Biomaterial Database

Fusimotor activity in masseter nerve of the cat during reflex jaw movements. 1980

K Appenteng, and T Morimoto, and A Taylor

1. Unit recordings have been made from the central ends of filaments of the masseter nerve in lightly anaesthetized cats. Evidence is presented to show that fusimotor activity may be distinguished from alpha motor activity. 2. During reflex cyclic movements induced by intra-oral stimulation, two distinct patterns of fusimotor firing emerged. One type of unit increased firing at the beginning and sustained this with little modulation throughout the movements. The other type was strongly modulated approximately in parallel with the alpha motor activity. 3. By comparison with records of jaw elevator spindle afferents under similar conditions, it was deduced that the sustained type of action was due to dynamic fusimotor neurones while the modulated type was due to static fusimotor neurones. 4. The patterns of fusimotor activity seen in these rhythmic movements under light anaesthesia agree well with the patterns deduced from spindle recordings in the conscious cat during mastication. 5. The results emphasize the importance of looking beyond a simple hypothesis of 'alpha-gamma co-activation' to explain fusimotor function. It is proposed that tonic dynamic fusimotor activity is set at the beginning of a movement to determine the incremental sensitivity of primary endings to stretch. The static fusimotor fibres are activated principally during shortening to help keep both primary and secondary endings active.

UI	MeSH Term	Description	Entries
D008334	Mandible	The largest and strongest bone of the FACE constituting the lower jaw. It supports the lower teeth.	Mylohyoid Groove,Mylohyoid Ridge,Groove, Mylohyoid,Grooves, Mylohyoid,Mandibles,Mylohyoid Grooves,Mylohyoid Ridges,Ridge, Mylohyoid,Ridges, Mylohyoid
D008406	Masseter Muscle	A masticatory muscle whose action is closing the jaws.	Masseter Muscles,Muscle, Masseter,Muscles, Masseter
D008410	Masticatory Muscles	Muscles arising in the zygomatic arch that close the jaw. Their nerve supply is masseteric from the mandibular division of the trigeminal nerve. (From Stedman, 25th ed)	Masticatory Muscle,Muscle, Masticatory,Muscles, Masticatory
D009046	Motor Neurons	Neurons which activate MUSCLE CELLS.	Neurons, Motor,Alpha Motorneurons,Motoneurons,Motor Neurons, Alpha,Neurons, Alpha Motor,Alpha Motor Neuron,Alpha Motor Neurons,Alpha Motorneuron,Motoneuron,Motor Neuron,Motor Neuron, Alpha,Motorneuron, Alpha,Motorneurons, Alpha,Neuron, Alpha Motor,Neuron, Motor
D009047	Motor Neurons, Gamma	Motor neurons which activate the contractile regions of intrafusal SKELETAL MUSCLE FIBERS, thus adjusting the sensitivity of the MUSCLE SPINDLES to stretch. Gamma motor neurons may be "static" or "dynamic" according to which aspect of responsiveness (or which fiber types) they regulate. The alpha and gamma motor neurons are often activated together (alpha gamma coactivation) which allows the spindles to contribute to the control of movement trajectories despite changes in muscle length.	Neurons, Fusimotor,Neurons, Gamma Motor,Gamma Motorneurons,Motor Neurons, Gamma-Efferent,Fusimotor Neuron,Fusimotor Neurons,Gamma Motor Neuron,Gamma Motor Neurons,Gamma Motorneuron,Gamma-Efferent Motor Neuron,Gamma-Efferent Motor Neurons,Motor Neuron, Gamma,Motor Neuron, Gamma-Efferent,Motor Neurons, Gamma Efferent,Motorneuron, Gamma,Motorneurons, Gamma,Neuron, Fusimotor,Neuron, Gamma Motor,Neuron, Gamma-Efferent Motor,Neurons, Gamma-Efferent Motor
D009068	Movement	The act, process, or result of passing from one place or position to another. It differs from LOCOMOTION in that locomotion is restricted to the passing of the whole body from one place to another, while movement encompasses both locomotion but also a change of the position of the whole body or any of its parts. Movement may be used with reference to humans, vertebrate and invertebrate animals, and microorganisms. Differentiate also from MOTOR ACTIVITY, movement associated with behavior.	Movements
D009119	Muscle Contraction	A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.	Inotropism,Muscular Contraction,Contraction, Muscle,Contraction, Muscular,Contractions, Muscle,Contractions, Muscular,Inotropisms,Muscle Contractions,Muscular Contractions
D009431	Neural Conduction	The propagation of the NERVE IMPULSE along the nerve away from the site of an excitation stimulus.	Nerve Conduction,Conduction, Nerve,Conduction, Neural,Conductions, Nerve,Conductions, Neural,Nerve Conductions,Neural Conductions
D009470	Muscle Spindles	Skeletal muscle structures that function as the MECHANORECEPTORS responsible for the stretch or myotactic reflex (REFLEX, STRETCH). They are composed of a bundle of encapsulated SKELETAL MUSCLE FIBERS, i.e., the intrafusal fibers (nuclear bag 1 fibers, nuclear bag 2 fibers, and nuclear chain fibers) innervated by SENSORY NEURONS.	Muscle Stretch Receptors,Neuromuscular Spindles,Receptors, Stretch, Muscle,Stretch Receptors, Muscle,Muscle Spindle,Muscle Stretch Receptor,Neuromuscular Spindle,Receptor, Muscle Stretch,Receptors, Muscle Stretch,Spindle, Muscle,Spindle, Neuromuscular,Spindles, Muscle,Spindles, Neuromuscular,Stretch Receptor, Muscle
D009475	Neurons, Afferent	Neurons which conduct NERVE IMPULSES to the CENTRAL NERVOUS SYSTEM.	Afferent Neurons,Afferent Neuron,Neuron, Afferent

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