Biomaterial Database

Some spinal mechanisms of negative motor phenomena in humans. 1995

P Ashby

Department of Medicine (Neurology), University of Toronto, Toronto Western Hospital, Ontario, Canada.

A sudden pause in motoneuron firing can occur (1) because many motoneurons have just discharged, (2) because motoneurons have been directly inhibited, or (3) because there has been a pause in the tonic drive responsible for their activity (Fig. 9) If there is a preceding burst of EMG activity, the silent period may be simply a consequence of inhibitory mechanisms activated by the motoneuron discharge-as from the AHP, Renshaw cell activity, or inhibitory effects from afferents excited by the muscle contraction. If there is no preceding burst of EMG activity, the silent period may be due to direct inhibition of motoneurons. If so, the H-reflex will be inhibited at the time of the silent period with the subject at rest. This inhibition could result from one of the many spinal inhibitory systems. Inhibition from Ia reciprocal inhibitory interneurons may be distinguished from inhibition from interneurons in Ib, group II, or cutaneous afferent pathways by the distribution of their actions to various motoneuron pools. If there is no preceding burst of EMG activity and the H-reflex is not inhibited at the time of the silent period with the subject at rest, then the silent period results from a pause in the tonic drive to motoneurons.

UI	MeSH Term	Description	Entries
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
D009412	Nerve Fibers	Slender processes of NEURONS, including the AXONS and their glial envelopes (MYELIN SHEATH). Nerve fibers conduct nerve impulses to and from the CENTRAL NERVOUS SYSTEM.	Cerebellar Mossy Fibers,Mossy Fibers, Cerebellar,Cerebellar Mossy Fiber,Mossy Fiber, Cerebellar,Nerve Fiber
D009434	Neural Pathways	Neural tracts connecting one part of the nervous system with another.	Neural Interconnections,Interconnection, Neural,Interconnections, Neural,Neural Interconnection,Neural Pathway,Pathway, Neural,Pathways, Neural
D005246	Feedback	A mechanism of communication within a system in that the input signal generates an output response which returns to influence the continued activity or productivity of that system.	Feedbacks
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
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