Shivering is a normal physiological reaction to decreased body temperature in an attempt to prevent hypothermia. The body's muscle pairs quickly contract in a quick, regular rhythm to drive blood to the affected muscles and create heat through work. As shivering is a reflex reaction, not under voluntary control, the lack of shivering or its presence when the patient is not cold are often symptoms of an underlying pathology. For example, in Insensitive, House noted that Hannah Morgenthal was not shivering although she was wet and had been outside. He eventually pegged her with CIPA, a disease where the nerves are unable to detect changes in body temperature. Conversely, in Don't Ever Change, Roz started shivering during a test where she was put in a warm room to induce sweating. She was later diagnosed with a hanging kidney.