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Neuro 3 Dessem


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Retrodiscal tissue
Highly vascular tissue occupying the area between the superior posterior lamina and the inferior posterior lamina. During translation, the blood vessels engorge with blood and increase the mass of the retrodiscal tissue which occupies the glenoid cacity. During retrusion, blood leaves the vessels and decreases total retrodiscal tissue mass.
Types of movement of the TMJ
It is a ginglymoarthrodial joint.
Glyglymus movement (hinge/rotatory)
Arthrodial movement (glising, translatory)
Types of jaw joint neural receptors and their descriptions.
Pacinian corpuscles: very few, sensory impulses conveyed via medium-sized axons, f(n): movement detection
Ruffini endings: mechanoreceptors, unencapsulated endings, medium sized axons, movement detection
Free nerve endings- small diameter axons and f(n) is nociception, pain/temperature/chemo(3)
Autonomic Innervation
What are the phases of mastication?
Opening phase (16-18mm)
Crushing phase of closure (contact with food)
Grinding phase of closure
Describe the hierarchical organization of motor function of rhythmic behaviors.
Higher control -->
Central pattern generators -->
Effector organs -->
Examples of rhythmic behavior that are thought to be regulated by pattern generating circuits...
What are the 3 types of neural circuits for generation of patterned behavior?
Half-center model* -- good for locomotion (walking)
Closed-loop model
Pacemaker model*

*primary source of rhythmic activity
Describe the pacemaker model.
Driver (D) activates a pacemaker cell (O) which results in either prolonged depolarization or a burst of action potential in P. This cell provides prolonged discharge in flexor motor neurons (F) while intervening inhibitory interneuron reduces activity in the extensor motor neurons and vice versa.
What are the neurotransmitters in pattern generation?
Glutamate acting through NMDA and AMPA receptors.

Also: GABA, NE, serotonin
The rhythm of mastication seems to be generated by which cells?
Medial bulbar reticular formation in the pons: located between the motor trigeminal nucleus and the inferior olive.
How does the cortex exert its action on the brain stem CPG?
via the corticobulbar tracts (mainly CONTRALATERAL).
also: the mesencephalic reticular formation also projects contralaterally to the CPG.
How is rhythm generated and what are the rhythm generators?
Stimulation of facial motor cortex (Cx) or corticobulbar fibers --> dorsal part of RPGC --> induce rhythmical firing in neurons in RGCo --> RGCc (coordinates activity in facial and hypoglossal motor neurons).
Neurons responsible for motor neuron bursts are located where?
In several clusters/nuclei surrounding the trigeminal motor nucleus.

Includes: supratrigeminal nucleus, principal sensory nucleus, subnucleus oralis, and the intertrigeminal nucleus.
What 3 elements are needed for generation of jaw opening and closing?
1) Inhibition of closers during opening
2) Generation of the opener burst
3) Generation of the closer burst (openers are NOT inhibited during closing).
Which neurons cause the inhibition of jaw closer motor neurons?
They are a group of inhibitory premotor interneurons; probably located in the supratrigeminal and intertrigeminal nuclei).
Which neurons cause the generation of the closer burst?
Neurons in the supratrigeminal region.
What is the presumed central circuitry of proprioceptive TMJ afferents vs. nociceptive TMJ afferents?
Proprioceptive (large diameter): synapse in principal sensory nucleus of V and projects up to the thalamus.

Nociceptive (small diameter): synapse in nucleus caudalis and then go up to thalamus.
TMJ: When you open the jaw to about 63 degrees, which muscle do you see a burst of activity in?
GG = genioglossus
Also activity in IC (inferior constrictor) muscle
Ia muscle spindle
muscle velocity, acceleration feedback
II muscle spindle
muscle length, position feedback.
What is the difference between proprioceptive feedback from the trigeminal vs. the spinal cord?
Trigeminal is highly focused (10% vs. 95%)
Interdental discrimation: what happens with vibration of mandible?

Reference --> thinner
Reference --> thicker
To thin: 70% correct to only 40% correct.

Going thicker: enhanced sensitivity (40 to 60%)

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