functional neuroanatomy and physiology of masticatory system

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  • 1. Functional neuroanatomy andphysiology of masticatory systemPreeti Kalia 3rd year PG student Department of ProsthodonticsAECS Maaruti College of Dental Sciences

2. You cannot successfully treat dysfunction unless you understand function 3. Functional neuroanatomy and physiology of masticatory systemNeuromuscular systemMuscleNerve Neuromuscularfunction Pain 4. NeuromuscularsystemNeurological Muscles structure 5. Muscles 6. Muscle function Isotonic contraction Isometric contraction Relaxation 7. Muscle function 8. Muscle function Eccentric contraction 9. Neurological structure 10. Types of neurons Afferent neurons Efferent neurons 11. Reticular formation 12. Thalamus 13. Hypothalamus 14. Limbic structure 15. Cerebral cortex 16. Sensory receptors Nociceptors Propriceptors Muscle spindle Golgi organ Pacinian corpuscle 17. Muscle spindles 18. Golgi tendon receptor 19. Pacinian corpuscles 20. Nociceptors 21. Neuromuscular functionReflex action:It is response resulting from a stimulus that passesas an impulse along afferent neurons to a posterior nerve root or its cranial equivalent 22. Monosynaptic reflex Polysynaptic reflex 23. Myotatic reflex 24. Nociceptive reflex It is a polysynaptic reflex Seen when hard food substances are taken in themouth 25. Reciprocal innervation The controlling mechanism of antagonistic group of muscles 26. Regulation of muscle activity Gamma charge keeps the alpha motor neuron reflex prepared to receive impulses Influence of higher centers 27. Major function of masticatory systemMasticationSwallowing Speech 28. Mastication Defined as act of chewing food 29. Chewing cycle 30. Mascles activity 31. Opening Start from static intercuspalposition muscle activity begins in theipsilateral inferior head of thelateral pterygoid muscleapproximately half way throughthe period of tooth contact. Follow closely by the action ofthe contralateral inferior lateralpterygoid muscles. Both superior and inferior headof th lateral pterygoid muscleare active during the openingphase. 32. Opening Early in the opening phase,digastric muscles become active and remain untilmaximum opening position During the opening phase, masseter, temporalis, medial pterygoid, and superior head of lateral pterygoid muscles are inactive. 33. Closing initiation of jaw closingthe inferior heads of the lateral pterygoid muscleceases their functioning and activity initiated in the contralateral medial pterygoid muscle 34. Closing Contralateral medial pterygoid controls the upward andlateral positions of the mandible Activity increases in the anterior and posterior temporalismuscle, in the deep and superficial masseter muscles,and in the ipsilateral medial pterygoid muscle anterior and posterior temporalis muscle, in the deep and superficial masseter muscles, and in the ipsilateral medial pterygoid muscle activity declines in activity at the onset of intercuspation. There appears to be reciprocal action between the inferior head of the lateral pterygoid muscle and the medial pterygoid muscle in same subject 35. Tooth contact during mastication Gliding contacts Single contact Average time for tooth contact is 194 minutes 60% Gliding contacts seen during grinding 56% gliding contacts seen during opening 36. Forces of mastication Maximum biting force in females 70 to 99 pounds Males 118 to 142 pounds Maximum bite force for molar 91 to 198 pounds Central incisors 29 to 51 pounds 37. Swallowing Series of coordinated muscle movements that moves bolus from oral cavity through esophagus to stomach 38. Somatic swallow Visceral swallow 39. Stages 40. Frequency of swallowing 590 times in 24 hours 146 cycles during eating 394 in between meals 50 cycles during sleep 41. Speech Important sounds formed by the lip are m,band p Teeth are important in saying s Tongue and palate are essential in forming d Tongue touches maxillary incisors to form th Lower lip touches maxillary incisors to form f and v 42. Pain Unpleasant sensation perceived in the cortex as a result of incoming nociceptive input. 43. Modulation of pain Non painful cutaneous nerve stimulation Intermittent painful stimulation Psychological modulation 44. Types of pain Central pain Projected pain Referred pain 45. Central excitatory effect Explains the mechanism of referred pain 46. Pain is inevitable. Suffering is optional. 47. References Okeson.J.P, Temporomandibular disorders and occlusion,6th edition , 2008, Mosby publication, St Louis, United States of America, pp:25-57