All play and no work: skits and models in teaching skeletal muscle physiology.

Abstract

IlluminationsAll play and no work: skits and models in teaching skeletal muscle physiologyAnandit John Mathew, Niranjini Chandrasekaran, and Vinay OommenAnandit John MathewDepartment of Physiology, Christian Medical College, Vellore, Tamil Nadu, India, Niranjini ChandrasekaranDepartment of Physiology, Christian Medical College, Vellore, Tamil Nadu, India, and Vinay OommenDepartment of Physiology, Christian Medical College, Vellore, Tamil Nadu, IndiaPublished Online:04 Apr 2018https://doi.org/10.1152/advan.00163.2017MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat INTRODUCTIONTraditional undergraduate medical teaching is in the form of didactic lectures with minimal relevant practical sessions. Didactic sessions have the advantage of addressing a large amount of material in a short span of time (4). However a main drawback of such sessions is the lack of feedback from students and a difficulty in holding the attention of the student for the entire period of the didactic lecture (5). With an aim to make didactic lectures more interesting, we looked at developing a low-cost method for interactive teaching of muscle physiology for undergraduate medical students in a large-group classroom setting.Undergraduate muscle physiology is traditionally taught in India as a series of didactic lectures followed by an assessment in the form of a written test. The didactic lectures are often aided by slide presentations, with videos and animations used as a supplement. We present, in this paper, two methods that were used to make the teaching of muscle physiology more interactive.MATERIALS AND METHODSThese methods were presented to a group of 100 undergraduate medical students, in the first year of medical training in South India. The process involved two alternative methods, namely the use of models and skits.ModelsFour models were constructed to depict the structure of actin, myosin, as well as the arrangement of actin and myosin in the sarcomere. This was done using standard textbook references (1–3). Low-cost materials that were easily available locally were used for these models.Materials used.Small plastic balls of four different colorsLarge plastic balls of two different colorsColored adhesive tapeVelcro stripsMetal wire (galvanized iron/copper)Bottle brushCyanoacrylate glueAcrylic paintsBraided nylon ropeModel 1: Structure of actin.Actin is made up of two strands of actin filaments (f-actin), each of which is made up of 13 molecules of globular actin (g-actin). The two filaments are arranged in an α-helix configuration.To construct the model of actin, each actin molecule was represented as a large colored plastic ball. A hole was drilled through the center of these balls. Thirteen such balls were strung on a metal wire to make an actin filament. The balls were fixed in place using cyanoacrylate glue. A second filament with contrasting colored large plastic balls was made and twisted over the first to form a double helix (Fig. 1A). An initial demonstration of this model showed the students the arrangement of multiple g-actin molecules forming f-actin.Fig. 1.A: two strands of f-actin arranged in an α-helix. B: actin α-helix showing the arrangement of the troponin-tropomyosin complex covering the myosin binding site.Download figureDownload PowerPointModel 2: Structure of myosin binding sites.In the second model (Fig. 1B), two separate large balls of different colors were strung together on a wire. A strip of Velcro stuck on each ball depicted the myosin binding site. Different colored small plastic balls were taken as follows.White: to depict calciumBlack: to depict troponin CYellow: to depict troponin TGreen: to depict troponin IA length of braided nylon rope was used to depict tropomyosin. A Velcro strip was fixed to this nylon rope to attach it to the myosin binding site (Fig. 1B).Model 3: Structure of myosin.Myosin comprises two heavy chains wound in an α-helix, each ending in a globular head. Each head has an alkali light chain and a regulatory light chain. The heavy chains have a tail and a hinge region.The arrangement of several myosin molecules around the M line was depicted by fixing four bottle brushes onto a wire (Fig. 2A). To construct the model of a single myosin molecule, two metal wires were twisted together to form the heavy chains. On the free end of each wire a large plastic ball was strung and fixed in place with cyanoacrylate glue. Strips of colored adhesive tape were placed on the heads to depict the light chains. A patch of Velcro tape was also fixed on each head to depict the actin binding site (Fig. 