Anatomy and Physiology

West Chester University

Spring 2014

CN V: Trigeminal

• CN V primarily responsible for mastication and sensation to the face. Innervating the tensor velar palatine, partially responsible for flattening and tensing of the soft palate and opening of the eustachian tube. Innervating an extrinsic laryngeal muscle (the anterior belly of the digastric) it also assists in the upward and anterior movement of the larynx.

• Testing: unilateral paralysis of CN V=deviation of the jaw to the side of the lesion and an inability to force the jaw to the opposite side of the lesion. Problems result from lower motor neuron lesions. UMN lesions that are unilateral do not affect cranial nerves since nuclei receive so many axons from the hemisphere.

• Sensory component to be tested: eyes closed and a cotton swab is used to stoke the face in 3 different areas of the nerve.

CN VII: Facial

• Facial nerve responsible for all movements of facial expression.• CN VII enables you to wrinkle your forehead, close your eyes tightly,

close your mouth tightly, pull back the corners or your mouth and tense your cheeks, pull down the corners of your mouth and tense your anterior neck muscles.

• Facial nerve also assists in pulling the larynx yp and back. Provides motor innervation to the sublingual and submaxillary salivary glands, guards the middle ear by innervating the stapedius muscle which dampens excessive movement of the ossicles in the presence of a loud noise. Also is partially responsible for taste.

• See pg. 147-148 Neurology of Speech Pathology for motor testing

CN VIII: VestibulocochlearCN IX: Glossopharyngeal

• CN VIII-takes afferent information from the internal ear to the nervous system. Responsible for sound sensitivity and changes in equilibrium. Testing vestibular function is not for the speech pathologist.

• CN IX-efferent to one muscle only-the stylopharyngeus. This muscle dilates the pharynx laterally and contributes to the elevation of the pharynx and larynx. Helps to clear the pharynx and larynx for swallowing. Testing: most of the functions of CN IX cannot be tested separately from those of CN X as the vagus has the predominant control over laryngeal and pharyngeal sensory and motor function-testing the gag-see pg. 151 of Neurology for Speech/Language Pathology.

CN X: Vagus

• Vagus means “wanderer”• Testing: Palatal fx: palate at rest, palatal arches-

observe symmetry, phonate “ah”; gag reflex; Laryngeal function eval by direct or indirect laryngoscopy to assess vocal cords, finer analysis of vocal cord movement using laryngeal stroboscopy-damage to the vagus nerve may cause paralysis or paresis of the vocal cord. Preliminary assessment of laryngeal function done through clinical voice eval-pg. 153/154 Neurology for SLP

CN XI: Spinal AccessoryCN XII: Hypoglossal

• CN XI: primary function is motor to help turn, tilt and thrust forward the hear or raise the strenum and clavicle if the head is in a fixed position and to the trapezius muscle responsible for shrugging the shoulders.

• CN XII: innervates the muscles for tongue movement: four intrinsic muscles of the tongue control tongue shortening, concaving (turning the tip and lateral margins upward), narrowing, elongating and flattening. Extrinsic muscles for tongue protrusion (genioglossus), drawing the tongue upward and backward (styloglossus), retraction and depression of the tongue (hyoglossus), the hyloglossus acts with the chondroglossus to elevate the hyoid bone, thus participating in phonation. Testing: pg 156/157/158

• Cranial nerve assessment critical for swallowing and speech production. Motor exam for swallowing should consist of the same maneuvers as for speech exam.

Development

• Week 1-Fertilization-zygote is formed (union of sperm and ova), slowly divides via mitotic division; blastocyst attaches to uterine lining (endometrium)

• Week 2- blastocyst becomes completely implanted; 3 preliminary structures begin to form

• Week 2.5 (day 18) neural groove-forms with folds on either side, neural plate-thickening of embryonic ectoderm, neural crest cells-form the sensory ganglia; in the head region neural crest cells migrate into the pharyngeal arches

• Week 3-follows the frist missed menstrual period, embryo develops:endoderm,mesoderm,ectoderm; neural vesicles visible at 3 weeks-prosencephalon (forebrain), mesencephalon (midbrain), rhombencephalon (hindbrain)

• Week 4- cranial 2/3 of neural tube develop into a future brain, caudal 1/3 will become the spinal cord

Development

• Weeks 6-12-cerebral hemisphere• Programmed cell death: more neurons than are needed are made

during development-neurons unsuccessful at making their connections are then lost by a pre-programmed neuronal cell death.

