Cardiovascular System

Cardiovascular System

Cardiovascular SystemComposition:•Blood•Blood vessels

ArteriesVeinsCapillaries

•Heart Function:•To transport substances around the body.

Blood Vessels

Capillary

Arteries• Carry blood away from heart to organs• Carry blood under high blood pressure• Thick muscular walls and round lumen• Blood high in O2 and low in CO2 and H2O

• Large elastic arteries close to heart help intermittent flow from ventricles become a continuous flow through the circulation

Veins• Carry blood to heart from the organs• Carry blood under low blood pressure• Thin muscular walls and Oval lumen• Blood low in O2 and high in CO2 and H2O• In limbs, contain valves at reg. intervals and are sandwiched between muscle

groups to help blood travel against gravity.

Valves in Veins

Capillaries

Capillaries• Connect arteries to veins• Arterioles and capillaries cause

drop in pressure due to overcoming the friction of blood passing through them.

• Thin walls formed from a single layer of epithelium cells

• Deliver protein-free plasma filtrate high in O2 to cells and collect CO2 and H2O

AortaCarotid Arteries

Superior Vena Cava

Inferior Vena Cava

Jugular Veins

Pulmonary Artery

Pulmonary Veins

Hepatic Vein

Hepatic Portal Vein

Hepatic Artery

Mesentric Arteries

Renal Arteries

Illiac Arteries

Renal Veins

Illiac Veins

Major Blood Vessels

Circulation of Blood• Each organ has an arterial and

venous blood supply.• Arterial supply brings blood to the

organ.• Venous supply drains blood

away.• Capillaries link the two supplies.

Circulation

The Heart

• Function is to pump the blood around the body i.e. Circulation.

• Structure– 4 Chambers– Valves– 4 major blood vessels– Coronary arteries and cardiac veins

External view of the heart

pulmonary artery

pulmonary vein

coronaryartery

left ventricle

right ventricle

inferior vena cava

right atrium

pulmonary vein

aorta

superiorvena cava

The vena cava carries deoxygenated blood from the body to the right atrium

superior vena cava(transports blood from the head)

inferior vena cava(transports blood from rest of body)

HRCS 3.2

The right atrium collects deoxygenated blood and pumps it to the right ventricle

right atrium

The right ventricle pumps deoxygenated blood to the lungs

right ventricle

The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs

Pulmonary artery

The septum separates the left and right sides of the heart

septum

The pulmonary veins carry oxygenated blood from the lungs to the left atrium

Pulmonary veins

The left atrium collects the oxygenated blood and pumps it to the left ventricle

Left atrium

The left ventricle pumps oxygenated blood to the body via the aorta

Left ventricle

HRCS 3.2

The aorta carries the oxygenated from the left ventricle to the rest of the body

Aorta

Aortic arch

HRCS 3.2

Atrio-ventricular valves prevent backflow of blood into the atria when ventricles contract

Bicuspid valve(mitral valve)

Tricuspid valves

Tendon

The semi-lunar valves prevent backflow of blood from the arteries into the ventricles

Aortic semi-lunar valve

Pulmonarysemi-lunar valve

The heart also needs its own blood vessels – coronary arteries and cardiac veins.

They supply the heart muscle with oxygen so that the muscle cells can respire. And remove waste carbon dioxide.

A blockage of these arteries leads to myocardial infarction (heart attack) because the heart muscle is deprived of oxygen and so dies.

Blood travels through the heart twice before returning to the body

The double circulatory system

Pulmonary Circulation Systemic Circulation

The cardiac cycle

• The events taking place in the heart during one heartbeat.

Control of the Cardiac CycleMyogenic•Cardiac muscle can contract on its own, without needing nerve impulses.

Sinoatrial Node (SAN)•Initiates contractions within the heart in the right atrium. •Acts as a clock, contracts spontaneously and rhythmically approx once a second, even when surgically removed from the heart.

HRCS 3.2

Cardiac Control Centre• Heart rate is regulated by the cardiac control centre found in

the medulla oblongata of the brain.

• The cardiac control centre is controlled by the autonomic nervous system.

– This system consists of sensory and motor nerves from either the sympathetic or parasympathetic nervous system.

– Sympathetic nerves increase heart rate

– Parasympathetic nerves decrease heart rate.

• The cardiac control centre initiates either sympathetic or parasympathetic nerves to stimulate the sino-atrial node to increase or decrease heart rate.

• There are three main factors which affect the activity of the cardiac control centre. They are neural, hormonal and intrinsic.

• Neural controlDuring exercise sensory receptors stimulate the cardiac control centre. These receptors include:-

– Proprio-receptors which sense that movement has increased.

– chemoreceptors which sense changes in chemicals in the muscles and blood. These changes include increased levels of carbon dioxide and lactic acid and increased acidity in the blood.

– baroreceptors which are sensitive to stretch within within the blood vessel walls. These detect increased blood pressure.

The cardiac control centre responds to this information by stimulating the sino-atrial node via the sympathetic cardiac accelerator nerve to increase heart rate.

Hormonal controlBefore and during exercise adrenalin is released in

the blood.This stimulates the sino-atrial node to increase heart

rate.

Intrinsic controlDuring exercise temperature increases which

increases the speed of nerve impulses which in turn increases heart rate.

Venous return increases heart rate which directly increases End-Diastolic Volume (EDV) and therefore stroke volume (Starlings Law).

Calculating The Length Of The Cardiac Cycle• How long do all the events taking place in the heart

during one heartbeat take?• Need to know the Heart rate (bpm) = 70 and the

number of seconds in a minute.• 1 beat (or a cardiac cycle) = 60 / 70 = 0.8 seconds.• The higher the heart rate, the shorter the cardiac

cycle.– This is only true until a limit is reached when the heart

would not have time to fill between successive cycles.

