Paramedic-cardiology 1

The correct answer is Purkinje fibers. Purkinje fibers are thousands of specialized cardiac muscle fibers that are located in the ventricles of the heart. They are responsible for the rapid conduction of electrical impulses, allowing for coordinated and efficient contraction of the ventricles. This ensures that blood is effectively pumped out of the heart to the rest of the body. The other options mentioned (bundle branches, internodal pathways, and cardiac myocytes) are also components of the cardiac conduction system, but they do not specifically represent the fibrils distributed throughout the ventricles like Purkinje fibers do.

Stimulation of alpha and beta receptors affects the heart, lungs, and blood vessels. Alpha receptors are found in the smooth muscles of blood vessels, and their stimulation causes vasoconstriction, leading to increased blood pressure. Beta receptors are found in the heart, lungs, and blood vessels. Stimulation of beta-1 receptors in the heart increases heart rate and contractility, while stimulation of beta-2 receptors in the lungs causes bronchodilation. Overall, the stimulation of both alpha and beta receptors affects the cardiovascular system by regulating blood pressure, heart rate, and lung function.

Cardiac output refers to the amount of blood pumped by the heart per minute. It is influenced by two main factors: heart rate and stroke volume. Heart rate refers to the number of times the heart beats per minute, while stroke volume refers to the volume of blood pumped by the heart with each beat. The combination of these two factors determines the overall cardiac output. Therefore, the correct answer is heart rate and/or stroke volume, as both factors play a significant role in influencing cardiac output.

Atropine and epinephrine can cause an increase in heart rate. Atropine is an anticholinergic drug that blocks the action of acetylcholine, a neurotransmitter that slows down the heart rate. By blocking this action, atropine increases heart rate. Epinephrine, also known as adrenaline, is a hormone that stimulates the sympathetic nervous system. It increases heart rate by binding to beta-adrenergic receptors in the heart, leading to an increase in the strength and rate of contractions. Therefore, both atropine and epinephrine can cause an increase in heart rate.

The correct answer is epicardium, myocardium, and endocardium. The epicardium is the outermost layer of the heart, also known as the visceral pericardium. It is a protective layer that covers the heart and contains blood vessels and adipose tissue. The myocardium is the middle layer and is composed of cardiac muscle tissue. It is responsible for the contraction of the heart and pumping of blood. The endocardium is the innermost layer and is a thin, smooth layer that lines the chambers of the heart and covers the heart valves. It helps to prevent blood clotting and provides a smooth surface for blood flow.

The QRS complex represents ventricular depolarization. It is a waveform on an ECG that represents the electrical activity associated with the contraction of the ventricles. The QRS complex consists of three main components: the Q wave, the R wave, and the S wave. This waveform is important in diagnosing and evaluating various cardiac conditions. The T waves represent ventricular repolarization, the ST segment represents the period between ventricular depolarization and repolarization, and the U wave is a small waveform that can sometimes be seen after the T wave and represents repolarization of the papillary muscles.

When auscultating the lungs of a patient with early pulmonary edema, crackles in the bases of the lungs at the end of inspiration are most likely to be heard. Pulmonary edema is the accumulation of fluid in the lungs, and crackles are abnormal lung sounds caused by the movement of air through fluid-filled airways or collapsed airways opening up. The crackles are typically heard at the bases of the lungs because fluid tends to accumulate in the dependent areas.

Drugs that have alpha or beta sympathetic properties are called sympathomimetics. These drugs mimic the effects of the sympathetic nervous system, which is responsible for the "fight or flight" response. By activating alpha or beta receptors, sympathomimetics can increase heart rate, blood pressure, and bronchodilation. They are commonly used to treat conditions such as asthma, hypotension, and cardiac arrest.

The correct answer is atrial depolarization. The P wave on an electrocardiogram (ECG) represents the electrical depolarization of the atria, which leads to their contraction. It is the first wave in the ECG and indicates the initiation of the cardiac cycle. The SA node, also known as the sinoatrial node, is responsible for initiating the electrical impulses that result in atrial depolarization. Therefore, the P wave represents the atrial depolarization that is initiated by the SA nodal discharge.

