EX1; Oral Musculature Flashcards
This muscle is very fast, has a high proportion of fast-twitch fibers; forms the majority of the body of the tongue
genioglossus
This muscle is predominantly fast and has two heads in series with functional implications; jaw opener
diagastric
This is a protractor muscle accompanying opening; dysfunction of superior head is associated with anterior displacement of TM disc
lateral pterygoid
These are strap like muscles involved in jaw opening
geniohyoid
mylohyoid
This jaw closing muscle has two parts; deep and superficial and slow fibers predominate on both parts
masseter
What are the myosin isoforms of the masseter
adult slow
embryonic, neonatal, alpha cardiac (latter serves in rhythmic contractions
What is the gradient (slow-fast myosin gradient) of the masseter
anterior to posterior
This may increase in level of slow myosin in which may cause slower, less powerful contractions that could affect chewing, speech, etc.
bruxing
This jaw closer contains more fast-type than myosin than masseter; with slow anteriorly and fast posteriorly compartmentalization
temporalis
Due to the compartmentalization in the temporalis, what could this mean for an injury/lesion
it may have differential effects
This jaw closer has predominately slow myosin and an anterior to posterior gradient
medial pterygoid
What is the general pattern involving the relative amount of slow myosin among jaw closers
greater amounts in deep and in anterior
less in superficial and posterior
(slow deep and anterior)
(fast superficial and posterior)
This is the sense of movement and position
kinesthesia
True or False
Masticatory muscles are under exquisite control
True; protects teeth and soft tissues from damage and ensures effective chewing
What does the rich sensory information originating from within the masticatory muscles provide
feedback to the CNS which provides the neural drive for contraction
True or False
There is continuously on-going sensory information from all muscles; of which normally not aware of it
True
What is the dimensions of a muscle spindle
1-3 mm in length
200µm in diameter
What are the two intrafusal fibers that make up muscle fibers
nuclear bad intrafusal fibers (2-3/spindle)
nuclear chain intrafusal fibers (4-6/spindle)
Most fibers in a muscle are what, which do the work (force, limb movement) associated with muscle contractions
extrafusal
What are the two types of efferent nerve fibers (10 or more/spindle)
gamma; fusimotor fibers (most common)
beta; fusimotor fibers (relatively rare, 1/3 of all spindles)
What are the two types of sensory nerve fibers
Ia afferent fibers; primary endings
II afferent fibers; secondary endings
True or False
There is lymph in the muscle spindle
True
A muscle spindle’s main mode of action is what kind of sensory
a length sensor; apply stretch to spindle; tension
This type of motor neuron maintains a high level of spindle sensitivity in shortened muscles
gamma
Afferent activity decreases when
as a muscle shortens; an important component of kinesthesia
What would happen if the internal adjustments in the spindle do not occur after a muscle shortens
The muscle would function over a range of short lengths where spindles would remain inactive
gamma motor neurons cause polar regions of intrafusal fibers to shorten, causing what
stretching equatorial regions restoring sensitivity
What is the correlation between the distribution of muscle spindles and of slow type muscle fibers
they mirror that of one another
These are receptors in skeletal muscles which are located in the junction between the ends of the muscle fibers and the tendon to which a muscle is attached
golgi tendon bodies
Where is the location of golgi tendon bodies
located in the tendon and positioned in-series with muscle fibers
What type of signals do the golgi tendon bodies generate
signals that are proportional to the amount of force generated by extrafusal muscle fibers (to the CNS)
What information is being picked up by the golgi tendon organs at the upper/middle/lower traces
upper; action potentials of GTO
middle; tension in GTO
lower; stretch applied to GTO
Many of the free nerve endings (those without specialized endings such as pacinian corpuscles) are nociceptive, which means what
they are activated by painful stimuli
others are activated by mechanical stimuli and such can provide information concerning joint position to CNS
This is a recording and analysis of muscle activations; action potentials along sarcolemma of muscle fibers (extrafusal)
