Cardiac and Lymphatic Systems FSQ

Coarctation of the aorta, a congenital defect in which the aorta is narrowed, would cause which of the following if left untreated? A. Decreased pressure in the lower limbs B. Decreased pressure in the pulmonic circuit C. Increased pulse pressure D. Decreased venous valve function

A. Decreased pressure in the lower limbs Explanation: Since the aorta is the first vessel to receive fully pressurized blood in the systemic circuit, if it was narrowed, blood flow (and thus pressure) would be reduced to the rest of the body. The narrowed vessel would have an increased resistance, backing up blood and increasing pressures prior to that vessel (such as the pulmonic circuit). Pulse pressure is the difference between the systolic pressure and the diastolic pressure, and since all systemic blood pressure is decreased, pulse pressure would also be decreased. There is no reason to assume an impairment of the venous valves.

Damage to which chamber of the heart would be most evident in the measurement of systolic blood pressure by a standard sphygmomanometer? A. Left ventricle B. Right atrium C. Left atrium D. Right ventricle

A. Left ventricle Explanation: Systolic blood pressure is measured during the contraction of the ventricles, and diastolic blood pressure is measured during relaxation. The left side of the heart is responsible for systemic circulation while the right side is responsible for pulmonic circulation, and specifically, the left ventricle provides the force for blood to be propelled from the heart into the systemic circulatory system. If this chamber were damaged and not providing the same amount of force, the difference would be seen in standard systolic blood pressure measurements. Changes to other chambers of the heart would not have as significant an impact.

During ventricular contraction, which of the following valves is open? A. The valve between the left ventricle and the aorta B. The valve between the left ventricle and the pulmonary artery C. The valve between the left ventricle and right ventricle D. The valve between the left ventricle and left atrium Your Answer

A. The valve between the left ventricle and the aorta Explanation: When the ventricles contract, the blood from the left ventricle is forced through the aortic semilunar valve and into the aorta, and the blood from the right ventricle is forced through the pulmonary semilunar valve and into the pulmonary vasculature. In a normal heart, there is no valve between the right and left ventricles or between the left ventricle and the pulmonary artery. While there is a valve between the left ventricle and left atrium, this bicuspid (mitral) valve is closed during ventricular contraction (systole) to prevent the back flow of blood into the atrium.

Atropine is a medication sometimes used to treat symptomatic bradycardia (slow heart rate). What is the most likely mechanism of action of atropine? A. Partial inhibition of slow sodium leak channels B. Acetylcholine antagonist C. Prevent Ca2+ binding to troponin in cardiac sarcomeres D. Acetylcholine agonist

B. Acetylcholine antagonist Explanation: Drugs used to treat bradycardia must act to increase heart rate. Acetylcholine has inhibitory effects on cardiac pacemaker activity, thus any drug that inhibits acetylcholine (i.e., an antagonist) will increase heart rate and a drug that mimics acetylcholine (i.e. an agonist) would lower heart rate. Preventing the binding of Ca2+ to troponin would prevent cardiac muscle contraction altogether; this is required to shift the position of tropomyosin such that the myosin binding sites on actin are exposed. Remember that cardiac muscle is organized in the same way that skeletal muscle is and contracts via the sliding filament theory. Finally, heart rate is determined by the slow-influx of sodium through leak channels in the cells of the SA node; inhibiting these would further decrease heart rate since the cells would reach threshold less often.

Irregular electrical activity is observed in one cardiac ventricle, but not the other. This defect in transmission is most likely found in which component of the cardiac conduction system? A. Atrioventricular node B. Purkinje fibers C. Sinoatrial node D. Internodal pathway

B. Purkinje fibers Explanation: The sinoatrial node supplies electrical signal to the atria and the atrioventricular node (via the intermodal pathway) and functions as the pacemaker of the heart. The internodal pathway carries impulses between the heart's two signaling nodes. A defect in the intermodal pathway or in either node would result in symmetrical changes to both ventricles. The right and left bundle branches bifurcate after the AV node and ramify to form the Purkinje fibers in the two ventricles, with each ventricle having its own separate set of Purkinje fibers. Electrical irregularities that are seen in one ventricle but not the other would most likely be linked to transmission issues in a component that is specific to one ventricle over the other.

