Test 7
 31. The retinal pigment epithelium:
a. is derived from the outer pigmented layer of the optic cup 

b. has a basal membrane facing the choroid that allows free 
    molecular transport between them 

c. has an apical membrane thrown into microvillae that surround the 
    outer segments of the photoreceptors 

d. daily phagocytoses 5% of each overlying outer segment 

e. produces bilirubin and biliverdin photosensitive pigments via 
    vitamin A metabolism 


32. The neural retina:

a. is made up of 6 cell types 

b. contains the first and second order neurones in the visual 

c. contains synapses between photoreceptors and amacrine cells 

d. contains an outer limiting membrane formed by fusion between 
    Muller cells and photoreceptors 

e. contains within its outer nuclear layer the cell bodies of bipolar, 
    horizontal amacrine, interplexiform and Muller cells 

f. has synapses between bipolar and ganglion cells within the inner
   plexiform layer 

g. contains myelinated fibres 


33. The photoreceptors:

a. number about 100 per ganglion cell 

b. are present in uniform concentration throughout the retina 

c. shed most of their discs at night 

d. both contain rhodopsin and iodopsin 

e. have outer and inner segments joined by a central connecting stalk 
    which contains a modified cilium 

f. differ in their synaptic endings ie. rods have spherules and cones 
   have pedicles 


34. With respect to the photoreceptors:

a. the rods and cones are the first order cells in the optic pathway 

b. they are responsible for conversion of photons of light into neural 
    signals via their photopigments, namely rhodopsin and iodopsin in 
    the rods and cones, respectively 

c. they respond to light by depolarising 

d.  they are maximally depolarised in the dark, also known as the 
     dark current 

e.  the extent of hyperpolarisation is dependent on the duration of the 
     light impulse 


35. With respect to the bipolar cells:

a. they can be sub-divided into villous and invaginating, depending 
    on their synaptic endings 

b. their receptive fields do not tend to overlap 

c. they synapse with fewer if associated with cones than when 
    associated with rods 

d. the receptive field size is dependent solely on the number of 
    photoreceptors to which they attach 

e. they hyperpolarise when responding to photoreceptor stimulation 

To test 8
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