A Biology Question about the eye... dont get it

Watch
This discussion is closed.
frixis
Badges: 0
Rep:
?
#1
Report Thread starter 16 years ago
#1
ok this question came in the exam so i dont know it by heart but the gist of it was : a girl standing in bright light infront of a mirror covers her eyes with her hand and closes them. after counting to 60 she quickly removes her hand and opens her eyes. describe the size of her iris and pupil right after and a minute after she does this

any ideas anyone?
0
SB
Badges: 2
Rep:
?
#2
Report 16 years ago
#2
(Original post by frixis)
ok this question came in the exam so i dont know it by heart but the gist of it was : a girl standing in bright light infront of a mirror covers her eyes with her hand and closes them. after counting to 60 she quickly removes her hand and opens her eyes. describe the size of her iris and pupil right after and a minute after she does this

any ideas anyone?
OK, immediately afterwards the pupil will be large, the circular muscles in the iris will be contracted and the radial muscles will be relaxed. This is because there is very little light entering the eye. The pupil increases in size as a result of stimulation from the rod cells travelling down the optic nerve to the visual cortex and causing impulses to be sent to the iris.

Then a minute later the bright light will have been detected by her rod cells. The pupil will get smaller to prevent the entrance of too much light and damage to the eye.

pathway: rod cells > bipolar cells > ganglion cells which all converge to form the optic nerve > visual cortex > motor neurons > muscles in the iris causing it to change pupil size

Hope that helps - I wasn't sure how much detail you needed so PM me if thats not enough,
skevvybritt x
0
Muse
Badges: 13
Rep:
?
#3
Report 16 years ago
#3
(Original post by skevvybritt)
pathway: rod cells > bipolar cells > ganglion cells which all converge to form the optic nerve > visual cortex > motor neurons > muscles in the iris causing it to change pupil size
Just a small note :p: , the pathway doesn't include the visual cortex in the direct pupillary reflex. The neurones synapse at the Edinger Westphal nucleus and the Oculomotor nucleus to form a complete circuit with no intrepretation from the cortex involved.
0
frixis
Badges: 0
Rep:
?
#4
Report Thread starter 16 years ago
#4
thanx .... got it wrong i did :P ... it was for 6 marks the whole things for 25... i wanted an A ... horrible horrible horrible!!!!
0
frixis
Badges: 0
Rep:
?
#5
Report Thread starter 16 years ago
#5
o n y can v we see stuff wen both our eyes are open even when the distance between the object and the eye is equal to that of the near point of one eye ?
0
X
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Have you made your mind up on your five uni choices?

Yes, and I've sent off my application! (194)
55.11%
I've made my choices but havent sent my application yet (49)
13.92%
I've got a good idea about the choices I want to make (40)
11.36%
I'm researching but still not sure which universities I want to apply to (33)
9.38%
I haven't started researching yet (21)
5.97%
Something else (let us know in the thread!) (15)
4.26%

Watched Threads

View All