heat loss or gain from the body

• conduction - when in contact with a cold environment

• convection - air movement can add or remove heat to the body

• radiation - the body will radiate heat if the environment is cooler than the body or gain heat from a hot environment

• evaporation - change of state from a liquid to a gas requires energy

• this will have a cooling effect

• core body temperature is maintained at a constant 37 degrees. The perihelion is often lower

• body temperature in excess of 43 degrees, hyperthermia is rapidly fatal as brain cells die

• hyperthermia is a core temperature of 35 - 32 degrees or lower

• death occurs at about 25 degrees

body temperature changes when wet or in water because water is a very poor conductor of heat

skin

• it has thermoreceptors in it

• largest organ

• major organ involved in thermoregulation

• largest organ in the body

heat gain or retention mechanisms

• vasocontraction of blood vessels supply capillaries in the skin.reduction of blood supply to the surface heat loss to the environment

• concentration of hair erector muscle raises hair on the skin and trapping an insulating layer of air close to the skin.AIR is a poor conductor of heat

shivering

• short,small contractions of skeletal muscle requires energy from respiration

• heat is produced as a by product

heat loss mechanisms

• sweating, exocrine sweat glands secrete sweat which is mainly water but contains sodium ions and small amount of urea

• sweat is deposited on the skin surface

• the evaporation of the water in sweat requires energy which is provided by the body’s heat in the cooling of the body

• vasodilation of vessels supplying capillaries in the skin increasing the blood supply to the surface of the skin.more heat is lost to the environment

• relaxation of hair erector muscles

• hairs lie flat reducing the insulating layer of air close to the skin

hormonal control of body temperature

• adrenaline releases produces a temporary increase in metabolic rate

• as more respiration takes place more heat is produced as by product

• increase in levels of thyroxine increases the metabolic rate long term

• an increase in metabolic rate will increase the rate of heat production

hyperthermia

• body temperature higher than normal as a result of failure of control mechanisms

• symptoms include

• dizziness,itchy skin,cramps,swelling of ankles

• causing fainting,confusion,irregular heat beat and result of death

hypothermia

• body temperature falls below norm

• the usual body warming mechanisms cannot warm the body enough

• severe hypothermia can cause unconsciousness weak and irregular heart beat,confusion

• death can result