What Do You Know About Cardiac Physiology? Trivia Quiz

Capillaries have the highest total cross-sectional area in the body. This is because capillaries are the smallest blood vessels and their large number and small size allow for a greater total area. Capillaries are responsible for the exchange of oxygen, nutrients, and waste products between the blood and tissues, and their high surface area facilitates efficient diffusion. Arteries, arterioles, venules, and veins have progressively larger diameters compared to capillaries, resulting in lower total cross-sectional areas.

Myocardial contractility refers to the ability of the heart muscle to contract and pump blood effectively. Calcium ions (Ca2+) play a crucial role in regulating this process. When calcium ions enter the myocardial cells, they bind to specific proteins, triggering the release of stored calcium ions from the sarcoplasmic reticulum. This increase in intracellular calcium concentration leads to stronger and more forceful contractions of the heart muscle. Therefore, the intracellular concentration of Ca2+ is best correlated with myocardial contractility.

Propranolol is a beta-blocker medication that works by blocking the effects of adrenaline on the beta receptors in the heart. By doing so, it decreases the heart rate, which means that the heart beats at a slower pace. This can be beneficial in conditions such as hypertension, angina, and certain arrhythmias, where a slower heart rate can help reduce the workload on the heart and improve overall cardiac function.

When the radius of the resistance vessels is increased, the capillary blood flow is increased. Resistance vessels are responsible for regulating blood flow by constricting or dilating their walls. When the radius of these vessels is increased, it allows for a greater volume of blood to flow through the capillaries, leading to an increase in capillary blood flow. This can result in improved oxygen and nutrient delivery to tissues and organs.

Standing quietly in the same position for 1 hour can lead to a decrease in central venous pressure. When an individual stands, blood pools in the lower extremities due to gravity, resulting in decreased blood return to the heart. This decreases the pressure in the central veins, which are the veins that return blood to the heart.

During isotonic exercise, the muscles contract and relax, causing movement of the joints. This type of exercise involves a constant load and results in a change in muscle length. Isotonic exercise typically leads to an increase in heart rate, stroke volume, and systolic blood pressure as the body works to supply oxygen and nutrients to the working muscles. However, total peripheral resistance, which refers to the resistance of blood flow in the peripheral blood vessels, is not increased during isotonic exercise. Instead, it may decrease due to the dilation of blood vessels in the working muscles to facilitate increased blood flow.

A drug that inhibits NO synthase would be expected to raise blood pressure. Nitric oxide (NO) is a potent vasodilator, meaning it relaxes and widens blood vessels, leading to a decrease in blood pressure. Inhibiting NO synthase would decrease the production of NO, resulting in vasoconstriction and an increase in blood pressure.

An increased size of the heart will cause an increase in myocardial O2 consumption because a larger heart requires more oxygen to function properly. This is because a larger heart has a greater mass and therefore needs more oxygen to supply the increased number of cells. Additionally, a larger heart may also indicate the presence of conditions such as hypertrophy or heart failure, which can further increase myocardial O2 consumption.

When there is an acute decrease in arterial blood pressure, the body initiates compensatory changes to restore blood pressure to normal levels. One of these changes is a decreased firing rate of the carotid sinus nerve. The carotid sinus is a specialized area in the carotid artery that senses changes in blood pressure. When blood pressure decreases, the carotid sinus nerve sends signals to the brain, which then activates the sympathetic nervous system. This leads to increased sympathetic outflow to the heart, resulting in increased heart rate and contractility. Therefore, a decreased firing rate of the carotid sinus nerve would be a compensatory change in response to decreased arterial blood pressure.

Gap junctions are the correct answer because they are specialized protein channels that connect adjacent cardiac muscle cells (myocytes). These channels allow for the direct passage of ions and small molecules, enabling the spread of action potentials and coordinated contraction of the heart. Gap junctions play a crucial role in maintaining the electrical and mechanical coupling between cardiac cells, ensuring efficient and synchronized contraction of the heart muscle. T tubules are invaginations of the cell membrane that help transmit the action potential to the interior of the muscle cell. Sarcoplasmic reticulum (SR) is a network of membranous sacs that stores and releases calcium ions for muscle contraction. Intercalated disks are specialized junctions that connect cardiac muscle cells and contain gap junctions along with desmosomes, which provide mechanical strength. Mitochondria are organelles responsible for producing energy in the form of ATP.

When the viscosity of the blood is increased, the resistance to blood flow also increases. This leads to an increase in mean blood pressure. As the blood becomes thicker and more resistant to flow, the heart has to work harder to pump the blood through the vessels, resulting in higher blood pressure.

Carbon dioxide (CO2) regulates blood flow to the brain. When CO2 levels in the blood increase, it causes blood vessels in the brain to dilate, increasing blood flow to the brain. This is known as cerebral vasodilation. The increased blood flow ensures that the brain receives enough oxygen and nutrients for proper functioning. Conversely, when CO2 levels decrease, blood vessels in the brain constrict, reducing blood flow. This regulation of blood flow helps maintain the balance of gases and nutrients in the brain and ensures its optimal performance.

