Cardio-Vascular System

Cardio-Vascular SystemPHED1Cardio-Vascular SystemIs what determines our ability to participate in aerobic/endurance eventsFunction: provide muscles with oxygen to sustain energyComponents of c.v. system;- Heart (cardio) pump- Blood vessels (vascular) transportation network -Blood transportation vehicle (carries oxygen)

AortaDe-oxygentatedVeinSeptumBicuspid x 2OxygenatedRightPressurePulmonaryTricuspid x 2Semi-lunar

http://www.youtube.com/watch?v=P_d0ykpzQgY&feature=related

The Cardiac CycleCardiac Cycle - The events of one heart beatOne cycle 0.8 second (72 cycles a minute)2 main processes contraction and relaxation of the heart muscle; Diastole lasts 0.5 seconds, represents the relaxation phase, chambers fill with bloodSystole lasts 0.3 seconds, represents the contraction phase, blood pushed out of chambers/heart

The Hearts Conduction SystemThe heart is myogenicThis means it generates its own electrical impulseThe impulse that it generates is spread throughout the heart and causes it to contract This is known as the cardiac impulse

The Spread of the Electrical ImpulseThe impulse starts in the SA Node (located at the top of the right atrium)Called the pacemakerThe impulse travels through the atria wallsThis causes both atria to contractThe cardiac impulse then reaches the AV nodeAlso located in the right atriumThe AV node helps delay the impulse to allow the atria to finish their contractionIt then spreads the impulse down the bundle of HisThis is located in the Septum of the heart

The bundle of His splits into left and right branchesThe impulse spreads around the ventricle walls through a network of purkinje fibresThis causes both ventricles to contractThe ventricles then relax The cycle is repeated with the next cardiac impulse

Cardiac Impulsehttp://video.about.com/heartdisease/Conduction-System.htm

Q. Describe how the sinoatrial node (SAN) and the atrioventricular node (AVN) control the increase in heart rate during exercise

SAN initiates heart beat/sends impulses;intrinsic/myogenic/pacemaker;spread of impulses through atria;atria contracts/systole;impulse reaches AV Node;Reduced delay of spread of impulses;Bundle of His;Purkinje fibres conducting impulses;ventricular systole/contraction;period of diastole/relaxation for filling;Cardiac DynamicsMake sure you have included these points:Cardiac output = heart rate x stroke volumeEjection fraction = the percentage of blood forced out of the heart per beatCardiac hypertrophy as the muscle walls have increased in size the contraction of the heart will be stronger, therefore pushing more blood out of the heart per beatBradycardia the term means slow heart (resting heart rate below 60 bpm)Stroke volume measured in ml per beat (average at rest 70 ml per beat)Heart Rate beats per minute (average at rest 72 bpm)Cardiac output in ml per minute or litres per minute (average at rest 5 litres per minute which would be 5000ml per minute)Changes to the Values During ExerciseTypes of ExerciseSub-maximal Exercise

Maximal Exercise -

Stroke VolumeIncreases during exercise why?At a linear rate to the speed/intensity of the exercise (up to about 40-60% of maximum intensity exercise)Once 40-60% of maximum intensity is reached stroke volume plateaus.Therefore stroke volume reaches its maximum during sub-maximal exercise

What causes stroke volume (and therefore Q) to increase?More blood is being returned to the heart this is called venous returnLess blood left in heart (End Systolic Volume)Increased diastolic filling occurs, this increases the pressure and stretches the walls of the ventricles, which means that a more forceful contraction is produced, This is known as Starlings Law (more stretch = more forceful contraction)

During maximal exercise the cardiac output will need to be increased, however stroke volume has already reached its maximum what happens to allow Q to increase?Heart rate increasesAs a result of this stroke volume starts to decrease the increase in hr means that there is not as much time for the ventricles to fill up with blood, so there is less to eject (causes the hr to increase even more)

Changes in stroke volume in response to increasing exercise intensity;

Heart RateBefore ExerciseIncreases above resting hr before exercise has begun known as Anticipatory Rise, is as a result of the release of adrenalin which stimulates SA nodeMaximal ExerciseIncreases dramatically once exercise starts, continues to increase as intensity increasesDecreases as exercise intensity decreasesReaches its maximum at ________________?

Changes in heart rate in response to increasing exercise intensity;

Heart Rate and Sub-Maximal ExercisePlateaus during sub-maximal exercise, called Steady State this means that the oxygen demand is being meetAfter ExerciseAfter exercise drops dramaticallyThen gradually decreases

Cardiac Output

Increases directly in line with intensity from resting up to maximumPlateaus during sub-maximal exercise

Changes in cardiac output in response to increasing exercise intensity;

Summary

When exercise starts Q is increased by an increase in both HR and SV. When the intensity of exercise increases above 40-60% of maximum intensity, SV plateaus and any further increases in Q come about as a result of an increase in HR.

Extension Questions RecapWhat happens to stroke volume during sub-maximal exercise?What happens to heart rate during sub-maximal exercise and what is this called?What happens to heart rate during maximal exercise?What happens to heart rate during sub-maximal exercise in warmer conditions?

Adaptations to the Heart as a Result of TrainingStroke VolumeHeart muscle increases in size, known as . . Cardiac Hypertrophy ANDAthletes heartThe left ventricle increases in size why this ventricle?Thicker walls of the heart allow a more forceful contractions, there more blood can be pumped per beat, resulting in an increase in. . . Stroke VolumeHeart RateDue to an increase in SV the heart will not have to pump as many times (both at rest and during exercise), resulting in a decrease in. . . Heart rate (at rest and during exercise)When an athletes resting heart rate falls below 60bpm it is known as . . . BradycardiaDuring sub-maximal exercise, a trained athletes heart rate would not rise as muchIt would reach steady state soonerAnd recover fasterGreater heart rate range resting heart rate is lower so there is more room for an increase when exercisingMaximum heart rate stays the same (220-age)

Cardiac OutputThe volume of cardiac output at rest. . . Stays the same (lower resting heart rate but increase in stroke volume)The maximum cardiac output of an individual. . . Increases, so a trained athlete can deliver oxygen to the muscles for a longer period of time)

Other FactorsThe percentage of blood that the heart pumps out per beat is known as ejection fractionA trained athlete experiences an increase in ejection fraction because their heart will pump more forcefully each beatEven though resistance training (strength) does not work the CV system, an athlete will still will experience an increase in the size of their heart muscle (myocardium) and therefore their stroke volume will increase (more forceful contraction)The heart itself will experience capillarisation this will increase the blood supply to the heart and ensure it continues to work for longer

Summary of ChangesHeart RateStroke VolumeCardiac OutputRestDecreases (below 60bpm = bradycardia)Increases -can contract more forcefully (as does ejection fraction)

Stays the sameExerciseLowers during sub-maximal exerciseGreater heart rate range (starts lower so has more room for increase)Maximum stays same (220-age)Increases as heart muscle is stronger can contract more forcefully (as does ejection fraction)Stays the same during sub-maximal exerciseMaximum cardiac output increases (athlete can last longer)