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reflex
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reflexive action Diagram showing the knee jerk reflex: a reflex hammer strikes the patellar tendon below the knee, activating a stretch receptor in the quadriceps muscle. This sends a signal through a sensory neuron to the spinal cord, where it connects to a motor neuron. The motor neuron then signals the muscle to contract, causing the lower leg to kick forward. The diagram also illustrates the pathway of sensory and motor neurons and their connection in the spinal cord.
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reflexive action
reflexive action The mechanism of reflexive action of the nervous system.

reflex

physiology
Also known as: response
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History

reflex, in biology, an action consisting of comparatively simple segments of behaviour that usually occur as direct and immediate responses to particular stimuli uniquely correlated with them. Many reflexes of placental mammals appear to be innate. They are hereditary and are a common feature of the species and often of the genus. Reflexes include not only such simple acts as chewing, swallowing, blinking, the knee jerk, and the scratch reflex, but also stepping, standing, and...

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