Production of Body Heat 1. Most body heat is a result of oxidation of the food we eat. - The rate at which this heat is produced is known as the metabolic rate. 2. Metabolic rate is affected by exercise , the nervous system , hormones , body temperature , ingestion of food , age , sex (lower in females except during pregnancy and lactation) , climate , sleep , and malnutrition . Basal Metabolic Rate (BMR) 1. Measurement of the metabolic rate under basal conditions is called the Basal Metabolic rate (BMR). 2. BMR is expressed in kilocalories per square meters of body area per hour (kcal/M2/hr). Loss of body Heat 1. Radiation is the transfer of heat as infrared heat rays from one object to another without physical contact. 2. Conduction is the transfer of body heat to a substance or object in contact with the body. 3. Convection is the transfer of body heat by the movement of air that has been warmed by the body.
Chapter 25 35 4. Evaporation is the conversion of a liquid to a vapor. HOMEOSTASIS OF BODY TEMPERATURE REGULATION 1. A normal body temperature is maintained by a delicate balance between heat-producing and heat-losing mechanisms. 2. The hypothalamus thermostat is the preoptic area. 3. Mechanisms that produce or retain heat are vasoconstriction, sympathetic stimulation, skeletal muscle contraction, and thyroxine production. 4. Mechanisms of heat loss include vasodilation, decreased metabolic rate, decreased skeletal muscle contraction, and perspiration. BODY TEMPERATURE ABNORMALITIES 1. Fever is an abnormally high body temperature most commonly caused by protaglandius, with interleukin-1 and mediators. 2. Heat cramps are painful skeletal muscle contractions due to loss of salt and water. 3. Heat exhaustion results in a normal or below normal body temperature, profuse perspiration, nausea, cramps, and dizziness. Rest and salt tablets are indicated. 4. Heatstroke results in decreased blood flow to skin reduced perspiration, and high body temperature: fluid therapy and body cooling are indicated. 5. Hypothermia refers to a lowering of body temperature.
Chapter 25 36 DISORDERS: HOMEOSTATIC IMBALANCES 1. Obesity is defined as a body weight 10 to 20% above desirable standard as the result of excessive accumulation of fat. a. Hypertrophic (adult-onset) obesity - there is an increase in the amount of fat in adipocytes but no increase in the number of fat cells. b. Hyperplastic (lifelong) obesity - in which there is an increase in the number of adipocytes, as well as an increase in the amount of fat within them. 3. Malnutrition refers to a state of bad or poor nutrition. 4. Phenylketonuria (PKU) - is a genetic error of metabolism characterized by an elevation of phenylalanine in the blood. 5. Cystic fibrosis (CF) is a metabolic disease of the exocrine glands in which absorption of vitamins A, D, and K and Calcium is inadequate. 6. Celiac disease is a condition in which the ingestion of gluten causes morphological changes in the small intestinal mucosa resulting in malabsorption.
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