Functional neuroanatomy and physiology of masticatory system
Preeti Kalia3rd year PG student
Department of ProsthodonticsAECS Maaruti College of Dental
Sciences
“You cannot successfully treat dysfunction unless you understand function”
Functional neuroanatom
y and physiology of masticatory
system
Neuromuscular system
Muscle Nerve
Neuromuscular
function
Pain
Neuromuscular system
Neurological structure
Muscles
Muscles
Muscle functionIsotonic contraction
Isometric contraction
Relaxation
Muscle function
Muscle function
Eccentric contraction
Neurological structure
Types of neurons Afferent neurons
Efferent neurons
Reticular formation
Thalamus
Hypothalamus
Limbic structure
Cerebral cortex
Sensory receptors
Nociceptors
Propriceptors
Muscle spindle
Golgi organ
Pacinian corpuscle
Muscle spindles
Golgi tendon receptor
Pacinian corpuscles
Nociceptors
Neuromuscular function
Reflex action:
It is response resulting from a stimulus that passes as an impulse along afferent neurons to a
posterior nerve root or its cranial equivalent
Monosynaptic reflex
Polysynaptic reflex
Myotatic reflex
Nociceptive reflexIt is a polysynaptic reflex
Seen when hard food substances are taken in the mouth
Reciprocal innervationThe controlling mechanism of antagonistic group of
muscles
Regulation of muscle activityGamma charge keeps the alpha motor neuron reflex
prepared to receive impulses
Influence of higher centers
Major function of masticatory system
Mastication
Swallowing Speech
MasticationDefined as act of chewing food
Chewing cycle
Mascles activity
OpeningStart from static intercuspal
position
muscle activity begins in the ipsilateral inferior head of the lateral pterygoid muscle approximately half way through the period of tooth contact.
Follow closely by the action of the contralateral inferior lateral pterygoid muscles.
Both superior and inferior head of th lateral pterygoid muscle are active during the opening phase.
OpeningEarly in the opening phase,
digastric muscles become active and remain until maximum opening position
During the opening phase, masseter, temporalis, medial pterygoid, and superior head of lateral pterygoid muscles are inactive.
Closing initiation of jaw closing
the inferior heads of the lateral pterygoid muscle ceases their functioning and activity
initiated in the contralateral medial pterygoid muscle
ClosingContralateral medial pterygoid controls the upward and lateral
positions of the mandible Activity increases in the anterior and posterior temporalis muscle, 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
Tooth contact during masticationGliding contacts
Single contact
Average time for tooth contact is 194 minutes
60% Gliding contacts seen during grinding
56% gliding contacts seen during opening
Forces of masticationMaximum 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
SwallowingSeries of coordinated muscle movements that
moves bolus from oral cavity through esophagus to stomach
Somatic swallow
Visceral swallow
Stages
Frequency of swallowing590 times in 24 hours
146 cycles during eating
394 in between meals
50 cycles during sleep
SpeechImportant 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
PainUnpleasant sensation perceived in the cortex as a
result of incoming nociceptive input.
Modulation of pain
Non painful cutaneous nerve stimulation
Intermittent painful stimulation
Psychological modulation
Types of pain
Central pain
Projected pain
Referred pain
Central excitatory effectExplains the mechanism of referred pain
“Pain is inevitable. Suffering is optional.
ReferencesOkeson.J.P, Temporomandibular disorders and
occlusion,6th edition , 2008, Mosby publication, St Louis, United States of America, pp:25-57