Cardiovascular System

1. 2.2 Cardiovascular System

2. Composition of Blood
• Erythrocytes (Red Blood Cells)
• Leukocytes (White Blood Cells)
• Platelets (Thrombocytes)
Plasma: liquid portion of blood and responsible for the transport of electrolytes,
proteins, gases, nutrients, waste products and hormones.
Blood performs a number of specialized functions:
▪ Transports nutrients, oxygen, carbon dioxide, waste products and hormones
to cells and organs around the body.
▪ Protects us from bleeding to death, via clotting, and from disease, by
destroying invasive micro-organisms and toxic substances.
▪ Acts as a regulator of temperature, the water content in cells, and body pH.

3. Composition of Blood
▪ It is heavier and more viscous than water and accounts for about 8%
of our total body weight.
▪ Healthy adult males have around 5-6 liters of blood and females
about 4-5 liters.
▪ Its color varies, depending upon the amount of oxygen it is carrying,
from dark red (oxygen poor) to scarlet red (oxygen rich)

4. Blood Circulation
• Blood is transported around the body through an extensive network of blood
vessels:
• Arteries: Large in diameter with thick muscular walls as there is high pressure exerted from the O2-rich
blood flowing through them away from the heart.
• Capillaries: Very thin walls. Extensive network of capillaries through tissues where exchange between
blood and tissues takes place.
• Veins: Receive O2-poor blood from the capillaries and deliver it back to the heart. Veins are thinner than
arteries because they carry mostly deoxygenated blood (low pressure). They contain valves to prevent
back-flow.

5. Circulation
• Blood is pumped around the body through a series
of blood vessels, from large muscular arteries to
narrower arterioles, to very narrow and thin
capillaries (where gas exchange occurs), to larger
flexible venules and then veins containing valves to
prevent back-flow. The heart has the primary
function of pumping blood around the body
(systemic circulation) and to the lungs (pulmonary
circulation).

6. Distinguish between the functions erythrocytes,
leucocytes and platelets
▪ Erythrocytes (Red Blood Cells): Carries oxygen and contains an oxygen-carrying
pigment called hemoglobin, which gives blood its red color.
○ Lungs to body
○ They live for around 120 days, and are replaced at the at the astonishing
rate of 2 million per second.
▪ Leukocytes (White Blood Cells): exist in our bodies to combat infection and
inflammation. They do this by ingesting foreign microbes in a process called
phagocytosis.
▪ Platelets (Thrombocytes): are involved in the process of clotting and help repair
slightly damaging blood vessels. Contains protein and antibodies produced by
immune system to fight diseases

7. Fun Facts!
• Your heart is about the same size as your fist.
• An average adult body contains about five liters of blood.
• All the blood vessels in the body joined end to end would stretch
62,000 miles or two and a half times around the earth.
• The heart circulates the body's blood supply about 1,000 times each
day.
• The heart pumps the equivalent of 5,000 to 6,000 liters of blood
each day.

8. Background information
• The heart is a two-sided pump made up of four chambers: the upper two chambers
called atria and the lower two called the ventricles.
• Each side contains an atria which receives blood into the heart and sends it into a
ventricle to be pumped from the heart.
• Atria and ventricle on each side (heart) are linked together by valves which prevent
backflow of blood.
• open/close by force in response to coordinated sequences of muscle
contractions.
• Valves allow blood to be pushed through with higher pressure
• On the right side of the heart, the right atrium and right ventricle work to pump
oxygen-poor blood returning from the body back to the lungs to be reoxygenated.
https://courses.lumenlearning.com/boundless-ap/chapter/the-heart/

9. Outline the relationship between the
pulmonary and systemic circulation
• Pulmonary circuit: circulation of blood
in which deoxygenated blood is
pumped from the heart to the lungs
and oxygenated blood is returned to
the heart.
• Only occurs between the heart and lungs
• Systemic circulation: circulation of
blood in which oxygenated blood is
pumped from the heart to the body and
deoxygenated blood is returned to the
heart.
• Only occurs between the heart and the
entire body

