week 4 Flashcards
(352 cards)
1
Q
What is the CNS consist of
A
brain and spinal cord
2
Q
What is PNS made up of?
A
All the neurons , or part of the neurons outside the CNS
3
Q
What does somatic nervous system control
A
Voluntary action via skeletal muscle
intentional movement that is done consciously
4
Q
What does autonomic nervous system control
A
involuntary visceral functions, such as breathing/ heart rate
no control over the skeletal muscle
5
Q
What is the PNS comprise of (what nervous system)
A
Somatic and autonomic nervous system
6
Q
What is enteric nervous system (ENS)
A
Part of the autonomic nervous system, control digestion and gut movement
Can work independently or get input from spinal cord
7
Q
What is the general function/ idea of CNS vs PNS?
(which one is control centre, which one is messenger)
A
CNS= response headquarter, control and make decision
PNS= messenger network, deliver command and bring sensory info
8
Q
What nervous system do most neurons belong to
A
CNS
9
Q
What does glia do? in CNS and PNS
A
Support and protect the neurons
10
Q
Where is ventricles located? What is it filled with
A
In CNS, filled with CSF
11
Q
What is CSF
A
cerebrospinal fluid, cushion the brain and provide nutrients, remove waste
12
Q
How are the ventricles connected
A
Lateral ventricles
Third ventricles
Fourth ventricles
Central canal of spinal cord
All filled with CSF
13
Q
What is gray matter consist of
A
Consist of nerve cell bodies, unmyelinated axons and dendrite
14
Q
How are the cell bodies arranged in gray matter, and what is the name of them?
A
In layers or clusters, called nuclei ( nucleus)
15
Q
What is the white matter consist of
A
Myelinated axons
White due to the myelination
16
Q
How are the axons in white matter arranged, and what’s the name?
A
Running in bundles, called tract
17
Q
How are clusters on neurons named in PNS VS CNS
A
CNS: nuclei (nucleus)
PNS: ganglia (ganglion)
18
Q
How are bundles of axons named in PNS VS CNS
A
PNS: nerve
CNS: tract
19
Q
What is the energy usage of brain? comparing to other body organ
A
It uses a lot of energy, as it is very important, conduct a lot of activities
Consume half of the body’s glucose
20
Q
Why is the CNS firing AP at a low rate? ( only 4% of neurons are firing)
A
To saves energy
Neurons communicate by firing AP down the axon, which use a lot energy
CNS firing at low rate can conserve energy
21
Q
How many segments are there in the spinal cord
A
31, each with a pair of spinal nerves
22
Q
Where is the dorsal root located? And what does it carry
A
Located at the back
It carries afferent signal, which goes from PNS into CNS
These signals are carries by dorsal root ganglion
23
Q
What is the spinal nerves consist of
A
Dorsal and ventral root
24
Q
Where is the ventral root located? And what does it carry
A
At the front
Carries efferent signal, which exit the CNS into the PNS and the body
25
What is motor signal carried by? (dorsal or ventral)
By ventral ganglion root, and send to skeletal muscle
26
Where is the grey matter located in spinal cord
In the middle of the cord, surrounded by white matter
27
What is the shape and component of spinal cord grey matter
Butterfly shape, with both dorsal and ventral horn on each side
Dorsal horn= back, send to CNS input
Ventral horon= front, exit CNS output
28
What is the somatic sensory nuclei and its location?
In the dorsal horn, and has long dendrites that extend toward soma outside CNS
Get signal from skin
29
What is the visceral sensory nuclei and its location?
In the dorsal horn
get signal from viscera (internal organ)
30
What is dorsal VS ventral
Dorsal= back
Ventral= belly, front
31
What is the autonomic efferent nuclei and its location?
Located in the ventral horn
Send signal/ command to smooth muscle/ glands
32
What is the motor nuclei and its location?
Located in the ventral horn
Send signal/ command to skeletal muscle
33
What is white matter of the spinal cord consist of
Axon tracts (axons bundle)
34
What is the ascending tract and location?
Mainly dorsal
Carry sensory signal to the brain
35
What is the descending tract and location?
