Olfactory & Visual Systems Flashcards
Human can detect about ___ different odorants.
10,000
The olfactory system is has a ___ (central/peripheral) origin.
peripheral
Where is the patch of olfactory epithelium located?
bilaterally, in the roof of the nasal cavity
The olfactory epithelium contains 3 million receptor cells. supporting cells, Bowman’s gland ducts, and sensory endings from CN ___.
V
The olfactory receptor is a small ___ neuron.
bipolar
The olfactory ___ ends in olfactory ___, from which 10-30 ___ spread over the surface in a layer of mucus secreted by ___ glands to stimulate chemosensitive cilia.
dendrite; vesicle; cilia; Bowman’s
T/F. Axons from olfactory receptors are among the thickest and fastest.
False, Axons from olfactory receptors, among thinnest and slowest.
The olfactory receptors collect into a series of bundles (only about 20) called ___ ___, pass thru holes in ___ plate of ethmoid bone and end in the ___ ___.
olfactory fila; cribiform; olfactory bulb
What makes up CN I?
Olfactory fila make up cranial nerve I
T/F. The Olfactory bulb develops as an outgrowth of diencephalon and reaches the contralateral hemisphere through the thalamus.
False, the olfactory bulb develops as an outgrowth of TELencephalon and reaches IPSILATERAL hemisphere with NO relay in thalamus.
The bulb also has interneurons made up of ___ cells (T) and ___ cells (G).
tufted; granule
T/F. Axons from the 100s of olfactory receptor neurons (go) that express a given odorant receptor converge on 1 or 2 glomeruli.
True
Mitral cells have axons that collect and join the olfactory tract but what does its dendrites form?
its dendrites form glomeruli.
T/F. Even though cells are intermingled in the olfactory epithelium, each type of olfactory receptor sends an axon to one glomerulus of a mitral cell.
True.
Axons from what cells are found in the olfactory tract?
axons of mitral and tufted cells
What is detected by collaterals to the anterior olfactory nucleus?
they regulate sensitivity of the olfactory bulb
T/F. The olfactory bulbs project to the olfactory cortex. Fibers project to both bulbs after crossing in the anterior commissure.
True.
Some fibers in tract end in olfactory ___ but most turn laterally and end in the ___ ___ ___, which is the main central projection for olfaction.
tubercle; lateral olfactory pathway
What are the two general areas that olfactory bulb projections end?
primary olfactory cortex and amygdala
What are the areas of the primary olfactory cortex that the olfactory bulb projections end in?
Cortex near lateral olfactory tract, a.k.a. piriform cortex
Cortex covering amygdala, periamygdaloid cortex
Small part of parahippocampal gyrus
What is another name for the cortex near the lateral olfactory tract where olfactory bulb projections end near?
piriform cortex
What two structures focus an image on the retina?
the cornea and lens
What does focus require?
the refraction of light
The lens accounts for about a ___ of the eye’s refractive power and plays a major role in adjusting ___ for near/ far objects.
third; focus
Where does most refraction occur?
Most refraction is in air-water interface at corneal surface.
T/F. All waves bend when they pass from a medium that allows fast propagation to one that only allows slower propagation.
True.
What structure affects the brightness and quality of an image focused on the retina?
iris
How is pupil size controlled?
by 2 smooth muscles in the iris:
pupillary sphincter and pupillary dilator
Which smooth muscle encircles the pupil and is stronger?
pupillary sphincter
T/F. A smaller pupil worsens ocular performance.
False, A smaller pupil improves ocular performance
What smooth muscle is arranged in radiating spokes from the pupil?
pupillary dilator
Light is processed by photoreceptors (rods and cones) that are close to or far away from the optic nerve?
far away
Photoreceptors synapse first on ___ and ___ cells.
bipolar; horizontal
Bipolar cells terminate on ___ cells and ___ cells. Horizontal cells spread ___ and interconnect receptors of bipolar and horizontal cells.
ganglion; amacrine; laterally
T/F. Amacrine cells interconnect bipolar cells, ganglion cells and other amacrine cells.
True.
The structure of the retina contains neatly arranged layers with ___ nuclear layers and synapses occuring in the ___ interposed layers.
3; 2
Photoreceptors make up what segment of the retina, outer or inner?
outer
T/F. Rod contain pigments and cones contain rhodopsin.
False, Rods contain rhodopsin and cones have cone pigments.
What is the function of a rod? cone?
