Course Content
🔬 Station 1 — Identification of Lipoma
Learning Outcomes Identify a lipoma from a provided gross specimen/image or histopathology slide. Identify the key morphological features supporting the diagnosis. Differentiate the lesion from an obviously malignant soft-tissue lesion when asked.
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Identification of Lipoma
🔬 Station 2 — Identification of Squamous Cell Carcinoma
Learning Outcomes Identify squamous cell carcinoma from a provided gross/microscopic specimen. Recognize the important morphological features of squamous differentiation. State the diagnosis from the findings provided.
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Identification of Squamous Cell Carcinoma
🔬 Station 3 — Fibroadenoma of Breast: Gross & Microscopic Identification
Learning Outcomes Identify fibroadenoma from a gross specimen or histological image. Recognize the important gross and microscopic points of identification. Give the final pathological identification.
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Fibroadenoma of Breast: Gross & Microscopic Identification
🧬 Station 4 — Karyogram Preparation & Chromosomal Abnormality Identification
Learning Outcomes Arrange chromosomes appropriately to prepare a karyogram. Determine chromosomal sex from the karyogram. Identify a common numerical chromosomal abnormality from a provided karyogram.
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Karyogram Preparation & Chromosomal Abnormality Identification
⚗️ Station 5 — Tissue Organ Bath: Identification, Setup & Tyrode Solution
Learning Outcomes Identify the major components of a tissue organ bath. State the function of the important components. Identify the constituents/purpose of Tyrode's solution. Demonstrate the basic placement/fixation of isolated ileal tissue in the organ bath.
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Tissue Organ Bath: Identification, Setup & Tyrode Solution
📈 Station 6 — Acetylcholine Dose–Response & Ceiling Effect
Learning Outcomes Demonstrate the effect of increasing doses of acetylcholine on isolated rabbit ileum. Recognize the ceiling effect. Interpret a provided tracing/dose-response recording. Plot or interpret the corresponding dose-response graph.
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Acetylcholine Dose–Response & Ceiling Effect
📉 Station 7 — Competitive Antagonism on Isolated Rabbit Ileum
Learning Outcomes Demonstrate/recognize surmountable antagonism using an agonist and antagonist. Interpret the experimental tracing. Explain the change in response after addition of the antagonist. Identify the pharmacological relationship demonstrated.
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Competitive Antagonism on Isolated Rabbit Ileum
👁️ Station 8 — Rabbit Eye Pharmacology: Identify the Unknown Drug
Learning Outcomes Assess/interpret pupil size, conjunctival appearance, corneal reflex and light reflex. Compare the test eye with the control eye. Interpret the pattern produced by an autonomic or local anaesthetic drug. Identify the most likely unknown drug from the observed findings.
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Rabbit Eye Pharmacology: Identify the Unknown Drug
📝 Station 9 — Medico-Legal Autopsy Report
Learning Outcomes Review supplied postmortem findings systematically. Complete the important components of an autopsy report. Formulate an appropriate final opinion from the supplied findings.
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Medico-Legal Autopsy Report
🧪 Station 10 — Toxicology Sample Collection & Preservation
Learning Outcomes Select the appropriate viscera/specimens required for toxicological examination. Select the appropriate preservative/container. Demonstrate or describe correct collection, labelling and handling of the sample. State essential precautions before dispatch.
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Toxicology Sample Collection & Preservation
⚰️ Station 11 — Identification of Postmortem Changes
Learning Outcomes Identify the postmortem change demonstrated on a model/image/specimen. Describe its characteristic features. Differentiate commonly confused postmortem changes where appropriate. State its basic medico-legal significance, particularly in relation to time since death.
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Identification of Postmortem Changes
🚑 Station 12 — Gastric Lavage / Stomach Wash on Manikin
Learning Outcomes Prepare the equipment required for gastric lavage. Demonstrate the correct sequence of gastric lavage on a manikin. Maintain patient safety and correct positioning during the procedure. Recognize situations in which the procedure should not be attempted.
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Gastric Lavage / Stomach Wash on Manikin
🧪🔬 AIM OSPE/OSCE Lab — Multisystem-I Module | 3rd Year MBBS
AIM OSCE / OSPE • MBBS