• Schizencephaly-split brain-showed asymmetry for speech and language functions indicating that the corpus callosum plays a role in transmitting language and experiments led to speculations that the two hemispheres function differently but integrated in brain function

• Spina bifida-divided spinal column, failure of caudal part of the neural tube closure

• Synaptic plasticity-modifications to neuronal connections after development is complete; can be made as an alternative pathway if damage occurs (therapy)

White Matter

• Subcortical-myelinated axons, relay system of motor impulses to the spinal cord, muscles and brain; makes up 60% of the brain; consumes 6% of the cerebral oxygen

• Motor and sensory pathways

Grey Matter

• Cortex

• Master commander-where motor function originates

• Brain surface-6 layers

• Makes up 40% of the brain

• Consumes 94% of the cerebral oxygen

Definitions

• Neurophysiology-study of the chemical process of the neurosystem and why it works

• Neuropsycholgy-psychologist who specializes in the study of mood/affect disorders due to damage of the nervous system

• Neuroscience: study of anatomical structures, cellular functions and physiological processes of the nervous system; focuses on the foundation of normal brain function (thus making the identification of abnormal sites/functions easier

Terms of orientation

• Planes of reference:*defined relative to imaginary axes of the body-you can rotate a structure in space and still

discuss the orientation of its parts.

*Frontal section or frontal view-divides the body into the front and back sections

*Frontal or coronal view-divides the body into front and back

Terms of orientation

*Sagittal section-divides the body into right

and left halves

*Transverse section-divides the body into

upper and lower halves.

*Anterior (ventral)-front surface of the body

*Posterior (dorsal)-toward the back

*Peripheral-away from the center

*Superficial-confined to the surface

*Reference for an organ-

-deep to another-closer to the axis of the

body

-distal-away from the midline

-medial-toward the midline

-Prone-on the belly/in a horizontal position

with the face down

-Supine-on the back/body in a horizontal position with the face up

• Horizontal or transverse

• Vertical or coronal

• Diagonal

DIRECTIONALITY SELF TEST

• Using your hands in relation to yourself:– Show SUPERIOR TO YOUR HEAD

– INFERIOR TO YOUR BODY

– ANTERIOR TO YOUR FACE

– POSTERIOR TO YOUR HEAD

– ABDUCT YOUR ARM

– ADDUCT YOUR ARM

– DIVIDE YOUR FACE SAGITTALY

– DIVIDE YOUR FACE TRANSVERSLY

– POINT TO THE MEDIAL ALSPECT OF YOUR FACE

– POINT TO THE LATERAL ASPECT OF YOUR FACE

Body Planes

Why Is This Important?

• Good question!

• All clinicians working with anatomical structures should know position to self and in relation to others

• Why? For assessment, documentation and treatment purposes

Nervous Tissue

• Nervous tissue is a highly specialized communicative tissue

• Nervous tissue consists of neurons or nerve cells-building block cells of the nervous system, comes in many sizes and shapes, brain has 100 billion neurons

• Function of nervous tissue is to transmit information from one neuron to another, from neurons to muscles or from sensory receptors to other neural structures

Nervous System

• The basic unit of the nervous system are neurons. All structures are made up of neurons

• Nervous tissue-neurons which transfer information; a communicating tissue; glialcells-support tissue-without glial cells the neurons would be incapable of storing information in long term memory,; critical in development of synapses which initiates communication between neurons

Central Nervous System

• CNS includes the brain-(cerebrum, cerebellum, sub cortical structures, brainstem) and the spinal cord; all of the CNS components are housed within bone-skull or vertebral column

• Cerebrum/cerebral cortex-most complex structure of the nervous system- all conscious sensory awareness and motor function, including perception, awareness, motor planning, preparation, cognitive function, attention, decision-making, voluntary motor inhibition, language and speech function.

