Transcript Rod cells vs cone cell

CH 10 Vision
Location, size, shape, color, texture,
movement, direction, speed
Star– sun light
Retina
Uveal tract—choroid, capillary-rich bed
and pigmented layer (melanincontaining cells), ciliary body, iris,
muscle
Sclera and cornea
3 layers
-Sclera and cornea
- uvea
-Retina
3 chambers
-Anterior
-Posterior
-Vitreous cavity
Fluid in anterior and
posterior chamber is
replaced every 2 hr
Glaucoma/ canals of schlemm
Phagocytic cells in vitreous humor
Floater – aging eye
Catarcts ; UV seems to be cause sunglass
Cornea-light refraction
Out of focus in water
Accomodation
Zonular fiber-connective tissue
Myopia and hyperopia
Pupil size – regulates by sympatic and parasympatic nerve
Cell body
of photoR
Cell body of
amacrine and
horizontal cell
1.
2.
3.
4.
5.
Photoreceptor
Bipolar cells
Ganglion cells
Horizontal cells
Amacrine cells
Photoreceptorbipolar cellsganglion cell
Outer plexiform layer; junction between
photoR-bipolar or horizontal cell
Photoreceptor; rod cells and cone cell
Amacrine cell
Transformed the Sustained response of
bipolar cell to on-off signal to ganglion
Transmit the signal of Photo R to ganglion cell
Unusual arrangement of retinal layer
replacement of photopigment
Hyperpolarization in response to light
Under dark, Ca2+ channel is opened
In light, the channel is closed
In dark, cGMP high, Ca2+, Na+ open
In light, cGMP drop, Ca2+ close
-40 mV
-65 mV
Retinal (an aldehyde of Vitamin A) + Opsin (differ by cone or rod cell)
In rod cell rhodosin
11-cis isomer light all-trans retinal activation of transducinphosphodiesterasecGMP drop channel close
Signaling amplication
One rhodopsin 800 transducin (8%)6 cGMP/one transducin200 channel closed (2%) 1 mV decrease
Light adaptation
Light  close Ca2+ channel low Ca in cell activation of quanylate
cyclease cGMP increase channel open
Restoring mechanism
Arrestin ; block the transducin activation and breakdown activated
rhodopsin
Trans-retinal is diffused into cytosol and converted into cis-retinal
Recruited into disk and form the inactive rhodopsin with opsin
Rod cell; low spatial resolution, extremely sensitive to
light
Cone cell ; high spatial resolution, low light sensitivity
Scotopic vision
Mesopic vision
Photopic vision
Light blindness
Macular degeneration
Rod cells vs cone cell
Photon =1: 100
Cone cell is not saturated by light, it can discern the noise
Rapid recovering activity (200 ms; 4 times faster than rod cell)
Rod cell rod bipolar cell amacrine cell (gap junction and synapse)cone bipolar
cell ganglion (convergence)
Cone cell cone bipolar cell ganglion cell
Convergence of cone cell may reduce resolution
90 million rod cell
4.5 million cone cell
Cone in fovea (1.2 mm) seems to be rod
cell because of too high density
Foveola– rod cell free region (0.3 mm)
6 o eccentric  acuity decreased to 75%
The reason for moving eye
3 kinds of cone cell
Blue, green, red
•Rod cell
•Each cone cell is color blind
Color blindness
Red and green  X-chromosome
Trichromatic
Blue Ch7
Dichromacy color blindness
Anomalous trichromats
Black and white Movie
Each ganglion cell response to small circular patch (receptive field)
Two classes of ganglion cell
On and off center ganglion cells (Figure 10.14)
Equal number of on and off center ganglion cells
On center ganglion deficiency, we can recognize darker spot. However, brighter spot was not
recognized
On center Bipolar cell
(metabotrophic R); grade
potentialglutamateaction
poteintial on on-center ganglion
Off-center bipoloar cell AMPA
(ionotrophic R)  glutamate offcenter ganglion
Figure 10. 15
Sign inverting
Luminance contrast
On center ganglion cell
On-center ganglion activity is
peaked when light/dark edge
Light adaptation
Relative brightness
Horizontal cell-GABA
CH 11. central visual pathways
What kinds of information we obtain from vision; luminance, spectral difference, orientation, motion
Ganglion cell axon optic disk (blind spot); no photoreceptor
Intracranial pressure detection by optic disk
Increasing brain pressure swelling optic disk
Vein and artiol
Optic chiasm; 60% of optic nerve fibers are crossed, whereas 40% fibers ongoing to thalamus and midbrain
Optic tract; contains fibers from both eyes
Optic nerveoptic chiasm1) hypothalamus circardian rhythms
2) PRETECTUM Edinger-westphal nucleus in midbrain (pupil reaction to light)
3) lateral geniculate nuceus optic radiationstriate cortex (Brodmann’s area): primary
visual pathway
4) superior colliculus
PRETECTUM; 동공반사
Lightretina optic nervepretectumedinger-westphal nucleusparasympatic fiber in cranial nerve pupillary muscle
Light response is identical in both eyes
Ganglion cells of Lateral genicular nucleus
convey the acuity, color, motion
Pretectum and hypothalamus  light intensity
Ganglion cells projected to hypothalamus and
pretectum express melanopsin (light sensitive
pigment, independently from rod and cone
cell)
Reason for how circardian rhythms can be
regulated in dark
Visual field
Visual field deficits
Anopsias; large area
Scotomas; small area
Carrying superior vision
Macular sparing; damage in cortex, partial visual deficit
The functional organization of the striate cortex
Orient selective neurons
Simple cell
Complex cells
Length or orientation
Binocularity
Each genuclulate neuron is monocular
Ocular dominance columss
stereopsis
Far cells
Near cells
It is acquired ability
If single eye is damaged or strabismus during infancy,
the ability of biocular stereopsis is reduced.
