Module 3 Flashcards
Components of the cardiovascular system
Heart atria, ventricles, blood vessels (arteries, capillaries, and veins) and AV valves
Major function of the CVS
The major function of the CVS is the transport of nutrients (including oxygen) and waste products of metabolism.
Systemic circulation
The left heart pumps blood to all organs of the body.
pulmonary circulation
The right heart pumps venous blood through the lungs, where carbon dioxide is exchanged for oxygen
how many chambers on each side of the heart
2 (atrium and ventricle)
Semilunar Valves
prevent back flow of blood from the aorta and pulmonary arteries into the left and right ventricles, respectively
Arterioles
bring blood to the capillaries and regulate the amount of blood supplied to the tissues
Venules
drain blood from the capillaries
Path of blood flow in the body
right atrium -> right AV valve (tricuspid)-> right ventricle->right semilunar valve (pulmonary)->pulmonary artery->lungs->pulmonary vein-> left atrium
characteristics of the heart muscle
striated, mononucleated (single nucleus per cell), and involuntary
syncytium
cells forming a functional unit : Heart muscle fibers are interconnected by intercalated discs to allow for rapid transmission of impulses from cell to cell.
Because of this, they form one functional unit
where does the heartbeat originate
spontaneously at the sino-atrial node (SA node)
SA node
sino-atrial node->a collection of specialized cardiac muscle fibers located at the junction of the cranial vena cava and the right atria
pacemaker of the heart
conduction system of the heart
Impulses from the SA node travel to the atria, and the atria contract -> Impulses reach the AV node -> Impulses are delayed at the AV node, allowing time for the ventricles to fill with blood -> Impulses travel through Purkinje fibers to the ventricles, which contract and eject blood into the aorta and pulmonary artery
systole
Contraction of heart muscle (usually refers to ejection of blood from ventricles into the pulmonary artery or aorta
Diastole
Relaxation of the heart muscle (usually refers to the filling of the ventricles with blood)
how can heart muscles generate a rythmic beat without nerve stimuli
Heart muscles are capable of depolarizing
Parasympathetic
this system is most active during rest. Its action on the heart is mediated through the paired vagus nerves (cranial nerve X, CN10). The parasympathetic effects on the heart can be summarized as follows:
Decreased rate of discharge at SA node
Decreased rate of conduction of impulses within the heart
Decreased rate and force of heart muscle contraction
sympathetic
system is most active during exercise and emergency situations, in order to supply more blood to the skeletal muscles and the brain. Sympathetic effects on the heart can be summarized as follows:
Increased rate of impulse conduction within the heart
Increased rate and force of heart muscle contraction
Cardiac output (CO). or cardiac minute volume
concept designed to express the amount of blood the heart pumps into the aorta, and thus systemic circulation, in a determined amount of time.
the equation for cardiac output
Cardiac output (CO) = heart rate * stroke volume
venous return
The amount of blood returned from the general circulation to the right atrium each minute should equal cardiac output in order for the cardiovascular system to maintain homeostasis.
Venous return = cardiac output (meaning: the heart pumps the blood that returns to it by the veins)
equation to estimate blood flow
Blood flow = (difference in pressure) / (resistance)
What determines resistance
arteriole diameter
vessels from highest to lowest pressure
aorta > arteries > arterioles > capillaries > venules > veins
What Is An Electrocardiograph (ECG)?
The ECG represents the sum of all action potentials in the cardiac muscle during each heartbeat. It is commonly used to evaluate the rhythm of the heart.
P wave
Represents depolarization of the atria.
PR interval
Interval from the first atrial depolarization to the beginning of the Q wave.
It decreases when heart rate increases, and vice versa.
A longer PR interval may indicate that conduction velocity through the AV node is slowed (e.g. heart block).
QRS complex
Represents depolarization of the ventricles. Note that there is no wave that represents repolarization of the atria; atrial repolarization is masked by the large QRS complex.
ST segment
This is the segment from the end of the S wave to the beginning of the T wave. It represents the period when the entire ventricles are depolarized.
T Wave
Represents repolarization of the ventricles.
QT interval
measured from the beginning of the Q wave to the end of the T wave. It represents the entire period of depolarization and repolarization of the ventricles.
Lub
Lub is the sound of the AV valves closing. “LUB” is called the first heart sound. The atrioventricular valves close when the ventricles begin to contract during systole.
other heart sounds
A third heart sound represents the rapid filling of the ventricles.
A fourth heart sound represents rapid ejection of blood from the atria into the ventricles.
The third and fourth heart sounds are not heard in small animals (dogs and cats), but they may be heard in large animals (horses and cows), or in animals with certain heart abnormalities.
Dub
the sound of the semilunar valves closing.
After the ventricles contract (systole) and blood is forced into the pulmonary artery and the aorta, the ventricles relax (diastole).
The semilunar valves prevent back flow of blood from the pulmonary artery and the aorta into the ventricles.
The semilunar valves close suddenly as the blood begins its backward flow toward the ventricle. This sudden closure of the semilunar valves yields the “DUB” or the second heart sound. A third heart sound represents the rapid filling of the ventricles.
what is a heart murmur
an abnormal heart sound caused by turbulent blood flow in the cardiovascular system. Abnormal heart sounds are often associated with conditions related to the valves.
systolic murmur
AV valve fails to close properly during systole because of valvular insufficiency
when the ventricle contracts blood will regurgitate back into the atria, causing turbulence and producing sound
Valvular regurgitation
occurs when heart valves do not close properly, and blood regurgitates (leaks) through the damaged valve. For example, bacterial infection can damage the mitral valve, causing regurgitation of blood back into the left atrium during systole.
Valvular stenosis
occurs when heart valves cannot open completely. For example, stenosis of the aortic valve is a congenital defect in some dog breeds. This makes it more difficult for the left ventricle to pump blood into the aorta because the opening of the valve is smaller.
diastolic murmur
if semilunar valves fail to close during diastole because of valvular insufficiency
blood which has just been ejected into circulation leaks back into the ventricle through the faulty valve
What Is A Heart Block?
any interruption of impulses transmitted through the heart.
atrioventricular (AV) block
results when there is a partial or complete interruption of impulse transmission from the atria to the ventricles
first degree heart block
P-R interval is prolonged
second degree heart block
there is an atrial P wave but no QRS-T. Dropped beats of the ventricles
Complete heart block
no impulses coming through from the atria
Bradycardia
decreased heart rate
what can abnormal electrocardiograms reflect
Dysfunction of the conduction system (heart block)
Enlargement of the heart
Damage to ventricular muscle
Tachycardia
increased heart rate
atrial tachycardia
the atria is beating so fast, that it begins depolarizing again before the ventricles finish repolarizing.
the ECG reveals that the P wave (which is due to atrial depolarization) is often superimposed on the normal T wave
