2007 Second Sitting

2007B 01: 1 candidate (14%) passed this question. Candidates were expected to base their answers around the variables involved in the equations that describe oxygen content in blood and oxygen delivery. Although most candidates mentioned changes in haemoglobin that increase oxygen carriage, a more complete discussion of the changes that influence cardiac output and peripheral circulation was often omitted.

2007B 02: 4 candidates (57%) passed this question. Good answers to this question were those that had a tabular format to the structure of the answer - for example column headed mechanism, sites, drug and side effects. Most common omissions were not to further describe how the different mechanisms of action of diuretics increased urine output, e.g. "disruption of the counter current multiplier system by decreasing absorption of ions from the loop of Henle into the medullary interstitium, thereby decreasing the osmolarity of the medullary interstitial fluid". There was ofter little mention of increased urine solutes and the effect the electro chemical effect had in promoting a diuresis. Examples of drugs were well done.

2007B 03: 1 candidate (14%) passed this question. Good answers to this question were those that gave an accurate account of the physiological effects, e.g. inhibition of the fast sodium channels in the His-Purkinje system as well as the atrial and ventricular myocardium, decreasing conduction velocity (differential conduction inhibition of RBB being more susceptible) and increasing duration of repolarization, and the absolute refractory periods. Once having done that the rest of the answer would have flowed more easily, e.g. ECG changes and conduction disturbances. The effects of tricyclic antidepressants on Na channels and as a consequence the cardiovascular conduction abnormalities were often omitted. Anti cholinergic (e.g. slowing GIT motility) and antihistamine effects (e.g. obtundation) were often overlooked. Also frequently overlooked were basic pharmacology relevant to treatment, e.g. lipophilic, large volume of distribution, systemic acidosis reduces the extent of protein binding and increases unbound (active) drug. Additional points were available to those who not only mentioned sodium bicarbonate, but also mentioned the principles behind its use for this circumstance

2007B 04: 4 (57%) candidates passed this question. It was expected candidates would outline the underlying principles of ultrasound imaging (reflection, scattering, refraction, and attenuation) and discuss that the basic image is the result of reflection of the transmitted ultrasound wave. Most candidates appreciated that the amplitude of the reflected echo is a function of the acoustic mismatch of the tissues and the angle of incidence and many candidates provided details mathematical descriptions concerning these principles. While high levels of technical details were not required the answer should include a mention of the use a piezoelectric transducer and that an ultrasound beam has 3 dimensions — Axial, Elevation and Lateral. Some comment of the modes of Display (A= Amplitude, M Time Motion, 21), etc) was expected. Extra credit was given for answers that included details regarding limits of depth of penetration (longer wavelength penetrate deeper, but loose image quality with longer wavelengths) and the varying properties of human tissue regarding refraction and attenuation (little refraction (path deviation) in human tissue and air attenuates). Specific comment on the Doppler Effect was required. It was expected candidates would described that it refers to the change in frequency of a sound wave reflected by a moving target and that the reflected frequency differs if moving toward or away. Correctly stating that the reflected Frequency is Higher Towards and Lower Away scored additional marks. Comments concerning obtaining the best Doppler images with lower frequencies (opposite to ultrasound) and colour Doppler attracted additional marks.

2007B 06: 4 candidates (57%) passed this question. It was expected candidates would describe that the maintenance of body temperature is a balance of heat loss and heat production and outline the seies of controls that are important in this process. An overview of the reflexes involved was expected with som ecomments on temperature receptors in skin for hot and cold, the hypothalamic integration and then the effector being the skin blood flow (vasodilation / vasoconstriction and A-V shunts). Answers were expected to include some comment on the fact that heat exchange occurs via radiation / conduction / convection / evaporation and requires a heat gradient and that skin blood changes can facilitate or impair this exchange. Using examples such as; if body needs to loose heat there is vasodilation and sweating often added clarity. Extra credit was given for discussing swet production and the principle and the principle of how that will allow increased heat loss with further credit given for discussing the impact of humidity. Credit was also given for mentioning piloerection, particularly if candidates went on to explain why this might be useful (even though not really applicable in man).

