Sensory Systems Flashcards
1
Q
The Eye
______ and _______ focus the light
______ detects the light
______ carries information to the brain
A
The Eye
cornea and lens focus the light
retina detects the light
optic nerve carries information to the brain
2
Q
Retinal organization
Label:
A
3
Q
Eyes are anchored to the brain by _______
A
Eyes are anchored to the brain by optic nerves
4
Q
How did eyes become connected to the brain?
A
- Eyes “sprouted” off the forebrain (prosencephalon) as opposed to connecting to it secondarily
5
Q
Morphogenesis of the eye
- the forebrain forms lateral evaginations, the ______
- Once these contact the overlying _______ they invaginate on themselves to become _______
A
Morphogenesis of the eye
- the forebrain forms lateral evaginations, the optic vesicles
- Once these contact the overlying ectoderm they invaginate on themselves to become bilayered optic cups
6
Q
- The inner layer of the optic cup will become the _______
- the outer layer will become the _______ and ______
- The overlying ectoderm will invaginate to form the ______
- Remaining ectoderm will form the ______
A
- The inner layer of the optic cup will become the retina
- the outer layer will become the retinal pigmented epithelium and iris
- The overlying ectoderm will invaginate to form the lens
- Remaining ectoderm will form the cornea
7
Q
Lens is specialized and arises from __________
A
Lens is specialized and arises from neurogenic placodes (ectoderm)
8
Q
What is the choroid fissure?
A
- The choroid fissure allows vessels to grow into the eye, nourishing the developing retina and lens
- Once vessels and axons have grown, the fissure closes, ensuring circular symmetry of the eye
9
Q
What is Ocular Coloboma?
A
- Coloboma results from a failure of the choroid fissure to close
- Defect may be in retina, iris, and/or lens
- Gap in the eye
10
Q
Lens invagination:
- Lens placode separates from _____ to form ______
- Formation of the lens requires signals from _______
A
Lens invagination:
- Lens placode separates from ectoderm to form lens vesicle
- Formation of the lens requires signals from optic vesicle
11
Q
Lens development:
- Cells on the posterior face of the lens vesicle differentiate into _______
- elongate ______
- Start to express ______, protein that makes lens transparent
A
Lens development:
- Cells on the posterior face of the lens vesicle differentiate into primary lens fibers
- elongate anterior-posteriorly
- Start to express crystallins, protein that makes lens transparent
12
Q
________ cells remain proliferative throughout life
Newly born cells migrate _______ and form _______
A
anterior lens cells remain proliferative throughout life
Newly born cells migrate peripherally and form secondary lens fibers (wrap around primary lens fibres)
13
Q
_______ make up 90% of protein in lens fibres
A
crystallins make up 90% of protein in lens fibres
14
Q
What are congenital cataracts?
Dr Norman Gregg linked ______ with congenital cataracts
A
- Cloudly lens often caused by crystallin mutations
- Many causes, both environmental and genetic, with ~100 genes implicated
- Dr Norman Gregg linked maternal rubella with congenital cataracts at a time when we didn’t know anything crossed the placenta
15
Q
The retina begins as a ________
A
The retina begins as a pseudostratified neuroepithelium
16
Q
Cell division (mitosis) happens at the ______ of the retina
A
Cell division (mitosis) happens at the apical surface of the retina
17
Q
The mature retina has 3 layers of cells (green) composed of ________ and separated by two ______ (red)
A
The mature retina has 3 layers of cells (green) composed of 6 types of neurons and 1 glia and separated by two synaptic layers (red)
18
Q
How are the various cell types of the retina generated?
A
- Temporal organization
- All progenitors in retina can give rise to any of the 6 types of neurons and 1 glia in the retina.
- Does so in waves
19
Q
What is the sequential order of retinal cell differentiation?
