PHYSIOLOGY - Thermoregulation Flashcards
What are poikilotherms?
Poikilotherms are ectothermic animals
What are homeotherms?
Homeotherms are endothermic animals
What is core body temperature?
Core body temperature is the temperature within the cranium, abdominal and thoracic cavities which have a very narrow temperature range
What is the shell body temperature?
Shell body temperature is the oral and skin temperature which have a very wide temperature range
Which six factors can influence the core body temperature?
Circadian rhythm of core temperature
Seasonal variations
Environmental variations
Exercise
Digestion
Gender
Why does the core body temperature fluctuate more in female animals?
Body temperature is influenced by steroids and thus fluctuates with the oestrous cycle in females
What are the three methods of heat transfer?
Radiation
Conduction
Evaporation
What is radiation of heat?
Radiation is the transfer of heat through electromagnetic waves
What is conduction of heat?
Conduction is the transfer of heat through direct contact between objects
How does convection affect the conduction of heat?
Convection enhances the conduction of heat as convection is the movement of fluid (like air or water) which will carry heat away from the surface and make the transfer of heat faster and more efficient
What is evaporation of heat?
Evaporation is the process by which liquid turns into a gas, taking heat with it
Which central nervous system structure regulates thermogenesis?
Preoptic area of the hypothalamus
Which two regions receive information from the preoptic area of the hypothalamus to regulate thermogenesis?
Heat promoting centre
Heat losing centre
Which three behavioural changes occur to increase body temperature?
Curled up posture
Huddling
Move to warm location
Which five physiological mechanisms increase body temperature?
Cutaneous vasoconstriction
Countercurrent exchange mechanisms
Piloerection
Shivering thermogenesis
Non-shivering thermogenesis
How does cutaneous vasoconstriction increase body temperature?
Cutaneous vasoconstriction redirects the blood flow to the core organs, increasing the core body temperature
Why is periodic vasodilation so important during cutaneous vasoconstriction?
Periodic vasodilation allows for blood flow to the periphery and skin to prevent cell death and necrosis in those areas
What are the two potential complications of cutaneous vasoconstriction?
Hypovolaemia
Frostbite
How does piloerection increase body temperature?
Piloerection is the contraction of the errector pilli muscles at the base of the hair follicles to trap air, increasing the insulating layer of air around the body to minimise heat loss
Which three behavioural changes occur to decrease body temperature?
Open posture
Dispersing
Move to cold location
Which two physiological mechanisms decrease body temperature?
Cutaneous vasodilation
Evaporative heat loss
How does cutaneous vasodilation decrease body temperature?
Cutaneous vasodilation increases the blood flow to the skin which increases the heat loss from the blood vessels into the environment, increasing heat loss and decreasing body temperature
What are the three mechanisms of evaporative heat loss?
Sweating
Panting
Spreading saliva on fur
What are the three adaptations seen in animals that live in chronically cold temperatures?
Increased thermal gradient
Increased metabolic rate
Decreased core temperature
Which two mechanisms are used to increase thermal gradient?
Burrowing
Development of winter fur
Which mechanism is used to decrease core temperature?
Hibernation
What are the three adaptations seen in animals that live in chronically hot temperatures?
Decreased thermal gradient
Decreased metabolic rate
Increased core temperature
Which mechanism is used to decrease thermal gradient?
Development of a summer coat
Which mechanism is used to increase core temperature?
Aestivation
What is aestivation?
Aestivation is a state of dormancy in which an animal enters during hot and dry period
List two thermoregulatory disorders
Pyrexia
Hypothermia
Describe the process resulting in pyrexia
Neutrophils and macrophages secrete endogenous pyrogen IL-1 which acts on the anterior hypothalamus to secrete prostaglandin E (PGE) which raises the set point for body temperature. The body will the shiver and undergo peripheral vasoconstriction to raise the body temperature
What happens to the body during stage one of hypothermia (core body temperature between 35-37°C)?
Shivering
Cutaneous vasoconstriction
Rapid and shallow breathing
Nausea
Muscles become less responsive
What happens to the body during stage two of hypothermia (core body temperature between 33-35°C)?
Violent shivering
Cutaneous vasoconstriction
Muscles are miscoordinated
Mild confusion
Extremities turn blue
What happens to the body during stage three of hypothermia (core body temperature between less than 32°C)?
Shivering stops
Obvious cognitive impairement
Obvious physical inability
Metabolic processes shut down
What happens to the body during stage four of hypothermia (core body temperature between less than 30°C)?
Decreased pulse
Increased heart rate
Decreased respiratory rate
Extremities blue and puffy
Incoherent/irrational behaviour
Major organ failure
Death
