TEMERATURE REGULATION IN AMPHIBIANS AND REPTILES

BIRDS

REPTILES HAVE DRY RATHER THAN MOIST SKIN WHICH REDUCES THE LOSS OF BODY HEAT THROUGH EVAPORATIVE COOLING OF THE SKIN.

THEY HAVE LOW METABOLIC RATE AND WARM THEMSELVES BY BEHAVIORAL ADAPTATIONS.

DURING HIBERNATION THE METABOLIC RATE SLOWS, AS DO HEART AND BREATHING RATES

EVERY TIME A MUSCLE CELL CONTRACTS, THE ACTIN AND MYOSIN FILAMENTS SLIDING OVER EACH OTHER AND THE HYDROLYSIS OF ATP MOLECULES GENERATE HEAT.

ESTIVATION

BROWN FAT

AMPHIBIANS

A STATE OF DORMANCY DURING SUMMER

BOTH BREATHING RATES AND METABOLISM DECREASES WHEN ENVIRONMENTAL TEMPERATURES ARE HIGH, FOOD IS SCARCE, OR WHEN DEHYDRATION IS A PROBLEM

A SPECIALIZED TYPE OF FAT FOUND N NEWBORN MAMMALS, IN MAMMALS THAT LIVE IN COLD CLIMATES, AND IN MAMMALS THAT HIBERNATE

THE COOLING MECHANISMS

BIRDS PANT TO LOSE HEAT THROUGH EVAPORATIVE COOLING.

SOME SPECIES HAVE A HIGHLY VASCULARIZED POUCH CALLED GULAR POUCH IN THEIR THROAT THAT THEY CAN FLUTTER TO INCREASE EVAPORATION FROM THE RESPIRATORY SYSTEM.

ANIMALS IN HOT CLIMATES HAVE MECHANISMS TO RID THE BODY OF EXCESS HEAT.

MOST AMPHIBIANS HAVE DIFFICULTY IN CONTROLLING BODY HEAT BECAUSE THEY PRODUCE LITTLE OF IT METABOLICALLY AND RAPIDLY LOSE MOST OF IT FROM THEIR BODY SURFACE.

REPTILES HAVE AN EXPANDABLE RIBCAGE WHICH ALLOWS FOR MORE POWERFUL AND EFFICIENT VENTILATION.

TEMERATURE REGULATION IN

AMPHIBIANS & REPTILES

AMPHIBIANS AND REPTILES ARE ECTOTHERMS.

THEY DERIVE HEAT FROM THEIR ENVIRONMENT AND THEIR BODY TEMPERATURES VARY WITH EXTERNAL TEMPERATURES.

SPECIALIZED CELLS IN THE HYPOTHALAMUS OF THE BRAIN CONTROL THERMOREGULATION FOR:

REPTILES

THE HYPOTHALAMIC THERMOREGULATORY AREAS

THE BROWN COLOR OF THIS FAT COMES FROM THE LARGE NUMBER OF MITOCHONDRIA WITH THEIR IRON-CONTAINING CYTOCHROMES

A LARGE AMOUNT OF HEAT IS PRODUCED WHEN BROWN FAT CELLS OXIDIZE FATTY ACIDS BECAUSE LITTLE ATP IS MADE.

BLOOD FLOWING PAST THE BROWN FAT IS HEATED AND CONTRIBUTES TO WRMING OF THE BODY.

HEATING CENTER

COOLING CENTER

CONTROLS VASOCONTRICTIONS OF BLOOD VESSELS, ERECTION OF HAIR AND FUR, AND SHIVERING OR NONSHIVERING THERMOGENESIS

CONTROLS VASODILATIONS, SWEATING, AND PANTING

TEMPERATURE REGULATION

IN BIRDS AND MAMMALS

SPECIALIZED NEURONAL RECEPTORS SENSE TEMPERATURE CHANGES

BIRDS AND MAMMALS ARE THE MOST ACTIVE AND BEHAVIORALLY COMPLEX VERTEBRATES

THEY ARE HOMEOTHERMIC ENDOTHERMS WHICH MEANS THEY CAN MAINTAIN BODY TEMPERATURE BETWEEN 35 TO 42 DEGREES CELSIUS WITH METABOLIC HEAT

MECHANISMS FOR PREVENTING HEAT LOSS

WARM NEURONAL

COLD NEURONAL

FEATHERS ARE EXCELLENT INSULATORS FOR THE BODY

AQUATIC SPECIES HAVE PERIPHERAL COUNTERCURRENT HEAT EXCHANGE VESSELS CALLED RETE MIRABILE IN THEIR LEGS TO REDUCE HEAT LOSS

MAMMALS THAT LIVE IN COLD REGIONS ALSO HAVE RETE MIRABILE BUT IN OTHER EXTREMITIES

HEAT PRODUCTION

IN BIRDS AND MAMMALS

BIRDS AND MAMMALS CAN GENERATE HEAT (THERMOGENESIS) BY MUSCLE CONTRACTION, ATPase PUMP ENZYMES, OXIDATION OF FATTY ACIDS IN BROWN FAT, AND OTHER METABOLIC PROCESSES.

TOPOR

NONSHIVERING

THERMOGENESIS

WHEN BOTH METABOLIC RATE AND BODY TEMPERATURE RE REDUCED TO PRODUCE A STATE OF DORMANCY

THE HORMONAL TRIGGERING OF HEAT PRODUCTION

SOME ANIMALS ENTER A STATE OF PROLONGED SLEEP IN WINTER BUT BECAUSE THEIR BODY TEMPERATURE REMAINS NEAR NORMAL, THIS IS NOT TRUE HIBERNATION

BLUBBER

NEGATIVE FEEDBACK MECHANISM

AN INSULATING FAT THAT HELPS MARINE ANIMALS TO MAINTAIN A BODY TEMPERATURE OF 36 TO 38 DEGREE CELSIUS

TRIGGERS EITHER THE HEATING OR COOLING OF THE BODY AND THEREBY CONTROL BODY TEMPERATURE

MAMMALS