Cardiovascular System 42.2

Question 1

Cardiovascular system steps

Answer 1

The right ventricle pumps blood to the lungs via the pulmonary arteries (smaller vessels) via the pulmonary trunk. As the blood flows through capillary beds in the left and right lungs, it loads oxygens and unloads carbon dioxide by diffusion. Oxygen-rich blood returns from the lungs via the pulmonary veins (right and left) to the left atrium of the heart. Next, the oxygen-rich blood flows into the heart’s left ventricle, which pumps the oxygen rich blood out to body tissues through the systemic circuit. Blood leaves the left ventricle via the aorta, which distributes blood throughout the body. The first branches leading from the aorta are the coronary arteries, which supply blood to heart muscle itself. Then branches lead to capillary beds in the head and arms. The aorta then descends into the abdomen, suppling oxygen rich blood to arteries leading to capillary beds in abdominal organs and legs. Within the capillaries, there is a net diffusion of oxygen from the blood to the tissues of carbon dioxide (produced by cellular respiration) into the blood. Capillaries rejoin, forming venules, which convey blood to veins. Oxygen-poor blood from the head, neck, and forelimbs is channeled into a large vein, the superior vena cava. Another large vein, the inferior vena cava, drains blood from the trunk and hind limbs. The two venae cavae empty their blood into the right atrium, from which the oxygen poor blood flows into the right ventricle.

Question 2

How does the blood flow from the atria to the ventricle?

Answer 2

Most of the blood from the atria into the ventricles while all four heart chambers are relaxed. The remainder is transferred by contraction of the atria before the ventricles begin to contract.

Question 3

Compare the atria and ventricles

Answer 3

The ventricles have thicker walls and contract with more force, especially the left ventricle which pumps blood throughout the body via the systemic circuit.

However, although the left ventricle contracts with greater force than the right ventricle, it pumps the same volume of blood as the right ventricle during each contraction.

Question 4

Systole

Answer 4

The contraction phase of the cardiac cycle

Question 5

Diastole

Answer 5

the relaxation phase of cardiac cycle

Question 6

Cardiac output

Answer 6

The volume of blood each ventricle pumps per minute

Question 7

What factors determine cardiac output?

Answer 7

1) heart rate: the rate of contraction
2) Stroke volume: the amount of blood pumped by a ventricle in a single contraction. (Avg. human stroke volume is 70 mL)

cardiac output can be influenced by these two factors

Question 8

What are valves made of?

Answer 8

Flaps of connective tissue ,

Question 9

Atrialventricular valve

Answer 9

lies between each atrium and ventricle. They are anchored by strong fibers, chordae tendinae, that prevent them from turning inside out during ventricular systole by connecting the valve cusps (tri & bi) to the papillary muscle seen on ventricle floor. Pressure generated by the powerful contraction of the ventricles closes the AV valves keeping blood from flowing back into the atria.

Question 10

Semilunar valves

Answer 10

Located at the two exits of the heart: where the pulmonary artery leaves the right ventricle and where the aorta leaves the left ventricle. These valves (pulmonary valves and aortic valves, 4 valves in total) are pushed open by pressure generated during contraction of the ventricles, so changes in bp control. pulmonary valve controls the opening from the right ventricle to the pulmonary trunk & aortic valve controls the opening from the left ventricle into the aorta.

Question 11

S1 “lub”

Answer 11

created by the recoil of blood against the closed AV valves

Question 12

S2 “dub”

Answer 12

due to the vibrations caused by closing of the semilunar valves

Question 13

Heart murmur

Answer 13

If blood squirts backward through a defective valve it can produce an abnormal sound

Question 14

Autorhythmic

Answer 14

Some cardiac muscles cells are autorhythmic, meaning they can contract and relax repeatedly without any signal from the nervous system.

Question 15

How are the contractions coordinated in the intact heart?

Answer 15

Impulses from the SA node (composed of modified cardio sites) first spread rapidly through the walls of the atria (atrial myocardia), causing both atria to contract in unison. During atrial contraction, the impulses originating at the SA node reach autorhythmic cells located in the wall between the left and right atria. These cells form a relay point called the atrioventricular node. Here the impulses are delayed for about 1 second before spreading to the heart apex. This delay allows the atria to empty completely before the ventricles contract. Then the signals from the AV node are conducted to the heart apex and throughout the ventricular walls by specialized called bundle branches and Purkinje fibers. Purkinje fibers found at the end of bundle branches and spread upwards the ventricular myocardium, distributing electrical excitation to cells of the ventricles, network more elaborate on left side.

The other autorhytmic cells are pacemakers, just not the pacemaker.

Question 16

Sinoatrial node

Answer 16

Group of autorhythmic cells located in the wall of the right atria, near where the superior vena cava enters the heart.

SA node (the pacemaker) sets the rate and timing at which all cardiac muscle cells contract. The SA node produces electrical impulses. Because cardiac muscle cells are electrically coupled through gap junctions, impulses from the SA node spread rapidly within the heart tissue. These impulses generate currents that can be measured when they reach the skin via body fluids.

Question 17

What physiological cues alter heart tempo by regulating the pacemaker function of the SA node?

Answer 17

Two portions of the nervous system, the sympathetic and parasympathetic divisions, are largely responsible for this regulation. And body temperature can also regulate pacemaker.

An increase of only 1C raises the heart rate by 10bpm, which is why your heart beats faster when you have a fever.

ex. when you stand up and start walking, the sympathetic division speeds up your pacemaker. The resulting increase in heart rate provides the additional oxygen needed by the muscles that are powering your activity. If you then sit down and relax, the parasympathetic division slows down your pacemakers, decreasing your heart rate and thus conserving energy.
i. e “flight or fight”, epinephrine (hormone) secreted by the adrenal gland speeds up the pacemaker

Question 18

What does the cardiovascular system help with?

