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The cardiovascular system

“My heart is a muscle. It pumps blood like a big

old black steam train” Tex Perkins

“I put my heart and my soul into my work, and have

lost my mind in the process” Vincent Van Gogh

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The cardiovascular system

• The cardiovascular system

• Components

• Anatomy of the heart

• The cardiac cycle

• The electrocardiogram

• The final question …

– How does the ECG trace for a single heartbeat corresponds to the cardiac cycle?

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Cardiovascular system

• Distributing oxygen

and nutrients to the

body

• Removing waste

products and carbon

dioxide

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Cardiovascular system

• Blood

• Blood vessels

• Heart

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Blood

• Transport of oxygen, nutrients, hormones and

enzymes around the body

• Transport of waste materials from tissues to

the organs of excretion

• Preventing loss of body fluids (clotting) after

accidents

• Regulating body temperature

• Fighting infections

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Composition of the blood

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Blood

• Plasma

– Transports minerals, nutrients, hormones,

enzymes, gases, antibodies, antitoxins, and waste

products

• Blood cells

– Erythrocytes - red blood cells

– Leucocytes - white blood cells

– Thrombocytes - platelets

Erythrocytes

• Transport of oxygen and carbon dioxide to and

from body tissues

• Contains haemoglobin (oxygen-carrying

substance)

• Average life span of 120 days

• Destroyed by the spleen

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Leukocytes

• Protection against infection

• Immune response

Thrombocytes

• Small, colourless, disk-shaped cytoplasmic

fragments

• Initiate contraction of damaged blood

vessels to minimise blood loss

• 10 day life span

• Accelerate blood

coagulation

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Bone marrow

• All blood cells are created in the bone marrow

for stem cells.

• Stem cells are multi-potential cells that can

evolve into several different cells.

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Blood vessels

Heart

ArteriesVeins

Arterioles

Capillaries

Tissues

O2CO2

Venules

• Transport the blood

– piping

• Gas exchange

– O2 in from lungs via heart

– CO2 out to lungs via heart

• 60,000 miles of blood

vessels (equatorial

circumference of the Earth is

24,901 miles)

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Arteries versus Veins

• Transport blood from

the heart

• Oxygenated blood*

• Lumen is small

• Thick muscular and

elastic walls

• High concentration of

nutrients

• Transport blood to the heart

• Deoxygenated blood*

• Lumen is large

• Thin walls, not muscular or elastic, but valves

• High concentration of waste products

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The heart

• Central organ of the cardiovascular system

• Pumps blood around the body

• Two separate pumps

– incoming to lungs from veins

– outgoing from lungs to arteries

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lunglung

rest of body

rest of body

more muscle

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Anatomy of the heart

• Size of a closed fist

• Lies in the cavity between the lungs

• Rests obliquely (right side below and almost in

front of the left)

• Surrounded by a sack - pericardium

• Composition

– 99% of is contractile cells (muscle)

– remainder are autorhythmic cells

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Cardiac Cycle

• Contraction of atria (atrial systole)

– Forces blood into ventricles

• Muscle action

• Additional force due to pressure differential from

empty ventricles

– Tricuspid and mitral valves open

– Pulmonic and aortic valve closed

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Cardiac Cycle

• Contraction of ventricles (ventricular systole)

– Forces blood into arteries

– Tricuspid and mitral valves closed

– Pulmonic and aortic valve open

• Atria refill with blood

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http://www.youtube.com/watch?v=rguztY8aqpk 20

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Timing of the Heart

The initiation of a heart beat is generated by the heart itself – autorhythmicity

primary pacemaker

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Timing of the Heart

• Autorhythmic cells in the heart

– Sinoatrial node - 70-80 action potentials/min

– Atrioventricular node - 40-60 AP/min

– Atrioventricular bundle - 20-40 AP/min

– Purkinje fibres - 20-40 AP/min

• The delay between atrial and ventricular initiation is

caused by transmission through the AV node.

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Timing of the Heart

• The heart beat can still be regulated by

external sources.

• Controlled by the autonomic nervous system

– Parasympathetic nerves

• acetylcholine decreases heart rate

– Sympathetic nerves

• noradrenaline increases heart rate

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Cardiac output

• Cardiac output is the amount of blood the

heart pumps out in one minute

• Cardiac output = heart rate x stroke volume

• Stroke volume is the amount of blood ejected

with each heartbeat

• Resting heart rate 70-73 bpm @ 18-25yrs

• HRmax = 205.8 − (0.685 × age)

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Add 4 bpm to these values for women

Age 18-25 26-35 36-45 46-55 56-65 65+

Athlete 49-55 49-54 50-56 50-57 51-56 50-55

Excellent 56-61 55-61 57-62 58-63 57-61 56-61

Good 62-65 62-65 63-66 64-67 62-67 62-65

Above Average 66-69 66-70 67-70 68-71 68-71 66-69

Average 74-81 75-81 76-82 77-83 76-81 74-79

Below Average 74-81 75-81 76-82 77-83 76-81 74-79

Poor 82+ 82+ 83+ 84+ 82+ 80+

Heart Rate

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• Heart rate is the primary measure of human activity

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Cardiovascular changes with aging

• Heart becomes smaller

• Contractile strength declines

• Cardiac output at rest diminishes 30% to 35% by age 70

• Veins dilate and stretch

• Coronary artery blood flow drops 35% between 20 and 60yrs

• Aorta becomes more rigid, causing systolic blood pressure to

rise

• Between 30 and 80yrs, the left ventricular wall grows 25%

thicker

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Blood pressure

• Systolic and diastolic blood pressure

– Systole and diastole refer to the entire heart

– Systolic blood pressure is the blood pressure during

ventricular contraction (short)

– Diastolic blood pressure is the blood pressure during

ventricular relaxation (long)

• Mean arterial blood pressure (MAP)

diastole3

2systole

3

1MAP +=

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Exercises

• Listening to the Heart

• Measuring blood pressure

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