Mainly ventral
Carry outgoing signals leaving the brain and CNS
36
What is the propriospinal tract and location?
Stay inside the spinal cord
Modulate signals within the spinal cord
37
What is spinal reflex
A sensory signal is carried to the dorsal horn by sensory fibre
These fibre excite the ventral horn neurons, and send a efferent signal toward the muscle for response, without waiting for the brain to make decision
Responding to stimuli without consulting the brain
38
What are the 3 main region of brain
Forebrain, midbrain and hindbrain
39
What is the midbrain consist of
Pon, Medulla, and cerebellum
40
What does pon do?
Connect brain stem to cerebellum
responsible for autonomic function
41
What is medulla (CNS)
The continuation of the spinal cord, regulate vital hormonic function
42
Where is cerebellum located
Behind pon, under cerebral hemisphere
43
What does cerebellum do
Integrating centre, used to coordinate complex movement, and receive movement instruction from the forebrain
44
What is midbrain responsible
Auditory and visual information
45
Where is midbrain
Sit above the pon
46
What is the brain stem consist of
Medulla, pon and midbrain
47
What does brain stem do
Main control centre for autonomic function and reflexes
48
Where does cranial nerves arise from
Brain stem
49
Where is the diencephalon
above midbrain
50
WHat is diencephalon consist of
Hypothalamus, thalamus, pituitary gland and pineal gland
51
What is telecephalon?
The cerebrum, which envelop other brain structure
52
What does thalamus do
Filter info going to/ from cerebral cortex, like an "packaging centre"
53
Where is corpus callosum part of
Cerebrum
54
What do pineal and pituitary gland do
secrete hormone
55
What does corpus callosum do
Large bundle of myelinated axons
connect the 2 hemisphere of cerebrum, allow communication
56
What is basal ganglia
Cluster of grey matter, deep inside brain
57
What is cerebrum consist of (general structure)
Two hemisphere, Left and right
58
What are the components of cerebral grey matter
Cortex, basal ganglia and limbic system
59
What is cortex? (general location)
Outer layer of cerebrum, not smooth
60
What is cereal lateralization? What happen IRL?
The 2 hemispheres function differently
Left hemisphere is better at math and language, and right hemisphere is better at spatial analysis
IRL, both hemisphere work together for most tasks
61
What are the for lobes of each hemisphere
Frontal, parietal, occipital and temporal
62
Where is temporal lobe of hemisphere
Side of the head, between ear and eye
63
What is cingulate gyrus part of
Limbic system
64
What does the limbic system response for
Emotion, behaviour and memory
65
What is hippocampus responsible? What happen if it's damaged
Hippocampus responsible for old & new memory
If damaged, patient will have difficulties forming new memory
66
What is hippocampus part of
The limbic system
67
What is amygdala part of
The limbic system
68
What are the 6 major division of brain
Cerebrum
Diencephalon
Mid brain
pons
cerebellum
medulla
69
What are cranial nerves
Nerves that enter/ leave the brain, rather than the spinal cord
Control function like vision, smell, hearing, etc
70
What is electricity, for brain
Fundamental language, the medium to process and communicate all information
71
What is equilibrium, in term of senses?
Sense of balance and motion
72
How is special senses detected (general)
using specialized organ
73
How is somatic sense detetced
Using skin as sense organ
74
What is proprioception sense
sense of body position to the world
75
What is nociception sense
sense of pain/ itch
76
what is the role of receptor in sensory system
They convert stimuli to electrical signal
77
What is transduction
The conversion of stimuli to electrical signal
78
What are the two type of cells that receptor cells can be? (what can they be in vision system, or hearing system)
Receptor cells can be neuron, or non-neuronal epithelial cells
79
What is receptor potential
Receptor converting stimulus energy into graded change in membrane potential
80
What is receptor potential dependent on
Since it is graded change, it is strength dependent
81
What will the receptor do, after having receptor potential
If receptor is neuron: fire AP, using graded potential, or secondary neuron
If it is not neuron: release neurotransmitter to trigger neuron firing AP
82
Is receptor potential all or none?
