2017 First Sitting SAQs

Generally there was a lack of detailed knowledge, incorrect facts and at times confusion between the sympathetic and parasympathetic nervous system functions. A lack of anatomical detail was common (the origin of preganglionic cell bodies was not described clearly, and parasympathetic ganglia were not often named and located). It was expected an answer would mention the central role of Acetylcholine as a neurotransmitter at preganglionic and post ganglionic neurons in the parasympathetic system. Target organs were identified correctly but the exact action was not specified e.g. pupillary constriction vs. dilatation, GI sphincter/bladder - contraction vs. relaxation. Detail concerning receptor physiology was not required. This is a question covering a core topic that no candidate passed. An overview of the arrangement and function of the autonomic nervous system is provided in several core physiology texts, including Ganong and Guyton.

Almost all candidates interpreted "metabolic fate" to mean absorption, digestion and transport of fat. Hence a lot of time was spent on this and little on the fate of fat once it enters the blood stream. The processes of neither beta oxidation, nor lipogenesis were not well understood. Ketone body production was better understood.

Candidates with a well organised answer scored highly. A list of drug interactions was not sufficient to pass, as the question asked to 'describe' the mechanism of drug interactions. Some candidates described the interaction but did not give examples. Common mistakes included using incorrect examples for a particular mechanism and describing the mechanism of action of drugs instead of drug interactions.

It was expected that candidates would discuss the major hormones produced (or activated) by the kidney. These included erythropoeitin, renin and calcitriol. Good answers included the following: the area where the hormone is produced or modified; stimuli for release; factors which inhibit release; and the subsequent actions / effects. Marks were not awarded for hormones that act on the kidney.

High scoring answers discussed the three major hormones involved in calcium regulation - parathyroid hormone, vitamin D and calcitonin. For each of these it was expected that candidates include: site of production, stimulus for release, inhibitory factors and actions. In the case of renin it was expected that candidates also include the actions of angiotensin and aldosterone. Very few answers discussed inhibitory factors or negative feedback loops.

This question encompasses a wide area of cardiovascular physiology. As a compare and contrast question this question was well answered by candidates who used a table with relevant headings. Comprehensive answers included: anatomy, blood volume, blood flow, blood pressure, circulatory resistance, circulatory regulation, regional distribution of blood flow, response to hypoxia, gas exchange function, metabolic and synthetic functions, role in acid base homeostasis and filter and reservoir functions. A frequent cause for missing marks was writing about each circulation separately but comparing. For example: many candidates stated 'hypoxic pulmonary vasoconstriction', but did not contrast this to 'hypoxic vasodilation' for the systemic circulation. Frequently functions of the circulations were limited to gas transport / exchange

High scoring answers began with a definition and normal values, followed by a detailed list of the consequences of decreasing the FRC. Some candidates included descriptions of the normal function of FRC, conditions that decrease FRC and ways of improving reduced FRC. These were not required and did not attract marks. Diagrams require correctly labelled axes, values & units.

Many candidates incorrectly stated that the PT assessed the intrinsic system and that the APTT assessed the extrinsic system. This led to subsequent errors in relating a coagulation test to the appropriate coagulation factors that it assessed. Some candidates produced elaborate diagrams of the coagulation cascade in isolation without relating it to the question.

Many candidates described how to perform a tracheostomy or the structure of the trachea rather than the relevant anatomical relations. It was expected that answers include anterior, posterior and lateral relations at the correct tracheal level including relevant vascular structures.

The anatomy component of answers frequently lacked required detail. Many candidates listed the observed differences in the waveforms however an explanation for these differences was required.

This question was generally well answered with good structure.

Many candidates did not include enough detail in their answers. Higher scoring answers included more depth such as the following: blood volume, left ventricular changes, arterial blood pressure, pulmonary artery pressures, risks of ischaemia, arrhythmias etc.

This question required a broad answer. It was generally well answered. Those candidates who scored well had a good structure to their answers e.g. grouping potential electrolyte disturbances together, and infectious risks together etc. and including methods used to minimise these risks in appropriate detail.

Candidates who scored well weighted their answers according to the marks allocation outlined in the question and adopted a good structure. A number of candidates confused the roles of tubuloglomerular feedback and the renin angiotensin aldosterone pathway.

This question was in two parts – the first part was worth 20% and candidates were expected to provide a definition of mixed venous blood as well as the partial pressure of oxygen in mixed venous blood (including normal range). Good answers also provided the varying PO2 from different tissue beds that make up mixed venous blood, where the ‘mixing’ occurs (the right ventricle) and where it is sampled (pulmonary artery). For the second part of the question, worth 80% of the marks, good answers included the relationship between mixed venous PO2 and mixed venous O2 content (including the shape and position of the HbO2 dissociation curve); the variables encompassed in the modified Fick equation; arterial oxygen content and its determinants; oxygen consumption (VO2); and cardiac output (CO). Including an outline of how each affects the value of mixed venous PO2. A number of candidates wrote about mixed venous oxygen saturation. Other common errors were: missing a number of key factors that affect PO2; and using an incorrect form and/or content of the modified Fick equation.

Many candidates didn’t distinguish between the different types of dead space. In general this topic was not well understood.

Most candidates attempted a structure however did not expand the answers within the categories: e.g. a passing mention of glucose homeostasis is insufficient to score full marks for the carbohydrate metabolism category.

Many candidates lost marks for poor quality diagrams with inaccurate labelling. An accurate diagram was required. Many answers lacked sufficient detail regarding contractility and afterload.

etter answers included details on CSF production (amount, site), reabsorption and factors which influences CSF and its circulation.