Human Anatomy & Physiology 12-13

Where is the heart located?

Mediastinum

How much does the heart pump a day?

Approx. 8000L of blood / day

What is a pulmonary circuit?

Carries blood to and from the gas exchange surfaces of the lungs

What is a systemic circuit?

Transports blood to and from the rest of the body

How does blood flow in the cardiovasicular system?

Blood flows through a network of blood vessels that extend between the heart and peripheral tissues

How does blood flow in the right atrium?

Right atrium receives blood from the systemic circuit and passes it to the right ventricle, which then pumps blood into the pulmonary circuit

How does blood flow in the left atrium?

Left atrium collects blood from the pulmonary circuit and empties it into the left ventricle, which pumps blood into the systemic circuit

What happens when the heart beats?

Atria contracts and then ventricles contract

What happens to the two ventricles?

They contract at the same time and eject equal volumes of blood into the pulmonary and systemic circuits

What does the right heart consist of?

Right atrium and right ventricle, taking systemic venous DEOXYGENATED blood from the body and pumping it to the lungs for oxygenation

What does the left heart consist of?

Left atrium and left ventricle, and receives OXYGENATED pulmonary blood from the lungs and pumps it systemically

What are the functions of arteries?

Carries blood away from the heart

What are the function of veins?

Returns blood to the heart

What is a valve?

Open and close to left blood flow from one area of your heart to another

They help ensure that blood moves at the right time and in the correct direction

What is the function of the auricle?

Two atria have relatively thin muscular walls and are highly expandable

When not filled with blood, the outer portion of each atrium deflates and becomes a lumpy wrinkled flap

What is a sulcus?

The coronary sulcus, a deep groove, marks the border between the atria and the ventricles

The anterior interventricular sulcus and the posterior interventricular sulcus are shallower depressions that mark the boundary between the left and right ventricles

What is the aorta?

Aorta is the main artery that caries blood away from left ventricle to body

Where does blood collect from the respiratory capillaries?

Blood collects into small veins that ultimately unite to form the four pulmonary veins

What does the posterior wall of the left atrium receive blood from?

Two left and two right pulmonary veins

What is a trabeculae carneae?

The internal surface of the right ventricle that contains a series of muscular ridges

What is a septa?

Chambers of the heart are separated by muscular partitions

What is the atria separated by?

Interatrial septum

What is the ventricles separated by?

Thicker interventricular septum

What fibrous flap does the blood travel by?

Tricuspid / Right atrioventricular (AV) valve

Chordae tendineae

Papillary muscles

What guards the entrance to the left ventricle?

Mitral valve / Left atrioventricular (AV) valve, or bicuspid valve

What is the function of the bicuspid valve?

Contains two cusps, not three

Permits blood to flow from the left atrium into the left ventricle

What does the pulmonary valve consist of?

Three semilunar (half-moon shaped) cusps of thick connective tissue

How does blood flow in the pulmonary valve?

Blood flowing from the right ventricle passes through this valve into the pulmonary trunk, the start of the pulmonary circuit

What does atrioventricular (AV) valves prevent?

Prevent the backflow of blood from the ventricles to the atria when the ventricles are contracting

Chordae tendineae and papillary muscles play important role in the normal function of the AV nodes

Ventricles relaxed —> Chordae tendineae are loose

What does the pulmonary and aortic semilunar valves prevent?

Prevent backflow of blood from the pulmonary trunk and aorta into the right and left ventricles

Semilunar valves do not need muscular braces, because the arterial walls do no contract and the relative positions of the cusps are stable

What happens when the ventricles contract?

Blood moving back toward the atria swings the cusps together, closing the valves

What happens when the aortic valve opens?

Aortic sinuses prevent the individual cusps from sticking to the wall of the aorta

What are the three sections of the heart wall?

Epicardium (pericardium)

Myocardium

Endocardium

What is the purpose of the epicardium?

Visceral layer of serous pericardium covers the surface of the heart

What is the serous membrane consist of?

An exposed mesothelium and an underlying layer of areolar connective tissue that is attached to the myocardium

What does the parietal layer of serous pericardium consist of?

Outer dense fibrous layer, an areolar layer, and an inner mesothelium

What is the purpose of myocardium?