Patients with Marfan syndrome experience increased elasticity in connective tissues, including those found in blood vessels. These patients often experience progressive aortic dilation, particularly through the ascending aorta and the aortic arch. Such dilation would be expected to have which of the following effects? A. The aortic semilunar valve would be expected to leak as the expansion of the aorta pulled on it resulting in changes to the first heart sound. B. The aortic semilunar valve would be expected to leak as the expansion of the aorta pulled on it resulting in changes to the second heart sound. C. The mitral valve would be expected to leak as the expansion of the aorta pulled on it resulting in changes to the second heart sound. D. The mitral valve would be expected to leak as the expansion of the aorta pulled on it resulting in changes to the first heart sound.

B. The aortic semilunar valve would be expected to leak as the expansion of the aorta pulled on it resulting in changes to the second heart sound.

Blood pressure is increased when: A. antidiuretic hormone increases sodium reabsorption in nephrons. B. sympathetic activation decreases the diameter of arterioles systemically. C. aldosterone increases water permeability in the collecting ducts of nephrons. D. parasympathetic innervation increases the flow of blood to digestive organs.

B. sympathetic activation decreases the diameter of arterioles systemically. Explanation: The choices "aldosterone increases water permeability in the collecting ducts of nephrons" and "antidiuretic hormone increases sodium reabsorption in nephrons" have the functions of the hormones backwards (and thus are wrong): aldosterone increases sodium reabsorption in nephrons and antidiuretic hormone increases water permeability. (Note that the two hormones working together would lead to an increase in total body salt and consequently, total body water, followed by an increase in blood pressure.) While it is true that blood flow to digestive organs is increased when the body is under parasympathetic control, this is not due to the direct action of the parasympathetic division on the blood vessels to those organs. The parasympathetic division actually does not innervate the blood vessels at all; the increased blood flow under these conditions is due to the withdrawal of sympathetic stimulation. Even if the parasympathetic division DID increase vessel diameter, this would not lead to an increase in blood pressure.

An unconscious patient arrives in the emergency room after being in a car accident. The patient has lost a severe amount of blood and will require a red blood cell transfusion. Which of the following blood types is the safest to transfuse into the patient? A. B- B. AB+ C. O- D. A+

C. O- Explanation: The administered blood should therefore have no antigens to trigger a response in the recipient: no ABO group antigens and no Rh factor. The safest blood to administer is O-.

The exchange of fluid between the blood in the capillaries and the surrounding tissues is the result of opposing osmotic and hydrostatic pressure differentials. Which of the following accurately describes the relationship between hydrostatic and osmotic pressure differentials in the capillaries? A. The osmotic pressure differential forces fluid out of the capillaries and into the tissues at the venous end. B. The hydrostatic pressure differential forces fluid out of the tissue and into the capillaries at the arterial end. C. The hydrostatic pressure differential causes fluid to move out of the capillaries at the arterial end. D. The osmotic pressure differential causes solutes and fluid to be filtered out of the capillaries at the arterial end.

C. The hydrostatic pressure differential causes fluid to move out of the capillaries at the arterial end. Explanation: Arterial pressure is higher than the pressure on the venous side of the capillaries. Thus, hydrostatic pressure tends to drive fluids out of the blood and into the tissues on the arterial side and back out of the tissues on the venous side. Osmotic pressure is greater in the plasma than in the interstitial fluid, because plasma has a much higher protein concentration; therefore, osmotic pressure tends to draw fluid into the blood, out of the tissues.

An increase in which of the following increases the O2 affinity of hemoglobin? A. Partial pressure of CO2 B. 2,3-BPG (2,3-bisphosphoglycerate) C. pH D. Temperature

C. pH Explanation: The O2 dissociation curve is shifted to the right (reduced O2 affinity) by an increase in any of the following: H+ concentration (decreased pH), partial pressure of CO2, temperature, and the concentration of 2,3-BPG. An easier way to remember this is to think of the conditions in an exercising muscle (which would benefit from a reduced O2 affinity that allows for easier oxygen unloading): hot, acidic, and hypercarbic (increased CO2). Therefore, the opposite conditions would lead to an increased oxygen affinity, i.e. a decrease in H+ concentration (increased pH), partial pressure of CO2, temperature and the concentration of 2,3-BPG.