2007B 08: 5 candidates (71%) passed this question. Good answers included the following description of, and types of, baroreceptors (e.g. stretch-receptors) their locations (e.g. walls of the aorta, carotid sinuses, the atria etc) the stimulus they respond to (e.g. pressure, volume) short term and long term responses, alteration to set points, impulse frequency / pressure curve a brief description of the afferent and efferent pathways and the resultant efferent effects (e.g. alterations to heart rate, blood pressure, etc)

2007B 09: 2 candidates (28%) passed this question Key Points: "Anaphylaxis" may be: True anaphylaxis: a symptoms complex following exposure of a sensitised individual to an antigen, produced by a type I hypersensitivity reaction, associated with IgE mediated mast cell degranulation Anaphylactoid reactions: Indistinguishable from true anaphylaxis, however the immune nature of the reaction is either unknown, or not due to a type I hypersensitivity reaction, immediate generalised reaction is a better term. i End-organ effects, e.g. H 1 and H 2 receptors

2007B 10: 2 candidate (28%) passed this question. The main points expected for a pass were An appreciation that the aim of controlling gastric emptying is to present the food to the small bowel for absorption in a controlled manner That there are both gastric neural and hormonal mechanisms e.g. Gastric volume and the hormone gastrin There are duodenal neural and hormonal mechanisms e.g. composition of the chyme, secretin and cholecystokinin and the influence of duodenal distension Extra points were given for mentioning the effect of sympathetic stimulation and pregnancy on gastric emptying Common problems were not enough knowledge, naming hormones but not saying what theirs action was and including drugs.

2007B 11: 1 candidate (14%) passed this question. The main points expected for a pass were Definition of hypoxia Physiological causes of hypoxaemia Formation of a lactic acidosis Development of hypocarbia secondary to stimulation of respiration from hypoxia and acidosis Explanation of the decreased bicarbonate concentration and negative base excess Extra points were given for more detailed explanation of the lactic acidosis, commenting on the anion gap and some consequences of hypoxaemia. A common problem was to incorrectly state the relationship between pH and hydrogen ion concentration.

2007B 12: 1 candidate (14%) passed this question. The main points expected for a pass were: The ratio of k off/k on is the dissociation constant A low value indicates that less drug is required to bind to the receptors affinity is the reverse of dissociation constant Clinical application of high affinity include large effect at lower concentrations Physiological factors could include temperature The main problem with this question was lack of knowlegde.

2007B 13: 1 candidate (14%) passed this question. Main points/concepts expected in answer. Surfactant: increases lung compliance decreases surface tension at alveolar air-water-interface prevents small alveoli from collapsing accounts for most of hysteresis in intact lung Lung elastic recoil: lung compliance changes in disease states Lung volume: lung compliance greatest around FRC lung compliance reduced at low and high lung volumes gravitational effects on regional lung compliance Pulmonary blood volume: Pulmonary venous congestion reduces lung compliance Lung size: Specific compliance = lung compliance / FRC Dynamic lung compliance: nfluenced by airways resistance lung compliance measured during normal breathing less than static lung compliance frequency dependence

2007B 14: 3 candidates (43%) passed this question. Second messenger - Hormone/drug - receptor binding is coupled to a subsequent series of intracellular biochemical events that precipitate the ultimate hormone/drug effect. Examples are G proteins an energy dependent process by which there is hydrolysis of G protein-associated GTP to GDP. There are both stimulating and inhibitory proteins which subsequently act to increase or decrease activity of the enzyme adenylyl cyclase, resulting in increased levels of cyclic adenosine 3 ',5'-monophosphate ( cAMP) in the cell which in turn activates protein kinases that phosphorylate various proteins, ion channels, and second messenger enzymes. Also G proteins stimulate hydrolysis of phosphatidyl-inositol-4,5-bisphosphate (PIP2) generating inositol-1,4,5-trisphosphate (IP3) and 1,2-diacylglycerol (DAG). Both systems increase intracellular calcium.