It is NOT action potential, but graded
So it is not all/ none
83
What is adequate stimulus?
It is the form of stimulus energy, that a receptor is most sensitive and responsive to
84
Does receptor only respond to their adequate stimulus
No
Receptor is most sensitive to adequate stimulus, but if other energy is strong enough/ powerful, they can trigger responds
85
How are sensory receptors classed?
Base on the adequate stimuli
Chemo/ mechano/ photo/ thermo/ nociceptors
86
What is eye receptor? (what class)
Photoreceptor, respond to light energy
87
What is hearing receptor? (what class)
Mechanoreceptor, since sound is vibration
88
What is Muller's law
Law of specific nerve energy, the specificity of receptor for a particular type of stimulus
89
What is receptor threshold
The minimum/ weakest stimulus that will cause a response in receptor
90
What does it mean to have low receptor threshold
The receptor is very sensitive, can detect very weak stimulus
91
What is perceptual threshold
The weakest stimulus that can cause a conscious perception in the organism, consciously aware of the presence of the stimulus/ sensing it
92
What are the 4 stimulus properties that must be distinguished by brain, in order to create accurate neural representation
Stimulus modality, intensity, duration and location
93
What is stimulus modality
The very fundamental, what type of stimulus it is
light/ sound/ touch, etc
94
How does sensory system indicate stimulus modality
By labeled line, telling you what type of sensory is being processed
what axon carry the signal reveal the modality
Activity on auditory pathway= sound, etc
95
What is population coding of intensity
Stronger stimulus= more neurons activated
Intensity of stimulus can be revealed by number of activated neurons
96
What is frequency coding
Stronger stimulus= higher frequency of AP firing
97
How are stimulus intensity revealed
By the collaboration of both frequency coding and population coding
98
How can stimulus duration be reflected the best
By the change in the stimuli, not the steady state
99
What does it mean for receptors and neurons to be dynamic? (in term of stimulus duration)
The response activities depend on the change of stimulus overtime
Sudden spike of stimulus can cause spike of response, but once the stimulus is steady, response decrease
100
What is adaptation to stimulus?
When stimulus is steady, response decrease and become silent, even if there is high stimulus level
101
How does phasic cell respond to stimulus
Respond briefly to change in stimulus, then cease and fade away when stimulus stay steady, no more response eventually
Best for detecting change
102
How does tonic cell respond to stimulus
Fire AP/ respond based on stimulus intensity
When stimulus is steady, it will still maintain the same level of response
Best for providing info on steady state intensity
103
How does phasic tonic cell respond to stimulus
Respond to change in stimulus
when stimulus is steady, it will decrease in response, but won't cease to zero/ no response
Carry information about both steady level and change of stimulus
104
What type of cells are retinal cells (phasic/ tonic/ phasic tonic)
Phasic
they respond to change in visual world, sensitive to movement, but go silent when visual image remain constant
105
Why wave at someone when trying to catch their attention?
Retinal cells are phasic
Moving arm motion activate more phasic cells, since they are sensitive to change but not steady
106
What is the benefit of phasic signals?
Communication can be more efficient, since the world is fairly stationary
Avoid redundant information (steady), only report change, more efficient
107
What is temporal change
Changes through time, between one moment and next
108
What is receptive field?
A specific are that sensory receptor is the most sensitive to stimulation
109
What is convergence?
Many presynaptic cells contact to a single post synaptic cell
Many primary sensory neurons synapse to one secondary neuron, and these secondary neurons again synapse on the tertiaries, and so on
110
What is the benefits of convergence
Allow secondary and higher neurons to combine data from many receptors, so more complex info processing can respond to vast amount of sensory data
111
What is the size of receptive field and the distribution?
Vary in size, frequently overlap
112
What happen to spatial resolution and neuron's sensitivity, when converging inputs onto a single sensory neurons
Increase sensitivity, decrease spatial resolution
113
What is spatial change
The difference between neighbouring regions in space
Eg darker region and lighter region
114
What is contrast, and what is the location of strong contrast
Contrast the spatial change, and strong contrast locate at "edge"
115
Why is our sensory system tuned to detect edge? Why is it efficient?
