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Orofacial Neurobiology - Lecture 02
Mastication & The Central Pattern Generator
18
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Professional
03/28/2012

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Term
The mastication cycle lasts about this long.
Definition
1 second
Term
What are the three phases of the mastication cycle?
Definition
Closing, Occlusal, Opening
Term
T/F: The jaw closing reflex is monosynaptic.
Definition

True

[image]

Term
Afferents in the jaw closing reflex travel to this region of the brainstem before synapsing on the trigeminal motor nucleus.
Definition
Mesencephalic nucleus
Term
Where do afferents first synapse in the jaw opening reflex? Where do the 2nd order neurons synapse?
Definition

Spinal trigeminal nucleus; Trigeminal motor nucleus

[image]

Term
What aspect of reflexes undermine the reflex theory of mastication?
Definition
They are extremely fast, yet mastication takes 1sec.
Term
How was curare used to disprove the reflex theory of mastication?
Definition
Administering curare would abolish reflexes but efferect patterns of mastication continued (could still chew even though afferents were not functioning).
Term
List the two components of the central pattern generator?
Definition

1. Rhythm generator

2. Burst generator

Term
Output from the central pattern generator is sent to this structure.
Definition
Trigeminal motor nucleus
Term
This component of the masticatory pathway is responsible for turning the process on.
Definition
Cortex; Recall the story of the baby in the highchair chewing.  Chewing ceased when the baby fell asleep and resumed again when the baby awoke.
Term
What is the role of the rhythm generator?
Definition

To establish the overall length of the cycle

[image]

Term
What is the role of the burst generator?
Definition

To establish the duration and pattern within the cycle.

[image]

Term
What is the purpose of the motor nucleus?
Definition
To drive the individual muscles.
Term
What is the purpose of the jaw muscles?
Definition
To convert the neural signals into force.
Term

Evidence for rhythm generator includes:

1. Correct anatomical projections from ________.

2. Electrical stimulation of cortex leads to ________.

3. That stimulation can be ________ or regular.

4. ________ abolish rhythmic activity.

5. Rhythmic activity seen in ________ animal.

Definition
Cortex; Rhythmic activity; Random; Lesions of pathway; Paralyzed
Term
List the two nuclei of the rhythmic generator and whether or not they are rhythmic.
Definition
Nucleus reticularis paragigantocellularis (not rhythmic); Nucleus reticularis gigantocellularis (rhythmic)
Term
T/F: Innervation of the rhythm generator is unilateral.
Definition
False. Each rhythm generator controls several places, inluding coordinating with the contralateral side.
Term
What aspect of muscle control gives evidence for the central pattern generator being a separate structure within the brain?
Definition
They can fire voluntarily or involuntarily.
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