10. Chambers
• Normal hearts have two upper and lower chambers.
• Upper chambers (right and left atria) receive
incoming blood.
• Lower chambers (right and left ventricles) pump
blood out of the heart
• Heart valves, which keep blood flowing in the correct
direction, act as gates at the chamber openings.
Remember…blue (right side) is deoxygenated
blood. Red (left side) is oxygenated blood)

11. Four Valves...in order of circulation
• Tricuspid valve:
• Closes off upper right chamber (atrium) that holds blood coming in from body
• Opens to allow blood to flow from top right chamber to lower right chamber
(right atrium to right ventricle)
• Pulmonary valve:
• Closes off lower right chamber (right ventricle)
• Opens to allow blood to be pumped from heart to lungs (via pulmonary
artery) to receive oxygen
• Bicuspid (Mitral) valve:
• Closes off upper left chamber (left atrium) to collect oxygen-rich blood from
lungs
• Opens to allow blood to pass from upper left side to lower left side (left
atrium to left ventricle)
• Aortic valve:
• Closes off lower left chamber that holds the oxygen-rich blood before it’s
pumped out to the body
• Opens to allow blood to leave the heart (from left ventricle to the aorta and
on to the body).
Remember…blue (right side) is deoxygenated
blood. Red (left side) is oxygenated blood)

12. Four major blood vessels
• Vena cava: large vessels (superior and inferior) that bring
deoxygenated blood from systemic circulation to the heart
• Pulmonary vein: carries oxygenated blood from lungs to left atrium
of the heart
• Aorta: artery which carries blood from the heart into systemic
circulation
• Pulmonary artery: take deoxygenated blood away from the right side
of the heart and into the capillaries of the lungs for gas exchange

13. 1. Aorta
2. Superior Vena Cava
3. Right Pulmonary artery
4. Right Pulmonary Vein
5. Right Atrium
6. Tricuspid valve
7. Right Ventricle
8. Inferior vena cava
9. Left Pulmonary Artery
10. Pulmonary vein
11. Left Atrium
12. Bicuspid valve
13. Aortic Valve
14. Left Ventricle
15. Aorta (leads to
abdominal aorta)

15. • Know these…
• The four chambers
• Four valves (bicuspid, tricuspid, aortic and pulmonary valves)
• The four major blood vessels (superior and inferior vena cava,
pulmonary vein, the aorta and pulmonary artery)

18. Summary
• Dense connective structures called valves prevent backflow of blood into
chambers by opening and shutting when the heart contracts and relaxes.
• Two lie between each atria and ventricle (the atrioventricular valves: tricuspid
on the right and bicuspid on the left).
• Both arteries coming from the heart have a semilunar valve on them to prevent
blood from flowing back into the heart (the pulmonary semilunar valve and the
aortic semilunar valve).
• The heart has its own blood supply via the coronary arteries

19. Describe the intrinsic and extrinsic regulation of heart
rate and the sequence of excitation in the heart muscle
• The heart is a very unique muscle because unlike any other muscle in
our body it does not require nerve stimulation to contract.
• It contracts on its own via specialized cells known as pacemakers
• Sinoatrial node (SA): Found on the wall of the right atrium.
Coordinates heart contractions.
• Atrioventricular node (AV): Found in the middle of the two
ventricles and two atria. Sends impulses down atrioventricular
bundle to ventricles
• The heart can actually continue to beat for a number of hours if
supplied with appropriate nutrients and salts.
• This is because the heart has its own specialized conduction system and
can beat independently of its nerve supply.

20. SA and AV nodes
• Sinoatrial node generates nerve impulses that
travel throughout the heart wall. This causes both
the atria to contract
• Regulated by autonomic nerves of peripheral nervous
system
• Parasympathetic and sympathetic autonomic nerves send
signals to the SA node to accelerate (sympathetic) or slow
down (parasympathetic) HR.
• Atrioventricular node: SA node impulses meet AV
node there’s a delay of about 10 seconds. This
delays allows atria to contract (emptying blood into
ventricles before ventricular contraction.
• This regulation (electrical signals) by AV node ensures
impulses don’t move too fast…result in atrial fibrillation-
irregular and rapid atria beats
Is there an increase or decrease of oxygen
demand when the HR is increased during
exercise?