Systole – contractionDiastole - relaxation

Composition of blood

Red Blood Cells• Also known Erythrocytes• Most common cell in the blood• Structure:

– Have an elastic membrane• Important to allow transport through small capillaries

– No nucleus• Provides large surface area to be exposed to Oxygen

– Contain the chemical haemoglobin• Gives the red colour• Contains iron• Carries the oxygen forming oxyhaemoglobin

• Can’t divide – limited lifespan of around 120 days• Made in the bone marrow

White Blood Cells

• Also called Leukocytes• Compared to erythrocytes:

– Large– Have a nucleus– Less of them

• Several types:

White Blood Cells - Granulocytes

• Most numerous of white cells• Contain granules in cytoplasm• Have lobed nucleus• Can change shape to engulf foreign particles

and micro-organisms (Phagocytosis)• Part of the immune system – fighting infection• Made in the bone marrow

White Blood Cells - Lymphocytes

• Lymphocytes– Round nucleus– Clear cytoplasm– Produce antibodies that attach to antigens on

microbes and toxins, neutralising them or preventing microbes from multiplying.

– Part of the immune system – fighting infection.– Made in lymphoid tissues

White Blood Cells - Monocytes

• Monocytes– Larger than lymphocytes– Large round nucleus– Clear cytoplasm– Phagocytosis– Can move into tissues– Made in bone marrow

Platelets• Also known as Thrombocytes

– Not true cells – fragments of cells– Involved in blood clotting

Plasma• Straw-coloured• Mainly water• Carries dissolved substances

• E.g. nutrients and gases and plasma proteins.• Plasma proteins are involved in clotting, transport,

defence and osmotic (water) regulation.• Carries cells

Composition of blood

• Can you identify the different components of the blood?

Functions of blood

Functions of the blood

• Oxygen is carried in the red cells

• Carbon dioxide is carried in the plasma

The Lungs


• digested foods are carried in the plasma

The digestive system


• Transports waste

substances such as Urea in the plasma

A kidney


• Transports Hormones in the plasma.

Sites of Hormone production and action


• Transports Leukocytes to fight infection.

Erythrocytes and Leukocytes.


• Transports heat.

A Flame

Cardiac Output

• STROKE VOLUME (SV) - volume of blood ejected from the heart when the ventricles contract (at rest = 70 cm3)

• HEART RATE (HR) – the number of (ventricle) contractions in one minute (at rest = 70bpm)

• CARDIAC OUTPUT (Q) – volume of blood ejected from the heart in one minute (at rest = 5Litres)

• Q = HR X SV

Calculating Cardiac Output

Calculating Cardiac Output

Measuring Stroke Volume• Cardiac catheterization is where the cardiac

output can be directly measured with a catheter in the heart. Stroke volume can then be back calculated from this.

• Sometimes, the stroke volume can be estimated with an echocardiogram (ultrasound of the heart), but those measurements are often inaccurate.

Case Study – Cheryl and Louis

1. Cheryl trains every day by doing cross country. She has a stroke volume of 95cm3 and a resting heart rate of 62bpm. Calculate her cardiac output.

2. Louis enjoys playing computer games. His stroke volume is 72cm3 and his resting heart rate is 72bpm. Calculate his cardiac output.

3. Explain the figures in light of their different lifestyles.

4. Explain how exercise benefits the cardiovascular system.

Blood Pressure• The force blood exerts on the walls of the blood vessels it is

passing.• Measured using a sphygmomanometer (‘sphygmo’ –

pronounced sfigmo).• Systolic bp – corresponds to ventricles contracting.• Diastolic bp – corresponds to ventricles relaxed and filling.• Written as systolic/diastolic

– e.g. 120/80 mm Hg• BP is highest in blood vessels nearer the heart.

Blood PressureNormal Blood Pressure - Blood pressure reading below 120/80 is considered normal.

High Blood Pressure - Blood pressure of 140/90 or higher is considered high blood pressure (hypertension). If one or both numbers are usually high, you have high blood pressure.

Low Blood Pressure – Blood pressure of 90/60 is considered low blood pressure. Blood pressure that is too low is known as hypotension.

The similarity in pronunciation with hypotension and hypertension can cause confusion.

Blood PressureNormal Blood Pressure Range

Systolic pressure (mm Hg) Diastolic pressure (mm Hg) Pressure Range130 85 High Normal Blood Pressure120 80 Normal Blood Pressure110 75 Low Normal Blood PressureHigh

High Blood Pressure Range

Systolic pressure (mm Hg) Diastolic pressure (mm Hg) Stages of High Blood Pressure210 120 Stage 4180 110 Stage 3160 100 Stage 2140 90 Stage 1

Low Blood Pressure Range

Systolic pressure (mm Hg) Diastolic pressure (mm Hg) Pressure Range90 60 Borderline Low blood Pressure60 40 Too Low Blood Pressure50 33 Dangerously Low Blood Pressure

Case Study – Paul• Paul fainted in an overcrowded stadium on a hot day. He had

to stand for a very long time. As the event had lasted a few hours, he had suffered from a lack of circulating blood to his brain, which had caused him to faint. His muscles were inactive for a lengthy period, the vlood had pooled in his leg veins, and he had also lost a lot of body water through sweating.

1. Can you suggest a way of avoiding fainting in these circumstances?

2. Describe the effect on Paul’s legs.3. Why is fainting an effective way of managing a lack of

circulating blood to the brain?

Finish

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Cardiovascular System