Edge provide info about spatial variation in the world, and it is important info about "changing"
More efficient reporting the "edge", rather the reporting the same info from the two regions
116
How is edges accentuated? (make the edge more noticable)
Lateral inhibition
117
What is lateral inhibition
Inhibiting the neighbouring cell, or the cells excited by neighbour, while exciting on cells
118
Where is lateral inhibition the strongest?
Th edge of contrast, which show contrast of areas with different stimulation
Outside the edge, the inhibition and excitation will cancel out
119
What is the pathway of most sensory pathway? (in brain)
Run via thalamus out to cortex (cerebrum)
120
Does olfactory neurons run through thalamus?
No
121
Where does equilibrium pathway mostly project to
Cerebellum
122
What does it mean our sensory processing is inference
Sensory data are incomplete, ambiguous
So the brain has to infer, and "guess" the meaning
Unconscious and rapid inference
123
The eye is divided into two chamber
What is the eye divided by?
lens
124
What is lens?
Transparent disk, focus light
125
What does zonules do
A ligament that suspend the lens, maintaining lens position
126
What is aqueous humor
Plasma like fluid that fill the anterior chamber
Nourish avascular cornea and maintain IOP
127
Where is the anterior chamber
In front of the lens
128
Where is the vitreous chamber
behind the lens
129
What is the vitreous humor / body
A clear jelly that fill the vitreous chamber, helps maintaining the eyeball shape, support retina, ensure clean and clear light entrance
130
Where is all the photoreceptor
On the retina
131
How does light enter eyes? (through what)
Pass from cornea, to the lens, through pupil
132
What is sclera
"white" of the eye, the outer wall of eyeball
maintain shape of eyeball
133
What is cornea
Transparent bulge at the front of the eye, continuous out with the sclera
Refract and bend light entering eyes
134
What does cornea and lens do
Focus the light onto the retina, where the photoreceptor is located
135
What is pupil
A hole in the iris, where light pass through to the lens
136
Is there blood vessel on the sclera
No, as blood can affect light absorption, disrupting vision
137
Where does the sclera continuous to
Brain dura maters, which is the protective cover of brain
138
How does brain tumor affect eyes?
Since dura matter is continuous to sclera, brain tumor pressure can cause swelling of the optic disc
139
Is the vitreous humor static
Yes, does not circular around
140
How does cornea get nutrients/ O2?
O2 from air (direct contact)
Nutrients from aqueous humor
141
What if there's excess fluid/ ion in cornea
Cornea has Na+/K+ pump, which can remove excess back to aqueous humor
142
What is the first (outmost) layer of eyes
Fibris/ fiber layer, containing cornea and sclera
143
What is the second layer of eyes (middle)
Vascular/ Uvea layer
Between sclera and retina
Rich in blood vessels, provide nutrients to retina and regulate blood flow, allow light entry/ focus
144
What is the 3rd layer/ inner layer of eyes
Retina, macula, fovea and optic disc
145
What is IOP
Intraocular pressure
146
What is the aqueous humor pathway
Produced by ciliary processes
Flow from posterior chamber
Flow through pupil, between cornea and lens
Then flow to anterior chamber, and drain via trabecular meshwork into canal of schlemm
147
What does trabecular meshwork do
Filter and regulate flow of aqueous humor
148
What does canal of schlemm do
Circular drainage pipe of aqueous humor
Collect and channel aq humor to vein
Regulate flow and IOP
149
What is glaucoma (eye disease)
Disruption of IOP and aqueous humor, pressure from excess liquid damage optical nerve
150
What is the size of the pupil, in respond to light brightness
Bright light: pupil constrict and shrink, reducing light entrance/ reaching lens
Dark: dilate, let more light in
151
What is the range of illumination that the eye operate over( sunny day VS dark night)
Eye works over a large range of illumination, so a sunny day is 100 millions time brighter, meaning eyes receive 100 million times more photon
152
What control the size of pupil?
