Ocr A2 Biology - Homeostasis - Control Of Body Temperature

Front 1

Animals are classed as ......... or ......... .

Back 1

1. ectotherms

2. endotherms

Front 2

Give two examples of ectotherms.

Back 2

Reptiles and fish.

Front 3

Give two examples of endotherms.

Back 3

Mammals and birds.

Front 4

How do ectotherms control their body temperature compared to endotherms.

Back 4

• Ectotherms can't control their body temperature so they change their temperature by changing their behaviour (e.g. reptiles gain heat by basking in the sun).
• Endotherms control their body temperature internally by homoeostasis. They can also control their temperature by behaviour (e.g. finding shade).

Front 5

What are ectotherms and endotherms internal body temperature dependant on?

Back 5

• Ectotherms temperature depends on their external temperature (their surrounding).
• Endotherms temperature is less affected by their external temperature (within certain limits).

Front 6

Explain if temperature levels affect activity levels in ectotherms and endotherms.

Back 6

• In ectotherms, their activity levels depend on the external temperature - they are most active at higher temperatures and less active at lower temperatures.
• In endotherms, their activity levels are largely independent of the external temperature - they can be active at any temperature (within certain limits).

Front 7

State three mechanisms to reduce body temperature.

Back 7

• Sweating
• Hairs lie flat
• Vasodilation

Front 8

How does sweating lower body temperature?

Back 8

• Sweat cools the skin.
• When sweat evaporates, it uses up energy on the surface of the skin to do so.
• This cools the skin.

Front 9

How do hairs lying flat lower body temperature?

Back 9

• Mammals have a layer of hair that provides insulation by trapping air (air is a poor conductor of heat).
• When it's hot, erector pili muscles relax so the hairs lie flat.
• Less air is trapped, so it is less insulated and heat can be lost easily.

Front 10

How does vasodilation lower body temperature?

Back 10

• When it's hot, arterioles near the surface of the skin dilate (called vasodilation).
• More blood flows through the capillaries in the surface layers of the dermis.
• This means more heat is lost from the skin by radiation and the temperature is lowered.

Front 11

State five mechanisms to increase body temperature.

Back 11

• Shivering
• Much less sweat
• Hairs stand up
• Vasoconstriction
• Hormones

Front 12

How does shivering increase body temperature?

Back 12

• Muscles contract in spasms to shiver.
• This makes the body shiver and more heat is produced from increased respiration.

Front 13

How does less sweat increase body temperature?

Back 13

• Less sweat is secreted when its cold, reducing heat loss.

Front 14

How do hairs stand up increase body temperature?

Back 14

• Erector pili muscles contract when its cold, which makes hairs stand up.
• This traps air and creates an insulating layer to prevent heat loss.

Front 15

How does vasoconstriction increase body temperature?

Back 15

• When it's cold, arterioles near the surface of the skin constrict so theres less blood flowing near the surface of the skin.
• This reduces heat loss.

Front 16

How do hormones increase body temperature?

Back 16

• The body releases adrenaline and thyroxine.
• This increases metabolism and so more heat is produced.

Front 17

In endotherms, the body ......... in mammals is maintained at a ......... level by a part of the brain called the ..........

Back 17

1. temperature

2. constant

3. hypothalamus

Front 18

The hypothalamus receives information about ........ from the .......... .

Back 18

1. temperature

2. thermoreceptors

Front 19

Thermoreceptors in the ......... detect internal temperature.

Back 19

hypothalamus

Front 20

Thermoreceptors in the ......... detect external temperature.

Back 20

skin

Front 21

What are thermoreceptors in the skin called?

Back 21

Peripheral temperature receptors

Front 22

Give a basic overview of the path of the impulse from the thermoreceptors.

Back 22

• Thermoreceptors send impulses along sensory neurones to the hypothalamus.
• The hypothalamus sends impulses along motor neurones to effectors.

Front 23

Draw a homeostasis cycle for the control of body temperature.

Back 23