Control of mastication Flashcards
What is the role of mastication?
Breakdown of foodstuffs
- preparation for swallowing
- increase surface area for chemical digestion
- release of chemicals for sense of taste
- stimulation of salivary flow
- growth and maintenace of oro-facial tissues
mechanics of mastication
Jaw movements
- chewing cycles
Cheek movements
- directing food
Tongue movements
- directing food
- crushing food
- mixing food and saliva
Lip movements
- (accepting food)
- retaining food: anterior oral seal
- directing food
the chewing cycle
0.5-1.2 seconds. duration phases
- Opening
- Fast Closing
- Slow Closing
- Intercuspal Phases
Control of mastication
Masticatory system:
- Complex muscle-joint system
- Symmetrical or asymmetrical jaw movements
- Large forces can be produced
- Up to 150N during mastication
- Maximum bite forces: 500-700N between molars
In control of mastication what are the 3 levels of control?
- Reflex
- Pattern generator
- Voluntary
What is a reflex?
Predictable response to a given stimulus
Stretch reflexes
Simple
Usually mono-synaptic
Examples:
- Knee Jerk Reflex
- Jaw Jerk Reflex
Role of stretch reflexes (phasic)
Phasic:
- Load compensation during chewing
- Stabilises jaw during vigorous head movements - e.g. during running
Protective reflexes
Polysynapic (>1 synapse) reflexes
Often a response to a noxious stimulus
Examples:
- Limb: Flexion Withdrawal reflex
- Jaw: Jaw “Opening” Reflexes
Describe jaw unloading reflex
Stimulus:
- Sudden closure following hard biting
- e.g. a hard/brittle food breaks
Response:
- Inactivation of jaw closing muscles
- Activation of jaw opening muscles
Result:
- Teeth do not crash together
Pathway poorly understood? Spindle unload