A
- Ganglion cell
- Horizontal cell
- Amacrine cells
- Cones
- Bipolar cells
- Rods
- Muller cells (glia)
20
Q
The ______ are the output neurons of the eye; they bundle together and exit the eye as the ______
A
The retinal ganglion cells (RGCs) are the output neurons of the eye; they bundle together and exit the eye as the optic nerve
21
Q
Visual pathway:
A
Retina → thalamus (lateral geniculate nucleus) → optic radiations → Visual cortex (occipital lobe)
22
Q
What are three issues that must be overcome regarding the visual pathway?
A
- Segregate Left Field vs Right Field
- Preserve Map of visual field (retina → brain)
- Right vs Left eye (segregate inputs)
23
Q
Some axons cross at the ______ between the eye and lateral geniculate nucleus (thalamus)
A
Optic Chiasm
24
Q
Visual Fields:
- Left visual field is captured by _____ sides of both eyes
- Right visual field is captured by _____
A
Visual Fields:
- Left visual field is captured by right sides of both eyes
- Right visual field is captured by left sides of both eyes
25
Which axons cross at the optic chiasm and why?
* Left visual field from the left eye crosses and the right visual field from the right eye crosses
* Left side of brain gets RIGHT VISUAL FIELD
* Right side of brain gets LEFT VISUAL FIELD
26
Axon guidance at optic chiasm
* The axons of right and left side RGCs express different \_\_\_\_\_\_\_\_
* Nasal vs Temporal
* Many guidance cues surround the \_\_\_\_\_
* The axons of RGCs that view the visual field on the same side behaviour at the chiasm
* Axons of RGCs that view the visual field on the opposite side behaviour at the chiasm
Axon guidance at optic chiasm
* The axons of right and left side RGCs express different _guidance cues receptors_
* Nasal vs Temporal
* Many guidance cues surround the _optic chiasm_
* The axons of RGCs that view the visual field on the same side **will cross at the chiasm (contralateral)**
* Axons of RGCs that view the visual field on the opposite side **will NOT cross at the chiasm (ipsalateral)**
27
Where do ganglion cell axons synapse?
After crossing, the axons travel to the **lateral geniculate nucleus (LGN)** a collection of neurons in the thalamus
28
Topographic mapping:
Organization of the visual field inputs is maintained in \_\_\_\_\_
Topographic mapping:
Organization of the visual field inputs is maintained in _lateral geniculate nucleus_
Gradients of guidance cues and receptors
29
What creates the topographic map?
* Gradients of guidance cues and receptors
* “dif postal code”
* Axons with specific receptors match based on guidance cues
30
Gradients of guidance molecule **receptor** expression in the ______ and gradients of guidance molecule **ligand** expression in ______ establish topographic mapping of retinal axons
Gradients of guidance molecule receptor expression in the _retina_ and gradients of guidance molecule ligand expression in _Lateral Geniculate nucleus_ establish topographic mapping of retinal axons
31
\_\_\_\_\_\_\_ carry visual information from the LGN (thalamus) to the Primary Visual Cortex (V1)
_optic radiations_ carry visual information from the LGN (thalamus) to the Primary Visual Cortex (V1)
32
Each LGN (and primary cortex) receives visual information for _____ but from \_\_\_\_\_
Each LGN (and primary cortex) receives visual information for _one visual field_ but from _both eyes_
33
RGC axons sort into ________ in the LGN
RGC axons sort into _eye-specific layers_ in the LGN before sending to the visual cortex
34
The different layers created in the LGN of left and right eye are sorted into _______ in the cortex
The different layers created in the LGN of left and right eye are sorted into **_ocular dominance columns_** in the cortex
35
What are two mechanisms that contribute to the sorting of Left and reight eye into ocular dominance columns
1. Guidance cues
1. Optic chiasm
2. Gradient map in LGN
2. Activity
36
Sorting of eye-specific inputs to LGN
* RGC axons from the left and right eyes initially overlap in the \_\_\_\_\_
* Segregation of the axons is dependent on \_\_\_\_\_\_\_
Sorting of eye-specific inputs to LGN
