Chapter 9-2
Visual system’s functional anatomy
our primary sensory experience is visual
far more of the human brain is dedicated to vision rather than other senses
Structure of retina
light energy travels from outside world through the pupil into the eyes then reaches a
light-sensitive surface which is called retina
structure of retina is composed of photoreceptors beneath the retinal neurons
even though the retinal neurons are in front of the photo receptor, but they do not
prevent the light from being absorbed because: 1. Retinal neurons are transparent 2.
photoreceptors are highly sensitive to light
photoreceptors + retinal neuronsperform amazing functions=> discriminate
wavelengths so we can distinguish colors and work in deafferent light intensities (bright
to dim)
brain can perform adjustments regardless of the orientation of the images it receives
example: you can wear glasses which invert visual images for several days, the world
would appear upside down at first but then suddenly everything appears right side up
again. Because the brain corrects the distortion.
Fovea
your vision is better in the central of your visual field than at the margins or periphery
photoreceptors are more densely packed at the center of your retina this region is
known as fovea
, Blind spot
small area of retina which is also known as optic disc
blood vessels enter and exit at the eye
also, fibres leading out of retinal neurons forms optic nerve, which goes to the brain at
this area
visual system solved the blind spot problem, how? optic disc is in a different location in
each eye
also, it is lateral to fovea: in right eye it is at the right side of the fovea and in the left eye
it is at the left side of the fovea
for people are blind in one eye the sightless eye cannot compensate for the blind spot in
the functioning eye, BUT the visual system compensates for the blind spot in many
other ways.
blind spot is important to neurologists
they indirectly view the condition of optic nerve while providing window on events
happening in the brain
in intercranial pressure increases (due to tumors or brain abscess=infection) the optic
nerve can swells, the reason is because optic nerve (just like other nerves) is surrounded
by CSF. Pressure inside the cranium can displace CSF and cause swelling in optic nerve
another cause of papilledema is inflammation of the optic nerve itself.
In most cases a swollen optic nerve will lead to losing sight in the person
Visual system’s functional anatomy
our primary sensory experience is visual
far more of the human brain is dedicated to vision rather than other senses
Structure of retina
light energy travels from outside world through the pupil into the eyes then reaches a
light-sensitive surface which is called retina
structure of retina is composed of photoreceptors beneath the retinal neurons
even though the retinal neurons are in front of the photo receptor, but they do not
prevent the light from being absorbed because: 1. Retinal neurons are transparent 2.
photoreceptors are highly sensitive to light
photoreceptors + retinal neuronsperform amazing functions=> discriminate
wavelengths so we can distinguish colors and work in deafferent light intensities (bright
to dim)
brain can perform adjustments regardless of the orientation of the images it receives
example: you can wear glasses which invert visual images for several days, the world
would appear upside down at first but then suddenly everything appears right side up
again. Because the brain corrects the distortion.
Fovea
your vision is better in the central of your visual field than at the margins or periphery
photoreceptors are more densely packed at the center of your retina this region is
known as fovea
, Blind spot
small area of retina which is also known as optic disc
blood vessels enter and exit at the eye
also, fibres leading out of retinal neurons forms optic nerve, which goes to the brain at
this area
visual system solved the blind spot problem, how? optic disc is in a different location in
each eye
also, it is lateral to fovea: in right eye it is at the right side of the fovea and in the left eye
it is at the left side of the fovea
for people are blind in one eye the sightless eye cannot compensate for the blind spot in
the functioning eye, BUT the visual system compensates for the blind spot in many
other ways.
blind spot is important to neurologists
they indirectly view the condition of optic nerve while providing window on events
happening in the brain
in intercranial pressure increases (due to tumors or brain abscess=infection) the optic
nerve can swells, the reason is because optic nerve (just like other nerves) is surrounded
by CSF. Pressure inside the cranium can displace CSF and cause swelling in optic nerve
another cause of papilledema is inflammation of the optic nerve itself.
In most cases a swollen optic nerve will lead to losing sight in the person
