Download Cardiovascular System

Cardiovascular System
Exercise physiology
What is blood?
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Blood is a specialised type of connective
tissue.
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 litres of
blood and females about 4-5 litres.
Its color varies, depending upon the amount
of oxygen it is carrying, from dark red
(oxygen poor) to scarlet red (oxygen rich)
What is the function of blood?
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Transports nutrients, oxygen, carbon dioxide,
waste products and hormones to cells and
organs around the body.
Protects us from bleeding to death, via clotting.
Protects us from disease, by destroying invasive
micro-organisms and toxic substances.
Acts as a regulator of temperature, the water
content in cells, and body pH.
What is the composition of blood?
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Erythrocytes (Red Blood Cells)
Leukocytes (White Blood Cells)
Platelets (Thrombocytes)
Plasma: liquid portion of blood
What is the function of RBC?
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Erythrocytes (Red Blood Cells): contain an
oxygen-carrying pigment called hemoglobin,
which gives blood its red color.
They live for around 120 days, and are replaced
at the astonishing rate of 2 million per second.
What is the function of WBC?
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Leukocytes
exist in our bodies to combat infection and
inflammation. They do this by ingesting foreign
microbes in a process called phagocytosis.
What are the functions of platelets?
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Platelets (Thrombocytes)
are involved in the process of clotting
help repair slightly damaging blood
vessels.
Describe the anatomy of the heart
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The heart is an involuntary muscle with striated
muscle fibres.
The heart is surrounded by pericardium that
anchors and protects it.
Lub-dub: closing of AV Valves (lub)
closing of the semilunar valves (dub)
Describe the anatomy of the heart
Cardiac Cycle video 1:52
How does the heart receive blood?
The heart has it’s own blood supply via the coronary
arteries. It branches off the aorta. It also has its own set
of veins.
What are the two types of circulation?
• Systemic & pulmonary
How are the two
related?
Blood Vessels
• Arteries: transport oxygenated blood away
from heart.
Pulmonary artery: carry deoxygenated blood
• Veins: carry deoxygenated blood to the heart.
Pulmonary vein: carry oxygenated blood
• Capillaries: carry food & oxygen to tissues,
carry waste away.
What prevents backflow in the heart?
What prevents backflow in the heart?
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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).
What is the difference in wall size of
the atria and ventricles?
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The atria act as receiving chambers for
blood returning to the heart. They are
relatively small and thin walled, because
they only have to pump blood the
relatively small distance into the
ventricles.
The ventricles are quiet large, because
they are responsible for propelling blood
from the heart into circulation around
the body.
Cardiac Cycle – Electrical Impulse
The sinoatrial (SA) node is a small mass of specialized
muscle in the posterior wall of the right atrium. Because
automatic self-excitation of the SA node initiates each
heart beat, setting the basic pace for the heart rate, the
SA node is known as the pace maker.
The end of the fibres of the SA node fuse with
surrounding atrial muscle fibres so that the contraction
spreads, producing atrial contraction.
Several groups of atrial muscle fibres conduct the
contraction to the atrioventricular (AV) node, which
spreads action potential throughout the rest of the heart
via specialised muscle fibres called Purkinje fibres. These
form the atrioventricular (AV) bundle OR bundle of his.
Cardiac Cycle video (electrical impulse)(1:38)
Cardiac Cycle – Electrical Impulse
Cardiac Cycle
• The complete sequence of events from the
beginning of one heart beat to the beginning
of the next.
• an electrical impulse (depolarization event) is
conducted through the myocardium causing
the cardiac cycle.
• Systolic/diastolic (Contraction/ relaxation)
pressures in the ventricles
Cardiac Cycle
WHAT?!!
The heart is able beat spookily after being separated
from the body of it’s owner (as seen in horror films)
is not totally a product of overactive imaginations.
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 it’s own specialized
conduction system and can beat independently of
it’s nerve supply.