Smooth muscles in the iris
153
How does pupil constrict under bright light
Parasympathetic signal from brain control the ring shaped circular muscle/ pupillary constrictor muscle to contract, shrinking the pupil
154
How does pupil dilate under dim light
Sympathetic signals contract the radial pupillary dilator muscle of the iris, dilating the pupil
155
What does it mean by focus? (how does pupil focus light)
Focus= small pupil limit light pass in, so eah point on retina only receive light from one direction in space
One spot receive one ray of light
156
What is the depth of view, when pupil is tightly constricted
We have full depth of view, everything we see is equally in focus
157
What is the depth of view, when pupil is dilated
Shallow depth of view
Only object in one specific distance are in focus, depending on lens
158
How to get retina image that is both bright and in focus?
Refraction, bending of light
159
What is refractive index
How much a medium bends light
160
What is the angle of fraction depends on
Density difference in the 2 medium, and the angle of light meeting surface
161
when does light bend
When it enters a medium with a different refractive index
162
163
Why is light refraction stronger in air than water
There is bigger difference in refractive index between air and cornea, than water and cornea( COLLAGEN)
164
What are in charged of refracting light in eyes
Mostly cornea (2/3) , the rest is lens (1/3)
165
How does lens adjust focus
It is flexible, can change shape to adjust focus for different distance
166
What is lens made up of?
Clear cells, a long cels without nuclei, packed with clear proteins (crystallins)
167
What is crystallins
Clear proteins packed in clear cells of lens
168
How does clear cell absorb nutrients
No blood supply, absorb nutrients from aqueous humor
169
What is the shape of eye lens
Convex, thicker in middle, thin at the edge
170
Why is lens convex
It makes light rays converge to a focal point
171
What happen when light enter lens is perfectly perpendicular
No bending, go straight through the middle
172
What is the result of a rounder lens, comparing the normal lens
Rounder lens bend more light, so it has a closer focal point (earlier convergence, stronger focus power)
173
Where should the focal point hit, to give a clear vision
Focal point fall on the retina
174
What happen if object draw closer, but the lens stay flat
Focal point (focus) fall behind the retina, give a blurry image
175
How to make a closer object in right focus? ( see a closer object clearly)
Make the lens rounder
Parasympathetic contract the ciliary muscle, reduce zonules tension, lens get rounder, more light bends and focal point moves forward
176
How to make see far object
Make the lens flatter
Sympathetic signals relax the ciliary muscle, tense up/ pull on the zonules, lense get flatter, focal point move backward
177
What happen when light is shined on one of the eyes
Trigger pupillary light reflex
Both eye will be stimulated to constrict
Bilateral response
178
What is the control of pupil dilation/ restriction
Autonomated
179
What is accommodation
Rounding the lens for near vision, changing the lens shapeW
180
What is the near point of accommodation
The limit of accommodation, the closest point that a person can focus
181
What is presbyopia
Lens stiffen by age, and accommodation ability decrease, harder to focus on closer object
182
What is hyperopia
Far sightedness
Not enough converge power, focal point fall behind retina, can't focus on closer object
183
What can cause hyperopia
Lens/ cornea doesn't have enough focusing power for convergence, or eyeball is shorter than normal
184
What is the treatment for hyperopia
Convex lens glasses, which helps increasing convergence
185
What is myopia
Short sightedness
Focal point falls in front of the retina, cannot see stuff far away
186
What is the cause of myopia?