Answer 18

Meet the demand of oxygen which helps generate ATP as well

Question 19

What does the systemic circuit serve?

Answer 19

All parts of the body, including some parts of the lungs that need oxygen rich blood in order to carry out their own needs and the walls of the heart too

Question 20

Heart location

Answer 20

within thoracic cavity

Question 21

Sulcus (groove)

Answer 21

there’s a coronary one (atrial ventricular) encircles the heart and separates the atria above from the ventrical below

Anterior and posterior interventricular sulcus which extends down towards the apex of the heart

these sulci the largest coronary blood vessels which supply the heart with the blood it needs

Question 22

Oracle (little ear)

Answer 22

theres an oracle at both the right atrium and left atrium , serving to help increase atrial volume

Question 23

Ascending aorta

Answer 23

curves over and forms aortic arch and there’s several branching off of vessels

Question 24

Atria

Answer 24

thinner walls due to role of receiving blood

Question 25

Fossil Ovalis

Answer 25

indentation seen in the interatrial septum, which partitions left and right side of atria. this indentation indicative of opening that used to be in fetal heart which under normal condition should close.

Question 26

Ventricles

Answer 26

make up the most volume of the heart and have interventricular septum , expect these chambers to separate oxygen content of heart

ventricles larger than atria

Question 27

Epicardium, myocardium, endocardium

Answer 27

three layers of heart wall

epicardium- outer layer, soft and infiltrated with fat

myocardium- makes up bulk of heart, responsible for contraction

endocardium- composed of endothelial cells and lines heart chambers, continuous with endothelial linings seen in blood vessels that leave and enter the heart

Question 28

Differences between walls of ventricles?

Answer 28

Walls of the left ventricle are much thicker than walls of the right ventricle. The cavity of right cavity is more crescent and slightly encloses the left ventricle.

Left ventricle directs blood to the rest of the body generating much more pressure because of the distance the blood needs to travel, and right ventricle travels to lung

Question 29

Cardiac cycle

Answer 29

Ventricular filling: time in which blood goes from atria down to ventricles, ventricles are relaxed (diastole). The pressure of left and right ventricle are lower than left and right atria allowing for movement of blood down pressure gradient. The atrialventricular valves are open. Higher pressures in pulmoary trunk and aorta and as a result the semilunar valves are in a closed state. Most of the filling will be passive but small part will be forced in through atrial systole to force out residual blood within chambers. At the end of this process, we’ll have end diastolic volume, total amount of blood seen within ventricle.

Isovolumetric contraction: beginning of ventricular systole, one of the shortest phases, the pressure in ventricles goes up exceeding atria, so atriaventricular valves are going to close. The increase in ventricular pressure isnt high enough to open semilunar valves so its not higher than pressure in pulmonary trunk so all valves are closed. the ventricular volume in ventricles hasn’t changed since ventricular filling because they have nowhere to go. Atrial diastole will begin.

Ventricular ejection: pressure within ventricles is high enough that semilunar valves are able to open ending ISVC phase and getting blood to flow into aorta and pulmonary trunk. Pressure within pulmonary trunk and aorta is approaching to that of the ventricle, so the force of the blood ejection is going to decrease considerable. There’s a rapid ejection but then it will be decreased. Ventricles will expel some of their blood but not all of their blood.

Isovolumetric relaxation: ventricular diastole, pressure is going to decline in the ventricles. This decline is going to change pressure between ventricular and semilunar (aorta and pulmonary) resulting in semilunar valves to close, causing S2 heart sound. Pressure in ventricles is still higher than the atria so atriaventricular valves are also going to be closed. All valves are closed so blood is not being ejected nor entering, and volume is going to remain constant for a short period of time. There is a change seen within ventricular pressure during ventricular systole impacts the amount of blood that is capable of being ejected, so entire volume doesnt get ejected during that portion, so during ISVC we see residual blood in both ventricles referred to as end systolic volume.

Question 30

Relationship in pressure and and volume?

Answer 30

• Pressure values on axis would be a little lower on the right side of the heart because of difference between amount of moment required for systemic and pulmonary circulation
• AV open: pressure seen in atria should exceed pressure in ventricles.
• AV close: ventricle pressure begins to rise
• Aortic and pulmonary closed: pressures within the vessels is exceeding that of the ventricles
• Blood is going to flow down a pressure gradient, ventricular volume is increasing when the pressure during atria is higher, the pressure of the ventricle is exceeding the vessels so blood flows from ventricle to aorta.
• Pressure changes cause volume changes IF valves are open. if valves are in open state then we see ventricular volume rising up. Ventricular volume with all valves are closed then volume remains the same.
• Volume of blood in ventricle is greatest at end of diastole. Smallest at the end of systole.

Question 31

ECG waves

Answer 31

P: atrial depolarization, produced when the SA nodes spreads throughout atria and atrial systole begins a little after p wave begins

QRS complex: ventricular depolarization, higher than atrial depolarization due to thickness of ventricle and increased force when ventricle contracts, producing a signal and generates greatest electrical current. Signal of AV spreads through myocardium.
Atrial repolarization is also happening during this time but because of how significant the QRS complex is during ventricular depolarization it masks atrial repolarization.

T: ventricles are relaxed

abnormaities in ecg can indicate problems of conduction system like at SA node or purkinje

depolarization: contraction (systole), more activity
repolarization: relaxation (diastole)