21. Parasympathetic innervation originates in the
cardiac centers in the medulla and passes to the
heart by way of the vagus nerves. Vagus nerve fibers
supply the SA and AV nodes. When stimulated,
these parasympathetic nerves release acetylcholine,
which slows the heart. This slowing of the heart is
called Bradycardia (under 60bpm)
• “Rest and digest”
Sympathetic nerves stimulate the release norepinephrine
or noradrenaline, which increases the heart rate as well as
the strength of ventricular contraction. This speeding up of
the heart rate is called Tachycardia (over 100 bpm)
• “Fight or flight”
Describe the intrinsic and extrinsic
regulation of heart rate and the sequence
of excitation in the heart muscle

22. Relationship between heart rate, cardiac output and
stroke volume at rest and during exercise
• Cardiac Output: total volume of blood pumped by the heart
per minute
• Product of blood pumped by each heart beat and number of
beats (heart rate)
• Measured in liters per minute
• Normal range is 4.0 – 8.0 l/min
• Cardiac output = stroke volume (SV) x heart rate (HR)/1000
• If Michelle’s stroke volume is 75 mL with each contraction and
her heart rate is 60 beats/minute, her cardiac output is 4,500
mL/minute (or 4.5 L/minute).
• Stroke Volume: the amount of blood pumped by each
ventricle in each contraction. The average volume is about
0.07 liters of blood per beat.
• Basal Heart Rate (resting heart rate): when heart rate is
reduced to its minimum (sleeping) Try this when
you wakeup!

23. Analyze cardiac output, stroke volume and heart rate
for different populations at rest and during exercise
• One response to exercise of the cardiovascular system is the
increase in cardiac output from around 5L at rest to between 20
and 30L during maximal exercise.
• The response is due to an increase in stroke volume in the rest to
exercise transition, and an increase in heart rate.
• Heart rate can reach 200bpm or more in some individuals. Maximal
cardiac output differs between people primarily due to differences
in body size and the extent to which they might be endurance
trained.

24. Analyze cardiac output, stroke volume and heart rate for
different populations at rest and during exercise
• An improvement in cardiac performance brought about by endurance training occurs as a
result of changes in:
• Stroke volume (increased)
• Heart rate (decreased for a set workload)
• Ventricular mass and volume (increased)
Homework! Complete a review of literature analyzing cardiac output, stroke volume and
heart rate data for different populations.
• Populations to consider:
• Males vs females
• Trained vs untrained
• Young vs old
• Location vs. location (city, state, region, country)

25. Be familiar with the differences
between populations. Complete in
workbook! Page 43.

26. Cardiovascular drift
• Cardiovascular drift is the upward drift of heart
rate over time, coupled with a progressive
decline in stroke volume and continued
maintenance of cardiac output.
• Occurs while exercise intensity remains constant
(endurance activates)
• Characterized by an increase in HR and decrease
in arterial pressure and stroke volume
• Connected to an increase in core temperature
and body water losses
• When there’s an increase in core body temp., the HR
increases. The body responds by increasing skin blood
flow to control temp. rise (homeostasis!)
• This creates “competition” between working muscles
(need large amounts of blood flow) and skin blood
flow

27. Cardiac drift and training
• Keep in mind two things when training or
competing for extended periods of time:
• How to optimize hydration (before, during,
after)
• If measuring heart rate during exercise, be
cognizant of cardiac drift since your HR may
rise up to 15% higher than you’re expecting.
• Has a knock-on effect if training session goal
is to be exercising in a specific HR zone

29. Systolic and diastolic blood pressure
• Blood pressure readings are given in two numbers: max amount your heart exerts while
beating and amount of pressure in your arteries between beats
• Systolic: the force exerted by blood on arterial walls during ventricular contraction.
• Top number
• Diastolic: the force exerted by blood on arterial walls during ventricular relaxation.
• Bottom number
• Research shows that systolic blood pressure (squeezing and pushing blood throughout the
body) is more important since it’s a good indicator of heart attacks or strokes.

