Transcript Sens4-Vision

Vision
Sense organs: eye
Receptor cell: photoreceptor
Receptor signal transduction mechanism:
activated opsin membrane receptor (transducin
G-protein) activates cGMP path to
hyperpolarization in light
Pathway of conduction: photoreceptor  bipolar
cell ganglion cell (as optic nerve)  thalamus
 visual cortex  visual assoc. area
Information passes from retinal photoreceptor cells to bipolar
neurons to ganglion neurons. (There is some convergence.)
photoreceptors
http://www.blackwellscience.com/matthews/rhodopsin.html
http://www.webvision.med.utah.edu/movies/trasduc.mov
What effect would a decrease in
phosphodiesterase activity in
photoreceptor cells have on vision?
A decrease in phosphodiesterase activity would lead to a higher
level of intracellular cGMP. This rise would, in turn, keep the
gated cation channels open and keep the photoreceptors
depolarized.
This would decrease the ability of receptor neurons to respond to
photons. And reduce the receipt of visual sensory information.
Vision
Pathway of conduction: photoreceptor  bipolar
cell ganglion cell (as optic nerve)  thalamus
 visual cortex  visual assoc. area
‘Shortsighted’ or ‘Near-sighted’
‘Farsighted’
http://www.clinicareinoso.com/conditns/refract.htm
Eye Muscles
Superior Oblique (IV)
Lateral Rectus (VI)
All others (CN III)
Inferior Rectus
Medial Rectus,
Superior rectus
Inferior Oblique
• Eye Lid: Levator Palpebrae