Flashcards in Oral Musculature Deck (74):
the genioglossus muscle is very fast, meaning it has a high proportion of ________
what are the "jaw opener" muscles?
2) lateral Pterygoid
what muscle contains two heads in a series?
the masseter has 2 parts: deep and superficial. Which part(s) contains mainly slow fibers?
the masseter has a "__________" i.e., slow-fast myosin gradient
bruxing may lead to increased levels of _______, which could lead to what type of contractions?
increased levels of slow myosin
could cause slower, less powerful contractions
the temporalis muscle is faster than the masseter, due to it's relative abundance of __________
due to the temporalis's ______________, the site of a lesion/injury could have differing effects
which 3 muscles contain an anterior-to-posterior myosin gradient?
Masseter, temporalis, Medial Pterygoid
(your "jaw closers")
jaw closing muscles generally have greater amounts of ______ myosin in deep layers and in anterior layers
what is Kinesthesia?
sense of movement and position
T/F: there is extremely rich sensory information originating from within masticatory muscles, which provide feedback to the CNS
what are the components of a muscle spindle?
-efferent nerve fibers
-sensory fibers (afferents)
what 2 types of muscle fibers are found in the muscle spindles?
1) nuclear bag intrafusal fibers (2-3)
2) nuclear chain intrafusal fibers (4-6)
most fibers in a muscle are "______" fibers which do the work associated with muscle contractions
what types of efferent nerves are found in muscle spindles
Gamma- fusimotor fibers (most common)
Beta- fusimotor fibers (rare)
which types of sensory fibers are found in muscle spindles? which are "primary" and which are "secondary"?
type 1a afferent fibers- primary endings
type 2 afferent fibers- secondary endings
what is the role of gamma motor neurons?
maintain high level of spindle sensitivity in shortened muscles
T/F: afferent activity increases as a muscle shortens
FALSE- Afferent activity DECREASES
*this is an important component of kinesthesia
what would happen if internal adjustments in the spindle do not occure after the muscle shortens?
the muscle would function over a range of short lengths where spindles would remain inactive
how do gamma motor neurons restore the sensitivity of a shortened muscle?
they cause polar regions of INTRAFUSAL fibers to SHORTEN
-stretches the equatorial regions of the spindles
T/F: the distribution of slow-type muscle fibers correlates to the distribution of muscle spindles
-wheres theres spindles, theres slow-type muscle
where are Golgi tendon organs? where are they found?
-receptors in skeletal muscles
-located in junction between ends of muscle fibers & the tendon to which they attach
-generate signals that are proportional to the amount of force generated by the extrafusal (working) muscle fibers
the golgi tendon organs will fire most rapidly when a _______ is applied
what is a EMG? how does it record and analyze muscle activations?
-records action potentials along sarcolemma of muscle fiber (extrafusal fibers)
T/F: a EMG will reflect the forces generated across a joint
mandibular movements during mastication are highly _______ and ________, depending on food consistency
rhythmic and specialized
which muscles lower/open the jaw during mastication? which ones elevate/close it?
openers- digastric and lateral pterygoid
closers- masseter, temporalis, medial pterygoid
list the three masticatory phases:
1) preparatory (transport)- tongue, lips, buccinator: highly variable depending on food consistency
2) reduction- food breakdown
3) preswallowing- food bolus formation
T/F: the chewing cycle is highly consistent across divergent species
which masticatory phases are very regular?
Reduction and pre swallowing
reduction is both very regular and rhythmic
what are the primary sites for control of mastication?
brainstem and cerebral cortex
what are the sensory nuclei for the central control of mastication?
1) Trigeminal sensory nucleus
2) Trigeminal mesencephalic nucleus
cells of the trigeminal sensory nucleus innervate what? where do they project?
innervate face and oral cavity
project to CEREBELLAR, as well as cerebral cortex
what cell bodies are found in the trigeminal mesencephalic nucleus? what sensory reception are they responsible for?
-cell bodies of spindle afferents from jaw CLOSERS
-mechanoreceptors in PDL (perio lig), gingiva and palate
what are the motor nuclei for mastication?
1) Trigeminal motor nucleus
2) hypoglossal motor nucleus
3) facial motor nucleus
what types of motor neurons project from the trigeminal motor nucleus? these have a high degree of ________ organization
alpha and gamma motor neurons of jaw muscles
they are topographically organized
(facial motor nucleus also shares this characteristic)
the hypoglossal motor nucleus contains motor neurons that control the _____ muscles
masticatory control depends on the interaction between which 3 CNS structures?
brainstem (where sensory/motor nuclei are found)
what is the role of the brain stem in masticatory control?
