rapid motor response to a sensory stimulus in which nerve impulses travel in an arc that includes the spinal cord but not the brain; in infants, may refer to one of several instinctive behaviors, such...rapid motor response to a sensory stimulus in which nerve impulses travel in an arc that includes the spinal cord but not the brain; in infants, may refer to one of several instinctive behaviors, such as crying and sucking, that help an infant survive layer of photoreceptor cells at the back of the eye, including rods that are particularly sensitive to dim light and cones that are sensitive to light of different colors
