Why does cardiac pain radiate over the chest and the left arm The motor neurons from the heart activate a reflex that causes vasoconstriction to the chest wall and arm muscles Motor neurons in the cord receive input from the dermatomes innervated by spinal segments T1-T5 as well as the heart Motor neurons form both converge on the frontal lobe. The sensory neurons from the heart activate a reflex that causes vasoconstriction to the chest wall and arm muscles Sensory neurons in the cord receive input from the dermatomes innervated by spinal segments T1- T5 as well as the heart A patient suffers from an upper neuron paralysis that affects the arm. The lesion can be in any of the following areas except: Pyramid Motor cortex Tectum of the midbrain Crus cerebri (cerebral pedunculi). Internal capsule
