Visual System Physiology Dr. Pierce Flashcards
The photoreceptors connect to the bipolar cells and they
Connect to the ganglion cells that go to the brain
When the photoreceptors are depolarized they make a
graded potential
Rods and cones release glutamate
All the time, the amount changed
Highest in the dark
GLUTAMATE acts INHIBITORY
When glutamate is released
The bipolar cell does not depolarize
Reason the GLUTAMATE is inhibitory
Binds to NMDA or non-NMDA, orrr nGluR6
Bipolar cells have the nGluR6
Glutamate ——> GCPR that closes cGMP gated na+ channels
This hyperpolarizes the BIPOLAR Cells
Activated Bipolar Cells release
Glutamate (EXCITATORY)——> NMDA or non-NMDA
Depolarized the ganglionic cells that sends through the optic nerve where it releases glutamate in the visual cortex
BIPOLAR CELLS send EXCITATORY NTS
Superior Colliculus
Connects to the tectospinal tract —-> Anterior horns of cervical vert.
= activates motor reflexes to move eyes in the right direction
=its about the intention of movement , not fixation of a moving object
=makes map of visual space to activate motor responses
Pectectum
Pupillary Reflex,
Sends ——> Edinger-Westphal then ——> Ciliary Ganglion to make the pupillary reflex
Hypothalamus= some fibers off the optic tract form the retinohypothalamic tract. Where do they go and what is their function
They terminate in the Supraorptic, suprachiasmatic, and paraventricular nuclei of the Hypothalamus
They have visual input to hypo = light-dark function of neuroendocrine and circadian rhythm
Hypothalamus also gets info from MG cells
Accessory Optic Nuclei (AON)
Advanced Visual Processing, nystagmus in response to prolonged large field motion
V1
Primary Visual Cortex of Broadman area 17
Identify edges and contours of objects
Redirects visual input to other parts of the brain to interpret what I see
V2
Greater part of area 18
Depth perception by analyzing info from both eyes
V3a
IDENTIFICATION OF MOTION
Is motion happening yes or no
V4
Complete processing of color inputs
LESION= Achromatopsia (if unilateral it can go unnoticed)
MT/V5
TRACKS motion across a scene by direction and context of background
Neurons detect direction of a moving edge
Oreintation Columns spawning down the 1-6 layers of the cortex
Neurons in a column get excited by a stimulus with the same angle of reflection of a visual line
Light hitting the kitchen table travel in a certain angle on a visual line
Ocular Dominance Columns span all 6 layers and around
Respond to input from one eye only
There are horizontal and vertical and diagonal orientation columns
What do they do
They are neurons that get input from that type of shape in an image
Blobs span all 6 layers as cylinders down
Sensitive to color
All 3 color cones are required that send neurons to these blobs
(Stain with Cytochrome Oxidase and look like polka dots)
Neurons mapped on the V1 primary visual cortex are through the 6 layers:
Stripes (Ocular Dominance Columns), Swirls (Orientation Columns), and Blobs
Melanopsin Ganglion (MG) cells
1-3% of ganglion cells that sense light = MG cells
They can also sense light like photoreceptors
They use MELANOPSIN
Sensitive to BLUE LIGHT and provides regulation of circadian rhythm
(Non-image-forming light-responsive system)
Where do the MG cells protect blue light information to
The Hypothalamus, Superchiasmatic Nucleus which signals the Pineal Gland to secrete melatonin in a rhythmic pattern
The melanopsin ganglion goes with the optic nerve since it is a type of ganglionic cell and if there is an optic nerve lesion
You loose your circadian rhythm also
patient with photoreceptors blindness
How will they respond to blue light pupillary reflex and circadian rhythm
Both stay intact
Blue light during the day
Blue light during evening or before sleep
Decrease inflammation after surgery and organ damage
Treat seasonal depression, alertness, cognition
Can disrupt melatonin release and delayed 1st REM
Processing visual information: DORSAL PATHWAY
WHERE PATHWAY (pitcher throws ball and you are looking at the ball movement to decide how to move your arms and swing the bat
Vision signal goes to the primary visual cortex V1—> V2/V3 —->V5/MT —->to send dorsal pathway to the parietal and frontal lobe
For associating vision with movement (complete motor acts based on what I see)
Processing visual information: VENTRAL PATHWAY
WHAT PATHWAY
Visual input goes to V1 primary visual cortex—-> V2—>V4—>inferior Temporal Cortex
Interpret images (recognize symbols, copy shapes, faces)
Facial Recognition
Unilateral damage can be possible
A glutamic GPCR that closes cGMP gated Na receptors in the retina is located where
On the bipolar cells responding to darkness
Which retinal cells make action potentials
Ganglionic cells
LGN
Regulated flow of information
