751. The volume of fluid in the interstitial space is dependent upon all of the following except
A. Capillary pressure
B. Capillary filtration coefficient
C. The cross sectional area of the capillary bed
D. The ratio of pre capillary to post capillary venular resistance
E. The oncotic pressure
752. Causes of increased interstitial fluid volume and oedema include all of the following except
A. Arteriolar constriction and venular dilation
B. Increased venous pressure
C. Decreased plasma protein level
D. Venous obstruction
E. Substance P
753. Factors increasing blood flow through the venous system include which of the following
A. Fluctuations in negative pressure during expiration
B. Intra abdominal pressure rises during expiration due to abdominal muscle contraction
C. The absence of valves in the system
D. Contractions of skeletal muscle
E. The high cross sectional area of the great veins
754. Conceming venous pressure, which of the following is false
A. Because sagittal sinus veins have rigid walls and carmot collapse, the pressure in the upright position is subatmospheric
B. The central venous pressure is normally 4-6 nunHg but varies with respiration
C. Central venous pressure rises during negative pressure breathing
D. Elevated central venous pressure occurs with expanded blood volume
E. Peripheral venous pressure rises with increasing distance from the heart
755. Which of the following are true of CD4+ cells
A. Are derived from bone marrow
B. Do not have Fc receptors
C. Have class II MHC receptors
D. Can be inactivated by cyclosporin (ILl gene transcription inhibition)
E. are unaffected by cytokines
756. Which is true of Hb
A. Abnormalities can lead to haemolysis in conditions such as spherocytosis and sickle cell anaemia because of increased RBC fragility
B. HbF has a lower affinity for 2,3 DPG and thus oxygen of HbA
C. Is the major oxygen and C02 carrier
D. Colours the blood; oxygenated (red), methaemoglobin (blue)
E. In normal venous blood caries 6 atoms of oxygen per molecule and so is 75% saturated with oxygen
757. Which is true of blood types
A. are determined by red cell surface agglutinogens
B. When incompatible between recipient and donor at transfusion usually result in recipient haemoagglutination
C. can help determine parenthood, ego the child of parents who are both type B must be type B
D. are determined by plasma agglutinins
E. Rh incompatibility between mother and foetus may necessitate intrauterine transfusion of the foetus with maternal compatible blood
758. Anticlotting mechanisms include
A. conversion of thrombin to protein C activator
B. Antithrombin III inactivation of activated factor VIII
C. Inactivation of tissue plasminogen activator
D. Inhibition of fibrinogen degradation products by thrombin
E. thromboxane A2, prostacyclin activity: the latter promoting vascular spasm and platelet aggregation, the former the reverse
759. Cardiac muscle usually contracts more forcefully when
A. cell membrane NaIK ATPase activity is stimulated, ego digitalis
B. ligand gated Ca channels are opened for longer periods
C. it is tetanic (individual responses fused before relaxation can occur)
D. the average sarcomere length increases
E. adrenaline activates B 1 receptors
760. Rhythmicity
A. is a consequence of the plateau (phase 2, Ca in) of depolarisationat the SA node
B. is a major feature where myocardial muscle differs from skeletal and smooth muscle
C. at the SA node is a consequence of prepotential
D. at the A V node is a consequence of sodium leak in during diastole
E. is accelerated in the A V node by neurohumoral effects on K channels