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Special Senses
Vision
Audition
Olfaction
Gustation
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BASIM ZWAIN LECTURE NOTES
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Vision
Background
Anatomy
Image
Formation
of the Eye
Hyperopia
(farsightedness)
3.
Emmetropia
(normal vision)
Myopia
(nearsightedness)
Gross
Opthalmoscopic
anatomy
appearance
1.
Distant
objects
Cross
Refraction
Accommodation
Pupillary
Additional
sectional
light
terms
by
cornea
reflex
anatomy
by
and
the
concepts
lens
a.
Eye
ball
is
too
short
Parallel
light
rays
are
focused
on
Processes
a.
Eye
ball
is
too
long
4.
Focal
distance
c.
Vitreous
humor--more
viscous
than
the)
a.Optic
disk
(
blind
spot,
no
vision
is
possible
a.
Light
rays
run
in
parallel
1.
Pupil
contribute
to
optical
qualities
Sequence
of
events
b.
Image
is
focused
at
a
point
behind
the
retina
without
accommodation
1.
Light
energy
is
transduced
into
neural
activity
Human
visual
systems
permit
light
reflected
off
b.
Light
rays
converge
in
front
of
the
3.
Closing
the
aperture
of
the
pupil
a.
Distance
between
the
refractive
e.
Extraocular
3.
Contraction
muscles--attached
of
ciliary
muscles
to
the
Retina
as
seen
through
the
pupil
aqueous
humor
1.
1.
External
Visual
field
features
of
the
eye
i.
Blood
vessels
originate
here.
The
vessels
1.
Light
entering
the
eye
is
focused
on
the
retina
2.
Light
rays
slow
of
the
eye
2.
Neural
activity
is
processed
by
the
brain
distant
objects
to
be:
the
retina
retina
Processes
a.
Only
light
rays
that
are
primarily
in
surface
and
where
the
light
rays
1.
Objects
within
9can
meters
eye
Tension
and
skull
on
and
the
suspensory
allow
movement
(aside:
in
photographs,
the
red
i.a.Pupil--opening
Lies
between
the
lens
and
the
retina
Structural
levels
a.
Total
space
that
that
allows
be
viewed
light
to
by
reach
a.
Lens--transparent
surface
that
contributes
shadow
the
retina
2.
Retina
converts
light
energy
into
neuronal
a.c.
Cornea
1. Localized
relative
to the
individual
within
his or
a.
Adjusts
for
different
light
levels
Lens
can
accommodate
for
distant
1.
Refraction
by
the
cornea
c.
Lens
can
accommodate
for
near
the
center
of
the
cornea
and
lens
are
converge
a.
Light
rays
do
not
travel
in
parallel
f.
Conjunctiva--membrane
ligaments
inside
the
appearance
of
the
eye
is
actually
1.
Gross
anatomy
ii.
Provides
spherical
shape
the
retina
the
retina
to
the
formation
of
images.
activity
Optic
nerve
fibers
exit
here
Note:
By way
of
analogy,
you
can
imagine
taking
her
environment
b.
Aqueous
humor
b.
Contributes
to
simultaneous
2.
Accommodation
by
the
lens
objects
but
not
for
near
objects
but
not
distant
2.
Opthalmoscopic
appearance
allowed
in
b.
Depends
on
the
curvature
of the
i.
Some
diverge
eyelid
is
released
attached
to
the
sclera
the
retina
photographed.
Double
3.
Axons
of
the
retinal
neurons
are
bundled
to
d.
Retina
b.
Iris--circular
i.
150
degrees
muscle
that
controls
b.iii.
Ciliary
muscles--change
the
shape
of
the
a
picture
with
a
camera.
The
eye
is
the
camera,
No
photoreceptors
2. Identified
based
on
size,
shape,
color,
and
past
3.d.
Light
rays
bend
3.
Pupillary
light
reflex
focusing
on
near
and
distant
objects
Condition
can
be
corrected
with
a
3.
Cross-section
anatomy
d.
Condition
can
be
corrected
with
a
b.
These
are
generally
not
focused
form
cornea
the
optic
nerves
2.
Lens
adds
refractive
power
g.
b.
Optic
Lens
nerve--axons
becomes
rounded
of
the
retina
leaving
flash
camera
causes
the
pupil
to
the
retina,
which
is
a
specialized
part
of
the
brain
i.
Inner
most
layer
of
cells
at
the
back
of
the
experience
ii.
diameter
90
on
temporal
of
the
pupil
side
lens
and
allow
focusing
b.the
Macula--area
of
the
retina
responsible
for
a.
Perpendicular
to
the
angle
(radius
of
2.
