The Heart

Valves of the Heart

A-V valves Semilunar valves

Tricuspid Bicuspid Right SV Left SV-bw RA - bw LA - bw RV - bw LV

and RV and LV and and pulmonary aortaartery

The Structure of the Heart

The Heartbeat Cycle

1. Heart is relaxed. AV valves are open.

DIASTOLE

SYSTOLE

2. Atria contract.

3.Ventricles contract. Semilunar valves are open.

The pumping action of the heart has two periods:

Systole: Contraction periodDiastole: Relaxation period

During diastole the heart muscle is relaxed and A-V valves are open.

Blood flows from the atria into ventricles . (This fills the ventricles %70 not fully.)

The Heartbeat Cycle

The Heartbeat CycleSystole begins with the contraction of atria. When atria contract they can pass all blood inside to the

ventricles, so ventricles are full of blood.Then ventricles contract and the pressure of contraction

closes A-V valves. The pressure also opens the semilunar valves. As a result blood flows from right ventricle to pulmonary

artery and transported to lungs;blood in the left ventricle flows into the aorta to be

carried throughout the body.

Heart SoundsHeart sounds are formed as a result of opening and

closing of A-V and semilunar valves. They are called the lub-dup sounds.

lub-dup sound

closing of closing of A-V valves semilunar valves

Heart Sounds

Lub sound: Ventricles contract Pressure increases

Mitral and tricuspid valves close

Dup sound: At the beginning of diastole pressure in the relaxed

ventricles drops below that in the arteries

Semilunar valves close

Heart Sounds

Lub hiss dup When A-V valves don’t close completely

(blood flows back into atria causes this sound)

Lub dup hiss When semilunar valves don’t close

completely (blood flowing back into ventricle causes this sound)

The Coronary ArteriesThey are the first arteries to branch

off from the aorta. They nourish the heart muscle.

If there is blood clot or accumulation of materials in coronary arteries this may cause heart attack.

The Coronary Arteries

Heart RateThe number of times the heart contracts each

minute is the heart rate or pulse rate. (The pulse is the expansion and relaxation that can be felt in an artery each time the left ventricle contracts and relaxes.)

It is measured by feeling the impact of blood on the wall of an artery.

Pulse can be felt in wriston each side of throat

Normal heart rate 50-80 (beats) times in a minute

In vigorous exercise 200 times a minute

Heart is made up of the cardiac muscle. Although the nervous system controls the contraction of other types of muscle, cardiac muscle has a built-in ability to contract.

Even when it is removed ftom the body, the heart will keep beating for a while in a special solution called Ringer solution.

Ringer solution contains NaCl, KCl and CaCl.

Control of the Heartbeat

Control of the HeartbeatThere are structures in the heart muscle which are called nodes. Sinoatrial node (SA node = pacemaker): is located in the wall of the right atrium near the opening of superior vena cava. Atrioventricular node (AV node): is located in the wall of right atrium near the septum (behind the tricuspid valve)

Control of the Heartbeat

Control of the Heartbeat SA node generates impulses, specialized fibers

carry impulses throughout the atria and stimulates AV node.

The group of fibers called bundle of His distribute the impulses through the ventricles from AV node.

Contraction of the heart begins when,

the heart receives electrical impulses from the SA node

atria contract the impulse reaches the AV node

the AV node triggers an impulse that causes the ventricles to contract

Bundle of His conducts the impulses through the ventricles.

Control of the Heartbeat

Control of the Heartbeat

. ..SA node

AV node

Bundle of His

The electrical current produced by heart can be recorded by a machine that produces an electrocardiogram (ECG).

The Rate of Heart Beat is Regulated by

Cardioaccelerator nerve Speed up the

pacemaker

Vagus nerve Slow down the pacemaker

[CO2] in blood

High temperature

Anxiety

Adrenalin

Cardiovascular nerve

Acetylcholine

Vagus nerve increases the

heartbeat rate

decreases the

heartbeat rate

Cardiac OutputThe amount of blood pumped by the left ventricle each minute is called cardiac output.

Resting: the heart pumps about 5 lt. of blood each minute.

Exercise: cardiac output may increase up to 37 lt. per minute.