سؤال قراءة ستيب محلول — فهم التفاصيل (تدريب 5089)

(1) The spinal cord is an information highway connecting the nervous system to the brain. Ascending neural areas send up sensory information, and descending areas send back motor-control information. A look at the neural pathways that control our reflexes, our automatic responses to stimuli, shows the spinal cords work. A simple spinal-reflex path is composed of a single sensory neuron and a single motor neuron, which often communicate through an interneuron. (2) One such path makes up the pain reflex. When your fingers touch a hot stove, neural activity excited by the heat travels via sensory neurons to interneurons in your spinal cord. These interneurons respond by activating motor neurons to the muscles in your arm, causing you to jerk your hand away. (3) Because the simple pain-reflex pathway runs through the spinal cord and out, you jerk your hand from a candle's flame before your brain receives and responds to the information that causes you to feel pain. Information travels to and from the brain by way of the spinal cord. Were the top of your spinal cord severed, you would not feel such pain. Or pleasure. Your brain would literally be out of touch with your body. Thus, you would lose all sensation and voluntary movement in body regions whose sensory and motor neurons connect with the spinal cord below its point of injury.