Albuterol possesses beta-2 specific properties. Beta-2 specific drugs primarily target the beta-2 adrenergic receptors found in the smooth muscles of the bronchioles, leading to bronchodilation. Albuterol is a commonly used bronchodilator that acts selectively on these receptors, relaxing the smooth muscles and improving airflow in conditions like asthma and chronic obstructive pulmonary disease (COPD). Dopamine, levophed, and epinephrine do not possess beta-2 specific properties and have different mechanisms of action.

During diastole, the ventricles of the heart relax and fill with blood. This is the phase of the cardiac cycle when the atrioventricular valves are open and blood flows from the atria into the ventricles. Approximately 80% of ventricular filling occurs during diastole because this is when the ventricles have the most time to fill with blood before the next contraction (systole) occurs.

The electrical impulse is slightly delayed at the AV node to allow time for the atria to contract and empty their blood into the ventricles. This delay ensures that the ventricles are filled with blood before they contract, maximizing the efficiency of the heart's pumping action.

Administering a drug that possesses a positive chronotropic effect means that it will increase the heart rate. This means that the drug will directly affect the heart rate, not stroke volume, blood pressure, or cardiac output.

Automaticity refers to the ability of the heart to generate its own electrical impulses without the need for stimulation from nerves. This means that the heart can initiate and regulate its own electrical activity, allowing it to maintain a regular heartbeat even in the absence of external signals. This is an important characteristic of the heart's electrical system, as it ensures that the heart can continue to beat rhythmically and effectively without relying on external factors.

The left side of the heart drives blood out of the heart against the relatively high resistance of the systemic circulation. This means that the left side of the heart pumps oxygenated blood to the rest of the body, which requires more force due to the resistance in the blood vessels throughout the body. In contrast, the right side of the heart pumps deoxygenated blood to the lungs, which has a lower resistance in the pulmonary circulation.

The correct answer is "is composed of the AV node and the bundle of His." The atrioventricular junction refers to the area in the heart where electrical signals are transmitted from the atria to the ventricles. It includes both the AV node and the bundle of His. The AV node is responsible for delaying the electrical signal before it is transmitted to the ventricles, allowing for proper coordination of atrial and ventricular contractions. The bundle of His then carries the signal down the septum of the heart, allowing for synchronized contraction of the ventricles.

The sinoatrial node is often referred to as the natural pacemaker of the heart. It is responsible for initiating the electrical signals that regulate the heartbeat. The statement "will normally outpace any slower conduction tissue" means that the sinoatrial node has the ability to generate electrical impulses at a faster rate than any other tissue in the heart. This ensures that the heart beats in a coordinated and efficient manner, with the sinoatrial node setting the pace for the rest of the heart.

The tunica media is the correct answer because it is the layer of the blood vessel that is made up of elastic fibers and muscle. This layer provides strength and contractility to the blood vessel, allowing it to expand and contract as needed to regulate blood flow. The tunica intima is the innermost layer of the blood vessel, consisting of endothelial cells, while the tunica adventitia is the outermost layer, composed of connective tissue. The arterial lumen refers to the central opening inside the blood vessel.

Contractility refers to the ability of the heart to vary the force of its contraction without stretching. This means that the heart can adjust the strength of its contractions to meet the demands of the body, without needing to change its size or stretch. Contractility is an important factor in regulating cardiac output and maintaining proper circulation throughout the body.

The brief pause between the P wave and the QRS complex represents a momentary conduction delay at the AV junction. This delay allows for the atria to fully contract and empty their blood into the ventricles before the ventricles contract. It is necessary to ensure efficient and coordinated contraction of the heart chambers.

