Olfactory and Visual systems Flashcards
Humans can detect ______ different odors.
10,000
Describe the olfactory epithelium….what is it?
- Patch in roof of nasal cavity (bilateral)
- Contains 3 million receptor cells, supporting cells, bowman gland ducts, sensory endings.
- It is the peripheral origin of the olfactory system
What is an Olfactory receptor?
A small bipolar neuron
- dendrite ends in olfactory vesicle, from which 10-30 cilia spread over the surface in a layer of mucous secreted by Bowman’s gland.
- Stimulate chemosensitive cilia
- Unusual among human neurons. (replaced every 1-2 months)
Axons from the olfactory receptors are among the _______ and _______.
thinnest and slowest
axons from olfactory receptors collect into a series of bundles called _________.
Olfactory fila
Olfactory film travel through ______ and end ________.
- Holes in cribriform plate of ethmoid bone
- end in olfactory bulb.
________ make up cranial nerve I.
Olfactory fila
Olfactory build develops as an outgrowth of ________.
Telencephalon
Describe the structure of the olfactory bulb. (Interneurons, Mitral cells….)
Bulb has interneurons = tufted cells and granule cells.
Mitral cells = axons collect join olfactory tract, dendrites form glomeruli.
What forms the glomeruli of the olfactory bulb?
Dendrites from the olfactory tract.
Where do olfactory fibers get sorted?
In the olfactory bulb.
What are the olfactory bulb projections to the cortex? (2)
- Axons of mitral and tuft cells.
- Collateral to anterior olfactory nucleus. (thought to regulate sensitivity of olfactory bulb)
* Fibers project to both bulbs (cross in midline in anterior commissure).
Where do olfactory bulb projection fibers travel?
Some fibers end in olfactory tubercle…
MOST turn laterally and end in lateral olfactory pathway.
Where do olfactory bulb projections END?
End in 2 areas
1) Primary olfactory cortex:
- Cortex near olfactory tract (Piriform cortex)
- Cortex covering amygdala (periamydaloid cortex)
- small part of parahippocampal gyrus
2) Amygdala
Where is Olfactory information sent to?
Hypothalamus, Thalamus, hippocampus, orbital cortex and Amygdala.
- direct projections and a THALAMIC relay to the association cortex *No thalamic relay to motor cortex.
- Goes to Olfactory association cortex = orbital surface of frontal lobe and anterior insula.
_____ & _______ focus image on retina.
Cornea & lens
_____ accounts for about 1/3 of the eyes refractive power.
lens *major role is in adjusting focus for near/far objects.
Where does most refraction take place?
In the air-water interface at corneal surface (70%)
______ affects the brightness and quality of the image focused on retina.
Iris
Pupil size is controlled by what two muscles?
- Pupillary sphincter = encircles pupil (stronger than dilator)
- Smaller pupil improves ocular performance
- Pupillary dilator = arranged in radiating spokes from the pupil (sympathetic innervation)
(Retinal structure)
______ is layer of rods and cones.
Photo receptors
Where do synapses occur in the retinal structure?
In the 2 interposed layers
- one cell types brings visual info in and the other sends it out.
- another type interconnects laterally)
_____ are highly specialized cells with different structural regions.
Photoreceptors (Rods and cones)
Describe the outer segment of the photo receptor….
Outer segment = contains visual protein.
- rods = rhodopsin (low acuity, monochromatic vision, dim light)
- Cones = cone pigments (high acuity color vision, needs light)
_____ is where nerve fiber layer converges and forms optic nerve.
Optic disk!
- No photo receptors here = blind spot!
The center of the Macula has a depression called the _____ that is rich in _____.
Fovea
cones
_____ is specialized for vision of highest acuity.
Fovea
***Briefly describe the optic pathway…..
- ganglion cell axons in optic nerve travel to…..
- The optic chasm where partial decussation takes place.
- Enter optic tract…
- Most fibers travel to lateral geniculate nucleus (LGN); thalamic relay for vision *others of to superior colliculus/hypothalamus.
- from LGN to visual cortex.
Optic tract fiber end in the ______ of the _______.
lateral geniculate nucleus (LGN) of the Thalamus.)
LGN Projects to where?
The visual cortex
Fibers representing inferior visual fields are most ______ in radiations.
Superior
Fibers representing superior visual fields are most _____ in radiations.
Inferior
Regarding Optic radiation in the internal capsule, the retrolenticular part is associated with what visual field?
Superior visual field
Regarding Optic radiations in the internal capsule, the Sublenticular part is associated with what visual field?
Inferior visual field
review the visual fields and fibers that supply them…..on desktop.
Great!
Describe the Structure of the Lateral geniculate nucleus…
- 6 layered precise retinotopic arrangement.
- Pattern the same in each layer so any given point in the visual field is represented as a column in all 6 layers.
- each layer gets input from one eye
What layers of the LGN get input from contralateral eye?
1,4,6
What layers of LGN get input from ipsilateral eye?
2,3,5
Optic radiations end rentiotopically in the ________.
Occipital cortex, above and below the calcarine sulcus. (Inferior fields above sulcus, superior fields below sulcus)
______ thin stripe of myelin in primary visual cortex (aka striate cortex)
Line of Gennari
_______ is loss of half of a visual field.
Hemianopia
_____ is loss of one quarter of a visual field.
Quadrantanopia
_______ is same loss of field in both eyes.
Homonymous
______ two eyes have non-overlapping visual field loss.
Heteronymous
Congruous = identical
Non-congruous = overlapping but not the same.
Damage anterior to chiasm affects what?
only ipsilateral eye
Damage at optic chasm affects Causes what?
Heteronymous deficits
Damage to optic tract causes what?
homonymous deficits
________ lobe can interfere with Meyer’s loop which represents ________ quadrants.
Temporal
Inferior retinal quadrants
Posterior cerebral artery infarction often results _________.
Deficit with sparing of macula.
How would a lesion at he optic radiating affect the pupillary light reflex?
It wouldn’t!
How would a lesion in the visual cortex affect the pupillary light reflex?
It wouldn’t because blind individuals can still exhibit this reflex if they are “Cortically” blind.
What are some of the “Other” destinations fro visual info?
Superior Colliculus
Hypothalamus
Suprachiasmatic nucleus gets direct retinal input.
- master timer of circadian rhythms, daily body temperature changes, hormone secretion.
What is the role of the primary visual cortex?
Breaks down visual info sound into component parts; irritation, color, depth, motion, brightness….
_ distributes said info to specialized parts of extra striate cortex.
What kind of processing does the cortex use?
Parallel processing
Visual cortex has a _____ organization.
Columnar
Describe the role of cortical modules and columns.
Columns in one cortical module analyze all aspects of visual info arriving from discrete areas of visual field.
Modules in foveal part analyze small areas of visual field, so ova has many more modules and therefore better resolution.
Where do the Dorsal and ventral streams of visual streams info begin?
In the LGN
Parvocellular layers are associated with_______ Stream.
Ventral stream
Magnocellular layers are associated with ______ stream.
Dorsal