Acetylcholine (ACh) has a negative inotropic effect on the heart. ACh is released by the parasympathetic nervous system and acts on muscarinic receptors in the heart. Activation of these receptors leads to a decrease in heart rate and a decrease in the force of contraction (inotropic effect) of the heart. This is in contrast to sympathetic stimulation, norepinephrine, and increased heart rate, which all have positive inotropic effects on the heart. Cardiac glycosides, such as digoxin, also have a positive inotropic effect on the heart.

During systole, the left ventricle contracts and pumps oxygenated blood into the aorta, resulting in an increase in pressure. However, the pressure differential between the left ventricle and the aorta is least during systole because the aortic valve opens, allowing blood to flow freely from the left ventricle into the aorta. This equalizes the pressure between the two chambers, resulting in the least pressure differential during this phase.

NOTE--- propranolol is a nonselective beta-blocker so it blocks both B1 & B2 but B1 are found in heart so it is the better choice here.

Massaging the foot can increase lymph flow from the foot because massage helps to stimulate the lymphatic system. The rhythmic pressure and movement applied during a massage can assist in moving the lymph fluid through the lymphatic vessels, promoting better circulation and drainage. This can help to reduce swelling and improve overall lymph flow in the foot.

After a hemorrhage, the body needs to conserve sodium to maintain fluid balance. Aldosterone is a hormone that is released or secreted in response to low blood volume or low blood pressure, such as after a hemorrhage. Aldosterone acts on the kidneys to increase the reabsorption of sodium, which helps to retain water and increase blood volume. Therefore, aldosterone is the correct answer as it causes an increase in renal Na+ reabsorption after a hemorrhage.

The velocity of blood flow is higher in the veins than in the venules because the veins have larger lumens and lower resistance compared to the venules. The veins also have valves that prevent backflow of blood, allowing for more efficient blood flow. In contrast, the venules are smaller in diameter and have higher resistance, resulting in slower blood flow.

Vasopressin does not dilate arterioles in the skin. Vasopressin, also known as antidiuretic hormone (ADH), is responsible for increasing water reabsorption in the kidneys, leading to vasoconstriction and increased blood pressure. It does not have a direct effect on the dilation of arterioles in the skin. Increased body temperature, epinephrine, bradykinin, and substance P can all cause vasodilation in the skin by relaxing the smooth muscle in the arterioles and increasing blood flow.

The liver has the most permeable capillaries compared to the other organs listed. This is because the liver plays a crucial role in detoxification and metabolism, and it needs to receive a large amount of blood flow to perform these functions effectively. The permeable capillaries in the liver allow for the exchange of nutrients, waste products, and toxins between the blood and liver cells. This high level of permeability ensures efficient filtration and processing of substances in the liver.

As blood passes through the systemic capillaries, the hemoglobin dissociation curve does not shift to the left. The hemoglobin dissociation curve represents the relationship between the partial pressure of oxygen and the percent saturation of hemoglobin. A shift to the left indicates an increase in hemoglobin's affinity for oxygen, meaning that it binds more tightly to oxygen at a given partial pressure. However, as blood passes through the systemic capillaries, there is a decrease in oxygen saturation due to oxygen being delivered to tissues. Therefore, the hemoglobin dissociation curve does not shift to the left in this situation.

Vasopressin is a hormone that helps regulate water balance in the body by increasing water reabsorption in the kidneys. It is released in response to low blood volume or increased osmolarity. Decreased pressure in the right atrium can be a sign of low blood volume, which would trigger the release of vasopressin to help conserve water and increase blood volume.

The kidneys have the greatest blood flow per 100 g of tissue compared to the other organs listed. The kidneys are responsible for filtering waste products from the blood and regulating fluid balance in the body. They receive a high volume of blood flow to perform these functions efficiently.

Catecholamines acting on a-adrenergic receptors constrict coronary arteries by a direct action on these blood vessels. This means that when catecholamines bind to a-adrenergic receptors in the coronary arteries, it causes the arteries to narrow or constrict. This constriction reduces the blood flow to the heart muscle, which can be beneficial in certain situations such as during exercise or stress when the heart needs more oxygen and nutrients. However, excessive or prolonged constriction of the coronary arteries can lead to inadequate blood supply to the heart, which can result in chest pain or even a heart attack.

During the reduced ventricular ejection phase of the cardiac cycle, the aortic pressure is highest. This is because during this phase, the ventricles have finished contracting and are starting to relax, causing the aortic valve to close. As a result, the blood that was ejected from the ventricles into the aorta is now trapped between the closed aortic valve and the contracting ventricles, leading to an increase in pressure within the aorta.