Magnocellular layer (M-Cell) larger receptive field, faster conduction; larger
cell body and extensive dendrite
Parvocellular layer (P-cell)color information, wavelength-dependent center
ganglion
Both ganglion cells received the information from cone cell
M-layer damage movement cognition defect without color vision deficit
Konioellular layer (K-cell) short wave length
Functional organization of extrastriate visual areas
Occipital, parietal, and temporal lobes
TM (middle temporal area); recognize moving without color
V4 color without moving
MT damaged patient  problem in pouring tea, dialogue (can not recognize
mouse movement), terrific accident
Cerebral achromatopsia
CH 12 The auditory system
Hearing loss
Rapid response (faster 1000 times than vision)
1. Trauma extremely loud,
explosion, gunfire
2. Infection of inner ear
3. Oto-toxic drug gentamycin etc
4. presbyacusis
More rapid warning to novel stimulation
Deafness vs blindness
Sound
3D wave; waveform, phase, amplitude (dB loudness), frequency (cycle per second, Hz; pitch)
Audible spectrum
20 Hz—20 kHz (infant can hear over than 20 kHz)
In general, 15-17 Hz is upper limitation in adult
•Small animals are sensitive to higher frequency (in Bat 20kHz—200kHz)
•Dolphin, bat
Sound wave external ear->middle ear (collect and amplifying) cochear (change airpressure to liquid wave) hair cell auditory nerve fiber
Music; The art or science of combining vocal or instrumental sounds with a view toward
beauty or coherence of form and express of emotion
The external ear
Pinnaconchaauditory meatus (30-100 fold amplifying 3kHz sound wave) tympanic
membrane
Human is sensitive 2-5 kHz sound
Recognize sound source
The middle ear; converting air pressure to liquid pulse
In normal, 99.9 % of air-wave is reflected when water meet (liquid is high impendent material)
However, sound wave in inner ear is amplified over than 200 fold than tympanic membrane
Overcome this problem by two mechanisms
1. Oval window; small diameter (energy of large tympanic membrane is converged to small oval window)
2. Lever action by middle ear bones (ossicles; malleus, incus and stapes)
Conductive hearing loss ; defect in sound transfer external hearing aid (Box C)
How escape the interanl sound and protect from loud noise?
 Two small muscles, which can regulate tympanic membrane tension
 Tensor tympani; regulated by cranial nerve V
 Stapedius ; by cranial nerve VII
They stiffen the ossicles and protect the inner ear
Paralysis of VII cranial nerve hyperacusis
Acoustic vibration can be transferred directly to inner ear through bone and tissues
Hearing loss and cochlaer implants
In general, monaural hearing loss peripheral damage
Peripheral hearing loss
1) conductive hearing loss; damaged in external or middle ear; occlusion of canal, rupture of tympanic Memb,
ossification of ossicle
2) sensorineural hearing lossl innner ear (cochlear hair cells or VIII nerve) genetic or environmental factors
The inner ear
Cochlear is key organ for hearing; it
transforms sonical energy to neural
impulses and amplifying
It also acts as frequency analyzer
10 mm, coiled structure, if uncoiled 35
mm
Two memb structures; tectorial memb. And
basialr memb.