Station 7 — Competitive Antagonism on Isolated Rabbit Ileum

Rapid Revision • Experimental Pharmacology • Tracing Interpretation • Viva

🎯 Task

CANDIDATE TASK

You are provided with an isolated rabbit ileum experiment using an agonist together with a second drug. Describe how you would demonstrate the drug interaction, interpret the resulting tracing or dose–response curves, and state the pharmacological relationship demonstrated.

⚡ Model Station Answer

What to say in the exam
Finding: After addition of the antagonist, the same dose of agonist produces a smaller response and a higher agonist dose is required.
Interpretation: Increasing the agonist concentration can restore the original maximum response, so the antagonism is surmountable.
Dose–response curve: There is an approximately parallel rightward shift, increased EC50 and reduced agonist potency, with essentially unchanged Emax.
Conclusion: This demonstrates reversible competitive antagonism.

🔎 Stepwise Procedure / Approach

  1. Mount the isolated ileal segment correctly in an organ bath containing suitable physiological solution and allow the tissue response to stabilize.
  2. Give progressively increasing doses or concentrations of the agonist and record the graded contractions using the same contact and washing cycle.
  3. Continue until the maximum response is obtained and establish the control agonist dose–response relationship.
  4. Wash the preparation, add a fixed concentration of the antagonist and allow adequate contact or equilibration.
  5. Repeat the graded agonist doses while the antagonist remains present and record the responses.
  6. Compare the two sets of responses: in the presence of antagonist, higher agonist concentrations are required to produce equivalent contractions.
  7. Confirm that sufficiently increasing the agonist can still produce approximately the same maximum response. A parallel rightward shift with preserved Emax indicates surmountable competitive antagonism.

Exam link: With acetylcholine + atropine, atropine competitively blocks muscarinic receptors. If the station instead uses histamine + an H1 antihistamine, apply the same principle of surmountable competitive receptor antagonism.

🖼️ Visual Learning

VISUAL 1

Competitive Antagonism: Experiment, Tracing and Dose–Response Shift

🎥 Practical Video

🎥 Practical Demonstration — ANS Control of Gut Smooth Muscle
Monash University • Medicine, Nursing and Health Sciences

This practical resource demonstrates the rabbit ileum preparation and experimental setup and allows students to observe how agonists and antagonists, including acetylcholine and atropine, alter ileal contractions.

▶ Watch Practical Video

 

📝 Important Viva Questions

Q1. What is competitive antagonism?

It occurs when an antagonist competes reversibly with an agonist for the same receptor binding site and its effect can be overcome by increasing the agonist concentration.
Q2. Why is competitive antagonism called surmountable?

Because sufficiently increasing the concentration of the agonist can overcome the antagonist and restore the maximum response.
Q3. What happens to the agonist dose–response curve in competitive antagonism?

It undergoes an approximately parallel shift to the right while the maximum response remains essentially unchanged.
Q4. What happens to EC50 and potency of the agonist?

EC50 increases, meaning a higher agonist concentration is required; therefore the apparent potency of the agonist decreases.
Q5. What happens to the efficacy or Emax of the agonist?

The maximum response is essentially preserved, so the agonist’s efficacy is not reduced by a simple reversible competitive antagonist.
Q6. What pharmacological interaction is demonstrated by acetylcholine and atropine on rabbit ileum?

Atropine produces reversible competitive antagonism of acetylcholine at muscarinic receptors.
Q7. How would you distinguish competitive from non-competitive antagonism using the dose–response curve?

Competitive antagonism typically produces a surmountable rightward shift with preserved Emax, whereas non-competitive antagonism typically reduces the attainable maximum response.

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