791. 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 llR, is reduced by scarring resulting in reduced heterometric response to preload
C. Afterload promotes sarcomere shortening while preload opposes it
D. Beta 1 receptor stimulation results in further sarcomere shortening and ultimately increased cardiac output
E. Increased venous tone decreases the myocardial sarcomere length
792. 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 (pcoT/R)
C. Velocity is equal to flow for any given diameter
D. Flow and resistance are both related, reciprocally, to the radius to the power of 4
E. Alveoli collapse in the absence of surfactant because as their diameter decreases in expiration the wall tension increases
793. Right atrial pressure
A. May fall to as little as -10 mmHg, but rarely more, at rest
B. May be 6 cm of blood normally
C. Will tend to fall with venoconstriction
D. Increases with exercise
E. Increases with inspiration
794. 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
E. Increased central venous pressure produces the same sympathetic response from atrial stretch receptors as elevated blood pressure produces from carotid sinus baroreceptors
795. Characteristics of the brain, CSF and cerebral circulation include
A. CSF volume of 150 mL at a lumbar pressure of 1-100 mm CSF
B. CSF / 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 of25 mLlmin, ie. 10% of total body consumption
796. Angiotensin II causes Ketones + 2+ o oo Glucose o 4+ o oo
A. Greater constriction of efferent than afferent arterioles
B. Greater constriction of afferent than efferent arterioles
C. Constriction of afferent arterioles only
D. Constriction of efferent arterioles only
E. Has no effect on arteriolar constriction
797. With regard to tuboglomerular feedback Protein o o 4+ o 3+
A. The GFR increases when flow through the distal tubule increases
B. The macula densa on the afferent arteriole is the sensor
C. The afferent arteriole is constricted by Thromboxane A2
D. It is designed to maintain sodium reabsorption
E. It does not operate in individual nephrons
798. With respect to the counter current system
A. The loops of Henle act as counter current exchangers
B. Solutes diffuse out of vessels conducting blood towards the cortex
C. Water diffuses out of ascending vessels
D. Water diffuses into the collecting ducts
E. Counter current exchange is passive and can operate even if counter current mUltiplication ceases
799. Regarding the osmolality of renal tubular fluid, it is
A. Hypotonic in the loop of Henle
B. Isotonic in the proximal tubule
C. Hypertonic in the distal tubule
D. Hypotonic in the collecting duct
E. Hypotonic in the proximal tubule
800. Renal autoregulation of GFR helps prevent large fluctuations in GFR despite wide variations in arterial blood pressure. With regard to autoregulation, which is true
A. The macula densa cells sense change in afferent arteriolar pressure
B. Falling GFR results in a feedback to decrease efferent arteriolar pressure
C. Falling GFR results in an increase in renin secretion from macula densa cells
D. Decreased macula densa concentration ofNaCI results in dilation of afferent arterioles
E. Decreased GFR decreases NaCI reabsorption in the ascending loop of Henle