P Wave corresponds to:
QRS corresponds to:
T wave corresponds to:
2nd degree AV block:
is a disease of the electrical conduction system of the heart. It refers to a conduction blockbetween the atria and ventricles.
The presence of second-degree AV block is diagnosed when one or more (but not all) of the atrial impulses fail to conduct to the ventricles due to impaired conduction.
**for every ventricular contraction your having two atrial contractions hence (2:1)
First heart sound occurs as:
AV valves close which signifies beginning of systole
**contraction of heart muscle**
period of contraction of the ventricles of the heart that occurs between the first and second heart sounds. Systole causes the ejection of blood into the aorta and pulmonary trunk. Lasting usually 0.3 to 0.4 second, ventricular systole is introduced by a very brief period of contraction, followed by the ejection phase, during which 80 to 100 cubic centimetres of blood leave each ventricle. During systole, arterial blood pressurereaches its peak
**relaxation of heart muscle, blood returns through R atrial and R ventricle**
in the cardiac cycle, period of relaxation of the heart muscle, accompanied by the filling of the chambers with blood. Diastole is followed in the cardiac cycle by a period of contraction, or systole, of the heart muscle. Initially both atria and ventricles are in diastole, and there is a period of rapid filling of the ventricles followed by a brief atrial systole. At the same time, there is a corresponding decrease in arterial blood pressure to its minimum (diastolic blood pressure)
Second sound occurs when:
SL valves close at the beginning of ventricular diastole
High volume equals:
low blood pressure = receive blood
Low volume equals:
high blood pressure = can't receive blood
mid to late diastole
heart blood pressure is low as blood enters atria and flows in ventricles
AV valves are open then atrial systole occurs
rising ventricular pressure results in closing of AV valves
Isovolumetric contraction phase
Ventricular ejection phase opens semilunar valves
atrial contracts, ventricle contracts and then AV valve closes. Blood pools and pressure continues to build up and forces the pulmonary valve to open. Then blood is pumped out, the blood pumped out is the stroke volume.
Phases of the cardiac cycle:
1.) Ventricular filling- mid to late diastole (blood pressure low, blood enters atria and flow in ventricles)
AV valves are open then atrial systole occurs
2.) Ventricular systole- atria relax, rising ventricular pressure causes AV valve to close. Ventricular ejection phase opens semilunar valve
3.) Isovolumetric relaxation- early diastole. Ventricles relax, back flow of blood in aorta and pulmonary trunk close semilunar valve
What is inside of the pericardial cavity?
It contains a supply of serous fluid. The serous fluid that is found in this space is known as the pericardial fluid.
the surface of the pericardial membrane that is in direct contact with the heart. Also called epicardium.
The outer layer of the pericardium which is a conical sac of fibrous tissue that surrounds the heart and the roots of the great blood vessels.
Describe the layers of the heart:
Epicardium: a serous membrane that forms the innermost layer of the pericardium and the outer surface of the heart.
Endocardium: a thin serous membrane that lines the interior of the heart
Myocardium: the middle and thickest layer of the heart wall, composed of cardiacmuscle.
What are the first arteries to branch off the aorta?
R and L Common carotid artery, subclavian artery, R and L coronary artery
Major stages of Cardiac Cycle
The first stage, "early diastole," is when the semilunar valves close, AV valves open. Heart is relaxed.
The second stage, "atrial systole," is when the atrium contracts, and blood flows from atrium to the ventricle
The third stage, "isovolumic contraction" is when the ventricles begin to contract, the AV and semilunar valves close, and there is no change in volume.
The fourth stage, "ventricular ejection," is when the ventricles are contracting and emptying, and the semilunar valves are open.
During the fifth stage, "isovolumic relaxation time", pressure decreases, no blood enters the ventricles, the ventricles stop contracting and begin to relax, and the semilunar valves close due to the pressure of blood in the aorta.
Connects two atria in fetal heart
In the fetus, the ductus venous: shunts a portion of the left umbilical veinblood flow directly to the inferior vena cava. Thus, it allows oxygenated blood from the placenta to bypass the liver.
is a blood vessel connecting the pulmonary artery to the proximal descending aorta. It allows most of the blood from the right ventricle to bypass the fetus's fluid-filled non-functioning lungs. Upon closure at birth, it becomes the ligamentum arteriosum.
After leaving the coronary sinus, where does the blood go?
It delivers deoxygenated blood to the right atrium,
What is the chordae tendinae?
are strong, fibrous strings attached to the leaflets (or cusps) of the heart on the ventricular side; i.e., the lower chamber. These strings originate from small mounds of muscle tissue, the papillary muscles, which project inward from the walls of the ventricle.
EDV (end diastolic volume)
amount of blood collected in a ventricle during diastole
ESV (end systolic volume)
amount of blood remaining in a ventricle after contraction
SV (stroke volume)
EDV - ESV = SV
Why is caffeine a positive inotropic factor?