Changes in cardiac contractility may be induced by medications that have a positive or negative inotropic effect. Inotropic agents directly affect the force of myocardial contraction. Positive inotropic agents increase contractility, while negative inotropic agents decrease contractility. These medications can be used to treat conditions such as heart failure or arrhythmias, where there is a need to enhance or reduce the strength of cardiac contractions. Therefore, the term "inotropic" is the correct answer as it specifically refers to the effect on cardiac contractility.

Stimulation of alpha receptors causes vasoconstriction. Alpha receptors are found in smooth muscle cells of blood vessels and when activated, they cause the contraction of these muscles, leading to a decrease in the diameter of the blood vessels. This results in increased vascular resistance and a decrease in blood flow. Therefore, the correct answer is alpha receptors.

A pure alpha agent refers to a medication or substance that specifically targets alpha receptors in the body. Alpha receptors are found primarily in blood vessels, and when stimulated, they cause vasoconstriction, which is the narrowing of blood vessels. This leads to an increase in blood pressure. Therefore, a pure alpha agent would cause marked vasoconstriction, explaining why the correct answer is "causes marked vasoconstriction."

Sympathetic nervous stimulation causes the dilation of the bronchioles. This is because the sympathetic nervous system is responsible for the "fight or flight" response, which prepares the body for intense physical activity. Dilation of the bronchioles allows for increased airflow to the lungs, enabling more oxygen to be delivered to the muscles. This physiological effect helps to enhance performance and increase oxygenation during times of stress or exercise.

Veins are more likely to distend when exposed to back pressure. This is because veins have thinner walls and less smooth muscle compared to arteries. When there is an increase in pressure within the veins, such as when there is a blockage or when blood flow is impeded, the veins are more likely to stretch and expand. This distension allows the veins to accommodate the increased volume of blood and helps to prevent damage to the vessel walls. In contrast, arteries have thicker walls and more smooth muscle, allowing them to withstand higher pressures without distending.

The right side of the heart is a low pressure pump because it receives deoxygenated blood from the body through the venae cavae and pumps it to the lungs for oxygenation. This is in contrast to the left side of the heart, which is a high pressure pump that receives oxygenated blood from the lungs and pumps it to the rest of the body. The right side of the heart has thinner walls and less muscle mass compared to the left side, allowing it to pump blood at a lower pressure.

Stimulation of the parasympathetic nervous system causes various effects on the body, including negative inotropy (reduced force of heart contractions), increased salivation, and negative chronotropy (slowed heart rate). However, dilation of the pupils is not a direct effect of parasympathetic stimulation. Instead, pupil constriction (miosis) is associated with parasympathetic activation. Therefore, the correct answer is dilation of the pupils.

The atrioventricular valve prevents the backflow of blood during ventricular contraction. This valve is located between the atria and ventricles and closes when the ventricles contract, preventing blood from flowing back into the atria. This ensures that blood is efficiently pumped out of the heart and prevents any regurgitation. The aortic valve, semilunar valve, and pulmonic valve are responsible for preventing backflow of blood in other parts of the heart, but they are not specifically involved in preventing backflow during ventricular contraction.

Atrial kick refers to the contraction of the atria against closed valves, specifically the mitral valve, during ventricular diastole. This contraction helps to push an additional amount of blood into the ventricles, contributing to ventricular filling. It is estimated that the atrial kick accounts for approximately 20% of the total ventricular filling during each cardiac cycle.

The effect on the velocity of electrical conduction is referred to as the dromotropic effect.

Cardiac output refers to the amount of blood that is pumped out by either ventricle per minute. It is a measure of the overall effectiveness of the heart in delivering oxygenated blood to the body's tissues. It is calculated by multiplying the stroke volume (the amount of blood ejected by each ventricle with each heartbeat) by the heart rate (the number of times the heart beats per minute). Therefore, cardiac output is a crucial parameter in assessing the heart's ability to meet the body's demands for oxygen and nutrients.

A healthy heart has the ability to easily increase its stroke volume by 50%. This means that when the body requires more blood to be pumped, the heart can efficiently adjust and pump out a larger volume of blood per beat. This flexibility allows the heart to meet the increased demands of the body during exercise or times of stress.