Lab 8 - Cardiac Cycle

Normal PR value?

0.12-0.20

Normal QT Value?

0.30-0.40

At what point during the cardiac cycle do the semilunar valves slam shut?

Following ejection or the onset of isovolumic relaxation (onset of ventricular diastole)

Which of the following correctly describes the PR interval?

From the beginning of the P wave to the beginning of the QRS complex

Define atriventricular valves

Helps with closing of the valves. prevent backflow from the ventricles into the atria during ventricular systole

What is isovolumic relaxation?

Helps with opening of valves. Blood must flow past the open atrioventricular valves in order to fill the ventricles during ventricular diastole. But there is too little pressure in atria and too much in ventricles for the AV valves to open... Isovolumic relaxation - Period during which the pressure within the atria rise and the pressure within the ventricles is declining. During this time, all valves remain close. Once the pressure is high enough in the atria, the atroventricular valves open and filling begins.

What is isovolumic contraction?

Helps with opening of valves. During ventricular systole, blood must be pumped out of the heart past the semilunar valves into the elastic arteries. But pressure within ventricles is high enough to close AV valves, but not enough to push semilunar valves open....Isovolumic contraction = during which pressure increases within the ventricles, while all valves remain closed. Once the pressure is sufficient to push the semilunar valves open, ejection of blood from the heart begins.

What creates the first heart sound?

When ventricular systole begins, the atrioventricular valves slam shut creating the first heart sound

isovolumic relaxation ends when which valves open:

atrioventricular valves

when does the second heart sound occur and which valves are involved:

beginning of vent. diastole; semilunar valves

What is a P Wave

corresponds to depolarization of the atria

Which of the above indicates that permanent damage has been incurred by some heart muscle cells?

deep Q wave

Which of the above indicates that heart muscle cells are not receiving enough oxygen, and are, therefore, at great risk of injury?

elevated ST segment

What suggests ischemia

elevated ST segment. Often accompanied by an inverted T wave

Define semilunar valves

helps with closing of the valves. Prevent backflow of blood from the elastic arteries into the ventricles during ventricular diastole

What does a short QT interval suggest

hypercalcemia

What does a long QT interval suggest

hypocalcemia

Which of the above would be considered inconsequential if it occurred alone (i.e. in the absence of other abnormalities)?

inverted T wave

What is the QRS complex

is the product of ventricular depolarization

What is ischemia

lack of adequate oxygen supply

What is infarction

previous, permanent damage to heart muscles

What is a QT interval

the time from the beginning of the Q wave through the end of the T wave

active filling of the ventricles occurs during which stage of atrial activity:

systole

Describe when the atrioventricular valves open and close? What sound(s) is(are) associated with these events?

"As the atrioventricular valves (as the name implies) separate the atria from the ventricles they must open to allow blood to flow from the atria into the ventricles. Therefore, it is expected that these valves will be open when the ventricles are relaxed. However, when the ventricles first relax, the pressure in the chambers is too high to allow filling. The ventricles must first pass through isovolumic relaxation, during which pressure is declining, before filling can begin. Thus, the atrioventricular valves will open immediately after the end of isovolumic relaxation to allow ventricular filling. Again noting the location of these valves, it is expected that they will close to prevent backflow of blood from the ventricles into the atria. The possibility of such a backflow arises when the ventricles contract. Therefore, these valve close at the beginning of ventricular systole. This closing produces the first heart sound. "

Describe when the semilunar valves open and close? What sound(s) is(are) associated with these events?

