Test 13
61.  With respect to the course of IVth cranial nerve:
a. the nerve exits the anterior aspect of the midbrain 

b. the nerve fibres exit below the inferior colliculus 

c. it decussates in he superior medullary velum 

d. it travels in the medial wall of the cavernous sinus 

e. travels in between III and V1 within the cavernous sinus 

62.  The abducent nerve nucleus:
a. lies within the midbrain beneath the facial colliculus 

b. supplies the ipsilateral lateral rectus 

c. lies beneath the floor of the 4th ventricle 

d. receives unilateral corticonuclear fibres 

e. is joined to the nuclei of III, IV and VII by the medial longitudinal


63.  With respect to the eye’s sensitivity to light:

a. it is capable of responding to light intensities over approximately 6 
    log units 

b. it has a high threshold of detection 

c. sensitivity is inversely proportional to threshold level 

d. adaptation is the capacity to modify the eye’s sensitivity to light of 
    varying colour 

e. there are two broad categories of adaptation – light & dark 


64.  With respect to mechanisms of adaptation:
a. pupil size plays a major role 

b. change in pupil size accounts for approximately 1 log unit change 
    in light intensity reaching the photoreceptors 

c. exposure of a photoreceptor to light decreases its intracellular 
    stores of Calcium, thereby activating adenylate cyclase 

d. guanylate cyclase replenishes cyclic GMP levels, which re-open 
    calcium channels, thereby restoring the ability of the 
    photoreceptor to respond to light 

e. the photoreceptor neural mechanism can provide for adaptation 
    over approximately 3 log units 


65.  With respect to colour vision:
a. the shortest wavelength of visible light is 475nm 

b. there are 4 cone pigments 

c. the cone pigments all consist of 11-cis retinal 

d. the 3 primary colours, when associated with light, are red, green 
    and blue 

e. the 3 primary colours, when associated with light, are red, green 
   and yellow 

To test 14
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