Jaw muscles and receptors Flashcards
What are the origins and attachments of the deep and superficial masseter muscle?
Superficial
Origin: zygomatic bone
Attachment: outer surface of angle of mandible
Deep
Origin: zygomatic process of temporal bone
Attachment: ramus of mandible
What are the origins and attachments of the deep and superficial temporalis muscle?
Superficial
Origin: temporal fossa + deep temporal fascia
Attachment: coronoid process
Deep
Origin: Infratemporal crest of sphenoid bone + infratemporal fossa
Attachment: medial side of coronoid process (tendon extends down to lower third molar)
What are the origins and attachments of the upper and lower lateral pterygoid muscle?
Upper
Origin: infratemporal crest of sphenoid bone + infratemporal fossa
Attachment: articulating disk + pterygoid fovea
Lower
Origin: lateral surface of lateral pterygoid plate
Attachment: articulating disk + pterygoid fovea
What are the origins and attachments of the deep and superficial medial pterygoid muscle?
Deep
Origin: medial surface of lateral pterygoid plate
Attachment: roughened area between Md foramen and angle of Md
Superficial
Origin: pyrimidal process + Mx tuberosity
Attachment: roughened area between Md foramen and angle of Md
What are the FOUR main muscles of mastication and their actions?
- Masseter (elevation and protrusion)
- Medial pterygoid (elevation and protrusion)
- Temporalis (elevation and retraction)
- Lateral pterygoid (opening and protrusion)
True or false: the medial pterygoid muscles help the lateral pterygoid muscles move the jaw from side to side
True
What are the FOUR types of motor units?
- S (slow-contracting, fatigue-resistant)
- FR (fast, fatigue-resist)
- FF (fast, fatigable)
extra:
- Fint (fast, intermediate fatigable)
What are FIVE ways in which the main motor unit types differ?
- Twitch speed
- Twitch strength
- Fatigue
- Motorneuron size
- Activation timing
What is one main way jaw muscle fibre type composition varies from limb/trunk muscles? (Link this to a purpose)
- Large quantity of hybrid fibres vs. limb/trunk
Purpose: - jaw requires ability to apply diversity of forces/movement
- jaw is also able to adapt
What are FIVE factors that may affect jaw fibre-type composition?
- Aging (less neonatal myosin)
- Hormones (e.g. testosterone)
- Food (hardness of food)
- Dentures/edentulousness
- Craniofacial morphology (e.g. open bite)
What are TWO ways to measure muscle activity?
- Electromyography (EMG)
- Mechanomyography (MMG)
What are FIVE steps to muscle contraction? (AP has reached synaptic terminal at motor end plate)
- ACh released, binding to receptors on muscle opening Na channels -> AP
- AP travels down T-tubules
- Sarcoplasmic reticulum releases Ca2+
- Ca2+ binds to troponin, moving tropomyosin to reveal active actin active site
- Myosin (thick chain) binds to actin -> contraction towards centre of sarcomere
How does the firing threshold at the input of a motorneuron compare with that of a sensory neuron?
Firing threshold of motorneuron much higher (requires integration of inputs to reach threshold)
How is recruitment timing of different motor unit types made possible?
The motorneuron types are of different sizes, larger ones having a larger firing threshold (ie. recruited last)
What are the corresponding functional and histochemical classifications of the motor unit types?
- S = Type I
- FR = Type IIA
- FF = Type IIB
