Answer;
Interneuron, motor neuron, effector
Step-by-step explanation;
Interneurons in the central nervous system (brainand spinal cord) connect sensory neurons to motor neurons. One or more interneurons in the spinal cord carry messages from a sensory neuron to a motor neuron.
Motor neurons conduct nerve impulses from the central nervous system (brain and spinal cord) to an effector. A single motor neuron carries messages from the spinal cord to an effector.
-Effectors respond to the impulses by contracting (if the effector is a muscle fiber) or secreting enzymes or hormones (if the effector is a gland).