Divided into two hemispheres and four lobes. responsible for coordinating muscle movement and maintaining posture. contains activity centers for thalamus, hypothalamus, optic chiasm, and pituitary gland. associated with visual reflexes and hearing. functions as a relay center within the brain. relay center for impulses to and from the spinal cord and controls heart, respiration, and vasomotor reactions. diencephalon mesencephalon cerebrum cerebellum medulla oblongata pons a. true b. false.