03/01/05RDN 8031 The Musculature RDN 803 Principles of Occlusion Reading: Mohl, et al., Chapter 7...
-
date post
19-Dec-2015 -
Category
Documents
-
view
223 -
download
1
Transcript of 03/01/05RDN 8031 The Musculature RDN 803 Principles of Occlusion Reading: Mohl, et al., Chapter 7...
03/01/05 RDN 803 1
The Musculature
RDN 803 Principles of Occlusion
Reading: Mohl, et al., Chapter 7
W.D. McCall, Jr., Ph.D.
•These slides are available at:http://www.acsu.buffalo.edu/~wdmccall/
03/01/05 RDN 803 2
Topics to be Covered
I. Properties of muscle
II. Muscles of mandibular function
III. Electromyography
IV. Some trigeminal reflexes
V. Selected dental controversies
03/01/05 RDN 803 3
I. Properties of Muscle
A. Common with limb muscle1. Length-tension curve
2. Force-velocity curve
3. Determinants of muscle force
B. Peculiar to jaw muscles1. Anatomy of origins and insertions
2. Location of some sensory cell bodies
3. Organization of some reflexes
03/01/05 RDN 803 4
The Length-Tension Experiment
1. Set muscle length 2. Stimulate nerve to muscle
3. Record force
03/01/05 RDN 803 5
Features:1. Tetanic force >
twitch force2. Fast & slow fibers
differ3. Part of force is
passive
03/01/05 RDN 803 6
The Force-Velocity Experiment
1. Set weight to lift 2. Stimulate muscle
3. Measure velocity
03/01/05 RDN 803 7
Feature:Faster is weaker
03/01/05 RDN 803 8
Features:1. Delay from action potential to twitch2. More force from a shower of action potentials
03/01/05 RDN 803 9
Determinants of Muscle Force
1. Length
2. Velocity
3. Delay from electrical to mechanical events
4. Number of motor units recruited
5. Frequency of stimulation
6. Anatomy of origin and insertion
03/01/05 RDN 803 10
II. Muscles of mandibular function
A. Jaw closing muscles1. Masseter
2. Temporalis
3. Medial pterygoid
B. Jaw opening muscles1. Anterior digastric
2. Lateral pterygoid
03/01/05 RDN 803 11
Origin: zygomatic process
of the maxilla and inferiorborder of zygomatic arch
Insertion:angle of the mandible
inferior, lateral side of ramus
Innervation:masseteric nerve
Function:elevate mandible
Masseter
03/01/05 RDN 803 12
03/01/05 RDN 803 13
03/01/05 RDN 803 14
Origin:temporal fossa and
temporal fascia
Insertion:coronoid process of
the mandible
Innervation:temporal nerve
Function:elevate mandible
Temporalis
03/01/05 RDN 803 15
03/01/05 RDN 803 16
03/01/05 RDN 803 17
Origin:pterygoid fossa
and medial surface of lateral pterygoid plate
Insertion:ramus and angle
of the mandible
Innervation:medial pterygoid
nerve
Function:elevate mandible
Medial Pterygoid
03/01/05 RDN 803 18
03/01/05 RDN 803 19
03/01/05 RDN 803 20
Sphenoid
03/01/05 RDN 803 21
03/01/05 RDN 803 22
Origin ofMedialPterygoid
03/01/05 RDN 803 23
Origin:lateral surface of
lateral pterygoid plate
Insertion:anterior neck of the
mandible
Innervation:branch of masseteric
or buccal nerve
Function:pull condyle and disk
along the eminence
Lateral Pterygoid -- Inferior Head
03/01/05 RDN 803 24
03/01/05 RDN 803 25
Origin ofLateralPterygoid,Inferior head
03/01/05 RDN 803 26
Origin:infratemporal fossa of greater sphenoid wing
Insertion:anterior neck of themandible
Innervation:branch of masseteric or buccal nerve
Function:pull condyle and diskalong the eminence
Lateral Pterygoid -- Superior Head
