Exam 3 Part 1 Flashcards
(62 cards)
0
Q
Which 3 cranial nerves emerge in a medial to lateral manner, respectively, at the junction of the pons and medulla?
A
VI, VII, VIII
1
Q
Which cranial nerve exits the ventrolateral pons through the middle cerebral peduncle?
A
V
2
Q
Which cranial nerves are associated with the lateral medulla?
A
IX and X
3
Q
Which cranial nerve exits the ventromedial medulla between the medullary pyramids and the inferior olive?
A
XII
4
Q
What is the only cranial nerve that does not originate in the brainstem?
A
XI
5
Q
What is the largest cranial nerve?
A
V
6
Q
What is the only cranial nerve to supply contralateral tissue?
A
IV
7
Q
Which cranial nerve exits into the space between the two cerebral peduncles on the ventral surface of the midbrain?
A
III
8
Q
What is the only cranial nerve to exit on the dorsal surface of the brainstem?
A
IV
9
Q
Which 2 cranial nerves enter the forebrain directly?
A
I and II
10
Q
5 Layers of Scalp
A
- skin
- subcutaneous connective tissue
- galea aponeurotica
- loose areolar tissue
- pericranium
11
Q
3 Compartments of Skull
A
- anterior cranial fossa- frontal lobe
- middle cranial fossa- temporal lobe
- posterior cranial fossa- cerebullum & brainstem
12
Q
Meninge Layers
A
in–>out
- pia
- arachnoid
- dura
13
Q
Dura Mater- 2 layers, forms what 2 things
A
Layers- meningeal & periosteal layer
Forms- falx cerebra & tentorium cerebella
14
Q
Arachnoid mater- holds what
A
CSF
15
Q
Pia mater: forms what
A
- forms a perivascular space called Virchow-Robin space around every blood vessel that enters the brain
- follows every gyri and sulcus
- fuses with the ependyma, the membranous lining of the ventricles, to form structures called the choroid plexus which produces CSF
16
Q
Spaces formed by the meninges and what they contain
A
- epidural space- contains middle meningeal artery
- subdural space- bridging veins travel across
- subarachnoid space- contains major arteries
17
Q
Venous system divided into superficial vs. deep system:
A
-veins pass thru arachnoid mater and enter the space b/w the 2 dura layers and then drain into the dural venous sinuses
Superficial- superior sagittal sinus and the veins that drain into it; drains the cerebral hemispheres
Deep- internal cerebral and basal vein that form the Great vein of Galen; drains into straight sinus (transverse sinus & sigmoid sinus)
18
Q
Ventricles that Hold CSF
A
2 lateral ventricles
3rd ventricle- within diencephalon
4th ventricle- within pons, medulla, and cerebellum
19
Q
Regions of lateral ventricles
A
- frontal/anterior horn
- body
- atrium
- occipital horn
- temporal/inferior horn
20
Q
Flow of CSF
A
lateral ventricles –> foramen of Monroe –> 3rd ventricle –>aqueduct of Sylvius or the cerebral aqueduct –> 4th ventricle
21
Q
Blood Brain Barrier
A
- blood/capillaries have no fenestrations or holes for diffusion
- Can allow passage of: fat soluble molecules, CO2, and O2
- blocks diffusion of bacteria or large hydrophilic molecules
- to pass, must utilize a transporter
22
Q
Blood-CSF Barrier
A
- capillary has fenestrations and are freely permeable
- choroid epithelial cells form a barrier between CSF and blood
- veins can absorb CSF via vacuolization of one way CSF getting pumped into slit-like opening that bursts through outside wall
23
Q
Circumventricular Organs
A