2B).Fig. 2.A: model depicting the arrangement of multiple myosin molecules on both the sides of the M line. B: model depicting the structure of the myosin molecule.Download figureDownload PowerPointUse of the models.These models were used during a 1-h teaching session to demonstrate the structure of actin and myosin. The demonstration of the models took about 20 min. Model 1 (Fig. 1A) illustrated the arrangement of globular actin forming filamentous actin and its double-stranded structure. This model also showed the students the myosin binding sites on each globular actin molecule. Model 3 (Fig. 2B) was used to explain the structure of each individual myosin molecule and the arrangement of multiple molecules (Fig. 2A). Model 2 (Fig. 1B) was used along with model 3 (Fig. 2B) to demonstrate the sequence of events that expose the myosin binding sites on actin in the presence of calcium (Fig. 3), and the binding of the myosin heads on the exposed site.Fig. 3.Use of models to depict the sequence of events to prepare actin for binding to myosin. A: calcium binds to troponin C. B: the troponin-tropomyosin complex moves away from the myosin binding site, thereby exposing it.Download figureDownload PowerPointThese models were used to demonstrate key steps involved in actin and myosin binding (Fig. 3).SkitsThe molecular events of skeletal muscle contraction were also demonstrated in the form of simple skits. A placard was made for each component of the events/elements of muscle contraction, beginning with the generation of the muscle action potential leading up to the contraction and subsequent relaxation of the muscle. Volunteers were chosen from among the students. Each student was given a placard, and his/her role was explained. Each student acted out the role of one of the key components of skeletal muscle contraction. A line was drawn on the floor with chalk in the front of the classroom to denote the sarcolemma and its T tubules. This divided the class into an intracellular and extracellular space. Another area was marked out in close proximity to the T tubules and was demarcated as the sarcoplasmic reticulum (SR).Cast.The skit utilized eight student volunteers, who had the following roles:• Student 1: Myosin molecule• Student 2: ATP molecule/ADP + inorganic phosphate (Pi) molecule• Student 3: Action potential• Student 4: Dihydropyridine receptor (DHPR)• Student 5: Ryanodine receptor (RyR)• Student 6: Calcium ions• Student 7: Troponin-tropomyosin complex• Student 8: Actin moleculeThe skit had six scenes that were presented during a 1-h teaching session. This time was sufficient for the preparation and presentation of the skit, as well as to clarify concepts related to the skit.Scene 1: Activation of myosin.See Fig. 4.Fig. 4.Scene 1: activation of myosin: A: student 1 represents myosin, and student 2 represents ATP. B: student 2 bumps shoulders with student 1, indicating ATP binding. C: student 1 extends his/her elbow to indicate the activation of myosin. Student 2 remains behind student 1, indicating that myosin is still bound to ADP and Pi.Download figureDownload PowerPointtheory.The myosin head has strong ATPase activity. It, therefore, hydrolyses ATP into ADP and Pi, releasing energy that is used to cock the myosin head. The ADP and Pi stay attached to the myosin head by forming new bonds.screenplay.Myosin heads were depicted by the arms of student 1. The role of ATP was played by student 2. To begin with, student 2 bumped shoulders with student 1 to show the hydrolysis of ATP by the head of myosin. Student 1 then extended his/her elbow to denote the cocking of myosin. Student 2 continued to hold on to the arms of student 1 from behind to denote the bonds of ADP and Pi with myosin. Student 1 stayed with his/her elbow extended until the binding with student 8 (actin) in scene 3.Scene 2: Increase in intracellular calcium.See Fig. 5.Fig. 5.Scene 2: increase in intracellular calcium. Scene depicts the sequence of events leading to increase in intracellular calcium. Student 3 (muscle action potential) runs and reaches student 4 (DHPR), who tags student 5 (RyR). Student 5 releases student 6 (calcium) and throws chocolates (calcium) into the classroom (muscle cell).Download figureDownload PowerPointtheory.The muscle action potential travels along the sarcolemma as a wave of depolarization into the T tubules. The depolarization of the T tubules opens the DHPRs. The DHPR has a mechanical coupling with the RyRs on the SR. When the DHPR opens, the RyR on the SR are also opened. When the RyR opens, there is a flooding of calcium into the sarcoplasm.screenplay.Student 3 (muscle action potential) ran along the border of the area