31. Systolic and diastolic blood pressure
• Numeric difference between the two is the pulse pressure
• Example: resting blood pressure is 120/80 millimeters of mercury (mm Hg), pulse pressure is 40!
• Pulse pressure greater than 60 is good indicator or heart attacks and other cardiovascular
diseases; especially for men
• Low pulse pressure= poor heart function
• High pulse pressure= leaky heart valves…old-timers
• Systolic and diastolic pressure should be considered…
• Higher systolic and diastolic pairs imply higher risk than lower pairs…
• 160/120mm Hg indicates a higher risk than 110/70mmHg even though pulse pressure is 40 in
both
• Stiffness of the aorta is the most important cause of elevated pulse pressure.
• Stiffness due to high BP or fatty deposits damaging walls of arteries, leaving them less elastic
(atherosclerosis).
• Treating high BP often reduces pulse pressure!

32. Analyze systolic and diastolic blood pressure data at
rest and during exercise
Blood pressure response depends on…
1. The muscle mass being used in exercise
2. Whether the exercise is static or dynamic
3. Body position
4. Temperature
• In a healthy individual there should be a slight increase in
systolic blood pressure (SBP) rather than diastolic blood
pressure (DBP) which should remain near resting levels.
The higher the intensity of exercise, the greater the rise in HR
will be, thus an increase in systolic blood pressure!

33. How systolic and diastolic blood pressure respond to dynamic
and static exercise
• Dynamic Exercise (isotonic): Increases systolic pressure in the first few minutes and then levels off; diastolic
pressure remains relatively unchanged
• Push-ups, curl-ups, bicep curls, squats
• Static Exercise (isometric): Can increase blood pressure dramatically – Muscular force/contraction
compresses peripheral arteries increasing the resistance to blood flow
• Planks, wall-sits, side planks
• Upper-Body Exercise: Exercise at a given percentage of V·O2max increases blood pressure substantially more
in upper-body compared with lower-body exercise
• In Recovery: After a bout of sustained light- to moderate-intensity exercise, systolic blood pressure
decreases below pre-exercise levels for up to 12 hours in normal and hypertensive subjects

35. In a healthy person with a ‘normal’ systolic
pressure of 120 mmHg, vigorous aerobic fitness
training can increase systolic pressure to 180
mmHg and take 10-20 minutes to return to resting
levels.
As exercise commences and cardiac output
increases, blood flow is shifted from the
organs of the body to the working muscles. Up
to 87% of circulating blood can go to working
muscles during prolonged vigorous exercise!

36. • Muscular strength and hypertrophy
training with heavy loads are two types of
training that can however have dramatic
effects on raising blood pressure.
• This is due to skeletal muscles under
strain from heavy load increase, which
makes the heart work harder to force
plush into the tightly contracted
muscles…Takes 20-40 minutes to return
to resting levels!

38. Fun fact about standing too long…
• When one stands still for a long period of time, e.g. when a soldier stands at attention, blood
pools in the veins.
• Within a few moments, pressure increases in the capillaries (veins are not accepting blood from them
because they are dammed up with their own), and some plasma is lost to interstitial fluid.
• After a short time as much as 20% of the blood volume can be lost from circulation in this way.
• Arterial blood pressure falls and blood supply to the brain is diminished, sometimes resulting in fainting!
• Study found that people that primarily stand on the job are twice as likely to develop heart
disease than their counterparts.
• Increases risk of carotid atherosclerosis due to additional load on circulatory system
• Increase in varicose veins
• And sitting at work is not strongly linked decreased risk of long-term conditions (heart
disease, diabetes, etc.)

