1.   1.  What is a reflex arc and why are they important2. Describe the sequence of events from an impulse in a motor neuron to contraction of a muscle.  

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A reflex is a response to a perturbing stimulus that acts to return the body to homeostasis. This may be subconscious as in the regulation of blood sugar by the pancreatic hormones, may be somewhat noticeable as in shivering in response to a drop in body temperature; or may be quite obvious as in stepping on a nail and immediately withdrawing your foot.A reflex arc refers to the neural pathway that a nerve impulse follows. The reflex arc typically consists of five components (3):1. The receptor at the end of a sensory neuron reacts to a stimulus.2. The sensory (afferent) neuron conducts nerve impulses along an afferent pathway towards the central nervous system (CNS).3. The integration center consists of one or more synapses in the CNS.http://uk.answers.yahoo.com/question/index?qid=20100905051523AA3ZIhC