761. During the ST segment of the electrocardiogram, there is
A. no current flow, all myocardial membranes positive outside, negative inside
B. normal current flow of repolarisation
C. inability of damaged myocardium to depolariseif ST elevated
D. current flow if other than on zero potential line
E. if elevated, current flow during diastole (TQ)

762. During the cardiac cycle
A. systole is the period of ventricular contraction, ie. between the 1 st and 2nd heart sounds (opening and closure of semilunar valves)
B. the stroke volume is increased by increasing the end diastolic volume, not the ejection fraction
C. ventricular contraction commences at the ECG R wave and is not completed until the end of the T wave
D. diastole is the period between opening and closure of the A V valves
E. jugular venous pressure waves occur at a. atrial systole C. ventricular systole (peak of pressure) V. just prior to opening A V valves

763. Which of the following statements about the heart is true
A. Starling’s law of the heart explains homometric regulation of cardiac output
B. compliance equals I/R, is reduced by scarring resulting in reduced heterometric response to preload
C. afterload promotes sarcomere shortening while preload opposes it
D. B I receptor stimulation results in further sarcomere shortening and ultimately increased cardiac output
E. increased venous tone decreases the myocardial sarcomere length

764. The lumen diameter of vessels, heart chambers and alveoli is important because
A. resistance is inversely proportional to the square of the radius
B. the wall tension necessary to balance transmural pressure is inversely proportional to the radius (PaTIR)
C. velocity is equal to flow for any given diameter
D. flow and resistance are both related, reciprocally, to the radius to the power of4
E. alveoli collapse in the absence of surfactant because as their diameter decreases in expiration the wall tension increases

765. Right atrial pressure
A. may fall to as little as -10 mmHg, but rarely more, at rest
B. may be 6 em of blood normally
C. will tend to fall with venoconstriction
D. increases with exercise
E. increases with inspiration

766. Which of the following statements regarding cardiovascular regularity mechanisms is true
A. The Cushing reflex is characterised by hypertension and tachycardia as cerebral interstitial fluid C02 accumulates when raised intracranial pressure compromised blood flow
B. increased baroreceptor discharge from the carotid sinus and aorta elevates blood pressure and heart rate via increased sympathetic discharge
C. noradrenaline, adrenaline, angiotensin II and vasopressin are all hormones responsible for local tissue blood flow autoregulation
D. in general, tissue blood flow is regulated according to tissue needs, cardiac output is regulated according to the sum of tissue flow and blood pressure is regulated independently of either local blood flow control or cardiac output control
E. increased central venous pressure produces the same sympathetic response from atrial stretch receptors as elevated blood pressure produces from carotid sinus baroreceptors

767. Characteristics of the brain, CSF and cerebral circulation include
A. CSF volume of 150mL at a lumbar pressure of 0-1 00 mrn CSF
B. CSF I plasma protein ratio of 1, glucose 0.6
C. weight of 1.4 kg suspended in CSF from dura mater by arachnoid trabeculae
D. susceptibility to convulsions at normal blood sugar levels in diabetics
E. oxygen consumption of 25 mUmin, ie. 10% of total body consumption

768. Concerning the Islets of Langerhans
A. The B cells make up 90% of the islets
B. the D cells secrete pancreatic polypeptide
C. Beef insulin is structurally more like human insulin than pork insulin is
D. The release of insulin involves depolarisation of the cell membrane, causing opening of calcium channels
E. Hyperkalaemia increases the secretion of insulin

769. In the thyroid gland
A. Passage of iodide from the thyroid cells into the colloid is an active process
B. RT3 is inert
C. Most T4 is metabolised to T3
D. Thyroglobulin is formed in the colloid
E. Thyroxine binding globulin has the highest capacity to bind thyroid hormones in the plasma

770. The effects of thyroid hormones include all of the following except
A. increased activity Na/K ATP ase
B. increased nitrogen excretion
C. increased levels of catecholamines
D. increased carbohydrate absorption from the gut
E. increased alpha myosin heavy chains in cardiac muscle fibres

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