-detect changes in chemical makeup of brain & have no blood brain barrier Organs: 1. subfornical organ 2. organum vasculosum 3. median eminence 4. neurohypophysis 5. pineal 6. subcommissural organ 7. area postrema
24
Edema in Brain: cytotoxic vs. vasogenic edema
1. Cytotoxic edema = excessive intracellular fluid; can occur due to vasogenic edema/ischemia/metabolic poisons
2. Vasogenic edema = excessive extracellular fluid by disruption of BBB; can occur due to infection/trauma/tumors
25
3 Layers of the Eye
1. sclera
2. uveal tract- choroid (capillaries & melanin), ciliary body (muscle, ciliary process produces aqueous humor), iris (adjust pupil)
3. retina
26
Lens Accommodation- distant vision vs. near vision
distant- flat lens
| near- round lens
27
Pupil size: light in, depth of field, spherical & chromatic aberrations
```
Small pupil:
-less light in
-increases depth of field
-reduces spherical & chromatic aberrations
Large pupil:
-more light in
-decreases depth of field
-increases spherical & chromatic aberrations
```
28
Retina: optic disc, macula lutea
Optic Disc- blind spot with no photoreceptors, arteries/veins/axons enter or leave
Macula lutea- highest visual acuity, fovea
29
Direct pathway of retinal neurons
photoreceptor --> bipolar --> ganglion
30
Horizontal vs. Amacrine Cells: where cell bodies are located, synapses where, function
Horizontal:
-cell bodies in inner layer
-form synapses within outer plexiform layer
-connections between photoreceptors & bipolar cells (increase sensitivity to contrast)
Amacrine:
-cell bodies in inner layer
-form synapses within inner plexiform layer
-transmit info from bipolar cells to ganglion cells
31
Retinal Pigment Epithelium
- helps remove old membranous receptor discs from photoreceptors
- capillaries for nutrients of photoreceptors
32
Phototransduction in Dark
- depolarization
- Na+ influx, K+ efflux
- increased cGMP opens channels
33
Phototransduction in Light
- hyperpolarization
- reduced Na+ influx, K+ efflux
- decreased cGMP closes channels
34
Light: absorbing a photon
1. cis retinal --> trans retinal
2. transducin activated
3. activates phosphodiesterase that hydrolyzes cGMP
4. decreased cGMP closes channels
5. hyperpolarization
35
Returning to Normal After Light
1. rhodopsin kinase phosphorylates rhodopsin
2. arrestin binds and blocks transducin
3. trans retinal dissociates from opsin into cytosol and becomes trans retinol
4. IRBP transports it into pigment epithellium
5. converted back to cis retinal
6. IRBP transports back to opsin
36
2 Important Factors in Light Adaptation
1. Calcium
| 2. interactions between horizontal cell and the terminals of photoreceptors
37
Light Adaptation
1. closure of channels from decreased cGMP --> decreased Ca2+ internal concentration
2. increased activity of guanylate cyclase leading to increased cGMP levels
3. increased activity of rhodopsin kinase that permits more arrestin to bind
4. increases affinity of cGMP gated channels for cGMP and reduces impact
38
Rods- sensitivity/resolution, type of vision, number, location, pathway
- light sensitive but low resolution
- scotopic vision (low light)
- lots!!
- highly convergent system (rod bipolar --> amacrine --> cone bipolar --> ganglion)
- located in periphery
39
Cones- sensitivity/resolution, type of vision, number, location, pathway
- less light sensitive, high resolution
- photopic color vision
- less!!