that had been marked to depict the sarcolemma to mimic the action potential that travels along the sarcolemma. When he/she reached student 4 (DHPR), he/she tagged student 4, who in turn tagged student 5 (RyR). Student 5 then released student 6 (calcium) into the classroom (muscle cell). He/she also threw a handful of chocolates into the classroom (muscle cell), which depicted the flooding of calcium from the SR into the muscle cell when the RYR open.Scene 3: Activation of actin.See Fig. 6.Fig. 6.Scene 3: activation of actin. Scene depicts the activation of actin. A: student 7 (troponin-tropomyosin complex) hides the myosin binding site (M) on student 8 (actin). B: student 6 (calcium) attaches to the student 7 (troponin-tropomyosin complex) and moves him/her behind student 8, thereby exposing the myosin binding site on actin.Download figureDownload PowerPointtheory.Calcium binds with the troponin C of the troponin-tropomyosin complex, which causes the movement of the troponin-tropomyosin complex away from the myosin binding sites of actin, thereby activating the actin molecule.screenplay.Student 7 (troponin-tropomyosin complex) stood with his/her arms linked with one arm of student 8 (actin) who was labeled as the myosin binding site of actin. When student 6 (calcium) entered the muscle cell, he/she linked arms with the other arm of student 7 and positioned student 7 behind student 8. This exposed the binding site for myosin on student 8.Scene 4: Formation of cross bridges.See Fig. 7.Fig. 7.Scene 4: formation of cross bridges. Scene depicts activated student 1 (myosin) binding to the myosin binding site (M) on student 8 (actin), forming a cross bridge.Download figureDownload PowerPointtheory.Once actin is activated by the exposure of its myosin binding sites, activated myosin binds with it (cross-bridge formation).screenplay.Once the myosin binding site on student 8 (actin) was exposed, student 1 (activated myosin) immediately linked his/her extended arm with student 8 to denote the formation of cross bridges.Scene 5: Power stroke.See Fig. 8.Fig. 8.Scene 5: power stroke. Student 1 (myosin) releases student 2 (ADP + Pi). Student 1 also pulls student 8 (actin) toward him/her.Download figureDownload PowerPointtheory.Once the myosin head is bound with actin, the myosin-Pi bond is broken, and the energy released is used to bend the myosin head at its hinge, pulling the actin filament with it. This is called the power stroke. ADP also dissociates from myosin, completing the cycle.screenplay.When student 8 binds to activated student 1, student 2 releases student 1 to denote the cleavage of the ADP-Pi-myosin bonds. Student 1 then flexes his/her arm, pulling student 8 toward him/her to denote the power stroke.Scene 6: Relaxation/release of cross bridges.theory.If action potentials continue to occur and adequate calcium is released from the SR, ATP binds with myosin, thereby releasing it from actin. Myosin immediately cleaves ATP and gets activated and binds with another actin site. Simultaneously, there are multiple other activated myosin heads that can bind with the same actin site. Therefore, there is a sequence of power strokes in multiple actin-myosin interactions referred to as cross-bridge cycling, leading to progressively increasing force generation.If action potentials stop, but sufficient ATP is present, then the ATP binds with the myosin head, releasing it from actin and activating it immediately thereafter. This causes the sarcomere to relax back to its resting length. Calcium is pumped back into the SR by the sarcoplasmic and endoplasmic reticulum calcium-ATPase.The series of events were performed while explaining the role of each event, component, and person, followed by repeated enactment of the sequences to reinforce the concept. This was supplemented with a projection of traditional schematics and animations depicting the series of events. The students were encouraged to stop the enactment at any point to clear doubts and clarify concepts. As the skit was enacted, each participant verbally described the sequence of events in which he/she was involved. This provided an added emphasis of the concept.Other Teaching Aids UsedThe skits and models were demonstrated as part of a 12-h lecture series on muscle physiology. During this series of lectures, the recording of the electromyogram was also demonstrated. A quiz competition between student groups was conducted at the end of the series. Students were also provided with lecture notes that covered the theory of muscle physiology.FEEDBACK RESULTSAn anonymous, written feedback was obtained from the students to assess the usefulness of the skits and models. Students were asked to rate their experiences using a 5-point Likert scale, which ranged from “very confusing” to “very helpful.” Eighty-three students completed the feedback form. The results of the feedback are shown in Figs. 9 and 10. The feedback received was extremely positive. Students stated that they enjoyed the interactive sessions and that it enabled them to understand and remember concepts better.Fig. 9.Feedback obtained from students regarding the usefulness of the constructed models in understanding muscle physiology.Download figureDownload PowerPointFig. 