1. Stretch reflex
1. Stretch Reflex
(1) Anatomy of Muscle Spindle (A)Muscle spindle o The muscle spindles detect a motor change in the length of the neuron muscle Extrafusal stretch receptors that report fibers the stretching of the muscle to neuron the spine Spindle o Each spindle consists of 3 afferent (a 10 intrafusal muscle fibers afferent enclosed in a connective tissue capsule Intrafusal fibers o These fibers are less than one quarter of the size of extrafusal muscle fibers (effector fibers)
(1) Anatomy of Muscle Spindle ⚫ The muscle spindles detect change in the length of the muscle -- stretch receptors that report the stretching of the muscle to the spine. ⚫ Each spindle consists of 3- 10 intrafusal muscle fibers enclosed in a connective tissue capsule ⚫ These fibers are less than one quarter of the size of extrafusal muscle fibers (effector fibers)
Anatomy of Muscle Spindle (A)Muscle spindle Motor neuron ● The central region of Extrafusal the intrafusal fibers fibers Motor which lack neuron myofilaments are noncontractile afferent (a afferent) ● serving as the receptive surface of Intrafusal the spindle(sensory fib ers receptor)
Anatomy of Muscle Spindle ⚫ The central region of the intrafusal fibers which lack myofilaments are noncontractile, ⚫ serving as the receptive surface of the spindle (sensory receptor)
Anatomy of Muscle Spindle o Intrafusal fibers are wrapped by two types of afferent endings that send sensory inputs to the cns o Primary sensory endings Type la fibers Innervate the center of the spindle o Secondary sensory endings Type II fibers Associated with the ends of the spindle la primary afferent from nuclear bag fiber 2 阝 efferent To extra. ll secondary fusal fibers afferent Plate Annulospiral endings B Nuclear bag fiber fiber 90 Trail ending Flower-spray ending
Anatomy of Muscle Spindle ⚫ Intrafusal fibers are wrapped by two types of afferent endings that send sensory inputs to the CNS ⚫ Primary sensory endings – Type Ia fibers – Innervate the center of the spindle ⚫ Secondary sensory endings – Type II fibers – Associated with the ends of the spindle
Components of muscle spindle Dynamic intrafusal Static intrafusal fiber fibers Static intrafusal fibers Primal Afferent la ending axons|ⅡI Secondar ending
Components of muscle spindle Static intrafusal fibers Dynamic intrafusal fiber Afferent axons Ia II Static intrafusal fibers Primary ending Secondary ending } }