* RGC axons from the left and right eyes initially overlap in the _LGN_
* Segregation of the axons is dependent on **_spontaneous_** _activity of RGC neurons_
* prenatally, random firing of cells near each other help with spatial organization
* Fire together wire together
37
Sorting of eye specific inputs to visual cortex
* LGN neurons primarily target layer ___ of the visual cortex
* _______ overlap initially
* Eye- specific inputs segregate ______ into adjacent fields
* Requires \_\_\_\_\_\_\_\_\_
Sorting of eye-specific inputs to visual cortex
* LGN neurons primarily target layer _4_ of the visual cortex
* _axon branches_ overlap initially
* Eye- specific inputs segregate _postnatally_ into adjacent fields
* Requires _vision in both eyes as the axons compete for territory_
38
What was the experiment that won Hubel and Wiesel the 1981 Nobel prize
* Visual cortex of cat with radioactive tracer from one eye
* Covered one eye of cat during critical period
* eye left open dominated the visual cortex
* Covered both eyes
* columns didn't change
39
What are 2 key parts of the olfactory system
1. Olfactory epithelium w/ primary sensory nn (olfactory receptor cells)
2. Axons contact 2nd order neurons in olfactory bulb
40
Olfactory cell sends axons through the _____ into the \_\_\_\_\_\_
Olfactory cell sends axons through the _ethmoid bone_ into the _olfactory bulb_
41
\_\_\_\_\_\_\_\_ form near nasals and differ into olfactory epithelium
* some of the cells differentiate into sensory nn known as \_\_\_\_\_
* extend axons a short distance to synapse with _____ cells in the \_\_\_\_\_\_
_Olfactory/nasal placodes_ form near nasals and differ into olfactory epithelium
* some of the cells differentiate into sensory nn known as _olfactory receptor cells_
* extend axons a short distance to synapse with _mitral_ cells in the _olfactory bulb_
42
At the same time as the primary sensory neurons are differentiating in the olfactory epithelium, the brain produces an outgrowth called the \_\_\_\_\_\_
* Here, neuroepithelial cells differentiate into ______ called \_\_\_\_\_
At the same time as the primary sensory neurons are differentiating in the olfactory epithelium, the brain produces an outgrowth called the _olfactory bulb_
* Here, neuroepithelial cells differentiate into _secondary neurosensory cells_ called _mitral cells_
43
Label
A
B
44
The cribriform plate (derived from \_\_\_\_\_\_) forms around the projections of the \_\_\_\_\_\_
The cribriform plate (derived from _neural crest_) forms around the projections of the _primary neurosensory cells_
45
As the brain and face grow, the axons of the ______ elongate to make the olfactory tracts
* Grow through ______ from \_\_\_\_\_
As the brain and face grow, the axons of the _mitral cells_ elongate to make the olfactory tracts
* Grow through _mesenchyme_ from _neural crest & bone formed around it_
46
Each primary olfactory neuron expresses only 1 type of \_\_\_\_\_\_\_
Each is expressed in a subset of neurons spread across the \_\_\_\_\_\_
These neurons converge together on the ______ of ______ forming structures called \_\_\_\_\_
Each primary olfactory neuron expresses only 1 type of _odorant receptor_
Each is expressed in a subset of neurons spread across the _olfactory epithelium_
These neurons converge together on the _dendrites_ of _specific mitral cells_ forming structures called _glomeruli_
47
Topographic mapping in olfactory system
* information is sorted based on the \_\_\_\_\_\_
Topographic mapping in olfactory system
* information is sorted based on the _olfactory receptors_
* _receptors themselves direct the axons_
48
Auditory system
* movement of fluid hits ____ and opens \_\_\_\_
Auditory system
* movement of fluid hits _cilia_ and opens _ion channels_
49
three bones of the inner ear:
Maleus
Incus
Stapes
50
The _______ is what opens when your ears “pop” to equalize pressure
The _pharyngotympanic tube_ is what opens when your ears “pop” to equalize pressure
51
label the ear
52
The _otic placode_ forms in the \_\_\_\_\_\_\_
The _otic placode_ forms in the _inner ear_