Accommodation
alters
light
rays
convex
lens
(e.g.,
increase
4.
Visual
information
is
distributed
to
several
concave
lens
c.
Permits
seeing
things
in
the
i.
2.4
cm
at
the
back
of
the
eye,
is
the
film,
and
the
parts of
Provided
by
changing
the
shape
3.
Perceived
to
be
moving
(or
not)
the
c.
eye
Greater
the
curvature
provides
constrict)
eye
c.
Aqueous
iii.
60
on
humor--fluid
the
nasal
side
behind
the
cornea
central
vision
(vs.
peripheral)
the
cornea)
between
the
curve
ofisthe
that
would
otherwise
run
in
parallel
refractive
power)
brain
structures
that
perform
different
functions
the
brain
that
process
visual
information
the
4.
Detected
in
a
wide
variety
of
lighting
conditions
foreground
and
background
in
focus
ii.
Distance
between
the
cornea
and
of
the
lens
h.
Cornea--transparent
greater
surface
covering
ii.
Transduces
light
energy
into
neural
2.
Sclera--outermost
Imagerays
formed
on
layer
the back
that
of
forms
the
the
c.d.
Fovea--center
of
the
retina
(where
most
of
cornea
and
the
plane
they
are
a.
Light
are
no
longer
focused
on
photoshop.
the
retina
the
the
irisrefraction
and
pupil
activity
eyeball
retina
is
reversed
and
inverted
the
cones
are)
traveling
on
the retina by the cornea
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BASIM ZWAIN LECTURE NOTES
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Vision
Microscopic Anatomy of the Retina
1. Rods--long, cylindrical,
many
disks
C.
Photoreceptors--two
kinds
based
on
A.Specialized
cells tapering outer
Characteristics:
5.
Connectivity
2.
Cones--shorter,
a.
Photopigment
isbut
in the
disk
Layers
4.
Distribution
(3
primary,
of
rods
there
and
are
conesa
appearance
and
function
of a.
the
retina
convert
a.
Photoreceptors
Central
segment,
retina
relatively
are
the
few
only
disks
cells
that
b.
Rods
acones
much
higher
pigment
Side
point:have
Inside
many
mammalian
eyes,
subdivisions)
a.Rods
and
are
distributed
c. respond
Ganglion
cells--fire
action
potential and
i.
a.
1:1
Photopic
(approximately)
to
light
conditions
correspondence
light
energy
into
concentration
There
is an additional
layer of
cells between
a.
regionally
Ganglion
cell
layer--cell
bodies
of cells
the
Cell
types
send
axons
to
the
brain
3.
Retina
is
therefore
a
duplex
b.
between
Ganglion
i.
Daytime
photoreceptor
cells
lighting
are
the
and
only
ganglion
output
neural
activity
c.
1000x
more
sensitive
to epithelial
light
thanlayer
The
photoreceptors
and
the
ganglion
b.
Center
cells
of
the
eye
(i.e.,
the
fovea)
a.Photoreceptors--the
only
light
4.
Distribution
of
rods
and
cones
d.
Horizontal
cells--receive
inputs
from
Photo
a.
Scotopic
retina
using
only
rods
c.
b.
Light
Peripheral
ii.
Primarily
travels
retina
through
cones
the
other
cell
B.
Cellular
architecture
cones
That
reflects
thein
light
back
out
again.
The
b.
Inner
i.
Only
nuclear
cones
layer--cell
bodies
of
the
sensitive
cells
the
retina
receptors
and
project
laterally
to
bipolar
cells
b.
Photopic
retina
using
primarily
cones
layers
i.
b.
Many
3
to
different
reach
photoreceptors
the
types
photoreceptors
of
cones
(rods)
based
converge
d.
Function
in
scotopic
conditions
Of
the
retina
photoreceptors
have
two
opportunities
to
bipolar
c.
Peripheral
cells
retina
i.
Transduce
light
energy
into
neural
e. Amacrine
cells--receive
inputs
from bipolar
d.
oni.At
on
aNighttime
the
single
type
back
of
output
photopigment
of
the
ganglion
eye
is
a
cell
pigmented
lighting
Be
exposed--greatly
enhances
night of
vision.
c.
Outer
i.
Primarily
nuclear
rods
layer--cell
bodies
the
signals
cells
and
project
laterally
to
ganglion
cells
epithelium
c.
Peripheral
i. Pigments
that
retina
absorbs
are
differentially
is
more
any
sensitive
light not
e.
All
rods
have
the
same
pigment
photoreceptors
ii. Fewby
cones
b.
