GCSE Physical Education

The Circulatory System

At the end of this topic you should know the following…

The role and components of the circulatory system;

The structure of the heart; How the circulatory system works; Definitions of…

Heart rate, stroke volume, cardiac output; The roles and characteristics of the 3 types

of blood vessels; The functions of blood cells; How the circulatory system is affected by

exercise.

The Circulatory SystemComponents are…1 The heart2 Blood vessels3 BloodMajor functions include…1 Transport of 0² & CO² to & from

the muscles 2 Temperature regulation3 Preventing infection

The Heart

1. The heart is a special type of muscle called…?

2. Why is it special?3. What is its main

job?4. Why is the heart

often described as a ‘double pump’.

5. Approximately how big do you think the heart is?

Answers

1. Cardiac muscle2. Because it never tires3. Pump blood around the body4. There are 2 circuits, the

pulmonary and the systemic5. Size of a fist

The Structure of the Heart

Labelling of the Heart;

The Circulatory System Using diagram of heart on previous slide describe the flow of

blood through the circulatory system. Deoxygenated blood from the body enters the right atrium

via the vena cava. Following its journey through the body, the blood has now

collected a number of waste products including CO². From the atrium the blood is now forced into the right

ventricle through the tricuspid valve Blood is then forced up into the pulmonary artery which

leads to the lungs Here blood picks up O² and deposits CO² The newly oxygenated blood is then forced back to the

heart through the pulmonary vein into the left atrium. Blood is then forced into the left ventricle through the

bicuspid valve and then into the aorta to supply oxygenated blood to all parts of the body.

Blood vessels

Blood vessels are needed to transport blood around the body

Arteries: carries oxygenated blood away from the heart to the organs & muscles

Veins: carry de-oxygenated blood back to the heart. This blood carries excess CO²

Capillaries: the smallest blood vessels. Lie close to the muscle allowing O² & CO² to pass to & from the blood & the muscles.

Blood VesselsVessels Characteristics

Arteries Connective tissue and smooth muscle (elastic) Blood travels under high pressure Oxygenated blood away from the heart Linked to arterioles Have pulses & thick walls

Capillaries One cell thick Allow gaseous exchange Linked to arterioles and venules

Veins Smooth muscle (non-elastic) Blood travels under low pressure Deoxygenated blood to the heartThinner walls Linked to venules

Blood pressure

Blood PressurePressure under which the blood

travels as it is ejected from the left ventricle

Blood vessel constriction increases BP; dilation reduces BP

1. DIASTOLE: Heart is relaxed, BP is reduced2. SYSTOLE:Heart contracts, BP is increased

BP during aerobic exercise; Systolic BP increases in direct

proportion to increased exercise intensity

Diastolic BP changes little if any during endurance exercise, regardless of intensity

Muscles help squeeze the blood through the veins back to the heart.

Note how valves work together.

Blood – what is it?? Blood accounts for

__8__% of total body weight.

It is made up of cells & platelets, which are suspended in plasma.

There are 3 parts to the blood:

1. Red & White Blood cells2. Platelets3. Plasma

Blood cells, Platelets & Plasma;

Red blood cells (erythrocytes) are extremely small and give the blood its red colour. A typical adult has about 4.8 to 5.4 million red blood cells.

The main function of these cells is to transport O² & CO² around the body

Oxygen is transported via a chemical called Haemoglobin

White blood cells (leukocytes) have the function of protecting the body from bacteria, viruses, infections & foreign bodies

Platelets (thrombocytes) are small cell fragments which help blood clotting

Plasma is mainly made up of water, but also includes waste, hormones, glycogen and nutrients.

Heart Rate

Heart rate defines as ……..‘The number of times the heart beats per minute’

RHR averages 60 to 80 beats per minute (bpm); can range from 28 bpm to above 100 bpm.

HR tends to decrease with age and with increased cardiovascular fitness.

Therefore resting heart rate is often used to indicate a person’s fitness levels.

HR is also affected by environmental conditions such as altitude and temperature

Stroke volume

Stroke Volume defines as ....‘The amount of blood pumped out of the heart by each ventricle during 1 beat/contraction’

SV increases with increasing rates of work. It also influences aerobic endurance capacity when

working maximally.

Stroke Volume Increases During Exercise Frank Starling mechanism—more blood in the

ventricle causes it to stretch more and contract with more force.

Cardiac output

Cardiac Output is defined as ..…‘The amount of blood pumped out of the heart by each ventricle in one minute.’

Resting value of cardiac output (Q) is approximately 5.0 L/min.

Q increases directly with increasing exercise intensity to between 20 to 40 L/min.

Value of increase varies with body size and fitness level

How can you calculate the Cardiac Output?Q = HR x SV

When exercise intensity exceeds 40% to 60% of maximum, further increases in Q are more a result of increases in HR than SV.

CHANGES IN HR, SV, AND Q

The Heart in Action

Homer Flanders

Heart Rate[beats per minute]

100 65

Stroke Volume[mls per beat]

90 70

Cardiac Output[litres per minute]

Complete the table [remember there are 1000ml in a litre!]