An atrial septal defect (ASD) allows oxygenated blood to flow from the left atrium into the right atrium through a hole in the heart wall. Surgical repair of pronounced ASD would help to prevent: A. attenuation of signal between the sinoatrial and atrioventricular nodes. B. loss of pressure in pulmonary veins. C. calcification of the aortic semilunar valve. D. additional stress on the pulmonary circuit from increased pressure.

D. Presence of ASD means that oxygenated blood is mixing with deoxygenated blood and is being returned unnecessarily to the lungs. Explanation: Higher pressure of the left side is translated to the pulmonary circuit which would cause more stress from increased pressure.

Which of the following does NOT carry oxygenated blood? A. Coronary arteries B. Femoral artery C. Carotid arteries D. Pulmonary artery

D. Pulmonary artery Explanation: The pulmonary artery carries deoxygenated blood from the right ventricle to the lung to pick up oxygen. The femoral artery carries oxygenated blood in the leg, the coronary arteries branch from the aorta to provide oxygenated blood to the heart muscle cells, and the carotid arteries carry oxygenated blood from the aorta to the brain.

Which of the following is FALSE regarding the pacemaker cells in the sinoatrial node? A. Pacemakers cells are present outside of the sinoatrial node. B. Voltage-gated potassium channels open to repolarize the membrane. C. Voltage-gated calcium channels open to depolarize the membrane. D. Voltage-gated sodium channels open to bring the cells to the threshold membrane potential.

D. Voltage-gated sodium channels open to bring the cells to the threshold membrane potential. Explanation: The instability is due to a steady influx of sodium ions across the membrane through sodium leak channels (not voltage-gated sodium channels).

Which of the following vessels carry oxygen-rich blood? I. Aorta II. Umbilical vein III. Pulmonary vein

I, II, III Explanation: The vessels that carry oxygen-rich blood include the aorta, the umbilical vein, and the pulmonary vein. The aorta carries oxygenated blood from the left ventricle into the systemic circulation (Item I is true). The umbilical vein returns oxygenated blood from the placenta to the fetal heart (Item II is true). The pulmonary veins return oxygenated blood from the lungs to the left atrium (Item III is true). Note that the terms "artery" and "vein" only denote direction of flow and not oxygen content; arteries always carry blood away from the heart and veins carry blood toward the heart.

An infant born with a congenital defect in the ventricular septum that causes a mixing of blood between the right and left ventricles is most likely to suffer from: I. poor tissue oxygenation. II. increased blood pressure in the pulmonary circuit. III. higher blood pH.

I. poor tissue oxygenation. II. increased blood pressure in the pulmonary circuit. Explanation: Item I is true: If blood between the left and right ventricles is mixed, then some deoxygenated blood from the right ventricle will mix with oxygenated blood from the left ventricle and be returned to the body. This blood, with its lower-than-normal level of oxygenation, will result in poorer tissue oxygenation. Item II is true: The left ventricle generates higher pressures than the right ventricle. If the two ventricles are essentially connected via a defect in the septum, the higher pressures from the left ventricle will translate to the right ventricle and into the pulmonary circuit. Item III is false: If blood from the right ventricle (on its way to the lungs) mixes with blood from the left ventricle (on its way to the body), the blood from the right ventricle never makes it to the lungs to get rid of its carbon dioxide (or pick up oxygen, this again is why Statement I is true). The blood with have a higher overall CO2 content, and therefore a lower pH.

Which of the following occurs in response to low blood pressure? I. Increased blood osmolarity due to aldosterone release from the pituitary gland II. Increased water retention due to ADH release from the pituitary gland III. Systemic vasoconstriction

II. Increased water retention due to ADH release from the pituitary gland III. Systemic vasoconstriction Explanation: In response to low blood pressure, angiotensin II stimulates aldosterone release from the adrenal cortex, not the pituitary gland

Which of the following is/are true about the relationship between heart contractions and the autonomic nervous system? I. The heart requires signals from the sympathetic nervous system in order to contract. II. The vagus nerve releases acetylcholine and slows the heart rate. III. The heart is capable of contracting in the complete absence of nervous system input.

II. The vagus nerve releases acetylcholine and slows the heart rate. III. The heart is capable of contracting in the complete absence of nervous system input. Explanation: Item I is false: the heart does not require input by the sympathetic nervous system in order to contract, it has its own pacemaker in the SA node

Which of the following blood components is responsible for coagulation? A. Leukocytes B. Platelets C. Erythrocytes D. Lymphocytes

Platelets