- direct pathway to ganglion cells
- located in fovea
40
3 Types of Cones for Color Vision
1. blue - short wavelength
2. green - medium wavelength
3. red - long wavelength
41
Types of Color Blindness (dichromatic = respond to only 2 wavelengths of light): protanopia, deuteranopia, tritanopia, anomalous trichomats
1. protanopia - can't detect long wavelengths (red-green blindness)
2. deuteranopia - can't detect medium wavelengths (red-green blindness)
3. tritanopia - can't detect short wavelengths (yellow-blue blindness)
4. anomalous trichomats - respond to all 3 wavelengths but have more overlap in wavelengths and need different intensities to make colors
42
On and Off Center Bipolar Cells
On Center (G protein): glutamate causes hyperpolarization
Off Center (AMPA): glutamate causes depolarization
43
Optic Tract Destinations
1. lateral geniculate nucleus (retinogeniculostriate pathway)- provides majority of what we see; primary visual pathway
2. superior colliculus- coordinates head and eye movements
3. hypothalamus (retinohypothalamic pathway)- suprachiasmatic nucleus; help with day/night cycle
4. pretectum- pupillary light reflex
44
Changes in image onto retina
images inverted & left-right inversed
45
Visual Field Deficits: anopsia vs. scotoma
Anopsia- large visual field deficit
| Scotoma- small visual field deficit
46
Path of superior visual field vs. inferior visual field
Superior visual field- around lateral temporal lobe to occipital lobe
Inferior visual field- in parietal lobe
47
Spatiotemporal Tuning Properties of Neurons in Primary Visual Cortex: LGN vs. visual cortex
LGN: center surround receptive field organization that responds to increase/decreases in luminance
Cortex: respond to bars of light or edges in certain positions
48
Primary Visual Cortex Neurons respond to (4)
1. orientation
2. direction of motion of the image
3. spatial frequency
4. temporal frequency
49
Architecture of Primary Visual Cortex- layers, LGN terminates where, spiny stellate neurons, no pyramidal cells
- 6 layers
- LGN terminates in layer 4C
- only spiny stellate neurons in 4C
- no pyramidal cells in 4C
50
Layers in LGN: magnocellular vs. parvocellular
1. Magnocellular- terminates in upper 4C & transiently responds to stimuli
- large cell bodies, large dendritic and receptive fields, large diameter axons
- no colors
- input from M ganglion cells
- damage effects perception of rapidly changing stimuli
2. Parvocellular- terminates in lower 4C & sustains response to stimuli
- small cell bodies, small dendritic and receptive fields, smaller axons
- conveys colors
- input from P ganglion cells
- damage effects visual acuity & perception of color
51
Cisterns
spaces or areas within the subarachnoid space
52
Koniocellular Pathway (K-cell): neurons located where, input, project to, convey
- Neurons located in the interlaminar zones b/w lateral geniculate layers
- Input from fine caliber retinal axons
- Project to layers 2 and 3
- Convey aspects of color vision
52
Binocular vs. Monocular Vision: Neurons in striate cortex, Neurons in LGN
Striate Cortex: mostly binocular
- have affinity for one or the other or both eyes
- neurons are arranged in columns based on this affinity = ocular dominance columns
LGN: monocular
- send axons to ocular dominance columns in layer 4
- neurons in layer 4 then send axons out to other neurons and merging the individual eye information
52
Stereopsis
- perception of depth
- binocular vision
- differences between the viewed image (point of fixation) from each eye are interpreted as depth
52
Neurons that contribute to stereopsis- far cells, near cells, turned zero
Far Cells- respond to retinal disparities beyond the plane of fixation
Near Cells- respond to retinal disparities before the plane of fixation
Turned Zero- respond to sites on the plane of fixation
52
Extrastriate Visual Areas- 2 systems
1. Ventral Stream: striate cortex to the inferior temporal lobe
- handles object recognition and fine resolution
2. Dorsal Stream: striate cortex to the parietal lobe
- handles spatial visual aspects
52
Glaucoma
- high interocular pressure due to poor drainage of aqueous humor
- can affect the blood supply to the eye leading to cell damage
52
Cataracts
-clouding of the lens
52
Ametropia (2 types)
- Ametropia: refractory problems leading to difficulty with vision
1. myopia - nearsighted (can see near); image focused before the retina
2. hyperopia - farsighted (can see far); image focused after the retina
52
Macular Degeneration (2 types)
- progressive loss of central vision due to a degeneration of photoreceptors
1. wet- exudative neovascular form
2. dry- nonexudative
52
Retinitis Pigmentosa
- due to apoptosis of photoreceptors
- dx based on clinical features = night blindness, decreased peripheral vision, narrowing of retinal vessels, clumps of pigment
