Past Years SNQ Answer by RCSI

Past Years (2006 & 2007) Questions And Answers Compilation. 2006 Q1. A 70 year old woman’s blood pressure is found to be elevated on two separate occasions (180/105). Describe the mechanisms of action and the possible adverse effects of two drug classes that you would consider using to lower blood pressure in this woman. Antihypertensive Drugs: ABCD AVAC ACE-Inhibitors •Beta-blockers •Calcium-channel blockers •Diuretics •Angiotensin II antagonists •Alpha-blockers •Vasodilators •Central sympathophlegics ThiazideDiuretics •Ex.Hydrochlorthiazide •MOA:.Inhibition of NaCl reabsorption in early distal tubule of renal nephron, decrease water reabsorption, decrease in blood volume. •S.E.s Fatigue Hypokalaemia Impotance Glucose intolerance Dyslipidaemia Hyperuricaemia Beta-blockers Examples Non-selective; Propranolol, β1 selective; Atenolol With vasodilatation; Pindolol(β1 selective antagonist and partial agonist at B2 adrenoceptors) Carvidalol (non-selective β-blocker but also α1 blocker) Nebivolol (releases NO) Mechanisms of action: decrease HR, and decrease CO Inhibition of rennin secretion - S.Es: Bronchospasm(non-selective) Worsening of peripheral vascular disease (non-selective) Glucose intolerance Dyslipidaemia Negative inotrophy Impotance Fatigue CNS effects, nightmares Q2. A 10 year old girl with asthma is still suffering recurrent moderately severe attacks of asthma despite treatment with an inhaled beta-2 adrenoceptor agonist. Discuss the mechanisms of action and side effects of two classes of drugs you would consider adding to her treatment regimen, so as to reduce frequency and severity of attacks.

Bronchodilators • B2 adrenoreceptor agonists • Muscarinic (M3) antagonists • Xanthines Anti-inflammatory Drugs • Glucocorticoids • Cromones • Leukotriene synthesis inhibitors & receptor antagonists

1. MUSCARINIC ANTAGONISTS Ipratropium Bromide - derivative of N-isopropylatropine Tiotropium bromide - Newer long-acting : Administration Given by inhalation – not well absorbed -little systemic effects. Mechanism of action Inhibition of the action of acetyl choline at M1, M2, and M3 muscarinic receptors. thus producing bronchodilation and reducing mucous secretion. Slower acting than B2 agonists.

2. XANTHINES Caffeine Theophylline Oral. Short T1/2. Sustained release preparations available Aminophylline IV.

MOA: Relax bronchial smooth muscle (bronchodilation) by inhibiting phosphodiesterase resulting in increased cAMP and cGMP. Also anti-inflammatory actions (inhibit the late phase) ? inhibition of phosphodiesterase present in inflammatory cells. Selective PD4 inhibitors (Roflumilast, Cilomilast) may be particularly beneficial in COAD)

Side Effects Narrow therapeutic range (27-80mmol/l) Side effects likely with concentrations >110mmol/l ® gastrointestinal: nausea / anorexia ® cardiovascular: arrhythmias can be fatal ® CNS: nervousness, tremor, seizures Pharmacokinetics Metabolised in the liver T1/2 increased by liver disease, heart failure and decreased by smoking and heavy drinking NB Drug interactions Pharmacokinetic Drug Interactions occur with Theophylline because of extensive Metabolism by Cytochrome P450 Enzymes Cytochrome P450 1A2 is the main isoform responsible for the metabolism of theophylline Erythromicin and Cimetidine are also metabolised by this isoform – hence competitive inhibition can occur when co-administered Enzyme inducers such as; Phenytoin, Carbamazepine, Rifampicin, Barbiturates, Alcohol result in reduced plasma concentrations and decreased effects of drugs (such as theophylline) which are extensively metabolised by Cytochrome P450 enzymes Note: Delayed onset (2-3 weeks) as enzyme induction requires synthesis of new protein. Note: Pharmacokinetic drug interactions are most important for drugs, such as theophilline, that have a low therapeutic index

Q3. Describe the treatment of arrhythmias, giving special attention to the Vaughan Class IV ( Ca channel blockers)

Verapmil

     

-Reduce cardia Block the L-type of Ca channel. contractility. Shorten phase 2 (plateau) Diltaizem Reduce contractility of heart. -Bradycardia Act on AV node Treat SVT Class V Digoxin -Hypokalaemia Increases vagal activity via its central action on the central nervous system. (Digitalis) -Nausea &  Thus, decreasing the conduction of electrical impulses through the AV node. vomiting.  Positive inotropic effect Williams classification and side effects of two classes of anti-arrhythmic drugs.

