16. HOMEOSTASIS Flashcards
Define homeostasis
Homeostasis is the maintenance of a constant internal environment
Recall the four levels in the body that are controlled by homeostasis
Temperature, pH, water potential and blood glucose concentration
Explain why temperature is controlled by homeostasis
To maintain the optimum temperature for enzymes
Explain why pH is controlled by homeostasis
To maintain the optimum pH for enzymes
Explain why water potential is controlled by homeostasis
To prevent the negative effects of osmostic imbalance on cells
Explain why blood glucose concentration is controlled by homeostasis
To prevent the negative effects of osmostic imbalance on cells
What are ectotherms?
Organisms that use the surroundings to warm their bodies
What are endotherms?
Organisms that rely on metabolic processes to warm up and maintain a relatively constant core body temperature, regardless of the temperature of the environment
If an ectotherm’s core body temperature falls below optimum, list the ways they might increase it
Bask in the sun, orientate their bodies towards the sun so the maximum surface area is exposed to the sun, extend their bodies to increase the surface area exposed to the sun, press their bodies against warm ground (conduction)
If an ectotherm’s core body temperature rises above optimum, list the ways they might decrease it
Seek shade, dig burrows, press their bodies against cool earth (conduction), move into water (conduction), minimise movement, orientate their bodies so the minimum surface area is exposed to the sun
Describe the two places body temperature is detected in endotherms
By peripheral temperature sensors in the skin, and by temperature sensors in the hypothalamus, which detect the temperature of the blood
If an endotherm’s core body temperature falls below optimum, list the ways they might increase it
Vasoconstriction, decrease the rate of sweating, shivering, hairs on the skin stand erect
How does vasoconstriction increase core body temperature?
By reducing heat lost through radiation from the blood
How does reducing sweating increase core body temperature?
By reducing heat lost through evaporation
How does shivering increase core body temperature?
By releasing more heat through increased muscle contraction and respiration
How do erect skin hairs increase core body temperature?
By increasing the amount of air trapped on the skin
If an endotherm’s core body temperature increases above optimum, list the ways they might decrease it
Vasodilation, rate of sweating increases, hair on the skin lie flat
How does vasodilation decrease core body temperature?
By increasing the heat lost through radiation from the blood to the environment
How does increasing sweating decrease core body temperature?
By increasing heat loss from the body as sweat evaporates from the skin
How do flat skin hairs decrease core body temperature?
By reducing the amount of air trapped on the skin
In terms of heat exchange, explain the effect of small organisms having a large surface area to volume ratio
A higher rate of heat loss, but also a higher rate of heat absorption
In terms of heat exchange, explain the effect of large organisms having a small surface area to volume ratio
A lower rate of heat loss, but also a lower rate of heat absorption
Define negative feedback
A system in which a change to the normal levels triggers a response which reduces the effect of the change
Give two examples of homeostatic levels that are controlled by negative feedback
The maintenance of blood glucose concentration around an optimum, and the maintenance of temperature around an optimum