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When we exercise, the skin looks red due to increased blood flow in the skin capillaries.

Unit 3 - Changes in Capillary Blood Flow for Heat Loss (H)

GCSE Biology explains how your body controls temperature by changing blood flow in the skin. Tiny surface vessels widen or narrow to lose extra heat or conserve warmth.

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Fascinating Fact:

In cold conditions, the skin arterioles narrow, which is called vasoconstriction. This reduces blood flow through surface capillaries.

In GCSE Biology, you learn how blood flow in skin capillaries is adjusted to help control body temperature. Widening or narrowing surface vessels changes how quickly heat moves out of the body.

Key Terms

Capillary: A very small blood vessel with thin walls where exchange of substances and heat between the blood and tissues takes place.
Vasodilation: The widening of blood vessels supplying the skin so that more blood flows near the surface, allowing extra heat to be lost.
Thermoregulation: The process of keeping body temperature within a narrow, safe range by changing blood flow, sweating, and other responses.

Frequently Asked Questions (click to see answers)

How do skin capillaries help the body lose heat?

When you are too warm, blood vessels supplying the skin become wider and more blood flows through surface capillaries. This increases heat transfer from the blood to the air around the body.

What is the difference between vasodilation and vasoconstriction?

Vasodilation is when blood vessels widen so more blood reaches the skin and more heat is lost. Vasoconstriction is when vessels become narrower so less blood reaches the surface and heat loss is reduced.

Why is changing blood flow to the skin important in GCSE Biology?

Changing blood flow to the skin is important because it helps maintain a stable core temperature. Keeping body temperature close to 37 °C allows enzymes to work efficiently and protects vital organs.

Try These Related Quizzes

1 .

Name the special cells responsible for detecting temperature changes.

Chemoreceptors

Thermoreceptors

Neuroreceptors

Baroreceptors

Chemoreceptors detect chemical changes, for example carbon dioxide levels

2 .

What is the core temperature for humans, in degrees C?

37.4

Enzymes start to become denatured at temperatures above 37 degrees C

3 .

Name the part of the brain that controls body temperature in mammals.

Medulla

Cortex

Thermoregulatory centre

Cerebellum

Receptor cells detect whether the blood is abnormally hot or abnormally cold

4 .

Skin contains thermoreceptors which send messages to which of the following, to start body responses to maintain body temperature?

Heart

Skin

Thermoregulatory centre

Adrenal gland

This is an example of a feedback system in the body

5 .

When we are cold, muscles shiver to increase...

heat generation

heat loss

cooling

evaporation

Shivering means that the muscles are working harder and therefore respiration will be greater, generating more heat

6 .

When blood vessels tighten and have a smaller lumen, we call this...

vasoconstriction

vasodilation

vasomotion

vasodirection

This reduces the volume of blood that can pass through the blood vessels

7 .

Thermoregulation is an example of...

keeping warm

homeostasis

hormonal control

keeping fit

Homeostasis is maintaining a constant internal environment. Internal body temperature needs to be kept within narrow limits

8 .

When we exercise, the skin looks red due to...

more blood being pumped round the body

less blood to the muscles

increased blood flow in the skin capillaries

increased sweating

This helps to get rid of excess heat from the core of the body

9 .

Which of the following encourages heat loss by evaporation?

Sweating

Urinating

Excretion

Breathing

Evaporation of water in sweat cools the skin due to the change of state from a liquid to a gas

10 .

To allow for more heat loss, the vessels supplying the skin capillaries undergo...

vasoconstriction

vasodilation

no change

leakage of fluid

Skin looks red due to vasodilation. This increases blood flow to the surface of the skin, allowing greater heat loss

Author: Donna Davidson (GCSE Biology Teacher & Examiner, Quiz Writer)

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