There are five main classes in the Vaughan Williams classification of antiarrhythmic agents:     

Class I agents interfere with the sodium (Na+) channel. Class II agents are anti-sympathetic nervous system agents. All agents in this class are beta blockers. Class III agents affect potassium (K+) efflux. Class IV agents affect the AV node. Class V agents work by other or unknown mechanisms.

Q4. The levels of plasma lipoproteins in human subjects are used diagnostically to evaluate cardiovascular risk. Name the two lipoproteins mainly responsible for cholesterol transport and state FOUR of the properties by which these two may be distinguished.     

   

Low density lipoprotein (LDL) Lower density, larger Contain a larger proportion of cholesterol than HDL Move cholesterol around to/from liver and peripheral tissues in the circulatory system As a result, cholesterol may be deposited in the walls of blood vessels and cause cardiovascular diseases such as atherosclerosis High density lipoprotein (HDL) Higher density, smaller Carry least amount of cholesterol Carry cholesterol back to liver for elimination from body



As a result, accelerate the removal of cholesterol from blood, reducing the likelihood of cholesterol becoming deposited in arterial walls  provide protection from cardiovascular diseases

Q5. A family travel to Australia to visit their relations. On arrival in Sydney, the mother experiences chest pain and is admitted to hospital. She is found to have a pulmonary embolus. Describe how a pulmonary embolus interferes with respiratory function.

      

Pulmonary embolus – blockage of pulmonary artery by matters such as fat, tumour or a clot from vein Decrease perfusion / underperfusion Larger ventilation/perfusion (V/Q) ratio Increased physiological dead space, wasted ventilation Increases PO2 and decreases PCO2 Alveoli contract, pulmonary artery relax Symptoms: dyspnoea, tachypnoea, pleuritic pain, cough, haemoptysis

Q6. Describe the intrinsic ability of the heart to adapt to changes in venous return. Illustrate your answer with a diagram. Venous return: The rate of blood flow back to the heart is the venous return. It normally limits cardiac output. VR at RA determines amount of blood flowing thru pulmonary circ (L.Atrium) and hence through systemic circ (at L.Ventricle) Cardiac output is affected by preload (: is the pressure stretching the ventricle of the heart, after passive filling and atrial contraction / LVEDP: L.ventricle end diastolic pressure) Preload affected by...VENOUS RETURN:  Left ventricle (LV) function curve, or Frank - Starling curve (1914):  Normal range of the LVEDP, 5-6 mmHg  Optimal initial preload, 15-20 mmHg (at optimal length of Sarcomere, 2.0 – 2.2 µm)  When the LVEDP > 20 mmHg, LV work is maintained at almost the same level, does not change with the increase of LVEDP  What affects LVEDP??  Period of the ventricle diastole (filling) – heart rate  Speed of the venous return (difference between the venous pressure and atrial pressure)



Mechanism: VR increase, LV work inc, smooth muscle stretching inc, LVEDP increase, more blood pumped out of heart, vice versa

Basically, heart gives away all that it receives. Concept of heterometric regulation: regulation depending upon change in size (i.e. LVP) Q7. In a group on a hiking tour to the historic site of Machu Picchu in the Peruvian Andes, some develop acute mountain sickness but others acclimatise normally to the high altitude. Describe the cardiovascular and respiratory changes that occur during acclimatisation.   

