CARDIAC CYCLE & HEART SOUNDS.ppt

CardiovascularCardiovascular

Cardiac Cycle and Heart SoundsCardiac Cycle and Heart Sounds

Cardiac Cycle refers to one complete Cardiac Cycle refers to one complete heartbeat.heartbeat.

The heart is actually 2 pumps situated side The heart is actually 2 pumps situated side by side, so a complete cycle consists of by side, so a complete cycle consists of contractions of both atria and both contractions of both atria and both ventricles.ventricles.

The average resting heart rate is The average resting heart rate is approximately 75 beats per minuteapproximately 75 beats per minute

Resting heart rate will vary with degree of Resting heart rate will vary with degree of physical conditioning as well as with physical conditioning as well as with disease statesdisease statesThe familiar “lub-dub” associated with the The familiar “lub-dub” associated with the function of the heart are known as heart function of the heart are known as heart sounds.sounds.The heart sounds are made by the heart The heart sounds are made by the heart valves snapping closed under contractile valves snapping closed under contractile pressure.pressure.

Cardiac Cycle and Heart SoundsCardiac Cycle and Heart Sounds

Heart Sounds and Cardiac OutputHeart Sounds and Cardiac Output

The “lub” is caused by the closure of the The “lub” is caused by the closure of the AV valvesAV valves

The “dub” is caused by the closure of the The “dub” is caused by the closure of the semi-lunar valve.semi-lunar valve.

Cardiac output (CO) is the amount of Cardiac output (CO) is the amount of blood pumped out of each side of the blood pumped out of each side of the heart ( meaning the ventricles ) in one heart ( meaning the ventricles ) in one minuteminute

The value of CO is calculated as the The value of CO is calculated as the product of the Heart Rate ( HR) multiplied product of the Heart Rate ( HR) multiplied by the Stroke Volume (SV)by the Stroke Volume (SV)

SV generally increases as the force of the SV generally increases as the force of the ventricular contractions increases.ventricular contractions increases.

CO = HR x SVCO = HR x SV

CO = 75 beats per min x 70mls per beatCO = 75 beats per min x 70mls per beat

CO = 5250 ml/minCO = 5250 ml/min


Generally speaking, blood starting in the Generally speaking, blood starting in the heart should complete a circuit of the body heart should complete a circuit of the body and arrive back in the heart in one minute.and arrive back in the heart in one minute.According to Starling’s Law of the heart, According to Starling’s Law of the heart, stroke volume is influenced by the amount stroke volume is influenced by the amount of stretching force applied to the muscle of stretching force applied to the muscle cells of the heart.cells of the heart.The more the cells are stretched, the great The more the cells are stretched, the great the contraction will bethe contraction will be


Starling’s Law of the HeartStarling’s Law of the Heart

A healthy, efficient heart only pumps about A healthy, efficient heart only pumps about 60% of the volume of blood in the 60% of the volume of blood in the ventricles.ventricles.Venous return is critical to the amount of Venous return is critical to the amount of stretching the heart undergoes.stretching the heart undergoes.If one side of the heart begins to pump If one side of the heart begins to pump more blood than the other, the increase in more blood than the other, the increase in venous return to the opposite ventricle will venous return to the opposite ventricle will force it to pump a larger volume of blood.force it to pump a larger volume of blood.

This helps prevent back ups and This helps prevent back ups and increased pressures in the system.increased pressures in the system.

Anything that increases the volume or Anything that increases the volume or speed of venous return will also increase speed of venous return will also increase the SV and CO.the SV and CO.

The squeezing actions of skeletal muscles The squeezing actions of skeletal muscles on veins also plays a major role in on veins also plays a major role in increasing venous return.increasing venous return.

Starling’s Law of the HeartStarling’s Law of the Heart

Muscular PumpMuscular Pump

Regulation of Heart RateRegulation of Heart Rate

Coronary contraction does not depend on Coronary contraction does not depend on stimulus from the nervous system, stimulus from the nervous system, because the heart has it’s own intrinsic because the heart has it’s own intrinsic pacemakers ( SA and AV nodes)pacemakers ( SA and AV nodes)

HOWEVER—heart rate can be temporarily HOWEVER—heart rate can be temporarily influenced by stimulus from the autonomic influenced by stimulus from the autonomic nerves.nerves.

