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TRANSCRIPT
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.