10.Feedback obtained from students regarding the usefulness of the skits in understanding muscle physiology.Download figureDownload PowerPointThere were 51.8% (n = 83) of the students who felt that the use of models was “very helpful,” 42.2% found them “helpful,” whereas 4.8% of students were neutral in their response. There were 1.2% of students who found the models to be “confusing.” There were no students for whom the use of models was “very confusing.”With regard to the skits, 57.3% (n = 82) found the skits “very helpful” in understanding muscle contraction, 31.7% found them “helpful,” whereas 9.8% gave neutral responses and 1.2% found the skits “confusing.”LimitationsThe models were created large for easy visibility with locally available materials. They were created primarily to focus on the structure of actin and myosin. They were hence not constructed to the same scale. This had to be taken into account during the presentation of the models.This skit requires adequate classroom space and eight students as actors. In the event that either space or student numbers are inadequate, the students who represented molecules such as ATP and Ca2+ can be represented using suitable props or placards.The events depicted in the skit deal with only the interaction between one actin and myosin molecule. The shortening of the sarcomere and the subsequent shortening of the muscle were not depicted. This would have to be discussed in later teaching sessions.DISCUSSIONDidactic lectures have often been criticized as being monotonous where students are just passive learners. It is not feasible to completely do away with didactic lectures in medical undergraduate teaching, as they serve as a convenient medium to introduce students to complex concepts from several sources. They can, however, be supplemented with other teaching tools.This article describes an interactive skit and models of skeletal muscle structure that can easily be integrated into didactic teaching of muscle physiology for undergraduate medical students. The three-dimensional nature of the models helped students understand and appreciate the structural aspects of skeletal muscle. The models are easy to construct and easily replicable in terms of both cost and skill. With this understanding of the structure, skits were used to demonstrate the sequence of events in muscle contraction. Although a large number of videos and animations dealing with muscle physiology are available freely, the live demonstrations of the models and skits provided an opportunity for the learning to be more fun and interactive. The students thoroughly enjoyed these interventions, making the learning process both informative and enjoyable.DISCLOSURESNo conflicts of interest, financial or otherwise, are declared by the authors.AUTHOR CONTRIBUTIONSA.J.M. conceived and designed research; A.J.M. and N.C. performed experiments; A.J.M., N.C., and V.O. analyzed data; A.J.M. and V.O. interpreted results of experiments; A.J.M., N.C., and V.O. prepared figures; A.J.M., N.C., and V.O. drafted manuscript; A.J.M. and N.C. edited and revised manuscript; A.J.M., N.C., and V.O. approved final version of manuscript.REFERENCES1. Barrett KE, Ganong WF (Editors). Ganong’s Review of Medical Physiology (24th Ed.). New York: McGraw-Hill Medical, 2012.Google Scholar2. Boron WF, Boulpaep EL (Editors). Medical Physiology (3rd Ed.). Philadelphia, PA: Elsevier, 2017.Google Scholar3. Hall JE. Guyton and Hall Textbook of Medical Physiology (13th Ed.). Philadelphia, PA: Elsevier, 2016.Google Scholar4. Richardson D. Don’t dump the didactic lecture; fix it. Adv Physiol Educ 32: 23–24, 2008. doi:10.1152/advan.00048.2007. Link | ISI | Google Scholar5. Stuart J, Rutherford RJ. Medical student concentration during lectures. Lancet 312: 514–516, 1978. doi:10.1016/S0140-6736(78)92233-X.Crossref | Google ScholarAUTHOR NOTESAddress for reprint requests and other correspondence: V. Oommen, Dept. of Physiology, Christian Medical College, Bagayam Campus, Vellore, Tamil Nadu 632002, India (e-mail: [email protected]ac.in). 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