Physiological effects of altitude are due to decrease in barometric pressure Air composition stays the same but PO2 in the air falls  PAO2 and PaO2 fall Lower amount of oxygen available to inhale (hypoxia), less oxygen reaches the blood (hypoxemia)  Cardiovascular: pulmonary hypertension, increased HR and CO  Respiratory: ventilation increases by 65% to bring in more oxygen at rapid rate  PACO2 and PaCO2 decrease (hypocaptic) Q8. On suddenly standing upright, you may feel dizzy and faint. Describe the reflex physiological response which normally counteracts postural hypotension.

Drop in bp sensed by baroreceptor increase firing rate to medulla activate sympathetic  increase hr  increase co  increase bp

Q9. Describe the changes in left ventricular pressure occurring during the cardiac cycle. Illustrate your answer with a diagram giving absolute values of pressure.

Q10. Prior to elective surgery for a hip replacement, a patient is found to have haemoglobin of 8g/dl. Discuss the balance between oxygen availability and demand in this situation. 

1.

2.

3.

4.

Things need to know o Source of oxygen o How body respond if  Demand increase  Demand decrease o Effect to pO2 & pCO2 o Example for each situation o Regulator Source of oxygen o From ventilation process o Diffuse to blood o Pump by heart If demand increase o Example – exercise o Effect – pO2 low, pCO2 high o How body respond  Ventilation – increase (accessory muscle)  Blood flow – increase to muscle (higher c. output, heart rate ) If demand decrease o Example – sleeping o How body respond  Ventilation – normal (not involve accessory muscle)  Blood flow – not focus to muscle Regulator

o Detector – chemoreceptor (central, peripheral) o Central controller – medulla, respiratory centre o Effector – respiratory muscle Q11. A young man is brought to the Accident and Emergency Department following a stab wound to the 4th right intercostal space and has developed a pneumothorax. List the layers of the chest wall that the knife has passed through. Where does the neurovascular bundle lie in the intercostal space and what does it contain? What are the surface markings of the pleural cavities? Answers. Layers of the chest wall that the knife has passed through: - Skin - Fat - External intercostal muscle - Internal intercostal muscle - Innermost intercostal muscle - Endothoracic fascia - Parietal pleura - Pleural cavity - Visceral pleura Neurovascular bundle: Lies within the costal groove (upper part of the intercostal space) The contains, from top to the bottom, are intercostal vein, intercostal artery, and intercostal nerve. The surface marking of the pleural cavity: -

About 2 cm above the clavicle At 4th costal cartilage, the left pleural line pass laterally, while the right line continues down - The lines pass obliquely laterally across the 6th costal cartilage - In the midclavicular line, the lines across the 8th rib - In the midaxillary line, they cross the 10th rib - In the midscapular line, they cross the 12th rib Q12. During a routine physical examination, you auscultate your patient’s chest. Describe or draw the surface markings of the heart and the heart valves. Indicate where you would place a stethoscope to listen to each valve. -

Heart border: upper left end: 2nd left CC, upper right end: 3rd right CC, lower right end: 6th CC, lower left end: 5th intercostal space, midclavicular line. Surface marking of the heart valves: retrosternal. Valve

