MEDICAL PHYSIOLOGY

Detailed explanation-1: -Shivering-nerve impulses are sent by the hypothalamus to the skeletal muscles to bring about rapid contractions that generate heat. Shivering therefore helps raise the body temperature. Increase in metabolic rate-the liver produces extra heat in order to raise the temperature of the body.

Detailed explanation-2: -The primary thermoregulatory adaptations to physical training in a cool environment include increased plasma volume, increased stroke volume, a lowered threshold temperature for the onset of sweating, and decreased rectal temperature in response to a given level of submaximal exercise.

Detailed explanation-3: -Five phenotypic adaptations may be described: reduced heart rate at a fixed work rate; expanded plasma volume; lower core temperature at an equivalent workload; supe-rior sodium and chloride reabsorption from sweat; and an elevated sweat secretion.

Detailed explanation-4: -Shivering thermogenesis is a response to sudden exposure to cold and is a major contributor to enhanced heat production. Nonshivering thermogenesis is also induced by exposure to cold and is the mechanism by which heat is produced by the calorigenic effect of epinephrine and norepinephrine.