03/01/05 RDN 803 27
SuperiorHead ofLateralPterygoid
03/01/05 RDN 803 28
Origin:posterior digastric
mastoid notch of temporalbone
Insertion:anterior digastric
lingual, inferior border ofthe mandible
Innervation:Posterior digastric--facial nerveAnterior digastric--mylohyoid, mandibular nerve
Function:Lower mandible, raise hyoid
Digastric
03/01/05 RDN 803 29
03/01/05 RDN 803 30
ANTERIOR DIGASTRIC
03/01/05 RDN 803 31
03/01/05 RDN 803 32
THE BIG PICTUREFUNCTION EXAMPLE NEURAL CIRCUIT LOCATION
Protection Jaw jerk, Reflex Brain stemJaw opening,Gagging
Rhythmic Chewing, Pattern generator Brain stemactivity Breathing,
Walking
Complex Speech Cortexfunction
03/01/05 RDN 803 33
III. Electromyography
A. Mechanism
B. Electrodes
C. Electronics
D. Caveats
E. Strengths
03/01/05 RDN 803 34
Across membrane: 90 mV Extracellular: about 90 V
A. MECHANISM: Muscle Action Potentials
EMG signal is attenuated at the skin by about 1000
03/01/05 RDN 803 35
B. ELECTRODES
03/01/05 RDN 803 36
Caveats
A. Electrical activity must be calibrated to be directly related to muscle force.
B. Jaw muscles are redundant: six jaw closers, and they all are active in closing. (You cannot control the muscles independently. The forces on the jaw must satisfy Newton’s equations.)
03/01/05 RDN 803 37
Determinants of Muscle Force
Item Seen in EMG?
A. Recruitment Yes
B. Frequency Yes
C. Length No
D. Velocity No
03/01/05 RDN 803 38
Strengths of Electromyography
A. Know precisely when muscle is active.
B. Know roughly how active.
C. Insight into activity of motor neuron.
03/01/05 RDN 803 39
IV. Some trigeminal reflexes
A. Jaw closing reflex
B. Jaw opening reflexC. Blink reflex
D. Tongue reflex
E. Gagging
F. Modulating influences
03/01/05 RDN 803 40
Types of Reflexes
• Postural• Protective• Cardiovascular• Respiratory• Digestive• Humoral
03/01/05 RDN 803 41
The Jaw Jerk Reflex (Postural)
R.M. Bradley, Figure 10-12
03/01/05 RDN 803 42
R.M. Bradley, Figure 10-13
The Jaw Opening Reflex (Protective)
03/01/05 RDN 803 43
V. Selected Controversies
A. Rest position: passive elasticity vs. active contraction
B. Mastication: alternating reflexes vs. central pattern generator
C. Electronic devices for TMD diagnosis
03/01/05 RDN 803 44
A. Rest position hypotheses
1. Passive elasticity2. Active contraction
a. Stretch reflexb. TMJ receptorsc. Airway patency
03/01/05 RDN 803 45
Rest Position: Evidence
Passive ElasticityLength-tension curve
Negative EMG search
Stretch reflexSleep in chair
MN inhibition in sleep
Positive needle EMG
Positive surface EMG
03/01/05 RDN 803 46
Su
rfac
e E
MG
,V
Vertical Jaw Opening, mm
03/01/05 RDN 803 47
B. Mastication hypotheses
A. Hypotheses 1. Alternating reflexes (Sherrington, 1917)
2. Central pattern generator (Lund, 1971)
B. Significance: part of the theme “Be skeptical and be critical”
03/01/05 RDN 803 48
C. Electronic devices for TMD diagnosis
Hypotheses:1. Resting EMG greater in TMD patients(No convincing evidence)
2. Jaw position differs in TMD patients(No convincing evidence)
03/01/05 RDN 803 49
Summary
I. Properties of muscle
II. Muscles of mandibular function
III. Electromyography
IV. Two trigeminal reflexes
V. Selected dental controversies
These slides are available at:http://www.acsu.buffalo.edu/~wdmccall/