2007B 16: 4 candidates (57%) passed this question. To pass this question, the candidate only needed to stage the range of normal blood glucose, define hypoglycaemia then give an overview of the body's response to hypoglycaemia (control of blood glucose - sensors, integrators, effectors). Additional credit was given for a more detailed description of the various responses. Few candidates mentioned the role of the sympathetic nervous system. Much time was wasted in giving detailed descriptions of metabolic pathways to the exlusion of an overview of the body's responses.

2007B 17: 2 candidates (29%) passed this question. Producing a list that included the following was required: - To trat hypertension and substance withdrawal. - To provide anxiolysis, sedation, analgesia, and sympatholysis. A brief discussion of the abilities of clonidine in each of these areas would have rounded off a good answer. Many candidates listed only a couple of uses of these agents, and then followed this with a comparison of clonidine and dexmedetomidine. Most answers did not include sufficient information to achieve a pass mark.

2007B 18: 3 candidates (43%) passed this question. To obtain a pass candidates needed to briefly define autoregulation and state the range of MAP over which this occurs, and why it occurs, then provide a more detailed discussion about the mechanisms thought to be responsible for this. The main site of autoregulation in the kidney is the afferent arteriole. There are two main factors that affect vascular tone in the afferent arteriloe, these are stretch-activated constriction of vessels (myogenic mechanism) and tubuloglomerular feedback (TGF). Both of the above mechanisms are important to maintenance of near-constant blood flow. Stretch results in membrane depolarisation, increased intra-cellular concentrations of Ca and ultimately, vasoconstriction. In tubulo-glomerular feedback, complex signals pass from the macula densa to the afferent arteriole, regulating its tone. The fundamental theme of TGF is that increased delivery of fluid and/or NaCl to the distal tubule causes vasoconstriction, thus limiting the flow (negative feedback). The major weakness in answes was again the failure to include sufficient information to acheive a pass mark.

2007B 19: 2 candidates (29%) passed this question. The main points expected were the determinants of myocardial oxygen supply. These include arterial oxygen content and coronary blood flow. Coronary blood flow deoends on coronary perfusion pressure and coronary vascular resistance and that most left coronary blood flow occurs in diastole. Tachycardia reduces diastolic time and hence left coronary blood flow. In comparison blood flow in the right coronary artery is continuous both in systole and diastole and is little affected by heart rate. A correctly labelled diagram of left and right coronary blood flow attracted extra marks. Unfortunately most diagrams were inaccurate, not labelled and had no units on the axes. Systolic compression particularly reduces blood supply to the left ventricular subendocardium which is most susceptible to ischaemia. Extra marks were given for describing metabolic autoregulation, the high oxygen extraction, explaining that oxygen supply cannot be increased by increasing oxygen extraction in the coronary circulation and describing the driving pressure differences in both coronary arteries in systole and diastole. A description of the determinants of myocardial oxygen demand was also required (e.g. left ventricular, preload, contractility, afterload, and tachycardia. This part of the question was particularly poorly answered.

2007B 20: 3 candidates (43%) passed this question. Most candidates did not appreciate that serum potassium is a function of two variables: 1. Total body potassium 2. Distribution between the extracellular and intracellular fluid compartments. Approximately 98% of total body potassium is intracellular due to the action of Na+/K+ ATPase. Potassium is important in the electrophysiology of excitable cells and changes in serum potassium can affect their function. Hence the importance of keeping the serium potassium within a narrow normal range. Again most candidates did not provide the overview that serum potassium levels reflect a balance between intake, output and transcellular distribution. Normal dietary intake is highly variable. Transcellular distribution by the mechanisms of insulin and glucagol, catecholamines and Beta2 activity and acid base changes all work to rapidly restore changes in details on the long term renal regulation of serum potssium involving distal tubult potassium secretion and aldosterone and also the effect of distal tubular flow and sodium excretion. The effects of hyperkalaemia were better described than the first part of the question. Most candidates concentrated on the cardiac effects where most marks were awarded. The effects of an increased potassium on the cardiac action potential earned extra marks. The correlation between actual serum potassium level and ECG changes is variable and depends on many factors including how acute or chronic the hyperkalaemia is. Tratment of hyperkalaemia was mentioned by a few candidates but attracted no extra marks.

