Biomaterial Database

Classification of motor units in flexor carpi radialis muscle of the cat. 1985

B R Botterman, and G A Iwamoto, and W J Gonyea

Motor units in the cat flexor carpi radialis (FCR) muscle, one of two primary wrist flexors, were classified into three groups: slow twitch, fatigue resistant (S); fast twitch, fatigue resistant (FR); and fast twitch, fatigue sensitive (FF). Classification was based on 1) the ratio of the tension-time area produced by a train of stimuli delivered at 40 pps and the maximum tension-time area (A40/Amax), and 2) the cumulative force index (CFI), calculated from a series of trains (40 pps) delivered intermittently for a period of 4 min. The CFI is defined as the ratio between the force accumulated in the last 2 min of stimulation to the first 2 min of stimulation. Motor units with values for A40/Amax greater than 0.50 were classified as type S units, and less than 0.50 as type F. A40/Amax is essentially equivalent to the "sag" profile of an unfused tetanus in its ability to separate units into "slow" and "fast" contracting units. In general, units with area ratios less than 0.50 had twitch contraction times less than 25 ms, whereas units with area ratios greater than 0.50 had contraction times greater than 25 ms. Separation of type F units into two groups was based on the CFI, with ratios less than or equal to 0.75 corresponding to type FF units and greater than 0.75 as type FR units. Type S units also had CFIs greater than 0.75. Based on this classification scheme, 40.4% of FCR motor units were type S, 37.5% type FR, and 22.1% type FF. The a priori assumption of three motor-unit types based on the distributions of A40/Amax and CFI was evaluated by cluster analysis. The analysis supported the assumption of three primary groups of motor units. Furthermore, when cluster formation proceeded to the point where only three clusters remained in the analysis, each of these clusters consisted exclusively of one type of unit (i.e., S, FR, or FF). The validity of the classification scheme was further tested by stepwise discriminant analysis. Units classified as types S, FR, and FF were predicted to be classified with 100% accuracy. All units had a high probability (a posteriori) of having group membership in their originally classified group (P greater than 0.99 for 129 units; P greater than 0.90 for 7 units). The duration of potentiated twitch contractions for type FR and FF units was found to be less than reported for most populations of hindlimb units.(ABSTRACT TRUNCATED AT 400 WORDS)

UI	MeSH Term	Description	Entries
D008959	Models, Neurological	Theoretical representations that simulate the behavior or activity of the neurological system, processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.	Neurologic Models,Model, Neurological,Neurologic Model,Neurological Model,Neurological Models,Model, Neurologic,Models, Neurologic
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
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
D009132	Muscles	Contractile tissue that produces movement in animals.	Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
D002415	Cats	The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801)	Felis catus,Felis domesticus,Domestic Cats,Felis domestica,Felis sylvestris catus,Cat,Cat, Domestic,Cats, Domestic,Domestic Cat
D005221	Fatigue	The state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli.	Lassitude
D005552	Forelimb	A front limb of a quadruped. (The Random House College Dictionary, 1980)	Forelimbs
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001369	Axons	Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.	Axon
D013116	Spinal Cord	A cylindrical column of tissue that lies within the vertebral canal. It is composed of WHITE MATTER and GRAY MATTER.	Coccygeal Cord,Conus Medullaris,Conus Terminalis,Lumbar Cord,Medulla Spinalis,Myelon,Sacral Cord,Thoracic Cord,Coccygeal Cords,Conus Medullari,Conus Terminali,Cord, Coccygeal,Cord, Lumbar,Cord, Sacral,Cord, Spinal,Cord, Thoracic,Cords, Coccygeal,Cords, Lumbar,Cords, Sacral,Cords, Spinal,Cords, Thoracic,Lumbar Cords,Medulla Spinali,Medullari, Conus,Medullaris, Conus,Myelons,Sacral Cords,Spinal Cords,Spinali, Medulla,Spinalis, Medulla,Terminali, Conus,Terminalis, Conus,Thoracic Cords