Partitions; scala vestibuli, scala media and
scala tympani; they can be mixed in end of
tube and filled with perilymph
SoundBasilar membrane vibration
Stereocilia
Mechanical energy electrical signal
Hair cells- atomic resonse and tens/msec, flask-shape epithelial cell conatining 30-100 stereocilia and single
kinocilium (kinocilium is disappeared after birth)
Rapid adaptation to constant stimuli  we can discriminate noise and signal
Direct and mechanical gate tip links
Arrangement of stereocilia
High intensity sound shear off the hair
bundle permanent hearing loss
30000 hair cells/15000/ear
Recent research stem cell for hair
cell
Resting potential of hair cell (-45-60
mV)
Gate open K+ influx Ca2+ channel
open vesicle transport VIII nerve
Endolymph; K+ rich and low Na+
(produced by blood)
Difference between hair cell and
endolymph; 125mV
It can make possible to inwarding K+
ion despite of enough K+ in hair cell
Endolymph” K-Rich, Na-poor, produced by stria vascularis
Perilymph: Na-rich, K-poor
Gap 125mV
Two kinds of hair cells
Inner hair cells; actual receptor (95% of auditory nerve)
three rows of outer hair cells; efferent axon of superior
olivary complex
Nonliner vibration of basilar membrane
Tinnitus cochlear produce sound
Tuning and timing
Figure 12. 11
Volley theory-sensitive about 3 kHz
Labelled line
Wave form
Ascending auditory system parallel organization
 Enter brain stem and from 3 nuclei
Cochlear nuclei
Dorsal
Posteroventral
Anterioventral
Superior Olive
Nucleus of lateral leminiscus
Inferior colliculus
Monaural hearing loss
Integrating information from two ear localization of sound source
Two different mechanism
Below 3 kHz time difference
Interaural time difference; 700 msec ; we can detect 10 msec we can detect 1 degree difference
Medial superior olive (MSO) binaural input; bipolor dendrites coincidence detectors
ipsilatertal anteroventral cochear nucleuslateral dendrite/medial dendritecontralateral anteroventral nucleus
Integrating information from two ear localization of sound source
Two different mechanism
Higher than 2 kHz; head is obstacle for sound wave propagation
Single ear detect sound, far ear shadow
Ipsilateral cochear nucleus activatng Lateral superior olive
Contralaertal ear inhibitory input LSOmedial nucleus of the trapezoid body (MNTB)
Sound travel auditory cortex
A1; primary auditory cortex; superior temporal gyrus
Ventral division; belt area (it is similar to V1 or S1)
Table 1.1.
Copyright © 2001
The Cranial Nerves and Their Primary Functions
Sinauer Associates, Inc.
Cranial nerve Name
Sensory and/or
motor
Major function
Location of cells whose
axons form the nerve
Clinical test of function
I
Olfactory nerve Sensory
Sense of smell
Nasal epithelium
Test sense of smell with standard odor
II
Optic nerve
Sensory
Vision
Retina
Measure acuity and integrity of visual
field
III
Oculomotor
nerve
Motor
Eye movements; papillary
constriction and
accommodation; muscles of
eyelid.
Oculomotor nucleus in
midbrain; EdingerWestphal nucleus in
midbrain
Test eye movements (patient can't
look up, down, or medially if nerve
involved); look for ptosis, pupillary
dilation
IV
Trigeminal nerve Motor
V
Trochlear nerve Sensory and motor
VI
Abducens nerve Motor
VII
Facial nerve
VIII
Auditory/vestibu
Sensory
lar nerve
Hearing;sense of balance
IX
Glossopharynge
Sensory and motor
al nerve
Sensation from pharynx; taste
Nucleus ambiguus; inferior
from posterior tongue; carotid
Test swallowing; pharyngeal gag reflex
salivatory
baroreceptors
X
Vague nerve
Autonomic functions of gut;
sensation from pharynx;
muscles of vocal cords;
swallowing
Dorsal motor nucleus of
vagus; vagal nerve
ganglion
XI
Accessory
nerve
Motor
Shoulder and neck muscles
Spinal accessory nucleus;
nucleus ambiguus;
Test sternocleidomastoid and trapezius
intermediolateral column of muscles
spinal cord
XII
Hypoglossal
nerve
Motor
Movements of tongue
Hypoglossal nucleus of
medulla
Sensory and motor
Sensory and motor
Trochlear nucleus in
Can't look downward when eye
midbrain
abducted
Trigeminal motor nucleus
Somatic sensation from face,
Test sensation on face; palpate
in pons; trigeminal sensory
mouth, cornea; muscles of
masseter muscles and temporal
ganglion (the gasserian
mastication
muscle
ganglion)
Abducens nucleus in
Eye movements
Can't look laterally
midbrain
Controls the muscles of facial Facial motor nucleus;
expression; taste from anterior superior salivatory nuclei in Test facial expression plus taste on
tongue; lacrimal and salivary pons; trigeminal (gasserian)anterior tongue
glands
ganglion
Eye movements
Spiral ganglion; vestibular Test audition with tuning fork;
(Scarpa's) ganglion
vestibular function with caloric test
Test above plus hoarseness
Test deviation of tongue during
protrusion (points to side of lesion)