15.3 Thermoregulation in endotherms Flashcards
Characteristics of endotherms
Mammals and birds are endotherms
They rely on metabolic processes to thermoregulate, despite the environmental temperature they tend to keep a stable core temperature
They have adaptations to maintain body temperature
Their metabolic rate is 5x that of ectotherms
How do endotherms detect a temperature change
Receptors detect changes in internal environment
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
Physiological adaptions of endotherms to thermoregulate
exothermic metabolic activity to keep warm, and energy-requiring physiological processes to cool down
Behavioural adaptions of humans to thermoregulate
clothes, housing, insulation
Three methods to cool down
VASODILATION
SWEATING
FLATTENING HAIRS/FEATHERS
Explain the process of shivering
As core body temperature falls, the body shivers – rapid, involuntary contracting and relaxing of large voluntary muscles in the body this produces metabolic heat
Explain the process of hairs/feathers raising
Erector pili muscles contract erecting the hairs, this traps an insulating layer of air to reducing skin cooling
Reduces heat loss to the environment helps warm up
Cold climate animals adaptions to thermoregulate
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
Explain vasoconstriction
Arterioles near skin surface constrict, arteriovenous shunt vessel dilates to minimise blood flow in capillaries close to the skin surface, minimising radiation helps us keep warm
How do fur/feathers aid cooling down in 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 large SA:V
Pale fur/feathers reflecting 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 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
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
