Pain Suppression (―Analgesia‖) System in the Brain and Spinal Cord The degree to which a person reacts to pain varies tr mendously. This results partly from a
capability of thebrain itself to suppress input of pain signals to the nervo ssystem by activating a pain
control system, called ananalgesia system.The analgesia system is shown in Figure 48-4. It consists of
three major components: (1) The periaqueductalgray and periventricular areas of the mesencephalon
and upper pons surround the aqueduct of Sylvius and
Chapter 48 Somatic Sensations: II. Pain,
Headache, and Thermal Sensations 587
portions of the third and fourth ventricles.
