Abstract
Effects of prior motion on ramp stretch responses of reflexive and areflexive muscles were measured in decerebrate cats. Soleus and gastrocnemius muscles were rendered areflexive by reinnervation a minimum of 9 mo before the terminal experiments. The introduction of a shortening phase prior to the ramp stretch increased the normalized initial stiffness of muscles and decreased the tendency to yield of the reinnervated muscles as compared with the case in which muscles contracted isometrically prior to stretch. Yielding was compensated by reflex action for all amplitudes of prior shortening in soleus and gastrocnemius muscles. The comparison of responses of untreated and reinnervated muscles indicated that the contribution of reflex action progressively declined with the amplitude of prior shortening as the extent of yielding diminished. In soleus muscle, during a variable delay period of isometric contraction interposed between shortening and lengthening force generation, initial stiffness and yielding returned to levels seen with isometric contractile history. However, these attributes recovered at different rates, suggesting that distinct processes are responsible for initial stiffness and yielding. Yielding was compensated for by reflex action regardless of the length of the interposed delay or of the amplitude of the prior shortening. These and previous findings indicate that the stretch reflex regulates muscular stiffness for a wide range of conditions. This regulation apparently arises from complementary mechanical properties of intrafusal and extrafusal muscle.
Original language | American English |
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Journal | Journal of Neurophysiology |
Volume | 90 |
DOIs | |
State | Published - Sep 1 2003 |
Keywords
- Cat
- Effect of Movement History
- Intrinsic Properties
- Reflex Compensation
- Reinnervated Triceps Surae Muscles
Disciplines
- Medical Cell Biology
- Medical Neurobiology
- Medical Physiology
- Medical Sciences
- Medicine and Health Sciences
- Neurosciences
- Physiological Processes