-can function autonomously
describe the jaw-closing reflex:
- afferent fibers from muscle spindles and cell bodies in mesencephalic nucleus:
-synapse on ALPHA motor neuron in trigeminal motor nucleus
- very fast: no modification from higher brain centers needed
describe the jaw-opening reflex
-stimulus in oral cavity excites afferents that terminate in spinal trigeminal tract nucleus cells
-synapse on interneurons, which, in turn, synapse on ALPHA motor neurons in trigeminal motor nucleus
-motor nucleus innervates jaw openers
the jaw-opening reflex is known as "__________" reflex, meaning it is highly modulated for a specific stimulus
what is the role of "higher centers" (in the brain) on mastication?
-modulation of mastication
- can be voluntary, but usually not
- can modulate the jaw-closing reflex (a little), as well as the jaw-opening reflex
what is the role of afferent fibers in mastication?
-modulates mastication depending on food consistency
-variable receptors involved with several types of input (hard vs soft food, chewy vs crispy)
-input to brain stem components as well as higher centers
T/F: Swallowing is a reflex after its initiated, and is normally unconscious
what are the components of swallowing?
-large area of the brain stem
-six cranial nerves
what occurs during the "preparatory phase" of swallowing?
-bolus is formed and positioned on the back of the tongue
-tip of tongue presses on maxillary incisors
-the part of the tongue touching the food rises laterally against buccal teeth
-the "glossopalatal sphincter" forms (its temporary)
what occurs during the INITIAL "oral phase" of swallowing?
-lips close, incisors move together
(forms oral seal)
-anterior 2/3rds of tongue moves up against maxillary alveolar ridge
(pushes bolus toward the pharynx)
what happens during the later "oral phase" of swallowing?
-base of tongue moves down and forward
(opens up chute to pharynx)
-palate moves up
(opens the glossopalatal sphincter)
-palate contacts posterior pharyngeal wall and the side walls of the nasopharynx are opposed
(prevents bolus from entering nasal cavity)
what group of muscles is referred to as the "facultative group" during swallowing?
muscles involved in preparatory and oral phases of swallowing
-mandibular (masseter, medial pterygoid, temporalis)
-facial (labial and buccinator)
what is the function of the contraction of the labial and buccinator muscles during swallowing
1) contributes to the formation of the oral seal
2) stabilizes the mandible
what occurs during the pharyngeal phase?
movement of bolus from oropharynx to esophagus
muscles involved in the pharyngeal phase of swallowing are collectively referred to as the "__________" of muscles
(vs the "facultative" set with preparatory and oral phases)
T/F: muscles of the pharyngeal phase are less consistent than preparatory or oral phases
false- they are more consistent
what occurs during the esophageal phase of swallowing?
movement of food along entire esophagus
-takes about 3 seconds
__________ waves of contraction move the bolus through the esophagus
what are the mechanisms that prevent aspiration of food during the pharyngeal phase of swallowing?
-respiration is inhibited
-larynx and upper esophageal sphincter elevate
-intrinsic muscles of glottis move vocal cords toward each other
-bolus moves through sinuses in pharynx
which stages of swallowing are voluntary? involuntary?
voluntary- preparatory and oral phases
involuntary- pharyngeal and esophageal phases
what are the brainstem sensory nuclei that are involved with swallowing?
-Nucleus tractus solitarius (NTS)
-trigeminal sensory nucleus
what are the brainstem motor nuclei associated with swallowing?
-facial, trigeminal and hypoglossal nuclei (5, 7 and 9)
the _____________ mediates interactions between the sensory and motor nuclei involved in swallowing
which interneurons initiate and time/program swallowing?
the DORSAL interneurons
the ventral interneurons play what role in during swallowing?
distribute the excitation to the swallowing motor nuclei
where does afferent information during swallowing originate? where does it travel to?
-originates in pharynx, larynx and esophagus
-info is sent to the NTS
-results in modulation of swallowing, depending on food consistency
T/F: infantile swallow programing of both obligate muscles and facultative muscles both begins in utero
False- obligate muscles are programmed in utero
-facultative muscles are markedly different: different patterns of activation before and after tooth eruption
T/F: BOTH jaw-opening and jaw-closing muscles have an important role in infant suckling
what is "emesis" also known as? what is its function?
function: rid the stomach of its contents (usually natty)
what are the different stimuli for vomiting/emesis
- physiological stimuli
- disease-related stimuli
what are the phases of vomiting?
a group of nuclei in the _______ coordinates the act of vomiting
(vomiting is under medullary control)
direct stimulation near the _____ in animals cause vomiting
(Nucleus tractus solitarius)
what are the characteristics of bruxism?
-forceful tooth clenching and grinding during sleep
-sometimes rhythmic chewing, sometime sustained contractions
-daytime tooth clenching is very similar to bruxism in terms of mandibular mechanics