Communication and Homeostasis Flashcards
1
Q
what is homeostasis
A
ability to maintain a stable and balanced internal environment despite external changes
2
Q
what is a negative feedback system
A
- work to reverse the initial stimulus
3
Q
what is a positive feedback system
A
- effectors are stimulated to reinforce the change and increase it
4
Q
what are the causes or temperature change
A
- exothermic chemical reactions
- latent heat of evaporation
- radiation
- convection
- conduction
5
Q
what are ectotherms
A
- use surroundings to warm their bodies
- invertebrate animals, fish, reptiles, amphibians
- cannot control temperature internally
- internal temperature dependent on external temperature
- activity levels depend on external temperature (more active at high temps)
- variable metabolic rate
- generate little heat
6
Q
what are endotherms
A
- control body temperature internally by homeostasis
- mammals, birds
- internal temperature less affected by external temperature
- activity level independent of external temperature
- high constant metabolic rate
- generate heat from metabolic reactions
7
Q
what are the mechanisms to reduce body temperature
A
- sweating
- hairs lie flat
- vasodilation
8
Q
how does sweating reduce body temperature
A
- more sweat secreted from sweat glands
- water in sweat evaporates and cools body
9
Q
how do hairs lying flat reduce body temperature
A
- layer of hair that provide insulation by trapping air
- erector pili muscles relax so hair lie flat
- less air is trapped so skin is less insulated and heat can be lost
10
Q
how does vasodilation reduce body temperature
A
- arterioles near the skin surface dilate
- more blood flows through capillaries in surface layer of the dermis
- more heat is lost by radiation
11
Q
what are the mechanisms to increase body temperature
A
- shivering
- less sweat
- hairs stand up
- vasoconstriction
12
Q
how does shivering increase body temperature
A
- muscles contract in spasms when cold
- body shivers and more heat is produced
13
Q
how does less sweat increase body temperature
A
- less sweat is secreted from sweat glands
- reduces heat loss
14
Q
how do hairs standing up increase body temperature
A
- erector pili muscles contract
- hairs stand up
- traps more air and prevents heat loss
15
Q
how does vasoconstriction increase body temperature
A
- arterioles near the skin surface constrict
- less blood flow through capillaries in the surface layer of the dermis
- reduces heat loss
16
Q
how does the hypothalamus control temperature
A
- thermoreceptors in the hypothalamus detect internal temperature
- thermoreceptors in the skin detect external temperature
- thermoreceptors send impulses along the sensory neurone to the hypothalamus sending impulses to motor neurones then effectors
