15.3 - Thermoregulation in Endotherms Flashcards
How do endotherms detect temperature change?
- Receptors detect changes in internal env., as do peripheral receptors (in the skin), detect surface temperature changes
- Blood temperature in the body is monitored by the hypothalamus temperature receptor – it is a thermostat for the body, keeping the body temperature in a dynamic equilibrium of 37oC±1
- Combination of detecting temperature changes in and out the body helps respond to changes, and pre-empts problems if changes occur
What are general methods of thermoregulation for endotherms?
Endotherms use physiological adaptations to thermoregulate, exothermic metabolic activity to keep warm, and energy-requiring physiological processes to cool down
Humans have behavioural adaptations – clothes, housing, insulation
What are the 3 methods for cooling down?
VASODILATION
SWEATING
FLATTENING HAIRS/FEATHERS
Explain the process of vasodilation
- Arterioles near skin surface dilate if the temperature rises, the arteriovenous shunt vessel (vessel that provides connection between arterioles and venules) constricts.
- Forcing blood through the capillary network near the skin, the skin then flushes and cools due to increased radiation
Explain the process of sweating.
- Rate of sweating increases as core temperature increases
- Sweat evaporates from the surface of the skin (through sweat glands), losing heat as it does, cooling the blood below the surface
- Sweat glands in some animals are locate in less hairy areas, these animals will open their mouths and pant when they get hot to lose heat as water evaporates
Explain how hairs/feathers aid cooling down endotherms
- Body temperature rises, erector pili muscles (hair erector muscles) relax, the hair then lies flat on the skin to avoid trapping insulating air. (Bears little effect in humans)
- Endotherms living in hot climates have anatomical adaptations as well.
- They minimise effect of high temps and maximise cooling ability due to the SA od the body, (large SA:V ratio) maximising cooling
- Pale fur/feathers reflecting radiation
What are methods that endotherms use to warm up?
Vasoconstriction
Decreased sweating
Raising hairs
Shivering
Explain vasoconstriction and decreased sweating
Vasoconstriction
- Arterioles near skin surface constrict, arteriovenous shunt vessel dilates to minimise blood flow in capillaries close to the skin surface, minimising radiation
Decreased Sweating
- Rate of sweating lowers as core temperature falls, sweat production stops
- Reducing evaporation from the skin
Explain the process of shivering and raising hairs
Raising Body Hairs & Feathers
- Erector pili muscles contract erecting the hairs, this traps an insulating layer of air to reducing skin cooling
- Reduces heat loss to the environment
Shivering
As core body temperature falls, the body shivers – rapid, involuntary contracting and relaxing of large voluntary muscles in the body
What are the 2 centres that control negative feedback for homeostatic mechanisms in the hypothalamus and what do they do?
Heat Loss Centre
- Activated when blood flowing through the hypothalamus increases, sends impulses through autonomic motor neurones to effector muscles triggering responses to lower core temperature
Heat Gain Centre
- Activated when blood flow through the hypothalamus decreases
- Sends impulse to trigger responses to raise core temperature
What adaptations to thermoregulation do cold climate animals have?
- Metabolic heat from exothermic reactions warm up the body
- Endotherms in cold climates have additional anatomical adaptations, such us minimised SA:V areas (small ears)
- Layer of thick insulating fat
- Hibernation – building up fat stores, building well insulated shelters to stop heat loss
- Polar bears have small ears, fur on their feet to insulate from ice
- The hairs on polar bear skin, are hollow trapping permanent layers of insulating air, the skin underneath is black to absorb radiation, they have a thick fat layer
- Females dig snow dens to keep warm whilst giving birth to cubs