Cardiac muscle tissue that forms the atria and ventricles

What is the muscular layer contain?

Cardiac muscle cells, connective tissues, blood vessels, and nerves

What is the purpose of the endocardium?

Covers the inner surfaces of the heart, including those of the heart valve

Made up of simple squamous epithelium and underlying areolar tissue

What is a characteristics of the right ventricle?

Right ventricle normally does not need to work very hard to push blood through the pulmonary circuit

Muscular wall of the right ventricle is relatively thin

What is a characteristics of the left ventricle?

4 - 6x times as much pressure must be exerted to push through the systemic circuit as through the pulmonary circuit

The left ventricle has an extremely thick muscular wall and is round in cross-section

What us a coronary ciruclation?

Supplies blood to the muscle tissue of the heart

What does the right coronary arteries consist of?

Right Atrium

Portions of both ventricles

Portions of the electrical conducting systems of the heart

What does the left coronary arteries consist of?

Left coronary artery supplies blood to the left ventricle, left atrium, and interventricular septum

What are the two types of cardiac muscle cells for heartbeat?

Specialized autorhythmic cells (pacemaker and conducting)

Contractile cells

What are specialized autorythmic cells (pacemaker and conducting)?

They conducting system control and coordinate the heartbeat

What are contractile cells?

Produce powerful contractions that propel blood

Electrical impulses of the conducting system initiate the contraction of the heart chambers

What is autorhythmicity?

Cardiac muscle tissues contracts on its own, without neural or hormonal stimulation

What are pacemaker cells?

System is a network of specialized cardiac muscle cells

What is depolarization?

Loss of the difference in charge between the inside and outside of the plasma membrane of a muscle or nerve cell

What is essential for establishing normal heart rate?

Pacemaker cells

What is the sinoatrial (SA) node?

Posterior wall of the right atrium

The primary driver of the heart rate (cardiac pacemaker)

What is the atrioventricular (AV) node?

At the junction between the atria and ventricles, near the opening of the coronary sinus

The pacemaker cells of this node send on signals from the cells of the SA node

AV node acts as backup to the SA node pacemaker cells

What is the purpose of conducting cells?

Interconnect the SA and AV nodes, and distribute the contractile stimulus throughout the myocardium

What are the conducting cells in the atria?

Internodal pathways

What are internodal pathways?

Distributes the contractile stimulus to atrial muscle cells (from the SA node to the AV node)

What are the conducting cells of the ventricles?

Atrioventricular (AV) bundle (Bundle of HIS)

Bundle branches

Purkinje fibers

What is pacemaker potential?

Each time a pacemaker repolarized, its membrane potential drifts toward a threshold

How can electrical events be recorded by?

Electrocardiogram (ECG)

What happens in the first step of ECG tracing?

An action potential is produced by the pacemaker cells of the SA node and takes approximately 50 msec to travel to the AV node

What happens in the second step of ECG tracing?

The action potential then spreads across the atrial surfaces by cell-to-cell contract

The stimulus affects only the atria

P wave → Atrial depolarization

What happens in the third step of ECG tracing?

The impulse slows as it leaves the internodal pathways and enter the AV node

The impulse takes about 100 msec to pass through the AV node

P-R interval → conduction through AV node and AV bundle

What happens in the fourth step of ECG tracing?

The impulse is conducted along the AV bundle and the bundle branches to the Purkinje fibers and the papillary muscles

Once an impulse enters the AV bundle, it travels to the interventricular septum and enters the right and left bundle branches

Q wave → beginning of ventricular depolarization

What happens in the fifth step of ECG tracing?

The purkinje fibers then distribute the impulse to the ventricular myocardium

The contraction of ventricle pushes blood into the aorta and pulmonary trunk

QRS complex → completion of ventricular depolarization

What is bradycardia?

Heart rate is lower than normal

What is tachycardia?

Heart rate faster-than normal

What is the P wave?

Depolarization of the atrial contractile cells

What is atrial contraction?

Depolarization of these cells

What is the QRS complex?

Appears as the ventricle contractile cells depolarize

Electrical signal is relatively strong, because the ventricular muscle is much more massive than that of the atria

What is the R wave?

