Joule Health Dictionary

A unit of energy. Two units are called by this name. The small calorie, or gram calorie, is the amount of heat required to raise one gram of water one degree centigrade in temperature.

The large Calorie or kilocalorie, which is used in the study of dietetics and physiological processes, is the amount of heat required to raise one kilogram of water one degree centigrade in temperature. The number of Calories required to carry on the processes necessary for life and body warmth – such as the beating of the heart, the movements of the chest in breathing, and the chemical activities of the secreting glands – is, for an adult person of ordinary weight, somewhere in the neighbourhood of 1,600. For ordinary sedentary occupations an individual requires about 2,500 Calories; for light muscular work slightly over 3,000 Calories; and for hard continuous labour around 4,000 Calories daily.

Under the International System of Units (SI UNITS – see APPENDIX 6: MEASUREMENTS IN MEDICINE) the kilocalorie has been replaced by the joule, the abbreviation for which is J (1 kilocalorie=4,186·8 J). The term Calorie, however, is so well established that it has been retained in this edition. Conversion from Calories (or kilocalories) to joules is made by multiplying by 4·2 .... calorie

An o?cially recognised measurement of heat: a unit is equal to the quantity of heat needed to raise the temperature of one pound of water by 1°Fahrenheit. One BTU is equivalent to 1,055 joules (see JOULE).... british thermal unit (btu)

The international system of measurement-units used throughout the sciences. SI units, which derive from metres, kilograms, and seconds, comprise seven basic units and two supplementary ones. Among the other base units are ampere (electric current) and mole (amount of a substance at molecular level). Derived SI units include joule (energy), pascal (pressure), becquerel (activity), and newton (force). (See APPENDIX 6: MEASUREMENTS IN MEDICINE.)... si units

The capacity to do work or effect a physical change. Nutritionists refer to the fuel content of a food as its energy.

There are many forms of energy, including light, sound, heat, chemical, electrical, and kinetic, and most of them play a role in the body. For instance, the retina converts light energy to electrical nerve impulses, making vision possible. Muscles use chemical energy obtained from food to produce kinetic energy, movement, and heat.

Energy is measured in units called calories and joules.

Because these units are extremely small, more practical units used in dietetics are the kilocalorie (kcal, 1,000 calories), and kilojoule (kJ, 1,000 joules).

Carbohydrates and proteins provide 4 kcal per gramme (g), fats provide 9 kcal per g (see metabolism).

In general, the energy liberated from the breakdown of food is stored as chemical energy in ATP molecules.

The energy in these molecules is then available for processes that consume energy, such as muscle contraction.... energy

The unit of energy equal to 1,000 joules, abbreviated to kJ. One kcal (see kilocalorie) equals 4.2 kJ.... kilojoule

A collective term for all the chemical processes that take place in the body. It is divided into catabolism (breaking down of complex substances into simpler ones) and anabolism (building up of complex substances from simpler ones). Usually, catabolism releases energy, while anabolism uses it.

The energy needed to keep the body functioning at rest is called the basal metabolic rate (BMR). It is measured in joules (or kilocalories) per square metre of body surface per hour. The BMR increases in response to factors such as stress, fear, exertion, and illness, and is controlled principally by various hormones, such as thyroxine, adrenaline (epinephrine), and insulin. (See also metabolism, inborn errors of; metabolic disorders.)... metabolism

Several different internationally agreed units (called units) are used to measure ionizing radiation. For example, the roentgen (R) measures the amount of radiation in the air, and the becquerel is the unit of spontaneous activity of a radioactive source such as uranium. For medical purposes, the most commonly used units are the gray (Gy) and the sievert (Sv).

The gray is the unit of radiation that is actually absorbed by any tissue or substance as a result of exposure to radiation. 1 Gy is the absorption of 1 joule of energy (from gamma radiation or X-rays) per kilogram of irradiated matter. The gray supersedes an older unit called the rad (1 Gy = 100 rads).

Because some types of radiation affect biological organisms more than others, the sievert is used as a measure of the impact of an absorbed dose. It uses additional factors, such as the kind of radiation and its energy, to quantify the effects on the body of equivalent amounts of different types of absorbed energy. The sievert replaces an older unit, the rem (1 Sv=100 rems).... radiation unit

a unit of heat equal to the quantity of heat required to raise the temperature of 1 pound of water by 1° Fahrenheit. 1 British thermal unit = 1055 joules. Abbrev.: Btu.... british thermal unit

n. a unit of work or energy equal to the work done when the point of application of a force of 1 dyne is displaced through a distance of 1 centimetre in the direction of the force. 1 erg = 10?7 joule.... erg

n. the *SI unit of absorbed dose of ionizing radiation, being the absorbed dose when the energy per unit mass imparted to matter by ionizing radiation is 1 joule per kilogram. It has replaced the rad. Symbol: Gy.... gray

n. a unit of heat equal to 100,000 British thermal units. 1 therm = 1.055 × 108 joules.... therm

n. the *SI unit of power, equal to 1 joule per second. In electrical terms it is the energy expended per second when a current of 1 ampere flows between two points on a conductor between which there is a potential difference of 1 volt. 1 watt = 107 ergs per second. Symbol: W.... watt