cardiology khan questions
What physical feature of large systemic arteries (resistance vessels) makes them relatively more responsive to changes in intracellular calcium concentrations?
All blood vessels have a tunica intima. This layer is made of endothelial cells, and is an essential structural component. Intracellular calcium is the cellular messenger The tunica media is a muscular layer, which can be contracted and relaxed to enact changes in blood pressure. A thick tunica media is characteristic of large systemic arteries. A thick tunica media explains the responsiveness of large systemic arteries to changes in intracellular calcium concentrations.
What physical feature of large systemic arteries (resistance vessels) makes them relatively more responsive to changes in intracellular calcium concentrations?
All blood vessels have a tunica intima. This layer is made of endothelial cells, and is an essential structural component. Intracellular calcium is the cellular messenger resulting in the contraction of smooth muscle. The tunica media is a muscular layer, which can be contracted and relaxed to enact changes in blood pressure. A thick tunica media is characteristic of large systemic arteries. A thick tunica media explains the responsiveness of large systemic arteries to changes in intracellular calcium concentrations.
A given arteriole has a resistance of 2. What would the new resistance of this vessel be if its radius were to double?
Resistance in a tube is equal to ((8^*L^*n8 ∗ L ∗ n8, start superscript, times, end superscript, L, start superscript, times, end superscript, n)/(π∗r4)), where L is the length of the tube, n is the viscosity, and r is the radius. Therefore, the resistance is proportional to 1/r^41/r 4 1, slash, r, start superscript, 4, end superscript. 2∝1/r4;R′∝1/(2r)4 R′∝(1/16)r4;(1/16)∗2= The new resistance would be ⅛
In terms of being open or closed, what is the state of the mitral and tricuspid valves (left and right atrioventricular valves, respectively) at the end of the first heart sound?
The first heart sound, "Lub," indicates that the heart has entered systole. Systole is typically defined as ventricular contraction. As the ventricles contract, the AV valves close to prevent regurgitation into the atria. The first heart sound indicates the closure of the Both are closed.
What layer of the heart would be most immediately susceptible to infections caused by bacteria circulating in the blood?
The myocardium is the muscular portion of the heart, and is the "middle" layer. The pericardium is a double walled sac which encloses the heart, which provides structural support and lubrication. Where the pericardium contacts the heart wall (at the myocardium), it is called the epicardium. The endocardium lines the inside of the heart and is in direct contact with circulating blood. Infectious bacteria carried in the blood would come into close contact with the endocardium, which would be most susceptible to infection.
Which heart valves are NOT actively closed by the contraction of muscular structures?
The papillary muscles contract during systole to prevent blood from flowing backwards within the heart. Blood flows from high pressure to low pressure. The papillary muscles are only necessary in areas where this fact may propagate flow in a backwards direction. The pressure generated by ventricular systole is substantial enough that it overcomes the pressure of the blood vessels they supply. This force opens the pulmonary and aortic valves, which then shut passively when the pressure of the ventricles is equal to or less than the pressure upstream. The mitral and tricuspid valves ae both atrioventricular valves. Semilunar valves are not associated with the papillary muscles, and are not actively closed.
At the instant following the second heart sound, which heart valves are open?
The second heart sound indicates the beginning of diastole. The second heart sound, "Dup," is due to the closure of the semilunar valves. The heart is in systole between the first and second heart sounds. During systole, the heart pumps blood from the ventricles, and the atrioventricular valves are closed to prevent regurgitation into the atria. The closure of the semilunar valves is the start of a brief period of "isovolumetric relaxation." All valves are closed during the second heart sound.
