MEDICAL EDUCATION TEACHING NOTE

Year : 2016  |  Volume : 1  |  Issue : 2  |  Page : 139-142

The 14^th Inter-medical School Physiology Quiz: Observations of common errors in the written test among students of 81 medical schools from 24 countries

Hwee-Ming Cheng, See-Ziau Hoe
Department of Physiology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia

Correspondence Address:
Dr. Hwee-Ming Cheng
Department of Physiology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur
Malaysia

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/2468-838X.196107

The 14^th Inter-medical School Physiology Quiz (IMSPQ) competition had 81 medical schools from 24 countries. Analyses of the written responses at the 14^th IMSPQ from a total of 334 students provide a useful teaching and learning insights. These observations, highlighted here, were gleaned from (i) the questions with most correct answers, (ii) the most unanswered questions, and (iii) the most wrongly answered questions. The IMSPQ is a unique annual physiology event that provides a global sampling of students' appreciation and understanding of core concepts in physiology.

Keywords: Education, misconceptions, physiology quiz

Table 1: List of countries and participants at the 14th Inter-medical School Physiology Quiz Click here to view

Table 2: Top ten team performances in the 14th Inter-medical School Physiology Quiz written test Click here to view

Table 3 Click here to view

1. Most correct responses [Table 3]a:
   1. The highest correct answer of 86% was in response to the effect of aldosterone and cortisol on arterial blood pressure. This should be basic core endocrine knowledge expected of all medical students. Students would have applied the knowledge that excess of cortisol will also lead to stimulation of the aldosterone receptors, with retention of sodium and water, and a resultant increased extracellular fluid (ECF) and blood volume. The true/false format does not tell us whether the students who responded correctly also had in mind the permissive effect of cortisol on the vascular responsiveness that also contribute to the increased total peripheral resistance in hypercortisol secretion
   2. Lung recoil has two components, the elastic and the surface tension effect. Still, <80% had a correct response to these basic essential aspects of lung mechanics. Of the 334 students, there were 42 students left the question blank, and 30 students disagreed wrongly with this correct statement. Some textbooks do not clearly specify between the lung elastic recoil and the nonelastic, lung recoil due to the collapsing inward force of surface tension
   3. The standard electrocardiography drawn on the same timescale as the cardiac cycle is a familiar multiparameter diagram that students refer to in studying cardiovascular physiology. The closing of the valves signify the beginning of either the systole (1^st heart sound) or the diastole phase (2^nd heart sound) of a cardiac cycle
   4. Insulin and glucagon are perhaps the most mentioned hormones with their generally opposite effects to each other. Insulin is hypoglycemic, and glucagon is released during hypoglycemia to maintain plasma glucose during times of energy demand or want. Both exercise and fasting are conditions of energy lack or demand that require plasma energy substrate to be sustained. The hyperglycemic glucagon is increased while the anabolic insulin secretion is inhibited so that glycogenolysis and gluconeogenesis can be effectively activated by glucagon
   5. Growth hormone, such as glucagon, is increased during situations that require ensuring an adequate supply of energy from glucose and fatty acids. Proteins are a last-resort energy source. The "anabolic" nature of growth hormone is then understood as a protein-sparing effect since growth hormone has both lipolytic and glycogenolytic "catabolic"-like actions. Although a fairly direct evaluation of hormone actions, there were slightly more than 25% of students who either were unsure or attempted this question wrongly.
2. Major uncertain, blank responses [Table 3]b:
   1. Quantitative aspects of physiology are a needed area to introduce at appropriate points in our teaching. A high 51% of students were unsure of how to handle the values give in the questions on the daily intestinal absorption of water. Stress should be given during our teaching on the large volume of reabsorbed fluid from the aqueous gastrointestinal (GI) secretions that are recycled daily. These secretions amount to a considerable volume of >5 L from the combined salivary, gastric, and pancreatic juices
   2. Definitions are essential in providing the pillars for explaining physiology. The transmural pressure is simply the difference between the internal and external pressure across the wall (mural) of a structure. The term transpulmonary pressure is just the transmural pressure across the alveolar wall that changes during a respiratory cycle. The external pressure for both the airways and the alveoli that influence their transmural pressure is then the same intrapleural pressure
   3. We assume that all students are familiar with testicular steroid hormones, the major testosterone being the main hormone. The role of nonsteroid peptide hormones secreted by the testes also contributes. One such major peptide regulator of pituitary follicle-stimulating hormone (FSH) that is needed for spermatogenesis is inhibin. Testicular dysfunction that leads to low plasma inhibin will result in a compensatory, elevated but noneffective plasma FSH levels in these cases of male infertility
   4. Concepts of osmolarity and tonicity are regularly misconceived by students. Arthur Vander's text gives perhaps the most comprehensive description of an isotonic solution. "An isotonic solution will contain a minimum of 300 mOsm/L of nonpenetrating (osmo-active) solutes regardless of the osmotic concentration of penetrating solutes." Thus, a hyperosmotic solution of two solutes (e.g., 400 mOsm/L) can still be isotonic with 300 mOsm/L of nonpenetrating solute (e.g., NaCl) and 100 mOsm/L of urea
   5. Surprisingly, quite a high 44% of students were unsure of the specific innervations of alpha and gamma innervations. Coactivation of alpha-gamma is necessary for maintaining the sensitivity of the muscle spindle reflex that provides continual afferent biofeedback during voluntary movements. The alpha innervates the extrafusal contracting muscle fibers while the gamma motor efferents supply the intrafusal muscle spindle sensory receptors.
3. Most incorrect responses [Table 3]c:
   
