Somatic Spinal Reflexes
The Stretch Reflex: This reflex causes contraction of a skeletal muscle in response to stretching that muscle. Sensory receptors in the muscle are called Muscle Spindles . This reflex occurs due to a Monosynaptic Reflex Arc meaning the reflex can occur by activation of a single sensory neuron that forms one synapse in the CNS with a single motor neuron. These reflexes (stretch) can be initiated by tapping tendons (patellar). This reflex is Ipsilateral, meaning sensory information enters the same side as the motor response leaves. All monosynaptic reflexes are ipsilateral. During a stretch reflex, there is a concurrent polysynaptic reflex occurring to the antagonistic muscles. Thus, when the stretched muscle contracts during a stretch reflex, antagonistic muscles that would oppose the stretch relax. This is termed Reciprocal Innervation . The stretch reflex is useful in the maintenance of posture. Ultimately, the stretch reflex operates as a feedback mechanism to control muscle length by causing muscle contraction.
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