Surface marking

Auscultation

Pulmonary

3rd CC, left sternal border

2nd cc, left sternal border

Aortic

3rd ICS, right sternal border

2nd cc, right sternal border

Mitral

4th CC, left sternal border

5th ICS, midclavicular line

Tricuspid

4td ICS, right sternal border

Left lower sternal border

1. Aortic region (between the 2nd and 3rd intercostal spaces at the right sternal border) (RUSB – right upper sternal border). 2. Pulmonic region (between the 2nd and 3rd intercostal spaces at the left sternal border) (LUSB – left upper sternal border). 3. Tricuspid region (between the 3rd, 4th, 5th, and 6th intercostal spaces at the left sternal border) (LLSB – left lower sternal border). 4. Mitral region (near the apex of the heard between the 5th and 6th intercostal spaces in the mid-clavicular line) (apex of the heart). Q13. Describe the diaphragm, with reference to its attachments and nerve supply. List the openings that exist to allow passage of structures between the thoracic and abdominal cavities; include the vertebral levels of these openings and name the structures which pass through them. Diaphragm is a sheet of muscle across the bottom of the ribcage, separating thoracic cavity and abdominal cavity. Attachment: 1. sternal origin- xiphoid 2. 6 costal origin a. 6 costal cartilages (7-12) 3. crura a. right crura T3/T4 b. left crura T2/T3 4. arcuate ligaments - median : across aorta - medial : across psoas minor - lateral : across psoas major Nerve supply: Phrenic nerve (C 3,4,5 “keeps the diaphragm alive”) 1. Right phrenic nerve – descend to diaphragm near orifice of IVC T8. 2. Left phrenic nerve – descend to diaphragm near cardiac apex (left, muscular portion) (motor- entire diaphragm, sensory- central tendon, sensory to the peripheral is by local intercostal nerves)

Openings: T8 – IVC, right phrenic nerve (at central tendon) T10 – oesophagus, R&L vagus nerve (and esophageal branches of left gastric arteries&veins) T12 – aorta, azygos vein, thoracic duct Q14. A 29 year old man develops shoulder pains following a tennis match. Explain with reference to their attachments, how the muscles of the shoulder girdle control rotation of the scapula when reaching out and opening a door. 1. flexion of the shoulder when reaching out a. anterior part of deltoid- attached from spine of scapula, acromium process, lateral 1/3 clavicle to humerus b. pectoralis major (clavicular part)- attached from clavicle, sternum and costal cartilages c. coracobrachialis d. biceps 2. extension of shoulder when opening a door a. latissimus dorsi (assist by teres major)– attached from spinous process (T6T12), sacrum, iliac crest and ribs (10-12) to humerus (floor of the bicipital groove) b. posterior part of deltoid – attached from spine of scapula, acromium process, lateral 1/3 clavicle to humerus (deltoid tuberosity) c. teres major – attached from inferior angle of scapula to intertubercular sulcus of the humerus (medial lip) d. triceps – attached from: i. long head: inferior glenoid tubercle of the scapula ii. lateral head: posterior humerus, above spiral grioove iii. medial head: posterior humerus, below the spiral groove to olecranon process of ulna 10‟

3. Abduction of Shoulder joint when reaching out Supraspinatus Supraspinatus fossa of scapula

Greater tubercle

Up to 90‟

Deltoid

Spine of scapula, acromium process, lateral 1/3 clavicle

Deltoid tuberosity

Rotation of scapula, allows another 60‟ abduction

Serratus anterior

Upper 8 ribs

Medial border of scapula

Trapezoid

Occipital protuberance

Origin of deltoid:

Ligamentum nuchae

Spine of scapula, acromium process, lateral 1/3 clavicle

Spinous process of C1-T7

Q15. A 29 year old man accidentally puts his hand through a sheet of glass, causing a laceration of his thenar eminence. Describe the movements of the thumb. Indicate the muscles involved and their innervation. Finger and Thumb Movements •Flexion –Thumb –bends medially along the palm –Fingers –bend anteriorly •Extension –Thumb –points laterally –Fingers –move posteriorly •Abduction/Adduction Movement of thumb forward (anteriorly) is abduction and Movement of thumb forward (anteriorly) is adduction The thenar eminence (ball of the thumb)–has a flexor pollicis brevis, an abductor pollicis brevis, and an opponens pollicis. Each of the muscles is supplied by T1 from median nerve. Flexion

bends medially along the palm

Extension

points laterally

Abduction

Movement of thumb forward (anteriorly)

Adduction

Movement of thumb backward (posteriorly)

FPL FPB EPL EPB APL APB AP

Median Median Radial Radial Median Radial Ulnar

2006 (repeat) Q1. A young women presents to the Accident & Emergency Department with dysphagia (difficulty swallowing), after swallowing a large piece of biscuit. Describe the structure, course and relations of the thoracic oesophagus. Describe the points at which the oesophagus is narrowed.

Q2. A young child is brought to the Accident and Emergency Department after inhaling a peanut. Describe the trachea and bronchial tree within the thorax, including their structure, position and relations. Into which segmental bronchus is an inhaled foreign body most likely to lodge if a patient is standing upright? Or lying down?



