The cells responsible for transmitting messages to the effectors are

Explanation

The cells that transmit messages to effectors are motor neurons, also known as efferent neurons. They Transmit impulses from the central nervous system (CNS) to effectors, such as muscles and glands. Motor neurons typically have long axons and short dendrites. while the sensory neutrons transmit impulses from sense organs to the CNS. When a stimulus is detected, the information is converted to an electrical signal and sent through a sensory neuron.

Hair cells are sensory cells that convert mechanical force into electrical signals. They are found in the inner ear and are responsible for hearing and balance. 

Relay neurons are neurons in the central nervous system (CNS) that connect sensory neurons to motor neurons. They are found in the brain and spinal cord. 

There is an explanation video available .