Temperature regulation Flashcards
What happens if temperature is too low?
Slow metabolism
Inadequate oxygen supply
Freezing of cells
What happens if temperature is too high?
Proteins denature
Inadequate oxygen supply
Membrane structure alterations
How is heat exchanged and what percentage of loss does each process make up?
Radiation = 60% (without contact), conduction = 3% (with contact), convection = 15% and evaporation = 22%
How do exotherms regulate temperature?
Heat is derived from the environment. Are conformers, temperature fluctuates with the environment.
How do endotherms regulate temperature?
Heat is derived from metabolism and temperature is relatively constant. They are regulators
How may exotherms regulate temperature?
By changing their behaviour, e.g. sitting In the shade/sun
What are the benefits of being an ectotherm?
Metabolic rate is 5 times slower than endotherms, so they use less energy, meaning they need less food and water. A large proportion of the diet can be devoted to reproduction, and are good colonisers of arid environments
What are the costs of being an ectotherm?
No nocturnal environmental niches can be filled, unless in the tropics
Cannot sustain high activity bursts at of risk of O2 debt
Anaerobic respiration leads to lactate accumulation which causes rapid fatigue
Susceptible to predation by endoderms
What are the benefits of being an endotherm?
Can sustain high activity bursts
Nocturnal activity in all habitats
Able to exploit cooler environments
Forage widely and migrate over long distances
What are the costs of being an endotherm?
Require larger body mass sizes with low SA:V ratio
Metabolic rate is 5x faster than for ectotherms
More energy use requires more food and water intake
Cannot devote a large proportion energy budget to reproduction
Poor colonisers of poor/arid environments
What is the thermoneutral zone?
Temperature range where animal doesn’t need to expend energy to maintain temperature. Upper and lower limit is set by the hypothalamus
What is the hypothalamus?
Part of the forebrain that functions in maintaining homeostasis, especially in coordinating the endocrine and nervous system, secretes hormones into the posterior pituitary gland
What is the pituitary gland?
An endocrine gland at the base of the hypothalamus, releases hormones produced by hypothalamus
What happens in vasoconstriction?
Diameter of superficial blood vessels decrease, blood flow to skin consequently decreases and skin cools. Less heat is lost to the environment by radiation, conduction and convection, heat is trapped in body core
What happens in vasodilation?
Diameter of superficial blood vessels increase, blood flow to the skin increases. Skin heat increases and more heat is lost to the environment through radiation, conduction and convection
Describe shivering mechanism
Rapid contractions of skeletal muscles - consumes ATP, which generates heat. Heat production is increased by. 500%.
How does adrenaline act in the body?
Released form adrenal medulla and stimulates flight or fight, increases heart rate
How does thyroxine act in the body?
Released from the thyroid, and increases basal metabolic rate
How does insulation conserve heat?
Cells are rich in mitochondria, which breakdown fuel into heat. Has a rich blood supply specialised for rapid heat production. Found in newborn mammals, hibernating mammals and the necks of human adults. Cells have no intracellular organelles and little blood supply
What are counter current heat exchangers?
Hot artery flows by colder veins and exchanges heat, so cold blood doesn’t return to the heart. Flow of adjacent fluids in opposite directions that maximise transfer of heat (or solutes)
What is brown fat?
Adipose tissue. specialised for rapid heat production
What is blubber?
Thick layer of vascularised adipose tissue under the skin of marine mammals. Low thermal conductivity of skin, with low metabolic activity
How are fur/feathers used to insulate?
Reduces convection by trapping a layer of warm air close to the skin surface. Effect is lost if air is replaced by water
How does perspiration function in heat loss?
Glands in skin secrete sweat into the surface to increase heat loss by evaporation - Water has greater capacity for absorbing heat than air, absorbs heat when it evaporates
How does panting function in heat loss?
Evaporation of moisture from mouth and tongue, and exchanges hot air in the lungs with cooler external air
What is the Gular flutter?
Birds rapidly flap membrane in the throat to increase evaporation
What is urohidrosis?
Birds defecate on legs for evaporative cooling
What happens if metabolic heat production cannot account for heat loss?
Hypothermia
What happens if evaporative cooling cannot account for heat gain?
Hyperthermia
What is the roe of thermoreceptors in the hypothalamus?
Detects blood temp
What is the role of thermorecptors in the skin?
Detect external temp
