Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Hypertonia ?
    ### Response:
    Hypertonia is a condition in which there is too much muscle tone so that arms or legs, for example, are stiff and difficult to move. Muscle tone is regulated by signals that travel from the brain to the nerves and tell the muscle to contract. Hypertonia happens when the regions of the brain or spinal cord that control these signals are damaged.
    