   A brief on the statements that generated the most number of wrong responses is also instructive and insightful for teachers of physiology. Common mistakes made can be due to two factors: either the mechanisms are hard to grasp or the mechanisms are hard to teach and convey, so students still have a loose understanding on these areas.
   1. A high 74% of students thought that secretion of water into the intestinal lumen was a primary cause of osmotic diarrhea. Perhaps these students associate this scenario with the case of dumping syndrome when gastric emptying is reduced, and a large hyperosmotic meal is still consumed against advice. In the dumping syndrome, there could indeed be a reverse transport of water into the lumen, and a hypovolemia is a consequence. However, in an intact GI system of a person with lactose intolerance, the watery stools are due to a reduced reabsorption of water. Daily water reabsorption is easily about 7 L/day, and interference with just the optimal water reabsorption will produce diarrhea caused by the osmo-active undigested lactose. This lactose osmotic diarrhea is analogous to the osmotic diuresis seen in glycosuria. In the nephrons, there is also no secretion of water in osmotic diuresis. The proximal convoluted tubules reabsorb around 70% of the glomerular filtrate (which is a high volume of 180 L/day)
   2. This high percentage of error hopefully is a marker of the students' carelessness and not a reflection of a misconception. Gastrin is a hormone secreted into the blood by the gastric antral G-cells and not into the lumen. The presence of gastrin in the gastric juice would, in fact, indicate some pathologic injury to the gastric cells with release of the gastrin hormone into the lumen
   3. The term "homeostasis" is a key physiologic word for understanding mechanistic events that regulate and control the integrative processes in the body. Drinking a large volume of water will lead to a hypotonic expansion initially. There will be a positive water balance. Although the plasma is made hypoosmotic as the plasma sodium concentration is lowered, the total body sodium is unchanged, i.e., there is no alteration of the sodium balance. Homeostatically, there should be no compensation to restore the sodium balance, and this will include natriuretic hormones. Students might theoretically imagine that stretch of cardiac volume receptors would trigger atrial natriuretic peptide. If that does occur as a significant physiologic event, we would end up with a loss of urinary sodium, and a negative sodium balance would be the result each time after we drink a large volume of just plain water. Plainly speaking that would not be physiologic!
   4. Some thoughts on this misperception on renal autoregulation have been shared in this journal.^[2] The classic textbook graphical representation of renal autoregulation shows a maintained blood flow over the regulatory blood pressure range of 60-160 mmHg. These in vitro data were derived from a denervated, isolated kidney and thus represent an intrinsic renal mechanism that is the independent of extrinsic sympathetic nerve input and circulating hormones. In vivo integrated response to a reduction of blood pressure to 80 mmHg will, however, trigger the baroreflex-activated increase in renal sympathetic activity. The renal arterioles will be vasoconstricted, an event that predominates over the underlying intrinsic autoregulatory response to vasodilate the afferent arteriole to achieve a normal renal blood flow (RBF). The temporary reduction in RBF is not critical for the kidneys and is part of the priority of the integrated body's response to maintain arterial blood pressure and cerebral perfusion
   5. The students should remember that we tell them that organic solutes generated from metabolism are both passively and actively secreted. Moreover, the hydrophobic organic solutes will be transported in the main, bound to plasma proteins. How then are the bound solutes released from the proteins and secreted by the tubules? There is a reversible equilibrium between the bound and the free solute in plasma. The free solute binds to polyspecific cationic or anionic transporters at the basolateral membrane of the renal epithelial cells. As some organic solutes are secreted, more is unbound from the proteins for secretion.

Summary

References

1.	Cheng HM, Hoe SZ. Update on the growth of the International Intermedical School Physiology Quiz. Adv Physiol Educ 2016;40:198-9.
2.	Cheng HM, Hoe SZ. Students′ convoluted trouble with renal autoregulation: A teaching note for students and physiology educators. BLDE Univ J Health Sci 2016;1:25-7.