Neural Control of Mastication

8/15/2019 Neural Control of Mastication

1/34


2/34

Muscles of MasticationMuscles of Mastication

Clinical significanceClinical significance--Normal function of the masticatory apparatusNormal function of the masticatory apparatus

--Dysfunction and difficulty in diagnosisDysfunction and difficulty in diagnosis

--MuscleMuscle--specific pathological conditionsspecific pathological conditions

Note:Note: most conditions are due to masticatorymost conditions are due to masticatory

problems, often related to occlusal and TMJproblems, often related to occlusal and TMJdysharmonydysharmony -- as mentioned in the TMJ lectureas mentioned in the TMJ lecture


3/34


Commonly accepted musclesCommonly accepted muscles

MasseterMasseter

TemporalisTemporalis

Medial pterygoidMedial pterygoid

Lateral pterygoidLateral pterygoid


4/34


5/34


Major musclesMajor muscles -- TemporalisTemporalis

OriginOrigin -- whole of temporal surface of thewhole of temporal surface of thecranium & the temporal fasciacranium & the temporal fascia

InsertionInsertion -- coronoid process of mandiblecoronoid process of mandible --

right down to retromolar fossaright down to retromolar fossa -- mediallymedially


6/34


Major musclesMajor muscles -- Medial PterygoidMedial Pterygoid

Attachments AttachmentsOriginOrigin -- Medial surface of lateral pterygoidMedial surface of lateral pterygoid

plate & pterygoid fossaplate & pterygoid fossa

-- Posterior surface of maxillaryPosterior surface of maxillary

tuberositytuberosity

InsertionInsertion -- Medial lower surface ofMedial lower surface of

mandibular ramusmandibular ramus


7/34

Lateral PterygoidLateral Pterygoid

Attachments Attachments

OriginOrigin -- Lateral surface of lateral pterygoidLateral surface of lateral pterygoidplate &plate &

-- Roof of the infratemporal fossaRoof of the infratemporal fossaInsertionInsertion -- Mandibular condyleMandibular condyle -- in thein the

fovea on the anterofovea on the antero--medial surface &medial surface &-- the TMJ disc & capsulethe TMJ disc & capsule (10%)(10%)


8/34


9/34

Control of mandibularControl of mandibular

movementsmovements

This is much more complex than simplyThis is much more complex than simplyconsidering the action of each muscleconsidering the action of each muscle

One must approach this from aOne must approach this from a

reflex arc systemreflex arc system


10/34


movementsmovements

Elements of a reflex arcElements of a reflex arcSensory inputSensory input

CNS processingCNS processingMotor outputMotor output


11/34


movementsmovements

Sensory inputSensory input = proprioception= proprioceptionReceptorsReceptors

Receptor fieldsReceptor fieldsTransmission to the CNSTransmission to the CNS


12/34


movementsmovements

Sensory inputSensory input -- proprioceptionproprioceptionReceptors:Receptors:

Muscle spindles = stretch receptorsMuscle spindles = stretch receptorsTendon organs = high threshold receptorsTendon organs = high threshold receptors

Pressure receptors (Meissner’s corpuscles)Pressure receptors (Meissner’s corpuscles)Naked nerve endingsNaked nerve endings -- non specificnon specific


13/34

Control of mandibular movementsControl of mandibular movements

Muscle spindleMuscle spindleTS of a spindleTS of a spindle

at high powerat high powerPhotograph taken Photograph taken

from John McGeachie’s from John McGeachie’s

research slides research slides


14/34


movementsmovements

Sensory inputSensory input -- proprioceptionproprioceptionReceptor fieldsReceptor fields

Covers all regions involved in masticationCovers all regions involved in masticationOral mucosa = huge surface areaOral mucosa = huge surface area

Teeth and peridental ligaments = huge areaTeeth and peridental ligaments = huge area

TMJs, capsules and associated ligamentsTMJs, capsules and associated ligaments

Muscles of masticationMuscles of mastication -- both sides = huge massboth sides = huge mass


15/34

Control of mandibular movementsControl of mandibular movements

RememberRememberMost of this movement is not corticalMost of this movement is not cortical

butbutOccurs at aOccurs at a subsub--cortical levelcortical level in the brainin the brain

stem by patterns of motor reflex activitystem by patterns of motor reflex activity


16/34

Muscles of masticationMuscles of mastication

Nervous reflexesNervous reflexesvia thevia the

Mesencephalic nucleusMesencephalic nucleus

M t ti flM t ti fl


17/34

Myotatic reflexMyotatic reflexdrawn by John McGeachiedrawn by John McGeachie

This diagram is in the lecture book - page 104


18/34

Muscles of masticationMuscles of masticationDiagram set up and outlineDiagram set up and outline

Posterior view of the mandiblePosterior view of the mandible

& hyoid bone& hyoid bonewith the brain stem abovewith the brain stem above


19/34

Brain stem

very

simplified

Hyoid bone

Mandible

Posterior view showing

Pterygoid plates above

condyle condyle

Zygomaticarch


20/34

Mylohyoid &

Digastric-anterior


21/34

LateralPterygoids


22/34

Medial

Pterygoids


23/34

Masseters


24/34

Temporalis


25/34

MCN

V

MN

V

Sensory input

via spindles

MotorNucleus of V

MesencephalicNucleus of V

Trigeminal

ganglion


26/34

MCN

V

MN

V

Motor output

via motor nerves


27/34

Bilateralresponse

PrincipalNucleus of V


28/34

Sensoryintegration


29/34

MCN - V integration


30/34

MotorIntegration


31/34

Reticularformation

Reticularintegration


32/34

Reticularformation

To otherMotor nuclei


33/34

Masticatory reflexesMasticatory reflexes

Physiological aspectsPhysiological aspectsfurther informationfurther information

Please read Professor Timothy Miles’ notesPlease read Professor Timothy Miles’ notes

on Masticationon Mastication

Chapter 5 Pages 40Chapter 5 Pages 40 -- 4949


34/34

Muscles of MasticationThe end

Documents

Neural Control of Mastication