Rods responds to low-acuity; monochromatic vision in dim-light
Cones responds to high-acuity, color vision and need a lot of light
Photons absorbed by the photoreceptors cause what type of potential?
receptor
What segment of the photoreceptor contain visual pigment?
outer segment
What segment of the photoreceptor contain mitochondria that synthesize pigment?
inner segment
Visual ___ synthesized and transported up the ___ ___ and incorporated into ___ membranes. Older disks at end are phagocytosed by ___ ___. Defects cause some types of retinal degeneration.
pigment; ciliary stalk; disk; pigment epithelium
What is the optic disk?
The area of the retina where nerve fiber layers converge and form the optic nerve
The optic disk contains no ___ and we have no awareness of a blank spot in our vision because the ___ fills in the space.
photoreceptors; brain
What structure is directly in line with the visual axis and at its center, a depression known as the fovea, contains elongated cones and no rods?
macula
What is the fovea specialized for?
vision of highest acuity
T/F. There are capillars and neurons located at the fovea.
False, there are no capillaries or neurons, they are all displaced to the side
Once optic nerve fibers enter the optic tract what is their path?
Most travel to lateral geniculate nucleus (thalamic relay for vision). Others go to superior colliculus, hypothalamus
What radiations have fibers representing the inferior visual fields?
the most superior radiations
The most inferior radiations represent which visual fields?
superior
Fibers from nasal half of retina cross ___ to the optic tract and fibers from temporal half of retina enter ___ optic tract. This way each optic tract “sees” the ___ visual field.
contralateral; ipsilateral; contralateral
What does the chiasm accomplish?
depth perception
What is the structure of the LGN?
It is a 6-layered, precise retinotopic arrangement with its pattern being the same in each layer so any given point in the visual field is represented as a column in all 6 layers.
T/F. Each layer of the LGN gets input from one eye.
True.
Layers ___, ___, & ___ receive information from the contralateral eye and layers ___, ___, & ___ get input from the ipsilateral eye.
1, 4, 6
2, 3, 5
What is the name of layers 1-2 of the LGN? 3-6?
Magnocellular layer (1-2) Parvocellular layers (3-6)
What is the function of the parvocellular layers of the LGN? Magnocellular?
Parvocellular layers - color and form
Magnocellular layers - movement and contrast
What was Dr. Tatsuji Inouye’s contribution to the visual system?
he described the retinotopic organization of primary visual cortex
Where do optic radiations end retinotopically?
in occipital cortex above (inferior visual fields) and below (superior visual fields) the calcarine sulcus
Where is the macula and peripheral visual fields located in the occipital cortex?
Macula is represented most posteriorly, peripheral fields more anteriorly
What is the line of Gennari?
A thin stripe of myelin in primary visual cortex, aka striate cortex, that parallels thecalcarine sulcus and extends a bit onto posterior surface and is surrounded by 18, which is surrounded by 19, visual association or extrastriate cortex.
What ending do we use to denote a loss of one or more quadrants of visual field?
-anopia or - anopsia
Define hemianopia.
loss of half a visual field
Define quadrantanopia.
loss of one quarter of a visual field
T/F. The same visual field lost in each eye is known as homonymous and when two eyes have non-overlaping visual field loss it is known as heteronymous.
True.
The congruous heteronymous is ___ however the noncongruous is ___ but not the same.
identical; overlapping
Damage anterior to chiasm only affects ___ eye. Damage at chiasm causes ___ deficits. Damage to optic tract causes ___ deficits.
ispilateral; heteronymous; homonymous
Temporal lobe lesion can interrupt Meyer’s loop , which represents ___ retinal quadrants.
inferior
___ ___ artery infarction often results in deficit with sparing of macula.
Posterior cerebral
T/F. The posterior cerebral artery does not overlap with the middle cerebral artery distribution.
False, it does.
What are the other area that visual information projects to if it bypasses the LGN?
superior collicululs
hypothalamus
suprachiasmatic nucleus
What nucleus gets direct retinal input, is the master timer of circadian rhythm, and regulates daily body temperature changes, hormone secretions, eating and drinking?
suprachiasmatic nucleus
What area distrbutes info to specialized parts of extrastriate cortex, allows for simultaneous, parallel processing and accounts for the speed in access visual info even though our neurons are slow?
primary visual cortex
The ___ cortex has columnar organization.
striate
T/F. Columns in one cortical module analyze all aspects of visual information arriving from discrete areas of visual field. Modules in foveal part analyze small areas of visual field, so fova has many more modules and therefore better resolution.
True
The parvocellular layers of the LGN process ___ streams of visual information and the magnocellular layers process ___ streams.
ventral; dorsal
T/F. Selective defected in the intrastriate cortex can lead to strange visual deficits in distinguishing colors, motions and faces.
False, it is in the EXTRAstriate.
