title: Mechanotransduction in the muscle spindle.
abstract: The focus of this review is on the principal sensory ending of the mammalian muscle spindle, known as the primary ending. The process of mechanosensory transduction in the primary ending is examined under five headings: (i) action potential responses to defined mechanical stimuli-representing the ending's input-output properties; (ii) the receptor potential-including the currents giving rise to it; (iii) sensory-terminal deformation-measurable changes in the shape of the primary-ending terminals correlated with intrafusal sarcomere length, and what may cause them; (iv) putative stretch-sensitive channels-pharmacological and immunocytochemical clues to their identity; and (v) synaptic-like vesicles-the physiology and pharmacology of an intrinsic glutamatergic system in the primary and other mechanosensory endings, with some thoughts on the possible role of the system. Thus, the review highlights spindle stretch-evoked output is the product of multi-ionic receptor currents plus complex and sophisticated regulatory gain controls, both positive and negative in nature, as befits its status as the most complex sensory organ after the special senses.
authors.affiliation: School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Aberdeen, AB25 2ZD, UK, g.s.bewick@abdn.ac.uk.
authors.forename: Guy S
authors.initials: GS
authors.lastname: Bewick
authors.forename: Robert W
authors.initials: RW
authors.lastname: Banks
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D006801:Humans; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D008954:Models, Biological; D009119:Muscle Contraction / Q000502:physiology*; D009470:Muscle Spindles / Q000294:innervation / Q000502:physiology*; D012026:Reflex, Stretch / Q000502:physiology*; D013314:Stress, Mechanical