2nd Session: Neuroanatomy of TMJ (1-15, Astorga)

Question 1

What is a reflex action?

Answer 1

A response independent of will. Results from a stimulus that passes as an impulse along an afferent neuron to a posterior never root or its cranial equivalent.

Question 2

What is a monosynaptic reflex action?

Answer 2

Occurs when the afferent fiber directly stimulates the efferent fiber int he CNS

Question 3

What is a polysynaptic reflex?

Answer 3

Present when the afferent neuron stimulates one or more interneuons in the CNS, which in turn stimulate the efferent nerve fibers.

Question 4

What is the myotactic reflex?

Answer 4

Stretch reflex! The only monosynaptic jaw reflex. Quick stretch = contraction. Very important to determine the resting position of the jaw.
Maintains the articular surfaces of the join in constant contact.

Question 5

What is the proprioceptive reflex?

Answer 5

Nociceptive reflex. Polysynaptic. Protective. Takes place when a hard object is suddenly encountered during mastication. A little complicated because must activate several muscle groups.

Question 6

What muscles are activated during the proprioceptive reflex?

Answer 6

The elevator muscles are inhibited to prevent further jaw closure on the hard object, BUT the jaw opening muscles must be activated to prevent damage form the teeth slamming together. ANTAGONISTIC INHIBITION

Question 7

What is the chewing stroke?

Answer 7

Each opening and closing movement of the mandible represents a chewing stroke. The movement pattern is tear shaped.

Question 8

What are the phases of the chewing stroke?

Answer 8

Opening phase & closing phase (divided into crushing and grinding phases).

Opening phase: drops straight down until 16-18 mm apart.

Closing phase: moves laterally 5-6mm from the midline

Question 9

Describe the closing phase in detail

Answer 9

1. traps food btw teeth
2. closes further and the buccal cusps of both the maxillary and mandibular arches align
3. Grinding phase begins - mandible is guided by the occlusal surfaces of the teeth

Question 10

What are the reported biting loads?

Answer 10

Female: 79 - 99 lbs
Male: 118-142 lbs

Question 11

Can equal force be applied to molars and incisors?

Answer 11

No! Max amount of force for molars (91 - 198 lbs) is several times that for incisors (29-51 lbs).