The right main bronchus is wider, shorter, and more vertical than the left main bronchus.



The cartilage and mucous membrane of the primary bronchi are similar to that in the trachea.



As the branching continues through the bronchial tree, the amount of hyaline cartilage in the walls decreases until it is absent in the smallest bronchioles. As the cartilage decreases, the amount of smooth muscle increases. The mucous membrane also undergoes a transition from ciliated pseudostratified columnar epithelium to simple cuboidal epithelium to simple squamous epithelium.



Standing upright? Or lying down? (probably standing up, because the trachea is straight vertically in this position…probably.)

Q3. A patient presents to her GP with a mass in the lateral breast and fullness in her axilla. Describe the structure of the female breast, including relations blood supply and lymphatic drainage. What structures in the axilla might be damaged during surgery?

What structures in the axilla might be damaged during surgery? It could be the brachial plexus, axillary art and vein. The lymph nodes can be removed surgically.

Q4. A footballer dislocates his shoulder during a match, damaging the axillary nerve. Describe this nerve, including its origin, course and distribution (motor and cutaneous). What is its root value? How would you test for its function clinically?   

Comes off the posterior cord of the brachial plexus at the level of the axilla (armpit) and carries nerve fibers from C5 and C6. The axillary nerve travels through the quadrangular space with the posterior circumflex humeral artery and vein. It supplies two muscles, deltoid (a muscle of the shoulder), and teres minor (one of the rotator cuff muscles). Sensory information from the shoulder joint, as well as the skin covering the inferior region of the deltoid muscle, regimental patch (Superior Lateral Cutaneous Nerve branch).



It lies at first behind the axillary artery, and in front of the Subscapularis, and passes downward to the lower border of that muscle. It then winds backward, in company with the posterior humeral circumflex artery, through a quadrilateral space bounded above by the Teres Minor, below by the Teres major, medially by the long head of the Triceps brachii, and laterally by the surgical neck of the humerus, and divides into an anterior and a posterior branch.



The anterior branch (upper branch) winds around the surgical neck of the humerus, beneath the Deltoideus, with the posterior humeral circumflex vessels, as far as the anterior border of that muscle, supplying it, and giving off a few small cutaneous branches, which pierce the muscle and ramify in the skin covering its lower part. The posterior branch (lower branch) supplies the Teres minor and the posterior part of the Deltoideus; upon the branch to the Teres minor an oval enlargement (pseudoganglion) usually exists. The posterior branch then pierces the deep fascia and is continued as the lateral brachial cutaneous nerve, which sweeps around the posterior border of the Deltoideus and supplies the skin over the lower two-thirds of the posterior part of this muscle, as well as that covering the long head of the Triceps brachii. The trunk of the axillary nerve gives off an articular filament which enters the shoulderjoint below the Subscapularis. The axillary nerve may be injured in anterior dislocations of the shoulder joint, compression of the axilla with a crutch or fracture of the surgical neck of the humerus. Clinical test includes o Abduction of shoulder >10. Paralysis of the teres minor and deltoid muscles. o Sensory of regimental patch



 

Q5. When putting up a shelf, you use a screwdriver to attach it to the wall. Define the movements of pronation and supination of the upper limb. Name and briefly describe the joints involved in pronation and supination. Name two pronators and two supinators. Pronation : Rotation of forearm to bring the palm facing backward.   

Supination : Rotation of forearm to bring the palm facing forward (supine position). Joint involved : Proximal & distal radioulnar joints (Where the radius and ulnar articulate, and both are synovial joints) Pronators : Pronator Teres & Pronator Quadratus

 Supinators : Supinator (Synergist) & Biceps Brachii (Main) Q6. In the human lung, the alveolar surface is composed of two main cell types. Compare briefly the metabolic functions and capabilities of type I and type II pneumocytes. Type I Pneumocyte Type II Pneumocyte Flat, small cells (Squamous) Large cells (Cuboidal) Unable to repair or regenerate (Because it Able to repair and regenerate cannot replicate) Responsible for gas exchange in the alveolus Produce surfactant which helps to reduce (Because its oxygen consumption is nearly surface tension of the alveolus zero) Q7. Draw and label a myocardial pacemaker potential. Relate each phase to the corresponding change in ion conductance.