Bipolar
cells--connect
photoreceptors
absorbed
to
light
sensitive
to
the
wavelength
photoreceptors
of
light
Rhodopsin
toi.ganglion
cells
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BASIM ZWAIN LECTURE NOTES
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Vision
Phototransduction
Note:
Most
of
have had(change)
the following
Photoreceptors
transduce
light
Functional
Dark
and light
considerations
adaptation
b. Allchanges
colors
created
experiences.
Getare
upmembrane
at night by
and
turn
energy
into
in
potential
a.
Three
different
opsins
6.
also
contain
opsins
1. Cones
Inon
complete
darkness
there
is
a
steady
mixing
the
proper
ratio
of
the bathroom light; leave a brightly
i.
Each
maximally
activated
2. In
influx
3.
Events
the
of
light
Na+
at
during
G-protein
which
phototransduction
depolarizes
coupled
receptors
the of
1.Analogous
to
transduction
red, to
green
and blue
lit room
go down
the basement
by
different
wavelengths
of
5.cGMP
Bleaching
photoreceptor
a.
Binding
Light
stimulation
is
of
converted
NT
membrane
activates
of
to
photopigment
GMP
G-proteins
(phosphoactivates
chemical
signals
into
electrical
c.
Colors
are
assigned
by
the
when there are no lights on.
light
Photoreceptors
no
longer
respond
at
b.a.Movement
G-proteins
diesterase
G-protein
hydrolyzes
activation
cGMP)
stimulates
various
a.
of
+
charge
across
the
signals
that
occurs
during
brain
based
on
a
comparison
Remember there are two different
ii.
Blue--430
nm
particular
light
intensities
Changes
associated
with
adaptation
effector
membrane
b.
G-proteins
Membrane
enzymes
is
hyperpolarizes
called
activate
the
various
dark
current
in
effector
response
to
synaptic
transmission
at
of the
readout of for
thedaytime
three that
visual
systems--one
iii.
Green--530
nm
b.
Activation
of
rods
by
light
bleaches
the
a.
Pupil
diameter
changes
c.Enzymes
enzymes
2.
light.
Na+
Na+
channels
channels
alter
the
responsible
close
intracellular
for
this
concencurrent
G-protein
coupled
receptors
cone
types
utilizes all cones and one for nighttime
iv.
Red--560
nm
photopigment
b.
Regeneration
(or
generation)
tration
c.
4.
Enzymes
Rhodopsin
of
cytoplasmic
decrease
(photopigment)
intracellular
second
located
messengers
in
are
gated
by
cGMP
White results
from
equal
that i.utilizes
all rods.
There
isofaunbleached
time
i.course
Changes
the
wavelengths
absorbed
by
(bleached)
d. cGMP
concentrations
stacked
2nd
messengers
disks
in
of
the
2nd
either
outer
messengers
directly
segment
or
(cGMP)
of
indirectly
rods.
It
a.
is rhodopsin
produced
continually
in
activation
of
all
three
necessary for the
rhodopsin
c.
Change
the
functional
circuits
to
allow
1:1
alter
d.
photoreceptors
is
comprised
membrane
in
2nd
of
retinal
ion
messenger
channels
and
opsin.
concentration
which
Opsin
alter
Home
Exitphotoreceptors to "come on line".
BASIM
ZWAIN
LECTURE
NOTES
rod
to ganglion
orstay
reverse
that
to
allow
membrane
closes
absorbs
achannels
light
Na+
potential
channel
i. Na+
open
in the
dark 1:1000
Vision
Connectivity
Neural
Circuitry
the Retina
Exercise
Exercise:
Look in
straight
ahead. Imagine a vertical
Where
would
aand
P-type
ganglion
cells
in
line
dividing
the
right
left side.
General
considerations
3. Bipolar
Connection
cells,
between
in
response
LGN
to
the
glutamate
Pathway
Target
of
optic
tract
eyes
and
brain
5. The
information
from
the
two
separate
theappearing
right nasal
retina
project?
1.Objects
to
the
left
are
in
the
left visual
Lateral
geniculate
nucleus
(LGN)
1.
Left
and
right
visual
worlds
are
processed
released
and
primary
by
photoreceptors,
visual
cortex
are
either
eyes
is kept
by
projecting
tocells
Photoreceptor
1. Optic
nerve,
receptors
optic
chiasm,
ganglion
optic tract
hemifield.
1.
Primary
target
is
the
LGN
(Left
LGN separate
layer
4 and
6) to
1.
Part
of
the
dorsal
thalamus
contralaterally
depolarized
or
hyperpolarized.
Connection
between
retina
and
LGN
a.
