Homeostasis Flashcards
What is the definition of homeostasis?
maintenance of constant internal environment, coordinated responses of organs/systems that automatically compensate for environmental changes
What nervous system does homeostasis involve?
Autonomic nervous system (reflexes)
What type of body regulator are mammals and birds?
homeotherms, low and high temperatures not tolerated
What is the function of the core body temperature?
protects vital organs
What is the core body temperature influenced by?
environment, exercise and metabolism
What is the thermoneutral zone?
Ambient temperature at which no adjustment is needed, no additional energy is required to maintain body temeprature
TNZ
Thermoneutral zone
What are upper and lower critical temperatures?
Lower (cold) and upper (hot) critical temperatures are the temperatures at which once past TNZ, animals will need to use energy to maintain homeothermic condition
What is hyperthermia? What are implications of it?
Heat stress, cells cannot functions as the enzymes and proteins become denatured, can result in death
What is hypothermia? What are the implications of it?
cold stress, cells can survive freezing but blood circulation and respiration will fail, can result in death
Where does energy come from in mammals and birds?
heat comes mainly from body production = endothermic
What are the three sources of heat production in mammals and birds?
metabolism, growth/production and exercise (80%)
What are the four physical processes that are used when heat is being transported by the blood?
- radiation
- conduction
- convection
- evaporation/condensation
What are two ways that extra-heat is produced by the body?
- Muscle activity - shivering
- non-shivering thermogenesis - increase in metabolism
What is a special characteristic of shivering?
100% of the energy produced through shivering goes into heat production
How does the body prepare to increase metabolism to produce heat?
- sympathetic NS secretes catecholamines (adrenalin) which increases metabolism
- And thyroid hormones are released which increase metabolism
How is extra heat lost?
Metabolic heat removed fromt he core by the blood through the skin
What is the relationship between the skin and blood flow?
Insulation property of the skin inversely proportional to the blood flow
What aspect of the integument impact low heat loss vs high heat loss through blood vessel heat transfer?
Amount of hair/plumage
What 3 methods of heat transfer are gradient laws? (from high to low)
Radiation, conduction and convection
What is radiation?
electromagnetic radiation is emitted and absorbed relative to the surface and temperature of the object/animal
What is conduction?
transfer through contact; depends on the conductivity
What is convection?
transfer via moving air or water
Which heat transfer method requires energy?
evaporation requires energy to break water molecules apart, however this is very efficient
How does evaporation occur in animals for body heat loss?
Through skin and airways
- passive evaporation: normal water loss
- sweating: active process under sympathetic nervous system (loss in ions)
- panting: rapid shallow breathing
- bathing: water absorb energy before evaporating
Can all the heat transfer processes occur simultaneously?
Yes
What is the integration center of thermoregulation in the nervous system?
Hypothalamus
What are the four components of an automatic reflex whereby thermoregulation occurs?
- Thermoreceptors - nerve cells
- Integration center - hypothalamus
- effectors
- neurons connected to muscles for shivering
- sympathetic nervous system for blood flow, sweat gland and metabolism
- hormones - pituitary
- voluntary component - behaviour change
What are the three steps to heat response?
- Heat receptors: in skin/body core
- Hypothalamus: anterior part is activation of heat-loss center
- effectors
- vasoconstriction fibers slow down resulting in vasodilation
- evaporative heat loss (sweating/panting)
- reduction of physical activity
- behavioural response
How is information transferred in heat receptors?
warm sensory fibers
Draw the response to heat diagram
refer to slide
What does sensitivity to heat in animals depend on?
animal and the external conditions
What animal has a hard time regulation body temperature?
Pigs: little sweat, small mouth
What do birds have that allows them to ventilate?
air sacs
What are the three steps to cold response?
- cold receptors: in skin/body core, much more numerous than warm fibers
- hypothalamus: posterior is the activation of heat-producing center
- effectors
- reduction in heat loss: vasoconstriction fibers fire, reduces heat loss through vesicular transfer, pili muscles contract
- production of heat: muscular contraction (shivering) by somatic motor system, sympathetic hormonal activity increases which increases metabolism
Which type of fat do hormones increase in during heat production?
brown fat
Draw the increase in heat production diagram
refer to slides
What are two adaptation mechanisms to heat?
- prolonged exposure to heat - lots of sweat, increase in aldosterone stimualtes reabsorption of Na+ and Cl- from sweat glands
- shedding
What are two adaptation mechanisms to cold?
- changes of fur coat, increase in insulation properties or subcutaneous fat
- hibernation: voluntary decrease in core body temperature, followed by rapid raise
How does a fever occur?
by resetting hypothalamic thermostat to higher temperature
What is a fever caused by?
pyrogens released during infection and tissue damage
How does hyperthermia occur?
temperature exceeds the regulating capability, heat production exceeds heat loss, through exposure to high temperatures
What are the symptoms of hyperthermia?
convulsions, nausea, loss of consciousness, death
How does hypothermia occur?
Heat loss exceeds heat production capability
What are the symptoms of hypothermia?
Slow nervous activity, muscular failure (cardiac pulmonary), death
When is hypothermia critical in the life stage?
newborns
