Iris ...

[opuntia]

It seems that i've never got the answers for all my questions
would the iris contraction and relaxation be there in blind people as it is in normal people?

[Crimson11]

as far as I know, it isn't. Considering that the contraction and relaxation of the iris is a reaction to stimulation so if the brain doesn't receive the stimuli (like in blindness) it wont send a message back instructing the iris to contract or relax

there's alot of diffrent types of blindness though, and I'm not sure about all of them

[victor]

I think it's a matter of oculomotoric and trochlear cranial nerve and blindness is a problem with an optic cranial nerve...

[MrMistery]

What does the trochlear nerve have to do with it? They only go to an eye muscle. I thought the iris is the responsability of nerve 3

[victor]

Nerve III and IV which are oculomotoric and throchlear are both control the eye muscle. So, indirectly connected with irises.

[Dr.Stein]

The contraction and relaxation of iris generated by pupilary sphincter muscle after stimulated by light. That muscle in innervated by nerve III.

If the blindness is caused by a broken nervous system, means that they cannot process the stimulus, so the iris will not react

[MrMistery]

As Dr.Stein said, although both nerves III and IV innervate the eye muscles, it is nerve III that inervates the iris

[victor]

Ow..I got it then...because my book wrote that nerve III and IV controls eyes' muscle..only that, no specific specification..thanks

[MrMistery]

nerve III: somatic muscles: right internal, right inferior, right superior, slanting(not sure about translation) inferior
vegetative muscles: iris and ciliar corp
nerve IV: slanting superior
nerve VI: right external
Anatomy... a curse put upon biologists to make them suffer
Cheers

[victor]

I've gotten it...the controlling of irises are controlled by autonom nerve which is:
Symphatetic for irises' dilator muscle to open the pupils wider.
Parasymphatetic for irises' sphincter muscle to make the pupils more narrow.
For the oculomotoric, throclear and abdusen are only affect in controlling somatic eyes muscles.

[b_d_41501]

Exactly. My Neurobiology course that I took last semester was extremely helpful in understanding the innervation of muscles and such things.

[victor]

This kind of thing is nearly made me confuse...there''re many muscles controlling eyes with many cranial nerve also...