oral physio Flashcards
genioglossus muscle
extrinsic tongue muscle. very fast with high amount of fast twitch fibers
what are the jaw opener muscles
- digastric
- lateral pterygoid (technically a PROTRACTOR)
- geniohyoid
- mylohyoid
digastric muscle is composed of mostly what type of fibers
fast
dysfunction of the superior head of the lateral pterygoid is associated with what
anterior displacement of the TM disc in TMJ dysfunction
there is a ___ amount of force generation needed for the jaw opening muscles
low amount of force generation….more important for movement instead of force production
what are the jaw closer muscles
- masseter
- temporalis
- medial pterygoid
the masseter muscle is composed of mostly what type of fibers
slow fibers (in both the deep and superficial parts)
what myosin isoforms predominate in the adult for the masseter muscle
slow fibers
what myosin isoforms predominate in the neonatal/embryonic masseter muscle
alpha cardiac
bruxing leads to ____ of the muscle
hypertrophy (gets larger)
bruxing hypertrophy leads to an increase in what
increase in the level of slow myosin…which could create less powerful contractions of the masseter which could affect chewing/speech/etc
the temporalis muscle is composed of mostly what type of fibers
faster type myosin than the masseter
the medial pterygoid muscle is composed of mostly what type of fibers
slower myosin
what is the pattern among jaw closer muscles (masseter, med pterygoid, temporalis)
compartmentalization….where there is greater amount of slow myosin fibers in the anterior and deep layers and faster myosin fibers in the posterior and superficial
what is kinesthesia
sense of movement and position
what provides feedback from the muscles to the CNS
rich sensory information is provided from the masticatory muscles to the CNS via sensory afferents. feedback can then be delivered from the CNS back to the masticatory muscles (to better control force generation and precision).
what are the two types of muscle fibers that make up a muscle spindle
- nuclear bag intrafusal fibers (clustered nuclei in the center of the fiber)
- nuclear chain intrafusal fibers (nuclei arranged in a chain/linearly within a fiber)
intrafusal refers to what
fibers that are WITHIN a muscle spindle rather than extrafusual fibers which are the muscle fibers that generate the “work” of a muscle during contraction (and are outside of the muscle spindle)
what are the 2 types of efferent nerve fibers associated with a muscle spindle
gamma and beta (rare)
what is the job of the efferent nerve fibers associated with a muscle spindle
to innervate the intrafusal fibers of the spindle
what are the 2 types of sensory/afferent nerve fibers associated with a muscle spindle
- 1a afferent/primary ending
2. II afferent/secondary endings
what is the job of the sensory/afferent nerve fibers of the muscle spindle
they adjust the incoming signal to the muscles by providing info to the CNS about what is going on w/in the muscle. the CNS needs to know what to tell the extrafusal fibers to do.
what is the difference b/w Ia and IIa afferent fibers
- Ia provide MORE DYNAMIC signals (report to CNS earlier and give a more “robust” signal) to the CNS, but their signal DISSIPATES more during the length of a muscle stretch
- IIa have a delayed response to the stimuli applied, but provide the signal more CONTINUOUSLY throughout the muscle stretch
what is the role of gamma efferent fibers within a muscle spindle
to maintain a high level of spindle sensitivity in SHORTENED muscles. when a muscle shortens, the gamma efferents signal to the intrafusal fibers (that they innervate) to shorten in their POLAR regions (outside of the muscle fiber). shortening of the polar region of intrafusal fiber causes lengthening of the equatorial (central) region of the muscle spindle. lengthening of the equatorial region of the spindle RESTORES THE SENSITIVITY of the spindle to future stretch stimuli
what would happen if the spindle didn’t “reset” its sensitivity after muscle shortening?
bc the spindle could not restore its sensitivity, the muscle (extrafusal fibers) would keep working over a range of short lengths where the spindles would remain inactive and not be able to send modulating info to the CNS (….assuming this could result in injury of some kind?)
what are golgi tendon organs
receptors located in jn b/w the ends of muscle fibers and tendon (located w/in the tendon in series with muscle fibers). they generate signals that are proportional to the amount of force generated by the extrafusal (working) muscle fibers
how does a GTO respond to increasing forces
the more force applied/done by the extrafusal fibers, the more tension applied to the GTO and theremore the more a.p produced by the GTO
what are free nerve endings in joints activated by….what doe they respond to
mostly activated by PAIN, but some activated by mechanical stimuli (to sense joint position)
what is an EMG
non invasive gathering of info that records and analyzes muscle activation patterns. they don’t reflect forces generated across a joint (bc antagonist muscles can create a net 0 force).
how can an EMG be clinically relevant?
see what muscles are activated or no longer activated after unilateral damage/surgery has been perfomed (i.e a unilater marginal madiblectomy…aka mandible removed on one side)
depending of food consistency, mandibular movements during mastication are both ____ and _____
highly rhythmic and specific (controlled by the CNS!)
what are the 4 phases of CHEWING
- slow opening
- fast opening
- fast closing
- slow closing (to protect teeth/soft tissues)
* *this is highly CONSISTENT across species (even if they have different feeding behaviors)
the type of ____ differs b/w species with different feeding behaviors
myosin!
carnivores–> masticatory
herbivores–> alpha cardiac (rhythmic)
omnivores–> unspecialized
what are the 3 phases of MASTICATION
- preparatory
- reduction
- pre-swallowing
* *variable activities of the openers and closers in ALL phases
characteristics of the preparatory phase
- it includes the transport of food
- highly variable depending of food consistency
- little EMG activity in jaw closers (obvi…bc you are putting food into your mouth)
characteristics of the reduction phase
- it includes the breakdown of food
- very regular and rhythmic
characteristics of the pre-swallowing phase
- it includes the food bolus formation
- very regular
what are the primary sites of control for mastication
- brainstem
- cerebral cortex
- and a little bit of the cerebellar cortex
* *these both include: nuclei, afferent fibers, and efferent fibers
the sensory nuclei that control mastication include
- trigeminal sensory nucleus
2. trigeminal mesencephalic nucleus
what is the role of the trigeminal sensory nucleus
fibers extending from here INNERVATE the face and oral cavity (sensory) and then PROJECT to the cerebellar and cerebral cortexs
what is the role of the trigeminal mesencephalic nucleus
fibers extending from here are coming from the:
- spindle afferents of jaw closers
- mechanoreceptors in the PDL/ gingiva/palate
the motor nuclei involved in the control of mastication include
- trigeminal motor nucleus
- hypoglossal motor nucleus
- facial motor nucleus
CN V, XII, and VII