 

SA node is the cardiac pacemaker Resting potential : About -55mV (Since the fast Na+ channel only active at around 60mV, therefore it is inactivated in SA node)  Na+ slowly gets into the fibre, thus depolarising it towards the threshold which is -40mV  Once it achieves the threshold, slow Ca2+/Na+ channel opens, leading to action potential of SA node  After about 200msec, Ca2+/Na+ channel closes and K+ leak channel opens  K+ leaves the cell and leading to repolarisation of SA node to its resting potential (55mV) Q8. Describe the cardiac actions of the neurotransmitters noradrenaline and acetylcholine. Noradrenalin (NA) Comparison Acetylcholine (ACh) Adrenergic (Beta 1 receptor) Receptor Cholinergic (M2 receptor) Adenylate cyclise (Increase Adenylate cyclise (Decrease 2⁰ messenger cAMP production) cAMP production) Sympathetic Type of ANS Parasympathetic Increase heart rate Effect on SA node Reduce heart rate  Open Ca2+/Na+ channels  Open K+ channels  Ca2+/Na+ enters  K+ leaves cardiac cells  Depolarise  Hyperpolarise  Bring the base (-55mV)  Bring the base further away

closer to threshold (-40mV), thus making SA node faster to be depolarized Increase contractility  Increase permeability of cardiac cells to Ca2+  Increase Ca2+ influx

Effect on Atria

from the threshold, thus making SA node harder to be depolarized Reduce contractility  Reduce the cAMP production

Q9. Compare and contrast the pressure differences in the systemic and pulmonary circulations, accompanied by numerical values. SYSTEMIC CIRCULATION: circulation of oxygenated blood from the left ventricle of the heart to the various tissues and of venous blood back to the right atrium of the heart, is high pressure circulation PRESSURES INVOLVED: SYSTEMIC PRESSURES

SYSTOLIC/DIASTOLIC

NOTES

Systemic blood pressure aorta

120/80mmHg

SBP mainly determined by CO DBP mainly determined by Total Peripheral Resistance

Pulse pressure (PP)

40mmHg

SBP-DBP

Mean Arterial Pressure (MAP)

93mmHg

=DBP + 1/3PP

Pressure in capillary beds

17mmHg

Right Atrial Pressure (RAP) and vena cava

0mmHg (range= 04mmHg)

RAP~JVP~CVP

So people measure JVP height to reflect venous return/ hydration state (i.e. as blood volume also affects v.return) and assess cardiac function Raised JVP>2cm = right side HF

PULMONARY CIRCULATION: Flow of blood from the right ventricle of the heart through the blood vessels of the lungs and back to the left ventricle of the heart, is low pressure circulation PRESSURES INVOLVED:

PULMONARY PRESSURES

SYSTOLIC/DIASTOLIC

NOTES

Pulmonary Artery

25/10mmHg

Pulse pressure

15mmHg

SBP-DBP

Mean pulmonary artery P

15 mmHg

DBP + 1/3 PP

Pulmonary capillaries

~7 mm Hg

Pulmonary venous P

~ 2 mm Hg (2-6)

Left atrial pressure

~2-6mmHg

Falls to ~0 in cardiac cycle Raised in Left Heart Failure

Pulmonary Capillary wedge pressure (PWP)

~7 mmHg A lil above LAP

-pressure measured in a pulmonary artery after occlusion of that artery. -provides an indirect measure of the left atrial pressure. - measured by a catheter wedged into the distal pulmonary artery -usually real LAP1 defective synthesis of the PAH enzyme cofactor, tetrahydrobiopterin • _Clinical Phenotype and management depends of residual PAH enzyme activity • _Phenylketonuria (PKU) phe>600μmol/L o PAH deficiency o DHPTR deficiency • _Hyperphenylalaninaemia Not required by pass students phe >180 μmol/L