PSYC 427 Lecture Notes - Lecture 6: Muscle Spindle, Skeletal Muscle, Afferent Nerve Fiber
Document Summary
Skeletal muscle is composed of two basic types of muscle fibres: extrafusal fibres (last class, large diameter) o. Intrafusal fibres (associated with sensory system in muscles) Large diameter muscle fibres which produce movement via the large diameter axon motor system. Motor innervation to extrafusal muscle via the motor system. Small diameter muscle fibres which are much shorter than extrafusal fibres and produce a low tension output. Intrafusal fibres are grouped together in a connective tissue capsule known as the muscle spindle. The spindle is mechanically in parallel to the extrafusal muscle fibres. (same side). When main muscle is stretched spindle is stretched. Imagine designing a system to transduce muscle length but when muscle is doing its work (contracting), the receptor which senses stretch has a conceptual problem. How can it transduce muscle length even when main muscle is contracting? receptor collapses. Receptor (stretch receptor) doesn"t work when muscle is working.