Based
on
their
response
toare
glutamate,
different
layers
of
the
LGN
Where
would
a the
P-type
ganglion
cells
in
Communicating
changes
inincolliculus
2. Light
Functional
considerations
energy
(or
its
absence)
is
2. 1.
Objects
appearing
to
the
right
the
right
2.
10%
goes
to
superior
1.Ganglion
Retina
tosix
cells
LGN
(lateral
geniculate
2.
Arranged
in
(6)
layers
(Draw--bended
a.
Information
about
the
left
visual
field
is
Exercise
the
left
temporal
retina
project?
(Given
the
left
hemifield)
bipolar
cells
can
be
classified
as:
visual
hemifield.
a.
Remember
the
nasal
retinal
sees
the
photoreceptor
function
to
the brain
Higher
Level
Cortical
Processing
Information
from
the
right
visual
field
transduced
into
a
chemical
signal.
in
the
midbrain
b.
In
darkness,
the
glutamate
released
by
the
nucleus
1.
Output
of
neurons
the
thalamus)
of
the
retina
knee;
6
dorsal,
1
ventral)
processed
by
the
right
side
of
the
brain
Now
where
would
a
P-type
ganglion
(Left
LGN
layer
3
and
5)
Close
your
left
eye.
Your
right
eye
sees
part
of
the
1.Nasal
retina
projects
to
layers
1,
4
and
6
3.
Layer
IVC
is
1.Cortical
divided
into
organization
two
tiers
i.
OFF
cells
("off"
refers
to
light
being
off)
temporal
part
of
the
hemifields.
1.
Only
ganglion
cells
fire
action
a.
crosses
In
response
to
the
to
left
dark,
side
photoreceptors
of
the
brain
are
Not
Discussed
3.
Hypothalamus
(SCN-circadian
photoreceptor
causes
an
IPSP
in
the
bipolar
2.
2.
LGN
Types
to
the
primary
visual
cortex
cells
in
the
right
nasal
retina
project?
Where
would
a
M-type
ganglion
cells
inby
3.
Layers
1
+
2
(most
ventral)
contain
large
b.
Information
about
the
left
that
is
seen
left
visual
hemifield.
Remember
that
images
as
seen
a.
Information
about
the
temporal
part
is
a.
Alpha
Arranged
in
6
layers
depolarize
when
there
is
no
light.
In
darkness,
i.
This
information
crosses
over
potentials
i.rhythm)
Decussation
depolarized
and
release
NT (glutamate).
cell
3.
the
a.
Primary
M-type
right
nasal
ganglion—large
visual
retina
cortex
project?
to
other
on
the
retinal
are
reversed.
Objects
in
the
temporal
neurons
and
are
referred
to
as
the
right
eye
does
not
cross
over
seen
by
the
nasal
retina
of
the
left
eye
b.
Beta
,Layer
IV
is
subdivided
the
glutamate
released
by
the
photoreceptor
b.
The
temporal
retina
of
the
opposite
eye
a.(Left
Axons
of
ganglion
cells
form
the
Information
from
the
left
crosses
to
the
2.
Photoreceptors
make
synaptic
contact
4.
Pretectum-reflex
control
of
the
LGN
layer
1)
part
of cortical
the
left left
hemifield
are
focused
onto of
theboth
nasal
b.
P-type
areas
ganglion—small
magnocellular
LGN
layers.
2.
Right
and
eyes
perceive
parts
i. pupil
This
information
goes
toopposite
the
right
LGN
4.
Magnocellular
into
LGN
three
layers
separate
project
causes
an
EPSP
in
the
bipolar
cell
sees
the
retinal
part
of
the
optic
nerve
with
right
bipolar
cells
either
directly
or
Where
and
would
lens
a
M-type
ganglion
cells
inof the
retina
of
the
left
eye.
Objects
in
the
nasal
part
4.
Layers
3IVC
- 6 contain
small
neurons
andC.
visual
worlds
layers
1,
4
and
6
to
alpha
layers--IVA,
B,
and
ii.
ON
cells
("on"
refers
to
light
being
on)
hemifield
c. hemifield
Not
information
crosses
indirectly
via
horizontal
theall
left
temporal
retina
project?
right
are
focused
oncells
the
temporal retina of
are
referred
to
as parvocellular
LGN(they
layers.
3.
Image
is
inverted
and
reversed
(Left
LGN
layer
2)
5.
Parvocellular
2.
LGN
LGN
projects
layers
project
hyperpolarize
when
there
is
no
light
i.
This
information
does
not
cross
over
i. Partial
decussation
the
left
eye. The
temporal retinal output does not
Home
Exit
towhen
IVCZWAIN
beta
primarily
to layer IVC
depolarize
thereLECTURE
is
light) NOTES
cross over.BASIM