Mechanical properties of single motor units in the rabbit masseter muscle as a function of jaw position

2001 ◽  
Vol 138 (2) ◽  
pp. 153-162 ◽  
Author(s):  
S. Turkawski ◽  
T. van Eijden
Keyword(s):  
Mechanical Properties ◽  
Masseter Muscle ◽  
Motor Units ◽  
Single Motor ◽  
Single Motor Units ◽  
Jaw Position

Modulation of stretch-evoked reflexes in single motor units in human masseter muscle by experimental pain

2000 ◽  
Vol 132 (1) ◽  
pp. 65-71 ◽  
Author(s):  
Peter Svensson ◽  
Timothy S. Miles ◽  
Thomas Graven-Nielsen ◽  
Lars Arendt-Nielsen
Keyword(s):  
Masseter Muscle ◽  
Experimental Pain ◽  
Motor Units ◽  
Single Motor ◽  
Single Motor Units

Mechanical properties of single motor units in the anterior belly of the digastric

1977 ◽  
Vol 62 (S1) ◽  
pp. S15-S15
Author(s):  
Peter F. MacNeilage ◽  
H. M. Sussman ◽  
R. K. Powers ◽  
J. R. Westbury
Keyword(s):  
Mechanical Properties ◽  
Motor Units ◽  
Single Motor ◽  
Single Motor Units ◽  
Anterior Belly

Functional Properties of Single Motor Units in Inferior Head of Human Lateral Pterygoid Muscle: Task Relations and Thresholds

2001 ◽  
Vol 86 (5) ◽  
pp. 2204-2218 ◽  
Author(s):  
I. Phanachet ◽  
T. Whittle ◽  
K. Wanigaratne ◽  
G. M. Murray
Keyword(s):  
Motor Units ◽  
Normal Function ◽  
Lateral Pterygoid Muscle ◽  
Jaw Movements ◽  
Single Motor ◽  
Single Motor Units ◽  
Rate Dependent ◽  
Fine Control ◽  
Jaw Position ◽  
And Control

The aim of this study was to clarify the normal function of the inferior head of the human lateral pterygoid muscle (IHLP). The hypothesis was that an important function of the IHLP is in the fine control of horizontal jaw movements. The activities of 99 single motor units (SMUs) were recorded from IHLP (22 recordings from 16 subjects). Most recording sites were identified by computer tomography (CT). All 99 SMUs were active during contralateral jaw movements with the teeth apart, and protrusive jaw movements with the teeth apart, and 81% (48 of 59 units studied during all 3 tasks) were active during submaximal jaw-opening movements. None were active on maximal ipsilateral or retrusive jaw movements with the teeth apart nor on jaw closing/clenching in intercuspal position; nor were they spontaneously active when the jaw was at the clinically determined postural jaw position. Thresholds of SMUs ranged from <0.2 mm of contralateral or protrusive horizontal displacements to 61–89% of the maximum contralateral or protrusive displacement, respectively. For the 35 units continuously active during the contralateral task, 23 (66%) were recruited within 2 mm of contralateral displacement [25 (63% of 40 units) for protrusion]. Recruitment thresholds (mm) of some of the units were rate dependent with thresholds significantly decreasing with increasing rate of horizontal jaw movement in protrusion and contralateral movements. At eight recording sites where up to six SMUs were able to be discriminated, the average thresholds of successively recruited SMUs were within a 1-mm increment of horizontal jaw displacement. After dividing IHLP into four regions, the SMUs recorded in the superior-medial zone exhibited significantly lower mean threshold values than for the SMUs recorded in the other zones (no units were recorded in the inferior-lateral zone). This provides suggestive evidence supporting previously proposed notions of functional heterogeneity within IHLP. Taken together, the data suggest that specific regions of the IHLP are capable of selective activation in a finely controlled manner to allow the application of the appropriate force vector (magnitude and direction) to effect the required condylar movement needed for the generation and control of horizontal jaw movements.

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