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What is the difference btwn a homeotherm and a poikilotherm?
- Homeotherm: stable internal temp regardless of external temp
- Poikilotherm: internal temp varies with external temp
How is heat produced in the body?
- Nonshivering thermogenesis (oxidize fats to produce heat)
How is heat transferred in body?
- Blood - capillaries = high SA
- Countercurrent - warm blood ran beside cold blood
How is heat exchanged with the environment?
- Convection - body warms surrounding air/water
- Conduction - body contacts cooler surface
- Radiation- IR rad absorbed by cooler objects
- Evaporation - sweat, saliva, secretions
What characterizes heat stroke?
- Peripheral vasodilation
- Increased evaporative cooling
What characterizes cold stress?
- Peripheral vasoconstriction
- Shivering & nonshivering thermogenesis
What characterizes fever?
Increased body temp due to increase in thermoregulatory set point
What is the shivering pathway?
- Central thermoreceptors (CNS)
- Peripheral thermoreceptors (Skin)
- Integration (Hypothalamus)
- Effectors (motor neurons)
What are 2 consequences of heat stress in cows?
- Acidosis-related troubles
- Reduced milk yield
What does temperature humidity index NOT account for?
- Milk yield
- Solar radiation
- Air movement
- Acculumation of heat load over time (several hot days)