EMG; electromyography
True or False
An EMG is an invasive gathering of information about patterns of muscle activations
False; it is non-invasive
EMGs do not necessarily reflect what
forces generated across a joint; solely responds to electrical information
What type of patterns can be revealed by an EMG
very interesting ones; like very precise timing of masticatory events relative to each other
True or False
an EMG can be used clinically to compare someone with normal masticatory functions with someone who has had a mandiblectomy
True
This is an extremely complex interaction between motor and sensory components of highly specialized muscles which is highly rhythmic and specific depending upon food consistency
mastication
Mastication has rich supplies of afferent information from where
muscles, oral cavity, and facial regions
Control and coordination is provided by what
the CNS
What two muscles are involved with lowering the mandible (opening)
digastric and lateral pterygoid
What three muscles are involved with elevating the mandible (closing
masseter, temporalis, and medial pterygoid
This type of animal has a large temporal is and jaw closers express masticatory myosin
carnivores
This type of animal has a large masseter; jaw closers express alpha cardiac myosin, no masticatory myosin
herbivores
This type of animal has relatively unspecalized mandibular features and a variable diet
omnivores
What are the four phases of the chewing cycle
slow opening
fast opening
fast closing
slow closing
What are the three masticatory phases
preparatory
reduction
pre-swallowing
This masticatory phase is for transport; tongue, lips, buccinator; highly variable depending on food and consistency
preparory
This masticatory phase is food breakdown
reduction
This masticatory phase is food bolus formation
pre-swallowing
There is little EMG activity during which masticatory stage
preparatory
When is the altering EMG activities during mastication
in openers and closers
Which phases of mastication are regular?
reduction (regular and rhythmic) pre swallowing (regular)
Each masticatory phase is dependent upon what
food consistency
What are the two primary control sites of the brain
brain stem and cerebral cortex
What three structures do the brain and cerebral cortex involve in the control of mastication
nuclei
afferent tracts of fibers
efferent tracts of fibers
What are the two sensory nuclei associated with control of mastication
trigeminal sensory
trigeminal mesencephalic
This sensory nucleus cells innervate the face and oral cavity; project to cerebellar, as well as cerebral cortex
trigeminal sensory
This sensory nucleus cell bodes of spindle afferents from jaw closers, mechanoreceptors in periodontal ligaments, gingiva, and palate
trigeminal mesencephalic
What are the three motor nuclei associated with control of mastication
trigeminal motor
hypoglossal motor
facial motor
This motor nucleus contains neurons of the facial muscles; topographically organized
facial motor nucleus
This motor nucleus contains motor neurons of tongue muscles
hypoglossal motor nucleus
This motor nucleus contains ɑ and Ɣ motor neurons of jaw muscles; high degree of topographic organization
trigeminal motor nucleus
This can function autonomously in the control of mastication, no input from higher centers required however normally does receive such input
brain stem
What does the brainstem “probably” contain
a pattern generator or neural oscillator for mastication
This reflex is monosynaptic; very fast with virtually no modulation from higher centers
jaw closing reflex
The cell bodies in the mesencephatic (sensory) nucleus synapses on what
the ɑ motor neurons in trigeminal motor nucleus
The jaw closing reflex uses these fibers from muscle spindles
afferent fibers
In the jaw opening reflex the stimulus in the oral cavity excites afferents that terminate the spinal trigeminal tract nucleus cells which synapse on interneurons which in turn synapse where
the ɑ motor neurons in trigeminal motor nucleus which innervate jaw openers
This is polysynaptic reflex; highly modulated for specific stimulus
jaw opening reflex
True or False
Mastication can be entirely voluntary; including that of jaw-closing and jaw-opening reflexes
True; but it is usually not
True or False
There are variable afferent receptors involved with the several types of input of food consistency; like hard vs soft, chewy vs cripsy
True
