muscle of mastication + jaw reflexes

Question 1

what are receptors in mastication

Answer 1

muscle spindle
tendon organ receptors
TMJ receptors
skin and mucosal receptors
PMR

Question 2

why are there may jaw closer muscle spindle, but little to none jaw opener?

Answer 2

jaw closer can react more adequately to disturbances of jaw movement than the digastric muscle
masseters have to regulate precisely their force during mastication, depending on the hardness of the food or on the need to manage an object kept between teeth (more muscle spindles as protective mechanism)
The consequences of jaw opening is not as pontentially hazardous as that of jaw closing. As biting through and through some food can cause damage

jaw opener designed to displace the jaw with maximal velocity. it is simply inhibition of jaw closer muscle

Question 3

explain tendon organ receptors

Answer 3

activated by the increased
stress on the tendons of the muscles

Question 4

component of reflex arc

Answer 4

receptor
sensory neuron
integration centre
motor neuron
effector

Question 5

component of jaw-closing/jaw jerk reflex

Answer 5

receptor: muscle spindle
primary afferent: spindle 1a afferent
cell body: mesenphalic nucleus V

Question 6

role of jaw jerk

Answer 6

maintain jaw rest position when head is moving up and down, say during exercise
when chewing, and texture suddenly change
eg, when bite nut, jaw reflex decrease so that there is decreased resistance

Question 7

periodontal reflexes

Answer 7

includes JOR and jaw jerk.

Question 8

explain theory of mastication.
(Peripheral input + Cortical input
+ Central Pattern Generator)

Answer 8

Central pattern generator, a structure in brainstem send alternating impulses to jaw openers and closers.
CPG sets rhythm for mastication, while receptors alters:
strength
duration
rate of force development.

painful stimulus/conscious decision can interrupt CPG activity

Question 9

phases of swallowing

Answer 9

buccal phase
- food enter oral cavity
- mastication and bolus formation
oropharyngeal phase
- tongue elevates and push bolus towards pharynx
pharyngeal phase
- soft palate elevated, sealing nasal cavity
- respiration stops
- larynx and hyoid bone move anteriorly +upward
- epiglottis tilt back to cover glottis
- adduction of vocal cord
oesophageal phase
- Glottis re-opens and breathing resumes
- Food then propelled by peristalsis,
wave like contractions down the oesophagus

Question 10

stretch reflex pathway

Question 11

what does the taste bud comprise of

Answer 11

50 cells of epithelial and sustentacular cell
40 microns

Question 12

location of taste in the tongue

Answer 12

sweet - tip of the tonuge
salty - anterior lateral of tongue
sour - posterior lateral of tongue
bitter - back of tongue
umami - middle of tongue