Cardiovascular System

Exercise physiology

What is blood?

Blood is a specialized 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?

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? Erythrocytes (Red Blood Cells) Leukocytes (White Blood Cells) Platelets (Thrombocytes) Plasma: liquid portion of blood

What is the function of RBC? Erythrocytes (Red Blood Cells): contain an

oxygen-carrying pigment called haemoglobin, which gives blood its red color.

They live for around 120 days, and are replaced at the at the astonishing rate of 2 million per second.

What is the function of WBC? 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?

Platelets (Thrombocytes) are involved in the process of

clotting help repair slightly damaging blood

vessels.

Describe the anatomy of the heart 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 its 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?

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 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 large, because they are responsible for propelling blood from the heart into circulation around the body.

What is the difference in wall size of the atria and ventricles?

Cardiac Cycle – Electrical Impulse

Cardiac Cycle video (electrical impulse)(1:38)

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 – 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(˂100bpm)• Radial, Carotid, Brachial readings• Max HR 220-age, MHR-RHR=WHR

The Heart & Body during exercise

• 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 & diastolicHow 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

PressureCategory

Systolicmm Hg

(upper #) Diastolic

mm Hg (lower #)

Normal

less than 120 and less than 80

Prehypertension 120 – 139 or 80 – 89

High Blood Pressure

(Hypertension) Stage 1

140 – 159 or 90 – 99

High Blood Pressure

(Hypertension) Stage 2

160 or higher or 100 or higher

Hypertensive Crisis

(Emergency care

needed)

Higher than 180 or Higher than 110

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 Resting heart rate decreases as a

result of aerobic training. This is due largely to an increase in stroke volume.

Adaptation to Exercise 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.

• 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

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, there 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. There 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

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 regulates heart rate?• SA node (pacemaker) (intrinsic control)

• Autonomic nervous system (extrinsic control)– Sympathetic: fight or flightepinephrine, norepinephrine underlies the fight-or-flight response, directly increasing heart rate, triggering the release of glucose from energy stores, and increasing skeletal muscle readiness.

– Parasympathetic: feed & breed, rest & digest

• Indirect factors -Stress hormones (adrenaline), thyroid hormones-Deep breathing, stimulants, medications-Emotions: anxiety increase HR, -happiness, depression lower HR-Dehydration, temperature, altitude.

What regulates heart rate?

VO2 Max

• What is VO2 max? (5min)

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

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.

• 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- Hyperventilation

VO2 max calculation- Fick equation

VO2 max = max cardiac output x max arterio-venous difference

VO2 max calculation- Fick 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.

Can be simplified to the following equation:

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

What happens to our bodies as a result of VO2 increasing?

VO2 Max- training

Increased stroke volume (increased cardiac output)Decreased resting heart rateIncrease capillary densityIncreased mitochondria number

As a result of the above you become:More efficient at extracting oxygen from blood More efficient at get oxygen to muscles for energy productionReduced rate of fatigue

Vo2 max- other factors

• Age• Genetics• Type of activity