• The brain is categorized into the autonomic nervous system and the somatic nervous system

Autonomic Nervous System

• The autonomic nervous system (ANS) governs involuntary activities of the visceral muscles or “viscera” including glandular secretions, heart functions, digestive functions

• ANS may be further divided into two subsystems:• sympathetic system-responds to stimulation through

energy expenditure; sympathetic responses include vasoconstriction (constriction of blood vessels-increase in blood pressure, dilation of pupils, cardiac acceleration (fight or flight responses)

• Parasympathetic system-”conserves energy”- which counters the responses of the sympathetic system-parasympathetic responses include slowing the heart rate, decreasing blood pressure and constriction of pupils.

Somatic Nervous System

• Somatic nervous system-voluntary bodily functions-under our conscious control

Embryology

• During the 4th week of embryonic development the brain (encephalon) is composed of the prosencephalon (forebrain), mesencephalon (midbrain) and rhombencephalon (hindbrain)

• Brain or encephalon further differentiates into the:• Telencephalon-cerebral hemispheres• Diencephalon-thalamus/hypothalmus• Mesencephalon-midbrain• Metencephalon-pons, cerebellum. The term bulb/bulbar

refers to the pons and medulla but is often used to refer to the entire brainstem, including the midbrain

• Myelencephalon-medulla oblongata

Cranial Nerves

• Cranial nerves are represented by roman numerals and represent the inverse height in the brainstem. CN’s 1-4 are at the level of the midbrain; CN’s V-VIII are at the level of the pons; CN’s IX-XIII are found in the medulla.

• Cranial nerves are based on 7 categories

• Cranial nerve functions are divided into general and special with areas of service being somatic and visceral. Nerves can be efferent, afferent or mixed efferent/afferent

Cranial Nerves

• CN I-Olfactory Nerve (Special Visceral Afferent)-not a true cranial nerve because it reaches the brain without passing through the thalamus. Mediates the sense of smell (olfaction)

• CN II-Optic Nerve (Special Somatic Afferent)-associated with the visual system

• CN III-Oculomotor Nerve (General Somatic Efferent/General Visceral Efferent)=GSE-all extrinsic ocular muscles except superior oblique and lateral rectus; GVE=light and accommodation reflexes (pupil restriction and focus)

Cranial Nerves (cont.)

• CN IV-Trochlear nerve (General somatic efferent) arises from the trochlear nucleus of the midbrain and innervates the ipsilateral superior oblique muscle of the eye which turns the eye down and slightly out.

• CN V-Trigeminal nerve (general somatic afferent/special visceral efferent)-important mixed nerve for speech production-provides motor supply to the muscles of mastication and transmits sensory information from the face. The nerve arises from the the motor trigeminal nucleus and sensory nucleus of the trigeminal within the upper pons and emerging from the pons at the level of the superior margin of the temporal bone. The nerve divides into 3 components:

Cranial Nerves (con’t)

• CN V-Trigeminal Nerve (con’t)• opthalmic branch-entirely sensory; the GSA • component transmits general sensory info

from the cornea, iris, upper eyelid, front of scalp

• Maxillary branch-only sensory-the GSA • component transfers info from lower eyelid,• nose, palate, upper jaw• Mandibular branch-sensory and motor-GSA • component transfers info from lower jaw and teeth, mucosa, cheeks,

temporomandibular joint, anterior two thirds of the tongue; SVE component transfers info

• to the muscles of mastication (internal and external pterygoid, temporalis, masseter) tensor tympani NOTE: taste is not mediated by the trigeminal nerve but pain from biting the tip of your tongue is.

Cranial Nerves (con’t)

• CN VI-Abducens (General Somatic Efferent)-lateral rectus muscle for ocular abduction

• CN VII-Facial Nerve (SVE,SVA,GVE) this nerve provides efferent innervation to the facial muscles of expression and tear glands, sense of taste for a portion of the tongue. It communicates the X vagus, V trigeminal, VIII vestibularcochlear and IX glossopharyngeal nerves; SVE-to facial muscles of expression, platysma, buccinator; SVA-taste, anterior two-thirds of the tongue; GVE-lachrymal gland (tears) mucous membrane of mouth and nose

Cranial Nerves (con’t)

• CN VIII-Vestibulocochlear Nerve (SSA)-auditory nerve-vestibular branch and acoustic branch/cochlear sensation-mediates auditory information and sense of movement in space.