"As the semilunar valves separate the elastic arteries from the ventricles, they must open in order to allow blood to be pumped from the ventricles. During ventricular systole the ventricles build pressure without pumping blood from the heart during isovolumic contraction and then begin to pump blood into the arteries during ejection. The semilunar valves, must, therefore, open at the end of isovolumic contraction/beginning of ejection. Because the semilunar valves prevent backflow of blood from the elastic arteries into the ventricles, they close at the beginning of ventricular diastole (when the risk of backflow first arises). Closing of the semilunar valves produces the second heart sound. "

"For the anatomical feature, name the major anatomical structures on the right side of the heart and their counterparts on the left side. Anatomical feature: valve between the ventricle and the elastic artery"

"Right heart: pulmonary semilunar valve Left heart: aortic semilunar valve"

"For the anatomical feature, name the major anatomical structures on the right side of the heart and their counterparts on the left side. Anatomical feature: elastic artery"

"Right heart: pulmonary trunk Left heart: aortic arch"

"For the anatomical feature, name the major anatomical structures on the right side of the heart and their counterparts on the left side. Anatomical feature: Veins delivering blood to the atrium"

"Right heart: superior and inferior vena cava Left heart: left and right pulmonary veins"

"For the anatomical feature, name the major anatomical structures on the right side of the heart and their counterparts on the left side. Anatomical feature: valve between the atrium and the ventricle"

"Right heart: tricuspid atrioventricular valve Left heart: bicuspid atrioventricular valve (mitral valve)"

when does the first heart sound occur and which valves are involved:

"beginning of vent. systole; atrioventricular valves "

A long QT interval would indicate which of the following?

A calcium imbalance

In the diagram below, A indicates:

Atrial diastole and ventricular diastole, the heart is completely at rest

In the diagram below, E indicates:

Atrial diastole and ventricular systole, the atria are filling with blood

Which EKG lead is used in this laboratory?

Lead II

What is the left heart features and function?

Left heart has left atrium and left venticle. Pumps blood to the systemic cirulation

The ST segment on the ECG is measured from the beginning of the wave to the beginning of the T wave. A normal ST segment is 0.12 - 0.20 seconds. In your laboratory subject, the ST segment is determined to be 0.26 seconds. This indicates:

Myocardial infarction (heart attack)

What is the normal value for the PR interval? Complete the following: PR interval is measured from the _________ of the P wave to the beginning of the ______ .

PR interval is measured from the ___beginning___ of the P wave to the beginning of the _QRS Complex___

The blood enters the atria from the veins and passes the atrioventricular valves both ______ (while both the atria and the ventricles are relaxed) and _____ (during atrial systole) as it flows into the ventricles.

Passively ; actively

At what point in the cardiac cycle do the semilunar valves (aortic and pulmonary) close and which sound is associated with this?

Right after ejection, causing the second heart sound

What is the right heart features and function?

Right heart has right atrium and right ventricle. Pumps blood to the lungs

What does the ECG measure?

The ECG measures the voltage changes across the body that result from the action potential activity of the heart.

In the diagram below, the arrow indicates:

The Period of Isovolumetric Relaxation

The atrioventricular valves close at which of the following points in the cardiac cycle?

The beginning of ventricular systole

The semilunar valves open at which of the following points in the cardiac cycle?

The end of the isovolumic contraction

What suggests infarction

abnormally deep Q waves

blood enters atria from veins throughout:

atrial diastole

blood is pumped past the atrioventricular valves during:

atrial systole

blood is pumped past the semilunar valves during:

ejection

What is a AV nodal block

extended PR interval. Abnormally long delay of the action potential at the AV node

Which of the above is also called a first degree AV nodal block?

long PR interval

Which of the above indicates hypocalcaemia?

long QT interval

describe the state of the atria during passive filling of the ventricles:

relaxed/diastole

isovolumic contraction ends when which valves open:

semilunar valves

Which of the above indicates hypercalcemia?

short QT interval

What is an extended PR interval mean

sign of an abnormally long delay of the action potential at the atrioventricular node. Such a delay is known as a first degree AV nodal block

What is the T wave

the result of ventricular repolarization

What is a PR interval

time between the beginning of the P wave and the beginning of the QRS complex

What creates the second heart sound?

when ventricular diastole begins, the semilunar valves slam shut creating the second heart sound