What is the ultimate goal in neural regulation of cardiovascular function?
We used the following multiple-choice question after a series of lectures in cardiovascular physiology in the first year of an undergraduate medical curriculum (n = 66) to assess whether students had understood the neural regulation of cardiovascular function. In health, neural cardiovascular mechanisms are geared toward maintaining A) cardiac output, B) total peripheral resistance (TPR), C) arterial blood pressure (BP), D) tissue blood flow. The same question was administered to 275 graduates preparing for postgraduate exams (but not following the same series of lectures as the undergraduates). In both groups, we found a large proportion of incorrect answers (70% in undergraduates and 85% in graduates) and sorted this out by offering a step-by-step explanation and two examples and found it successful: 1) What happens to BP and heart rate (HR) when a person loses 500 ml of blood ( approximately 10% of blood volume) in one minute? 2) What happens to your BP and HR as you get out of bed after a night's sleep? Flow = perfusion pressure/resistance to flow; cardiac output = BP/TPR; BP = cardiac output x TPR = [stroke volume (SV) x HR] x TPR. In both examples, BP decreases and is rapidly brought into the normal range by the arterial baroreflex mechanism. TBF is regulated chiefly by varying local vascular resistance (autoregulation). In summary, the ultimate goal of all neural cardiovascular reflex mechanisms is to maintain arterial BP within a range in which tissues can regulate their own blood flows. Cardiovascular control during exercise was used as an example to emphasize these facts. A discussion of this kind triggered interest in the minds of students and graduates, helping them get rid of a major misconception in about 20-40 minutes.
Prakash
E S
ES
Department of Physiology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry 605 006, India. drespraskash@yahoo.com
Madanmohan
Pal
Gopal Krushna
GK
D004504:Education, Medical, Undergraduate / Q000379:methods*; D006801:Humans; D009424:Nervous System Physiological Phenomena; D010827:Physiology / Q000193:education*