Sympathetic nerves can act to increase or Sympathetic nerves can act to increase or decrease the heart by stimulating the SA decrease the heart by stimulating the SA or AV nodes.or AV nodes.Parasympathetic nerves act to decrease Parasympathetic nerves act to decrease the heart ratethe heart rateBeing excited or startled can cause a rapid Being excited or startled can cause a rapid increase in heart rate.increase in heart rate.Heart rate can also be influenced by Heart rate can also be influenced by hormoneshormones


Epinephrine and Thyroxine mimic the Epinephrine and Thyroxine mimic the effects of the sympathetic nerves.effects of the sympathetic nerves.

Ion concentrations also has a rofound Ion concentrations also has a rofound influence on the heart.influence on the heart.

Decreased Ca+ will depress the heart rateDecreased Ca+ will depress the heart rate

Excessive Ca+ will cause prolonged Excessive Ca+ will cause prolonged contractions, and possibly stop the heart contractions, and possibly stop the heart from beating. from beating.


CHF and Blood VesselsCHF and Blood Vessels

When the pumping efficiency of the heart When the pumping efficiency of the heart is depressed so that circulation is is depressed so that circulation is inadequate to meet tissues needs, inadequate to meet tissues needs, congestive heart failure (CHF) results.congestive heart failure (CHF) results.

CHF is usually a progressive condition, CHF is usually a progressive condition, and in most cases reflects diminished and in most cases reflects diminished coronary circulation by coronary coronary circulation by coronary atherosclerosisatherosclerosis

Each side of the heart can fail Each side of the heart can fail independentlyindependently

If the left side fails, pulmonary congestion If the left side fails, pulmonary congestion will occur.will occur.

The right side continues to pump blood, The right side continues to pump blood, but the left side is unable to push but the left side is unable to push oxygenated blood into systemic circulationoxygenated blood into systemic circulation


The blood vessels of the lungs become The blood vessels of the lungs become swollen with blood, and the increased swollen with blood, and the increased pressure forces fluids to leak from pressure forces fluids to leak from circulation and into the lung tissue, circulation and into the lung tissue, resulting in pulmonary edema.resulting in pulmonary edema.

Suffocation will result if this condition is Suffocation will result if this condition is untreated.untreated.


If the right heart fails, blood is not moved If the right heart fails, blood is not moved out of the systemic circulation, and out of the systemic circulation, and peripheral congestion will occur.peripheral congestion will occur.This results in edema in distal parts of the This results in edema in distal parts of the body, such as the feet, ankles and hands.body, such as the feet, ankles and hands.Failure of one side of the heart places Failure of one side of the heart places increased strain on the opposite side of increased strain on the opposite side of the heart—eventually leading to whole the heart—eventually leading to whole heart failureheart failure


Blood VesselsBlood Vessels

Blood circulates through the body within Blood circulates through the body within the vasculature.the vasculature.

In decreasing size order, vessels carrying In decreasing size order, vessels carrying blood away from the heart are, arteries, blood away from the heart are, arteries, arterioles, capillary beds.arterioles, capillary beds.

In increasing size order, vessels carrying In increasing size order, vessels carrying blood back towards the heart from the blood back towards the heart from the capillary beds are, venules, and veinscapillary beds are, venules, and veins

The walls of most blood vessels consist of The walls of most blood vessels consist of three layers called tunics.three layers called tunics.

The innermost layer is called the tunica The innermost layer is called the tunica intima.intima.

Tunica intima consists of a thin layer of Tunica intima consists of a thin layer of closely fitted endothelial cells.closely fitted endothelial cells.

It is very smooth, to allow for smooth flow It is very smooth, to allow for smooth flow of bloodof blood


The tunica media is the middle layer of The tunica media is the middle layer of tissue, and is primarily smooth muscle tissue, and is primarily smooth muscle tissue and elastic connective tissue.tissue and elastic connective tissue.

This smooth muscle is controlled by the This smooth muscle is controlled by the sympathetic nervous system, which sympathetic nervous system, which changes the diameter of the blood vessels changes the diameter of the blood vessels


The tunica externa is the outer-most layer, The tunica externa is the outer-most layer, and is mostly fibrous connective tissue and is mostly fibrous connective tissue that supports and protects the vessel.that supports and protects the vessel.The walls of arteries are usually thicker The walls of arteries are usually thicker than those of the veins.than those of the veins.Veins are subject to less pressure than Veins are subject to less pressure than ateries, but move blood against gravity.ateries, but move blood against gravity.Veins contain one way valves to prevent Veins contain one way valves to prevent backflow of bloodbackflow of blood


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CARDIAC CYCLE & HEART SOUNDS.ppt