Assignment
1. List the flow of blood, starting with where it first enters the heart after going through the systemic circuit and ending with it re-enters the systemic circuit after leaving the heart. You must include all heart chambers, valves and blood vessels that the blood encounters on its path.
2. What happens (increase or decrease) to stroke volume if.......
(a) afterload increases? _________________
(b) preload increases? _________________
(c) the sympathetic nervous system is activated? _________________
Explain the physiological reason for your answers in each of the three situations. In other words, HOW/WHY does stroke volume change in each of the three situations?
3. An increase in afterload (i.e. aortic stenosis) results in a decrease in blood flow in the systemic circuit. What physiological mechanisms could help to raise blood flow and thus compensate for the higher afterload? Provide three possible mechanisms. Hint: you would have tried out these compensatory mechanisms in activity 7 of the PhysioEx experiment. Which of the three types of compensation was the best at restoring blood flow?
4. One form of blood doping is injection of the hormone erythropoietin (EPO), which stimulates red blood cell production and thus the oxygen carrying capacity of the blood. How could blood doping impact blood flow to tissues in the body? In light of this, why is blood doping dangerous? Be sure to explain the reasoning behind your answer using the physiological principles studied in this lab. Hint: Think about the data you gathered in the PhysioEx experiment on the parameters that regulate blood flow. Also, consider what would happen to blood viscosity as a result of having a higher number of red blood cells in it.
5. People with high blood pressure can be placed on Beta blockers, which are drugs that bind to the beta adrenergic receptors on the heart and reduce the activation of the heart by the sympathetic nervous system. How does using a beta blocker decrease blood pressure? Be sure to explain the reasoning behind your answer using the physiological principles studied in this lab. Hint: Consider this equation Pressure = CO * R as you answer this question.
6. Congestive heart failure is when the heart is unable to provide sufficient blood flow to the systemic circuit. This can occur as a result of a heart attack. One treatment option for patient's with CHF is an angiotensin II receptor blocker/antagonist (losartan). (a) Look up the mechanism of action of angiotensin II in the circulatory system and then consider what would result if this was blocked with losartan. What is the mechanism? (b) Based on this information, what is the benefit of losartan as a treatment for a weaker heart? Hint: Consider this equation CO = P/R as you think about your answer.