Still beating heart
Review
• Cardiovascular System: function, parts
• Blood: function, composition
– WBC, RBC, Platelets, Plasma
• Heart: function, anatomy, cardiac cycle,
electrical impulse(SA, AV nodes…)
– Atria & ventricle sizes/differences
• Pulmonary & Systemic circulations
• Blood Vessels: veins, arteries, capillaries
Heart Rate
• Pre, during, post exercise measurements
– Baseline, intensity, recovery observations
• 10s, 15s, 30s HR readings
• Average HR 60-80bpm, lower for athletic
population
• Bradycardia (˃60bpm), Tachycardia(˂60bpm)
• Radial, Carotid, Brachial readings
• Max HR 220-age, MHR-RHR=WHR
The Heart & Body during exercise
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Response of HR & BP
Cardiac output, stroke volume
Ventricular mass & volume
Cardiovascular drift
Activity type- exercise type
Blood distribution- blood vessel response
Vo2 max
cardiac output, stroke volume and
heart rate
• Cardiac Output = the amount of blood
pumped from the heart in one minute. This
measured in liters per 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 = when heart rate is reduced
to it’s minimum. E.g. when sleeping.
Blood Pressure
• The blood pressure is the pressure of the
blood within the arteries. It is produced
primarily by the contraction of the heart
muscle. It's measurement is recorded by two
numbers.
• Tools: stethoscope, sphygmomanometer
– Systolic & diastolic
How to take BP video
Blood Pressure
Systolic
• The top number, which is also the higher of the two numbers,
measures the pressure in the arteries when the heart beats
(when the heart muscle contracts).
Diastolic
• The bottom number, which is also the lower of the two
numbers, measures the pressure in the arteries between
heartbeats (when the heart muscle is resting between beats
and refilling with blood).
Blood Pressure
• What is the AHA recommendation for healthy
blood pressure?
Blood
Pressure
Category
Systolic
mm Hg
(upper #)
Normal
less than
120
and
less than 80
Prehyperten
sion
120 – 139
or
80 – 89
High Blood
Pressure
(Hypertensio
n) Stage 1
140 – 159
or
90 – 99
High Blood
Pressure
(Hypertensio
n) Stage 2
160 or
higher
or
100 or higher
or
Higher than 110
Hypertensiv
e Crisis
Higher than
(Emergency
180
care
needed)
Diastolic
mm Hg (lower #)
Blood Pressure
AHA Recommendation
For overall health benefits to the heart, lungs and circulation, perform
any moderate- to vigorous-intensity aerobic activity using the following
guidelines:
•Get the equivalent of at least 150 minutes of moderate intensity
aerobic physical activity (2 hours and 30 minutes) each week.
•You can incorporate your weekly physical activity with 30 minutes a
day on at least 5 days a week.
•Physical activity should be performed in episodes of at least 10
minutes, and preferably, it should be spread throughout the week.
•Include flexibility and stretching exercises.
•Include muscle strengthening activity at least 2 days each week
Blood Pressure
• What is cardiovascular drift?
– If you begin a 90 minute steady state ride on your
bicycle at a controlled intensity, your heart rate
may be 145 after 10 minutes. However, as you
ride and check your heart rate every 10 minutes,
you will notice a slight upward "drift". By 90
minutes, your heart rate may be 160. Why is this
happening if intensity is held constant?
Blood Pressure
• What is cardiovascular drift?
– There are two explanations.
– As you exercise, you sweat. A portion of this lost fluid
volume comes from the plasma volume. This decrease
in plasma volume will diminish venous return and
stroke volume. Heart rate again increases to
compensate and maintain constant cardiac output.
Maintaining high fluid consumption before and during
the ride will help to minimize this cardiovascular drift,
by replacing fluid volume.
Blood Pressure
• second reason for the drift during an exhaustive
exercise session. Your heart rate is controlled in
large part by the "Relative" intensity of work by
the muscles. So in a long hard ride, some of your
motor units fatigue due to glycogen depletion.
Your brain compensates by recruiting more motor
units to perform the same absolute workload.
There is a parallel increase in heart rate.
