The Circulatory System:Heart Physiology

Heart Structure Review

Objectives1. Describe how the heart works.– How blood moves through the heart– How blood is sent to the lungs– How blood is sent to the body

2. Describe the heart’s conduction system.3. Explain the significance of the numbers

associated with blood pressure (i.e. 120/80).– Learn how to take blood pressure using a

sphygmomanometer and stethoscope.

What will we be doing today?

• Lecture– Background information on how the heart works.

• Activity– Blood pressure• Resting• Active (if we have time)

How the heart works…

• What is the main job of the heart?– To push blood to the lungs so it can pick up

oxygen.– To push blood to the tissues of the body so those

tissues can get oxygen.

• How does it accomplish these two tasks?

Picture shows movement of blood through the heart and body.

How the heart works…• Step 1: Blood low in oxygen enters the right atrium

via the superior and inferior vena cava.

How the heart works…• Step 2: The right atrium contracts, pushing blood

through the (tricuspid) valve into the right ventricle.

How the heart works…• Step 3: The right ventricle contracts pushing the blood

through the (pulmonary)valve, into the pulmonary artery and into the lungs.

How the heart works…• Step 4: As blood is pushed into the lungs it is also

pushed out of the lungs, back toward the heart.

How the heart works…• Step 5: The oxygenated blood enters the left atrium

via the pulmonary veins.

How the heart works…• Step 6: The left atrium contracts, pushing blood

through the (mitral) valve into the left ventricle.

How the heart works…• Step 7: The left ventricle contracts pushing blood through the

(aortic) valve, into the aorta and out to the tissues of the body.

How the heart works…• Step 8: The tissues of the body deoxygenate the

blood, and the whole process starts over again.

• Both atria contract at the same time.

• This is followed by both ventricles contracting at the same time.

• Blood is pushed to the lungs and body tissues at the same time.

How the heart works…

• What actually makes the heart beat? What makes the chambers contract?– Electric impulses generated in the heart.

• What chambers are the first to contract in the heart?– The atria.

• Where do you think the electric impulses originate?– The atria.

How the heart works…

• Electric impulse generated in the sinoatrial (SA) node.

• Causes the atria to contract.

How the heart works…

• Impulse moves to the atrioventricular node.

• Spreads to the ventricles.

• Causes the ventricles to contract.

Video of heart beating

Blood Pressure

• Blood exerts a pressure on the walls of blood vessels.

• Blood pressure is the measure of the pressure exerted by the blood on the walls of the blood vessels.

• One of the major factors contributing to blood pressure is the force of each heart beat.

Blood Pressure

• Each time the heart beats, the pressure exerted by the blood on the blood vessels increases.– This is called the “systolic pressure.”

• During the resting period when the heart is not beating, there is also a pressure present.– This is called the “diastolic pressure.”

Blood Pressure• How a blood pressure cuff (sphygmomanometer) works:

1. Cuff is applied to the arm and pumped up.2. The pressure exerted by the cuff is increased so that it is more

than the pressure exerted by the heart.• Blood flow in the arm stops.• Doctor listens to artery in the arm with a stethoscope.

3. The pressure in the cuff is slowly released. At some point the pressure exerted by the heart will be more than the pressure exerted by the cuff.• Blood will begin to flow again.• Doctor can hear this through the stethoscope; sounds like a heart

beat.• The pressure reading at this moment is the “systolic pressure”.

4. Pressure is continually released from the cuff. Doctor listens until they can’t hear the “heart beat” anymore.• The pressure reading at this moment is the “diastolic pressure.”

Blood Pressure

• Pressure is measured in “mm Hg” (millimeters of mercury)

• In a blood pressure reading of 120/80, the “120” is the systolic pressure.– Stands for 120 mm Hg.

• The “80” is the diastolic pressure.– Stands for 80 mm Hg.

Let’s try it!!!