Caffeine increases cAMP which increases calcium in cell which equals a stronger cell contractions.
What are papillary muscles?
located in the ventricles of the heart. They attach to the cusps of the atrioventricular valves (also known as the mitral and tricuspid valves) via the chordae tendineae and contract to prevent inversion or prolapse of these valves on systole (or ventricular contraction).
Describe the structure of the valves of the heart:
Blood passes through a valve before leaving each chamber of the heart. The valves prevent the backward flow of blood. Valves are actually flaps (leaflets) that act as one-way inlets for blood coming into a ventricle and one-way outlets for blood leaving a ventricle. Normal valves have three flaps (leaflets), except the mitral valve, which only has two flaps.
What makes the heart valves open and close?
When the ventricles relax, atrial pressure exceeds ventricular pressure, the AV valvesare pushed open and blood flows into the ventricles. However, when the ventricles contract, ventricular pressure exceeds atrial pressure causing the AV valves to snap shut.
What is a functional syncytium?
Cardiac muscle cells are electrically connected by gap junctions and thus the entire myocardium behaves as as single unit.
**heart contracts as single unit where skeletal muscle can use motor unit to contract a portion of the muscle**
What is a pacemaker potential?
the pacemaker potential(also called the pacemaker current) is the slow, positive increase in voltage across the cell's membrane (the membrane potential) that occurs between the end of one action potential and the beginning of the next action potential.
Where does most of the calcium come from when the calcium concentration rises during a cardiac action potential?
The majority of calcium comes from Sarcoplasmic Reticulum (SR) but the calcium from the outside is what stimulates the massive amount to be released from S.R. = Ca2+ spark
Why does cardiac muscle have a long refractory period?
Cardiac muscle has a refractory period equal to the contraction. 250 milliseconds. If the heart stays contracted it will not receive blood.
Can the heart be tatananized?
NO. The cardiac muscle fiber absolute refractory is a long period of time (longer then skeletal muscles), so you cannot tetanize cardiac muscle fibers because it has to relax before it is able to contract again.
Stenosis of the mitral valve may cause an increase in pressure in the?
Mitral stenosis means that the valve cannot open enough. As a result, less blood flows to the body. The upper heart chamber swells as pressure builds up. Blood and fluid may then collect in the lung tissue (pulmonary edema), making it hard to breathe.
What is the refractory period of cardiac muscle?
a refractory period is a period of time during which an organ or cell is incapable of repeating a particular action
the amount of time it takes for an excitable membrane to be ready for a second stimulus once it returns to its resting state following an excitatio
What does KCL do to the heart?
decreased heart rate and cardiac arrest. Depolarizes membranes.
What does verapmil do?
Decreased heart rate. Calcium channel blocker. anitarythmic agent.
What does digitalis do?
Decreases heart rate. Strengthens contractions. Inhibits Na/K pump and enhances Ca++ entry.
The PR interval is the time in seconds from the beginning of the P wave to the beginning of the QRS complex. It corresponds to the time lag from the onset of atrial depolarization to the onset of ventricular depolarization. This time lag allows atrial systole to occur, filling the ventricles before ventricular systole
**heart enters diastole at end of PR interval**
The ST segment is the flat, isoelectric section of the ECG between the end of the S wave (the J point) and the beginning of the T wave. It represents the interval between ventricular depolarization and repolarization
The heart lies in the mediastinum? T/F
TRUE. is the central compartment of the thoracic cavitysurrounded by loose connective tissue, as an undelineated region that contains a group of structures within the thorax. The mediastinum contains the heart and its vessels,
If the stroke volume were 70ml/beat how much blood might be pumped in one day in a normal person? Cardiac Output =
CO = HR (75 beats/min) x SV (70ml/beat)
CO = 5250 ml/min = 5.25 L/min = 7560 L/day
What is angina pectoris?
is the medical term for chest pain or discomfort due to coronary heart disease. It occurs when the heart muscle doesn't get as much blood as it needs. This usually happens because one or more of the heart's arteries is narrowed or blocked, also called ischemia.
What is the dicrotic notch?
is the suddend drop in pressure after systolic contraction. This drop is caused by the flow back of blood in the arteries when the valve is still in closing up phase. Also cardio flow also contribute to this drop of pressure as some of the blood enter the cardial circuitry.
When do isovolumetric contractions occur?
early systole, during which the ventricles contract with no corresponding volume change. This short-lasting event takes place when both the AV valve and SL valve are closed.
What happens to the heart when the vagus nerve is cut?
increased heart rate by about 25 beats per minute.
What is angina?
a condition marked by severe pain in the chest, often also spreading to the shoulders, arms, and neck, caused by an inadequate blood supply to the heart.
What is congestive heart failure?
a weakness of the heart that leads to a buildup of fluid in the lungs and surrounding body tissues.
What is dilated cardiomyopathy?
Cause is unknown.
Stretched and flabby ventricles.
May be caused of Congestive heart failure or drugs.
Cardiac calcium increases.