Consequently, a ride that began at heart rate 150,
can end up with you exhausted and at a heart
rate of 175, 2 hours later, even if speed never
changed!
Adaptation to Exercise
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Resting heart rate decreases as a result of
aerobic training. This is due largely to an
increase in stroke volume.
Adaptation to Exercise
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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.
Adaptations to Exercise
• One response to exercise of the cardiovascular
system is the increase in cardiac output from
around 5 liters at rest to between 20 and 30
liters 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.
Adaptations to Exercise
• 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
Adaptations to 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)
Distribution of Blood
• Because arteries are large, their walls offer
little resistance to blood flow, even when
meeting the demands of exercise.
• Arterioles have a much smaller diameter and
offer a great deal of resistance to blood flow.
• As blood flows through the capillaries, most of
the pressure caused by the action of the heart
is spent.
Distribution of Blood
• 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.
Distribution of Blood
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On the other hand 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.
What regulated Heart rate?
• SA node (pacemaker)
• Autonomic nervous system
– Sympathetic: flight or flight
epinephrine, norepinephrine underlies the fight-orflight response, directly increasing heart rate,
triggering the release of glucose from energy stores,
and increasing skeletal muscle readiness.
– Parasympathetic: feed & breed, rest & digest
work opposite each other.
What regulates Heart rate?
• Indirect factors
-Stress hormones (adrenaline), thyroid
hormones
-Deep breathing, stimulants, medications
-Emotions: anxiety increase HR,
-happiness, depression lower HR
-Dehydration, temperature, altitude.
VO2 Max
How well your body can transport and use oxygen
during exercise
The more CO2 you expel the closer
you are to fatigue, you no longer
use O2 for energy.
Proper Units: mL/kg/min
O2/body mass/time
• What is VO2 max? (5min)
VO2 Max
VO2 max- Hyperventilation
• A certain workload -- intensity along with duration of
exercise -- induces hyperventilation, according to
findings by "The British Journal of Sports Medicine."
This onset during exercise is caused by changes that
your body undergoes to prepare for the increase in
activity. In anticipation of exercise, your brain sends
signals to the respiratory center to increase breathing
to meet oxygen demands. In certain situations, such as
panic or accumulation of lactic acid from intense
exercise, breathing may become abnormally rapid and
hyperventilation occurs.
VO2 max- Hyperventilation
• Hyperventilation is a state of uncontrolled, rapid
breathing. The fast-paced breathing expels more
carbon dioxide from your body than usual, causing
your blood's carbon dioxide level to drop and its pH to
rise. As a result, the arteries constrict, causing feelings
of dizziness or light-headiness. Other symptoms of
hyperventilation include chest pain, numbness or
tingling in the arms, weakness and confusion.
Hyperventilation can be brought on as a result of the
changes that occur in your body during exercise.
VO2 max calculation- Fick equation
VO2 max = max cardiac output x max arterio-venous difference
VO2 max calculation- Fick equation
Can be simplified to the following equation:
VO2 max = max cardiac output x max arteriovenous difference
Where:
max cardiac output = stroke volume x heart rate
max a-vO2 difference = artery O2 conc. – veins O2 conc.
VO2 Max
•Bjorn Daehlie - Norwegian cross-country skiing - VO2 max score: 96.0
•Espen Harald Bjerke - Norwegian cross-country skier - VO2 max score: 96.0
•Greg LeMond - Professional cycling - VO2 max score: 92.5
•John Ngugi - World XC Champion distance running - VO2 max score: 85.0
•Steve Prefontaine - Running - VO2 max score: 84.4
•Lance Armstrong - Professional cycling - VO2 max score: 84.0
VO2 Max- training
What happens to our bodies as a result of VO2
increasing?
Increased stroke volume (increased cardiac
output)
Decreased resting heart rate
Increase capillary density
Increased mitochondria number
As a result of the above you become:
More efficient at extracting oxygen from blood
More efficient at getting oxygen to muscles for
energy production
Reduced rate of fatigue
Vo2 max- other factors
• Age
• Genetics
• Type of activity