculate nuclei

Cranial Nerves

Cranial Nerves   Oculomotor Nerves (III)   Primary function   Motor (eye movements)

  Origin   Mesencephalon

  Pathway   Superior orbital fissures of sphenoid

  Destination   Somatic motor: –  superior, inferior, and medial rectus muscles –  inferior oblique muscle –  levator palpebrae superioris muscle

Cranial Nerves   Oculomotor Nerve Structures   Oculomotor nerve   Controls four of six eye-movement muscles   Delivers autonomic fibers to ciliary ganglion: –  ciliary ganglion: controls intrinsic muscles of iris and lens

Cranial Nerves   The Trochlear Nerves (IV)   Primary function   Motor (eye movements)

  Origin   Mesencephalon

  Pathway   Superior orbital fissure of sphenoid

  Destination   Superior oblique muscle

Cranial Nerves   The Abducens Nerves (VI)   Primary function   Motor (eye movements)

  Origin   Pons

  Pathway   Superior orbital fissures of sphenoid

Cranial Nerves

Cranial Nerves   The Trigeminal Nerves (V)   Primary function   Mixed (sensory and motor) to face

  Origin   Ophthalmic branch (sensory): –  orbital structures –  nasal cavity –  skin of forehead, upper eyelid, and eyebrow –  part of nose

Cranial Nerves   The Trigeminal Nerves (V)   Origin   Maxillary branch (sensory): –  lower eyelid –  upper lip, gums, and teeth –  cheek and nose –  palate and part of pharynx

  Mandibular branch (sensory): –  lower gums, teeth, and lips –  palate and part of tongue

Cranial Nerves   The Trigeminal Nerves (V)   Pathway   Ophthalmic branch: –  superior orbital fissure

  Maxillary branch: –  foramen rotundum

  Mandibular branch: –  foramen ovale

Cranial Nerves   The Trigeminal Nerves (V)   Destination   Sensory nerves: –  sensory nuclei in pons

  Motor nerves of mandibular branch: –  muscles of mastication

Cranial Nerves   Trigeminal Nerve Structures   Trigeminal nerves   Largest cranial nerves   With three major branches

  Semilunar ganglion   Contains cell bodies of sensory neurons

Cranial Nerves

Cranial Nerves   The Facial Nerves (VII)   Primary function   Mixed (sensory and motor) to face

  Origin   Sensory: –  taste receptors on anterior 2/3 of tongue

  Motor: –  motor nuclei of pons

Cranial Nerves   The Facial Nerves (VII)   Destination   Sensory: –  sensory nuclei of pons

  Somatic motor: –  muscles of facial expression

Cranial Nerves   Facial Nerve Structures   Facial nerve branches   Temporal   Zygomatic   Buccal   Mandibular   Cervical branches

Cranial Nerves   Facial Nerve Structures   Geniculate ganglia   Hold cell bodies of sensory neurons

  Pterygopalatine ganglia   Postganglionic fibers innervate glands (lacrimal, nasal cavity, and pharynx)

  Submandibular ganglia   Innervate salivary glands

Cranial Nerves

Cranial Nerves   The Vestibulocochlear Nerves (VIII)   Primary function: special sensory   Vestibular branch: –  balance and equilibrium

  Cochlear branch: –  hearing

  Origin   Receptors of inner ear

  Pathway   Internal acoustic meatus of temporal bones

Cranial Nerves   Vestibulocochlear Nerve Structures   Vestibular branch   Originates at receptors of vestibule (balance)   Connects to vestibular nuclei of pons and medulla oblongata

  Cochlear branch   Originates at sensors of cochlea (hearing)   Connects with cochlear nuclei of pons and medulla oblongata

Cranial Nerves

Cranial Nerves   The Glossopharyngeal Nerves (IX)   Primary function   Mixed (sensory and motor) to head and neck

  Origins   Sensory: –  posterior 1/3 of tongue –  part of pharynx and palate –  carotid arteries

Cranial Nerves   The Glossopharyngeal Nerves (IX)   Pathway   Jugular foramina between occipital and temporal bones

  Destination   Sensory: –  sensory nuclei of medulla oblongata

  Somatic motor: –  nerves involved in swallowing

Cranial Nerves   Glossopharyngeal Nerve Structures   Superior and inferior ganglion   Sensory neurons of tongue and pharynx

  Otic ganglion   Synapse visceral motor fibers

Cranial Nerves

Cranial Nerves   The Vagus Nerves (X)   Primary function   Mixed (sensory and motor)   Widely distributed in thorax and abdomen

  Origins   Sensory: –  part of pharynx –  auricle and external acoustic meatus –  diaphragm –  visceral organs of thoracic and abdominopelvic cavities

Cranial Nerves   The Vagus Nerves (X)   Pathway   Jugular foramina   Between occipital and temporal bones

  Destination   Sensory: –  sensory nuclei and autonomic centers of medulla oblongata

Cranial Nerves   Vagus Nerve Structures   Vagus nerves   Branch and radiate extensively

  Superior (jugular) ganglion and inferior (nodose) ganglion   Hold sensory neurons

Cranial Nerves

Figure 13–26 The Vagus Nerve.

Cranial Nerves

Figure 13–26 The Vagus Nerve.

Cranial Nerves   The Accessory Nerves (XI)   Primary function   Motor to muscles of neck and upper back

  Origin   Motor nuclei of spinal cord and medulla oblongata

  Pathway   Jugular foramina between occipital and temporal bones

  Destination   Internal branch: –  voluntary muscles of palate, pharynx, and larynx

Cranial Nerves   Accessory Nerve Structures   Spinal root   Motor fibers that originate in anterior gray horns of first five cervical segments of spinal cord

  Cranial root   Motor fibers that originate in medulla oblongata

  Internal branch   Joins the vagus nerve

Cranial Nerves   The Hypoglossal Nerves (XII)   Primary function   Motor (tongue movements)

  Origin   Motor nuclei of medulla oblongata

  Pathway   Hypoglossal canals of occipital bone

Cranial Nerves

Cranial Reflexes   Cranial Reflexes   Monosynaptic and polysynaptic reflex arcs   Involve sensory and motor fibers of cranial nerves   Clinically useful to check cranial nerve or brain damage

Cranial Reflexes