2007B 21: 2 candidates (29%) passed this question The key words in this questions were “compare and contrast”, “cardiovascular effects” and “induction dose”. Some candidates described aspects of both drugs other than the cardiovascular effects but gained no marks for this. Better answers used a combination of a table plus some explanation to contrast the cardiovascular effects of the two drugs concentration on aspects such as heart rate, cardiac output, vascular resistance and blood pressure. Many candidates were confused by the direct versus the indirect cardiovascular effects of both drugs Propofol probably has no direct negative inotropic effect. Ketamine has a direct myocardial depressant action but this effect is overridden by the centrally mediated sympathetic action of the drug. The effect of both drugs on the baroreceptor response alone is a difficult area as there is significant interplay between the direct cardiovascular effects of the drugs and their effect on the baroreceptor reflex. Allowance was made for this in the marking. Propofol resets the baroreceptor reflex producing a slower heart rate for a given level of blood pressure. Overall both drugs depress the baroreceptor reflex. Comparison of the effects on cerebral, coronary, renal and hepatic blood flow earned extra marks.

2007B 22: 2 candidates (29%) passed this question. The main points expected for a pass were: CSF is formed by ultra filtration and secretion CSF volumes and turnover Flow through the ventricles and subarachnoid spaces Absorption through the arachnoid villi Relationship between and absorption and pressure This is not a question about intracranial pressure so no points were given for Munore Kellie doctrine etc, Also no points were given for the functions of CSF. Diagrams need to have the axes labelled correctly.

2007B 23: 3 candidates (43%) passed this question. Common drugs listed were: Beta 2 agonists salbutamol and adrenaline, Steroids, Magnesium, Phosphodiesterase inhibitors. In order to obtain marks for that class of drug the mechanism of action had to be described e.g. for theophylline; acts as a bronchodilator by inhibiting the breakdown of cyclic AMP and cyclic GMP. There were several excellent answers to this question.

2007B 24: 0 candidates passed this question. The main points for a pass were Patient factors: Normal value for the difference between end tidal and arterial CO2 Physiological factors e.g. alveolar dead space, failure to plateau of the capnograph trace Pathological factors e.g. cardiac arrest, air embolism, asthma Equipment factors: Leaks, Occlusion, Samling site errors etc A common mistake was to state that dead space caused the difference between end tidal and arterial carbon dioxide but not which type of dead space. The Bohr equation was not required. VIVAs A. Pharmaceutics B. Pharmacokinetics C. Pharmacodynamics D. Variability in Drug Response E. Cellular Physiology F. Respiratory Asthma in extremis - NMJ, NMJ blocking drugs How would you measure gas flow Causes of low PaO2 Ventilator graphs - P,V waveform G. CVS Explain physiological basis of ECG Cardiogenic shock (BP,CI,SCR given). What drugs would you use to improve BP H. Renal I. Body Fluids and Electrolytes J. Acid Base K. Neuro L. Musculoskeletal Asthma in extremis - NMJ, NMJ blocking drugs M. ANS N. Liver Describe physiology of bilirubin production and clearance O. GIT P. Nutrition and Metabolism Q. Haematology Heparin as Prophylaxis against DVT after Acute Stroke - data table R. Thermoregulation S. Immunology T. Microbiology U. Endocrine V. Obstetrics W. Measurement and Monitoring X. Procedures