NERVOUS SYSTEM SPECIAL SENSE
SPINALCORD
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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It is ipsilateral.
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It causes contraction of the agonist muscle.
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It causes an inhibitory arc in the antagonist muscle.
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It causes an inhibitory arc in the agonist muscle.
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Detailed explanation-1: -When a stretch reflex is activated, it not only causes contraction of the synergistic muscles, but also caused relaxation i.e. has an inhibitory effect on the antagonist muscles. Once a stretch reflex occurs, the impulse is sent from the stretched muscle spindle, to the alpha motor neuron.
Detailed explanation-2: -Thus, when a muscle spindle is stretched and the stretch reflex is activated, the opposing muscle group must be inhibited to prevent it from working against the resulting contraction of the homonymous muscle (Figure 2.2). This inhibition is accomplished by an inhibitory interneuron in the spinal cord.
Detailed explanation-3: -The classic stretch reflex involves the stretch receptor in the skeletal muscle spindle and its afferent Ia fiber in the posterior nerve root, which directly or indirectly excites the alpha motor neuron in the spinal cord.
Detailed explanation-4: -The antagonistic muscle is inhibited during the reflex while the agonist muscle contracts. [8] This action occurs polysynaptically through the Ia inhibitory interneuron, which inhibits alpha motor neurons to the antagonistic muscle.