Which part of retina consists of only cones?
Fovea centralis
optic nerve
Blind spot
Orasmata
A.
Fovea centralis
Fovea centralis is a small, central pit composed of closely packed cones in the eye. Ability for vision is highest in the fovea.
Optic nerve is a bundle of more than 1 million nerve fibres that carry visual messages. It is composed of retinal ganglion cell axon and glial cells.
Blind spot is a small portion of the visual field of each eye that corresponds to the position of the optic disk within the retina. There are no photoreceptors in the optic disk and therefore, no image detection takes place.
One of the examples of the action of the autonomous nervous system is
knee-jerk response
pupillary reflex
swallowing of food
peristalsis of the intestines
Which one of the following depresses brain activity and produces feelings of calmness, relaxation and drowsiness?
Valium
Morphine
Hashish
Amphetamines
Which of the following is the part of mid brain of rabbit?
Diencephalon
Cerebrum
Corpora quadrigemina
None of the above
Now-a-days cornea transplantation is very popular. The reason is that it
is easy to preserve
transplanted very easily
can be easily obtained
does not link with blood supply and immune system
Unidirectional transmission of a nerve impulse through nerve fibre is due to the fact that
nerve fibre is insulated by a medullary sheath
sodium pump starts operating only at the cyton and then continues into the nerve fibre
neurotransmitters are released by dendrites and not by axon endings
neurotransmitters are released by the axon endings and not by dendrites.
Cornea transplant in humans is almost never rejected. This is because
it is composed of enucleated cells
it is a non-living layer
its cells are least penetrable by bacteria
it has no blood supply