39. Compare the distribution of blood at rest and the
redistribution of blood during exercise
Let’s go workout…
1. The nervous system prepares body to secrete hormones to signal dilation of blood vessels in heart and
working muscles
• More training= systems act faster and more efficiently to redistribute blood
2. Blood redistribution takes a couple of minutes…
• Stopping or starting slows the effects
• Ever started quickly and felt out of breathe…?
• Ever stopped abruptly and felt dizzy…? Blood pools in working muscles from sudden reduction of muscle contractions
to return blood to the heart

40. Compare the distribution of blood at rest
and the redistribution of blood during
exercise
4. Number of capillaries in muscles increases with training
• Blood becomes thinner and flows better
• Flow of blood through capillaries is crucial for maximum exertion
5. # of RBCs slightly increases
• Adaptation to aerobic training allows for more water and dissolved proteins to be added to the plasma volume to thin blood
6. Results in an increase in total plasma volume and decrease in concentration of RBCs
 At rest the blood is distributed to the working internal organs
 During exercise the blood is distributed to the working muscles
 It takes little pressure to force the blood through veins because they offer little resistance to blood flow. Their diameters
are large and vein walls are so thin they can hold large volumes of blood.
 During exercise increased muscle contraction results in increased flow of blood through the veins and into the heart,
thereby increasing cardiac output.

41. During exercise the muscles that are being used become the main demand on blood flow.
Since more blood is directed towards these active muscles, arterioles dilate supplying muscles
Active muscles can demand up to 90% of total blood during exercise compared to only 20% at
rest.

42. Cardiovascular adaptations resulting from endurance
exercise training
• During prolonged sub-maximal exercise
(performed to calculate maximal
performance) at a fixed intensity,
cardiac output is maintained at same
level
• This is due to the demand remaining
constant with stroke volume and heart
rate at values higher than rest
• Capillarization increases
• Capillarization- density of capillaries increase
providing working muscles with more oxygen
rich blood while removing carbon dioxide
• Resting heart rate decreases as a result
of aerobic training. This is due largely to
an increase in stroke volume.
“What happens to the body
during a marathon”- 5:00 minute
video

44. Cardiovascular adaptations resulting from endurance
exercise training
• Stroke volume increases due to an increased
cardiac hypertrophy (muscle size)/left ventricular
volume from aerobic training.
• Therefore, for every heart beat, a trained athlete
can pump more blood from the heart to the
working muscles.
• The maximum arteriovenous oxygen difference of a
trained athlete usually exceeds that of an
untrained person. The training effect may be due
to adaptations in the mitochondria, increased
myoglobin content of muscles, or improved muscle
capillarization.
Effect of high intensity training on capillarizaiton and
presence of angiogenic factors in human skeletal muscle

45. Maximal oxygen consumption
• The most commonly used indication of an individual’s aerobic fitness is the
maximal oxygen uptake (VO2 max) which is the maximum rate an individual can
take in and use oxygen.
• VO2 is calculated by measuring the volume of air being exhaled at progressively
increasing intensities of exercise. As the oxygen demands increase, so does VO2.
• VO2 max represents the maximum aerobic capacity of an individual. At this
point, the person will stop exercising because they will no longer be able to
continue.
• Arterio-venous oxygen difference (a- v O diff) is the difference in
2
the oxygen content of the blood between the arterial blood and the venous
blood. It indicates of how much oxygen is removed from the blood
in capillaries as the blood circulates in the body. It is measured in (mL O2/100 mL
blood)
VO2 max = CO x (a-v) O2 diff Fick’s equation
Arterial blood= oxygenated
blood in lungs, pulmonary
vein, left chambers of heart
and arteries. Flows away
from heart.
Venous blood= has passed
through blood capillaries in
veins, right chambers of heart
and pulmonary artery. Flows
towards heart

46. • Training-induced changes in the heart and cardiovascular system can increase VO2max.
• The main training response is an increase in stroke volume at sub-maximal and maximal values
• More blood can fill left ventricle and muscle develop more capillaries (supply more O2 to
muscles)

47. • Endurance athletes have high
VO2max scores
• Gender: due to size, absolute
VO2max are lower in women
• Age: VO2max increases during
childhood and adolescence
and peaks in early 20s for men
and mid-teens for women.
• In adulthood, for both
genders, VO2max declines 1%
each yr.
• This reflects gradual decline in
max. HR that can be achieved.
• Exercise: highest values are in
cross-country skiers- place
more O2 demand on upper
and lower body and postural
muscles.
Maximal oxygen consumption Factors

49. • Research the variability between the following:
• trained versus untrained
• males versus females
• young versus old
• athlete versus non-athlete
• Mode of exercise
Maximal oxygen consumption variability
in populations and exercise