VT 100 Lec. 7 Thermoregulation (wk. 3)

Thermoregulation

• Body temperature is determined by balance between heat production and heat loss.

• Normal physiological function depends on relatively constant body temp

Energy

• The body is an energy transformer used for:

  •    Growth

  •    Movement

  •    Maintaining    homeostasis

  •    Reproduction

  •    “Useful products”

• Animals get energy through the chemical reaction of nutrients taken in as food plus radiant energy from the sun

• Chemical reactions, heat and work are products of energy use within the body

Body Temperature

• Body Temperature is the temperature recorded on a thermometer inserted into the rectum deep enough to record the core (or internal) temperature

• Temperature of skin surface may be higher or lower than core

• Temperature may change depending on the type of surface animal is placed upon

• Effects of both internal and external insulating layers important to consider during animal restraint

 

Homoiotherm

• Capable of regulating temperature internally

• Also called “warm-blooded”

• Primarily controlled unconsciously within the body

• Birds and mammals

Poikilotherm

• Rely on external sources for heat and coolness to regulate body temperature

• Also called “cold-blooded”

• Primarily controlled through behavior adaptions

• Reptiles, fish, amphibians

Heat Production

• Heat gained by increased production or by absorption of heat from the environment

• Heat production can be achieved through

  1.  Muscle tone  - shivering

  2.  Exercise

  3.  Fever

  4.  Brown Fat

Heat

• Heat captured from environment is through:

  1.  Radiation

  2.  Conduction

  3.  Convection

Heat through Radiation

• Electromagnetic waves transfer energy without heating the intervening air.  

• The Sun is the most important source of thermal radiation

• All warm objects (including animals) give off radiant energy

• No direct contact needed

Heat through Conduction

• Direct transfer of heat between an animal and an object.

• The direction is from higher to lower temperature

Heat through Convection

• Transmission of heat by movement of a medium surrounding or within an object:

  • Air

  • Water

  • Blood

Heat Conservation

• Heat is conserved through vascular responses:

1. Blood vessels near surface constrict to allow skin temperature to drop without jeopardizing core temperature

2.Velocity of blood flow increases which decreases exposure time to cold

Heat Reduction (cooling)

Takes place through:

   1.  Conduction

•        direct contact

   2.  Convection

•        transfer via a    medium

   3.  Radiation

   4.  Evaporation

   5.  Excretion

Adaptation

Behavioral changes allow animals to exist in different climates

Hypothermia

• Body temperature decreases when heat loss exceeds heat production or gain

• Below 93.2 degrees F in homoiotherms –impaired – below 86F completely eliminated (death)

• Newborns have undeveloped thermoregulatory ability

Causes of Hypothermia

• Exposure to wind

• Soiled or moistened hair coat

• Restraint on a cold surface

• Prolonged immobility

• Chemical restraint drugs & anesthesia

• Surgery

  • placement/position

  • shaving & wetting

  • cleaning solutions

  • Open incision

  • vasodilatory drugs

Treatment for Hypothermia

• Rapid warming of whole body is necessary

• Warm water bath

• Warm water enema

• Warm saline IV

• Circulating water pad

• Incubator

• Warm towels

• Circulating warm air

• Heat lamps

• Monitor until you are sure they are thermoregulating on their own

Hyperthermia

• Excessive elevation of core temperature

• Predisposing factors:

  • Increased ambient temperature

  • Humidity

  • Excessive muscle exertion or metabolic activity

• Other factors:

  • Physical structure

  •  Dehydration

  •  Use of vasodilator drugs

  •  Trauma

  •  Restraint

Hyperthermia: life limits

• The maximum body temperature compatible with life is ten degrees F above normal.

• Hyperthermia increases metabolic rate and cellular oxygen consumption

Hyperthermia Clinical Signs

• Increased heart rate

• Increased respiration

• Open mouth breathing

• Sweat & salivate profusely at beginning

• Pulse weakens

• Restlessness

• Slow responses

• Uncoordinated

• Convulsions

• Collapse

• Death

Treatment

• Cool water

  • Bath,  spray, towels

• Enema

• Alcohol bath

• Circulate air

• May cause delayed illnesses, kidney and liver problems  

• Supportive care and monitor for several days