How Much Do You Know About Cardiac Physiology? Trivia Quiz

The SA node is known as the cardiac pacemaker because it is responsible for initiating the electrical impulses that regulate the heart's rhythm. It is located in the right atrium of the heart and generates electrical signals that cause the atria to contract. These signals then travel to the AV node, Bundle of His, and Purkinje system, which help to coordinate the contraction of the ventricles. Therefore, the SA node is the correct answer as it plays a crucial role in regulating the heart's rhythm.

The Purkinje fibers/system are specialized cardiac muscle fibers that are responsible for transmitting electrical impulses throughout the ventricles of the heart. These fibers are located on the inner ventricular wall, allowing for efficient and coordinated contraction of the ventricles.

The SA node, also known as the sinoatrial node, is responsible for initiating the electrical signals that regulate the heart's rhythm. It acts as the natural pacemaker of the heart. The SA node is influenced by various factors, including body temperature. When the body temperature is higher, the SA node tends to increase its firing rate, resulting in a higher heart rate. Additionally, the SA node is composed of specialized cells called P cells. Therefore, both statements B and C are true, as higher body temperature leads to a higher heart rate and the SA node is composed of P cells.

aV1 is not part of a normal 12-lead ECG. The standard 12-lead ECG includes leads I, II, III, aVR, aVL, aVF, V1, V2, V3, V4, V5, and V6. Each lead provides a different view of the heart's electrical activity. However, aV1 is not one of the standard leads used in a 12-lead ECG.

Increase in cAMP (cyclic adenosine monophosphate) and Ca++ (calcium) L channel opening suggests that NE (norepinephrine) from sympathetic nerve endings activates the B2 adrenergic receptors. Activation of B2 adrenergic receptors leads to an increase in intracellular cAMP levels, which in turn activates protein kinase A. Protein kinase A phosphorylates and activates Ca++ L channels, leading to an increase in calcium influx into the cell. This ultimately results in increased contractility and heart rate, as well as smooth muscle relaxation.

Bradycardia refers to a slower than normal heart rate. Vagal stimulation refers to the activation of the vagus nerve, which is responsible for slowing down the heart rate. Therefore, it is correct to say that bradycardia is a slowing due to vagal stimulation.

The given answer, "ALL OF THE ABOVE," is correct because all of the statements mentioned in the options are false about an ECG. An ECG does not represent the algebraic product of the action potentials, it is not based on Einstein's triangle, and bipolar leads are not a newer technology than unipolar leads. Therefore, all of the statements are false.

When Ach is released at the SA node, it binds with M2 receptors and leads to hyperpolarization. This means that the cell membrane becomes more negative, which decreases the likelihood of the SA node firing an action potential and slows down the heart rate. M2 receptors are inhibitory in nature and their activation by Ach leads to the opening of potassium channels, causing an efflux of potassium ions and hyperpolarizing the cell. This ultimately results in a decrease in heart rate.

The statement "A, B and D" is false because the correct options are 1st deg - not all impulses reach ventricle, 1st deg - PR interval shortened, and 3rd deg - ventricles beat faster than atria. This means that in 1st degree heart block, all impulses do reach the ventricle, the PR interval is prolonged rather than shortened, and in 3rd degree heart block, the ventricles beat slower than the atria, not faster.

The correct answer is "All of the above." The SA node is composed of large round cells, has many organelles, and develops from the embryonic right side. Additionally, the cells in the SA node are connected by gap junctions.

The AV node does not increase left ventricle (LV) contraction. Instead, it delays the activity of the SA node so that the atria can empty before the ventricles contract. The AV node also relays signals from the SA node to the AV bundles. It is located in the interatrial septum. Therefore, the statement "Increases LV contraction" is not true of the AV node.

Pacemaker potentials are the spontaneous depolarizations that occur in certain cells, such as cardiac pacemaker cells, that generate rhythmic electrical activity. These depolarizations are produced by the opening of Ca++ L channels, which allow the influx of calcium ions into the cell. This influx of calcium ions triggers the impulse, leading to the generation of an action potential and subsequent contraction of the cardiac muscle. Therefore, the correct answer is that Ca++ L channels produce the impulse.

The Bundle of His is a specialized bundle of cardiac muscle fibers located in the interventricular septum of the heart. It is responsible for conducting electrical signals from the atrioventricular node to the ventricles, allowing for coordinated contraction of the ventricles. The given options do not accurately describe the function or location of the Bundle of His, so the correct answer is "none of the above".

M2 receptor activation decreases intracellular cAMP and decreases Ca++ channel opening. This means that when the M2 receptor is activated, it leads to a decrease in the levels of cyclic adenosine monophosphate (cAMP) inside the cell. Additionally, it also results in a decrease in the opening of calcium (Ca++) channels. This suggests that M2 receptor activation has an inhibitory effect on these cellular processes, reducing the levels of cAMP and the opening of Ca++ channels.

The given answer states that none of the options provided are true. This implies that the statements mentioned in options A, B, and C are all incorrect. Therefore, the sympathetic nervous system does not decrease frequency while keeping potential the same, nor does it increase frequency while changing potential. Additionally, the vagal nervous system does not increase both frequency and potential.