When the ventricles begin contracting shortly after the peak of the R wave

What is the T wave?

Repolarization of the ventricular contractile cells

What is the P-R interval?

Start of atrial depolarization to the start of the QRS complex (ventricular depolarization) rather than to R

What is the Q-T interval?

Time required for the ventricles to undergo depolarization and repolarization

Lengthened by electrolyte disturbances, some medications, conduction problems, coronary ischemia, or myocardial damage

How do the purkinjie fibers distribute the stimulus?

To the cardiac contractile cells, which form the bulk of the atrial and ventricular walls

What are cardiac contractile cells interconnected by?

Intercalated discs

What are the two phases of the cardiac cycle?

Systole

Diastole

What happens during the systole phase?

The chamber contracts and pushes blood into an adjacent chamber or into an arterial trunk

What happens during the diastole phase?

The chamber fills with blood and prepares for the next cardiac cycle

What are the phases of the cardiac cycle?

Atrial systole

Atrial diastole

ventricular systole

Ventricular diastole

What happens during atrial systole?

Atria contract, filling the ventricles completely with blood

Lasts 100 msec

What happens during atrial diastole?

Continues until the start of the next cardiac cycle

What happens during the ventricular systole?

Begins at the same time as atrial diastole

Ventricles push blood through the systemic and pulmonary circuits and toward the atria

What happens during the ventricular diastole?

Filling occurs passively, and both the atria and the ventricles are relaxed

The next cardiac cycle begins with atrial systole, which completes the filling of the ventricles

Lasts 530 msec

What happens first in the contraction-relaxation event?

Atrial contraction begins

Ventricles are already filled to about 70% of their normal capacity, due to passive blood flow during the end of the pervious cardiac cycle

What happens second in the contraction-relaxation event?

Atria eject blood into the ventricles

As atria contract, rising atrial pressures provide the remaining 30% by pushing blood into the ventricles through the open right and left AV valves

What is end-diastolic volume (EDV)?

Each ventricle contains the maximum amount of blood that it will hold in the cardiac cycle

Typically 130 mL

What happens third in the contraction-relaxation event?

Atrial systole ends

AV valves close; As atrial systole ends, ventricular systole begins

As the pressures in the ventricles rise above those in the atria, the AV valves are pushed closed

What happens fourth in the contraction-relaxation event?

Isovolumetric ventricular contraction occurs

Ventricles are contracting, but blood flow has yet to occur

Ventricular pressures are not yet high enough to force open the semilunar valves and push blood into the pulmonary or aortic trunk

Ventricles are in isovolumetric contraction

Ventricular pressures are rising

What happens fifth in the contraction-relaxation event?

Ventricular ejection occurs

Ventricles exceeds that in the arterial trunks, the semilunar valves are pushed open and blood flows into the pulmonary and aortic trunks

Ventricles now contract isotopically: the muscle cell shorten, and tension production remains relatively constant

What happens sixth in the contraction-relaxation event?

End of ventricular systole approaches, ventricular pressures fall rapidly

Blood in the aorta and pulmonary trunk now starts to flow back toward the ventricle, and this movement closes the semilunar valves

What is a dicrotic?

Small, temporary rise produces a valley in the aortic pressure tracing

What happens seventh in the contraction-relaxation event?

Isovolumetric relaxation occurs

All the heart valves are now closed, and the ventricular myocardium is relaxing

Ventricular pressures drop rapidly over this period because the elasticity of the connective tissues of the heart and cardiac skeleton helps re-expand the ventricles toward their resting dimensions

What is isovolumetric relaxation?

Ventricular pressures are still higher than atrial pressures; blood cannot flow into the ventricles

What is the eighth in the contraction-relaxation event?

When ventricular pressures fall below those of the atria, the atrial pressures force the AV valves open

Blood now flows from the atria into the ventricles

Both the atria and the ventricles are in diastole, but the ventricular pressure continue to fall as the ventricular expand

What is S1 considered as?

Lubb

What is S2 considered as as?

Dupp

What is cardiac output?

The amount of blood pumped by the left ventricle in 1 minute

blood flow through peripheral tissues

What is heart rate?

Number of heartbeats per minute

What is stroke volume?

Amount of blood pumped out of a ventricle during each contraction