control of body temperature PART 2

control of body temperature

thermoregulation

what system controls body temperature?

nervous system

what controls body temperature in mammals

hypothalamus→ detects change in blood temperature

thermoregulatory centre

located in the hypothalamus

where are thermoreceptors found? (2)

-skin

-hypothalamus

name of thermoreceptor in skin

peripheral thermoreceptors

roles of thermoreceptors in skin and hypothalmus?

skin

-thermoreceptors in the skin detect changes in external temperature (temp of skin)

hypothalamus

-thermoreceptors in the hypothalamus detect changes in blood temperature (internal temp)

describe how body temperature is controlled

-thermoreceptors detect a change in temperature [peripheral thermoreceptors detect external temp]

-they send impulses to the thermoregulatory centre in the hypothalamus

-hypothalamus processes the information and sends impulses to effectors

-effectors respond to restore body temperature to normal by negative feedback [mention if they increase heat loss or produce more heat]

physiological responses when body temperature is too high (3)

[-effect on body temp

-how do effector respond in terms of heat]

they reduce body temperature by:

-sweating

-hairs lie flat

-vasodilation

[effectors respond to increase heat loss from the body]→ mention when asked how is body temp controlled 

explain the effect of the mechanisms:

-sweating

-hairs lie flat

-vasodilation

sweating

-heat supplied by the body is used for evaporation

-sweat evaporates from the surface of the skin, removing heat from the body. This cools the skin down and reduces body temperature.

hairs lie flat

-erector muscles relax so hairs lie flat→ less air is trapped, reducing insulation and heat can be lost more easily→ this reduces body temperature (since air is a good insulator)

vasodilation

-vasodilation of arterioles (arterioles dilate) increases blood flow through capillaries near skin surface→ this means more heat is lost by radiation from the skin→ this reduces body temperature

[always mention reduces body temp]

[your face is red/pink due to increase of blood flow through capillaries near skin surface]

physiological responses when body temperature is too low 

[-effect on body temp

-how do effector respond in terms of heat]

they increase body temperature by:

-shivering

-vasoconstriction

-hairs stand up

-hormones (releasing adrenaline and thyroxin)

-less sweat

[effectors respond to produce more heat]→ mention when asked how is body temp controlled 

explain the effect of the mechanisms:

-shivering

-vasoconstriction

-hairs stand up

-hormones (releasing adrenaline and thyroxin)

-less sweat

[state whether the mechanism conserves heat or produce heat]

shivering [produce heat]

-muscles contract to generate heat through increased respiration  [remember respiration produces heat]

vasoconstriction [conserves heat]

-vasoconstriction of arterioles reduces blood flow through the capillaries near skin surface→ reduces heat loss by radiation 

hairs stand up [conserve heat]

-erector muscles contract so hairs the hairs stand up→ this traps more air to reduce heat loss

releasing adrenaline and thyroxin [produce heat]

-these hormones increase metabolic rate so more heat is produced

less sweat [conserve heat]

-less heat is lost through evaporation

endotherms mostly use physiological responses but uses some behavioural responses

examples:

-when too hot

-when too cold

when too hot:

-move to a cooler, shaded area

-reduce activity

-spread out limbs to increase surface area→ increases heat loss

-use water to cool down

when too cold:

-move to a warmer area

-increase activity

-curl up to reduce surface area→ decreases heat loss

-human wear clothes

some animals (e.g. dogs) have few sweat gland so ..

they increase panting to increase evaporation of water from the mouth→ removes heat from body→ reduces body temperature

[hot environment adaptation]

some animals have large, thin ears (e.g. elephants). how does this adaptation help them control their body temperature?

-have a large surface area→ increases heat loss

-thin→ blood flows close to the skin surface to lose heat

[hot environment adaptation]

some animals have light coloured fur. how does this adaptation help them control their body temperature?

-reflects sunlight→reduces absorption from the sun→ absorb less heat

[hot environment adaptation]

being nocturnal. how does this adaptation help them control their body temperature?

Active at night when temperatures are cooler → reduces heat gain from environment

[hot environment adaptation]

hibernation. how does this adaptation help them control their body temperature?

-reduces metabolic rate → conserves energy when temperatures are low

[cold environment adaptation] 

some animals have small ears. how does this adaptation help them control their body temperature?

-have a small surface area→ reduces heat loss

[cold environment adaptation]

some animals have thick fur. how does this adaptation help them control their body temperature?

-traps air→ increases insulation→ reduces heat loss

[cold environment adaptation]

is a person likely to feel hungry more quickly in a hot or cold environment?

-cold environment

→body must generate more heat to maintain body temperature.

→This requires more energy, so the metabolic rate increases.

→energy stores (e.g. glucose) are used faster, making you feel hungry sooner.