OCB04-2015 Control of mastication Flashcards
What factors affect chewing?
Dentition
Salivary flow
Muscle strength/ age
Food consistency/ structure
What muscles of mastication are responsible for closing?
Masseter
Temporalis
Medial Pterygoid
What muscles of mastication are responsible for opening?
Digastric
Intrinsic and extrinsic tongue muscles
What are other muscles that contribute to chewing?
Sub-hyoid muscles that stabilise hyoid for digastric to pull against
What are the 4 phases of mammalian masticatory movement in one ingestion cycle?
Fast closing
Slow closing
Slow opening
Fast opening
What is the tongue movement during fast opening and closing?
Tongue retracts to allow food to enter the mouth
What is the tongue movement during slow opening and closing?
Tongue moves forward and elongates below food
What is the tongue movement mainly during opening?
Styloglossi and genioglossus act together to form a longitudinal trough in the dorsal surface of the tongue
What is the function of the styloglossi and genioglossi forming a longitudinal trough in Dorsal surface of tongue?
Pushes food to the posterior oral cavity if both SG contract together
Or if food is not ready for swallowing it pushes it towards the cheek teeth if one SG contracts
What is the tongue movement during pre-swallowing?
Tongue presses food against the hard palate
What are different textures and properties of food detected by?
Mucosal mechanoreceptors to enable modulation of masticatory pattern according to food consistency
Where does afferent feedback occur from?
Other mechanoreceptors: muscle spindles, Golgi tendon organs and periodontal ligaments
What does the trigeminal motor nucleus contain?
cell bodies of alpha and gamma motoneurons which innervate jaw muscles
What are jaw-opening alpha motoneurons excited primary by?
Inputs from central pattern generator that drives chewing
What are jaw-closing alpha neurons excite by?
Inputs from CPG that drive chewing and inputs from muscle spindles
What are jaw-closing alpha motoneurons inhibited by?
Strong stimuli to mucosal and periodontal ligament afferents
What are the 2 other motor nuclei?
Hypoglossal motor nucleus
Facial motor nucleus
What is involved in hypoglossal motor nucleus?
Some crossover to the contralateral side
Some inputs also from the CPG to coordinate tongue movement with opening and closing
What is involved with facial motor nucleus?
Sends special visceral efferent fibres to facial muscles of mastication
Also innervates the posterior digastric which contracts with anterior digastric
What is muscle activity elicited by?
A reflex (opening or closing) CPG responsible for chewing
Where is CPG?
In the brainstem
Where does the drive from the CPG come from?
Motor cortex which initiates the reflex
Peripheral sensory receptors
What are neurons in the dorsal swallowing group responsible for?
Generating swallowing patterns
What are neurons in the ventral dorsal swallowing groups responsible for?
distributing the required efferent response to the motor neurons
How many circuits does the CPG consist of?
2 mutually re-enforcing circuits
How does the CPG circuits work?
When one is active, it inhibits function of the other, so 1 is only active at a time
The 2 circuits are connected via inhibitory connection
Circuit 2 remains inactive until there is a synaptic depression
Is the CPG alone efficient?
If the brainstem is cut off from afferent inputs then basic rhythmical movement will still occur bu the movement cannot be modulated according to other afferents such as the size of the food bolus in normal mastication
What does dysfunction of the masticatory area result in?
persons inability to recover normal masticatory functions as the cortex is responsible to initiate feeds and tongue posture in adults
What is swallowing?
A sequence of muscle contractions and relaxations which move material from the oral cavity to the stomach
What are the 3 phases of swallowing?
Oral phase
Pharyngeal phase
Oesophageal phase
What is the oral phase?
Conscious movement
Food bolus is moved back to an IX innervated area
What is the pharyngeal phase?
Reflex movement
Elicited by bolus stimulation of IX receptors
What is oesophageal phase?
Reflex autonomic movement
Moves the bolus down the oesophagus
Where is the hyoid?
base of the tongue
