The Heart

Pulmonary Circulation and Systemic Circulation The heart is considered to be a double pump because it pumps blood through 2 different loops: 1. pulmonary circulatory loop 2. systemic circulatory loop

Pulmonary loop System loop

1. Pulmonary Circulation – the right side of the heart is responsible for the pulmonary circulation it pumps deoxygenated blood to the lungs (where it is oxygenated) and back to the left side of the heart

2. Systemic Circulation – the left side of the heart is responsible for the systemic circulation it pumps oxygenated blood to the entire body and back to the right side of the heart

Which side of the heart has to work the hardest? the left side, because it has to pump blood to the entire body

the right side does not have to work as hard because it is only pumping blood to the lungs

Structure of the Heart: Your heart is divided into 4 chambers: 2 upper chambers called atria right atrium and left atrium right atrium left atrium

2 lower chambers are called ventricles (right ventricle and left ventricle) right ventricle left ventricle

The right side of the heart is separated from the left side by a wall of tissue - septum

it is important that this septum remain intact because the right side pumps deoxygenated blood, while the left side pumps oxygenated

The right atrium is separated from the right ventricle by a valve – tricuspid valve

The left atrium is separated from the left ventricle by a valve – mitral (bicuspid) valve

this valve prevents blood from flowing backward into the left atrium once it has entered the left ventricle

Why do we want to prevent the backflow of blood in the heart? The heart is a pump – for it to work effectively, it must pump blood in one direction only

Flow of Blood through the Heart: blood re-enters the heart through the superior and inferior venae cavae

the superior vena cava collects blood returning from the head and arms, while the inferior vena cava collects blood returning from the trunk and legs

vena cavae  enter right atrium  pass through the tricuspid  enter right ventricle  pass through the pulmonary valve  enter the pulmonary arteries (to lungs to get O2)  exit lungs through the pulmonary veins  left atrium  pass through the mitral valve  left ventricle  pass through the aortic valve  enter the aorta (largest artery)  pass through entire body

Conduction System of the Heart The normal rate and rhythm of your heartbeat is regulated by a special region of cardiac muscle cells called the sinoatrial node (SA-node)

since the SA-node regulates your heartbeat it is called the pacemaker the SA-node is located in the upper portion of the right atrium

it generates an impulse 60 -75 times per minute (heart rate) every time the SA-node generates an impulse, it spreads very rapidly to all other cardiac muscle cells in both atria, causing them to contract at the same time

when both atria contract, blood is forced into the ventricles

The impulse generated by SA-node does not stop in the atria – it will be picked up by another special region called the atrioventricular node (AV-node)

the AV-node is located in the lower portion of the right atrium

it receives the impulse and passes it to a network of fibers called the Bundle of His

the Bundle of His spreads the impulse rapidly to all cardiac muscle cells of both ventricles, causing them to contract

when ventricles contract, blood is sent from right ventricle to the lungs, and from the left ventricle to the body

If the AV-node is damaged, the impulses generated by the SA-node can not reach the ventricle the atria would contract at their normal rate, but the ventricles would contract only about 30 times per minute

this condition is called a heart block it can be treated by installing a pacemaker

If the SA-node is damaged the AV-node would take over however, the AV-node would send out impulses about 50 times per minute

you can survive a heart rate this slow; however, in a young individual, or in older, extremely active individuals, a pacemaker would be installed

Devices that Monitor Heart Function 1. Sphygmomanometer – device that measures blood pressure

this device can give you 2 readings: the systolic pressure and diastolic pressure Systolic pressure is a measure of the pressure of the blood against the wall of the artery during contraction of the heart

normal values run from 100 - 130

Diastolic pressure is a measure of the pressure of the blood against the wall of the artery during relaxation of the heart normal values run from 70 – 90

Blood pressure readings are reported as the systolic pressure written over the diastolic pressure thus, normal blood pressure reading would be 120/80

If the systolic pressure is consistently above 200, the person is said to have hypertension (high blood pressure) can be dangerous if it is not controlled

can lead to heart damage, stroke (ruptured blood vessels in the brain), or kidney failure

2. Electrocardiograph (ECG) – device that measures electrical changes that occur in the heart

every time your heart beats, an ECG records 3 separate waves: P wave – measures contraction of atria

QRS wave – measures contraction of the ventricles

T wave – measures relaxation of the ventricles

by examining the shape of these 3 waves on the ECG, a doctor can determine if the heart is functioning normally for example, if the SA-node is damaged, an ECG would show a QRS wave and T wave, but no P wave

if the heart cannot be repaired by surgery, a heart transplant is possible normal abnormal

The first human heart transplant was performed in 1967, by Dr The first human heart transplant was performed in 1967, by Dr. Christiaan Barnard, in Capetown, South Africa

Heart and Blood Vessel Disease diseases of the heart and blood vessels are the leading cause of death in the US

1. Myocardial infarction = heart attack heart attacks occur because a portion of the heart dies when it does not receive enough blood

heart attacks are caused by: fat deposits that build up in, and close off, the coronary arteries (arteries that feed the heart muscle)

blood clots that form elsewhere in the body, break free, and become lodged in the coronary arteries

2. Atherosclerosis – build up of fatty deposits in the inner walls of arteries in the body

can cause stroke if it closes off artery leading to the brain can cause a heart attack if it closes off one of the coronary arteries the fatty deposits are composed mainly of cholesterol

3. Arteriosclerosis – hardening of the arteries occurs when calcium is added to the fatty deposits caused by atherosclerosis

is harmful because it causes the heart to work harder and elevates the blood pressure