• CN IX-Glossopharyngeal Nerve (GSA,GVA,SVA,GVE,SVE) sensory and motor functions; GVA-somatic (tactile,thermal,pain sense) from posterior one third of tongue, tonsils, upper pharynx, Eustachian tube, mastoid cells; SVA-taste, posterior one third of tongue; GSA-somatic sense of external auditory meatus and skin of ear; SVE-innervation of stylopharyngeus, superior pharyngeal constrictor; GVE-innervation of parotid gland for salivation

Cranial Nerves (con’t)

• CN X-Vagus Nerve (GSA,GVA,SVA,GVE,SVE)-motor and sensory-GSA-cutaneous sense from external auditory meatus; GVA-sensory from pharynx, larynx, trachea, esophagus, viscera of thorax, abdomen; SVA-taste buds near epiglottis and valleculae; GVE-to parasympathetic ganglia, thorax, abdomen; SVE-striated muscles of larynx and pharynx

Cranial Nerves (cont.)

• CN XI-Accessory Nerve (SVE) Cranial portion joins with the X Vagus to form recurrent laryngeal nerve to innervate intrinsic muscles of larynx; spinal portion innervates sternolcleidomastoid and trapezius

• CN XII-Hypoglossal Nerve (GSE)-innervation to the motor function of the tongue-each hypoglossal nucleus served by the contralateral corticbulbar tract- NOTE: lesion of LMN produces ipsilateral damage (tongue deviates toward side of damage)because fibers of the corticobulbar tract decussate before reaching the hypoglossal necleus; left UMN damage=right tongue weakness

Classes of Cranial Nerves

• GSA General Somatic Afferent (sensory)-related to pain, temperature, mechanical stimulation of somatic structures (skin,muscles,joints)

• GSA General Somatic Efferent (motor) innervates skeletal (striated) muscles

• GVA General Visceral Afferent (sensory)from receptors in visceral structures (e.g digestive tract)

• GVE General Visceral Efferent (motor) autonomic efferent fibers• SSA Special Somatic Afferent –special senses-sight, hearing,

equilibrium• SVA Special Visceral Afferent-special senses of smell, taste• SVE Special Visceral Efferent-innervation of muscle of branchial arch

origin: larynx, pharynx, face

Swallowing

• Gustation-(taste)-taste derives the desire to continue eating which fulfills nutritional requirements. Taste receptors (taste buds) are a class of sensors known as chemoreceptors which respond when specific chemicals come in contact with them

• Zones of taste receptors-sweet tastes being sensed at the tip, salty ath the sides in front and sour at the sides in the back, bitterness on the posterior tongue; reality is that all tastes can be sensed all over the tongue

• Papillae are prominences on the tongue, pink or gray in color and make the tongue look rough.

Swallowing

• Taste is mediated by 3 cranial nerves-VII facial nerve=sense of taste from the anterior 2/3rd’s of the tongue involving sweet, salty, sour sensations; IX glossopharyngeal nerve transmits primarily bitterness information from the posterior 1/3rd of the tongue; VII facial innervates the taste receptors of the palate; X Vagus innervates the taste receptors of the epiglottis and esophagus

• Tastes elicit salivation as well as ingestive responses including tongue protrusion to receive the food, release of insulin, mastication and deglutition. Bitter and sour tastes typify poisons and often will elicit protective responses-gagging, coughing, apnea, salivation-tastes can elicit motor responses than may or may not be under volitional (or conscious) control

Swallowing

• Olfaction (smell)plays a role in appetite and taste-olfactory sensors last about 60 days before being replaced by new sensors

• Tactile (touch) mediated by mechanoreceptors which are sensors that are sensitive to physical contact. 4 classes of thermal stim-warm, hot, cool, cold

• Salivation (production and release of saliva into the oral cavity)-a motor response, essential component of taste, mastication, deglutition-when saliva mixes with tasteless starch, the combination produces sugars that taste sweet and make the food more desirable. Product of 3 major glands-parotid, submandibular, sublingual

• Glands are activated by the stimulation of taste receptors (anterior 2/3rds of the tongue), mediated by VII facial nerve (sublingual and submandibular) and IX glossopharyngeal nerve (parotid gland)