Homeostasis Flashcards
Physiological homeostasis
Maintenance of the body’s internal environment within certain tolerable limits despite changes in the body’s external environment.
How is homeostasis brought about?
By the process of negative feedback.
Does negative feedback require energy?
Yes
Principle of negative feedback control -
A factor can increase or decrease from its norm, this will be sensed by receptors for that factor. Messages will be sent form the receptors to the effectors which bring about a corrective response to lower or raise the factor back to its norm or set point.
If no change in factor nothing will happen.
2 types of thermoregulation
Ectotherm and endotherm
Ectotherm
An animal which is unable to regulate its heat by physiological means - they obtain most of their body heat by absorbing it from their surroundings. (Conformer)
Examples of ectotherms
Fish, amphibians and reptiles
Endotherm
An animal which is able to maintain its body temperature at a relatively constant level irrespective of external temperature changes. Heat generated by their high metabolic rate. (Regulator)
Examples of endotherms
Birds and mammals
Importance of temperature regulation -
So that the temperature is kept at an optimum for enzyme controlled reactions and diffusion rates for maintenance of metabolism.
How is diffusion affected by temperature?
Diffusion such as oxygen and carbon dioxide are faster at warmer temperatures
Which has higher energy cost ectothermic or endotherm?
Endotherm
What does negative feedback and thermoregulation require?
Hypothalamus, nerves, effectors and skin.
The hypothalamus is …
The body’s temperature monitoring centre.
How does hypothalamus work?
Receives impulses form the heat and cold receptors of the skin, it also contains thermoreceptors which detect changes in blood temperature which reflect changes in the body core temperature.
Temperature control by the hypothalamus-
After detecting changes in blood temperature or from nerve impulses from the skin, the hypothalamus will send messages to the sweat glands, skin arterioles, hair erector muscles and skeletal muscles.
Role of skin in temperature regulation
In responses to nerve impulses form the hypothalamus, the skin will act as an effector
Vasodilation
When too hot, capillaries to the skin surface dilate allowing the blood to the surface to lose heat by radiation
Increased rate of sweating
Heat energy is used to convert the water in sweat to vapour bring about a lowering of body temperature
Relaxation of hair erector muscles
Prevents heat being trapped in a layer of air next to the skin and allows heat being lost.
How is overheating corrected in relation to metabolism.
Metabolism decreases so heat produced is decreased.
How is overheating corrected
Relaxation of hair muscles, vasodilation, decrease in metabolism and increased rate of sweating
Vasoconstriction -
When body temperature decreases, the arterioles constrict which allows only a small volume of blood flow to the surface capillaries, so less blood flow to the skin - decreasing the temperature lost by radiation.
Corrective responses to decrease in body temperature
Vasoconstriction, decreased rate of sweating, hair erector muscles contract, increased metabolic rate and shivering.
Decreased rate of sweating -
Reduces heat lost by evaporation of sweat.
Hair erector muscles contract -
Raised hairs will trap a layer of insulating air reducing heat loss
Increased metabolic rate -
Means more heat will be produced
Shivering -
Muscle contractions generate heat.
How does the thermoregulating centre (hypothalamus) communicate with the effectors
Via nerve impulses