Too much light convergence by cornea/ lens, or elongated eyeball
187
What is the treatment for myopia
Using concave lens glasses, which diverge light instead of convergence
Allow light to spread out more, counter too much light bending in myopia
188
What is photoreceptor
Light sensitive neurons, convert light energy into electrical signals that the brain can interpret
189
Are there more cones or rod
Rods
189
What is the conversion of light energy to electrical signal called
phototransduction
190
What are the 2 main types of photoreceptor in retina
Cones and rods
190
What cells are cones and rods? What do they do? (receptor activity)
Neurons
Do not fire AP
respond to stimuli by generating MP
191
what is the membrane potential of photoreceptor based on
Light intensity
Brighter light= more potential
192
What are the structure of cone and rods (what is it made up of)
Inner and outer segments
193
What is the outer segment
Membrane folds into disk like structure, contain visual pigments that respond to light and initiate phototransduction
194
What is the inner segments
Contain nucleus and organelles for protein synthesis
In the basal layer, contain a synapse that release neurotransmitter glutamate
195
What is glutamate in photoreceptor
Neurotransmitter, binds to receptor
196
Where does the receptor point toward
Back of the eyes
197
How does light travel in retina
Travel through multiple layers, eventually reach rods and cones at the back
198
Where is the receptor located in the retina
Deep in the retina
199
What is RPE
Retinal pigment epithelium
RIght next to rod and cones
Recycle visual pigments, absorb excess light, support nourish and regenerate photoreceptor
200
How does photoreceptor detect light? (what do they use)
Membrane bound visual pigments
201
What is rhodospin
visual pigment in rods
202
How does visual pigment conduct phototransduction
When light hit them, pigment changes shape and trigger chemical cascade, hyper polarize cell and reduce glutamate release
203
When is photoreceptor more active
In dark, as it is depolarized
204
What is happening to the rods when it is dark
Rhodspin is inactive
cGMP is constantly produced, which bind CNG, allow Ca2+ influx
Ca2+ influx depolarize rods, and glutamate is released
205
What is happening to the rods when there's light enter
Light entrance hit rhodopsin, activate it into metarhodopsin 2, changed shape
G-protein cascade is set off, which cGMP is cut to GMP
Reduce CNG binding, so reduce calcium influx
Rods is hyperpolarized, glutamate release decrease, which signal for "light detection"
206
What is rhodopsin made up of
Opsin and 11-cis retinal
207
What is 11-cis retinal
Actual light detector in the rhodopsin
Transform to all-trans retinal when activated by light
After activation, undergo RPE cycle, reform 11-cis retinal, and reform rhodopsin, so system is reset
208
What is 11-cis retinal made from
Vitamin A derivative
209
What is the sensitivity of rods VS cones (when do they work)
Cones is less sensitive, responsible for bright light vision, can't operate in dim light
Rods operate only in low light, and is bleached out under daylight
210
Why doesn't rod work in bright environment
Rhodopsin is broken down by light, so they cannot sense light
Bleached out in daylight
211
Why is the air plane cabinet dimmed? Not bright? (why wouldn't they keep the airplane cabinet bright)
When in light environment, rod doesn't operate
Rods operate in dark environment, but they require longer time to rebuild and reset from the bleached out state (dark adapt)
If you suddenly enter a dark environment from a bright environment, you won't be able to see (rods is resetting, cones does not work)
212
Are photoreceptors evenly distributed
No they are densely packed in macula, especially the fovea region (central pit of macula)
213
What is fovea responsible for
It is densely packed with cone
Important for detailed vision (reading)
214
What is the blind spot
A hole where axons carrying visual info exit the eyeball to form optic nerve, no receptor is found
215
How is cones distributed
Almost all in the fovea
216
How is the rods distributed
Mainly in the more-peripheral retina region
217
When you look at dim star, why do you see it clearly when u look slightly away from it
Peripheral retina is packed with rods, which is more light sensitive than fovea, which is packed with cones
218
How does photoreceptors converge?
Photoreceptor synpase onto bipolar cell, and bipolar cell synapse onto ganglion cells.
219
What is the convergence in peripheral retina VS fovea
Peripheral retina: greatest in convergence
Fovea: least, sometimes 1:1 ratio of cones to bipolar cell
220
What is horizontal cell
Cells between photoreceptor and bipolar
send inhibitory feedback to neighbouring photoreceptor, create lateral inhibition, enhance light and dark contrast, define edges
221
What is amacrine cells
Between bipolar and ganglion cells
Suppress noise, highlight on sudden changed
222
What is the receptive field of bipolar cells
Centre-surround
Center= light directly affect bipolar cell activity
surround= indirect affect, via horizontal cell
223
What are the two type of bipolar-cell receptive field
On centre and Off centre
224
What is on centre cells
Centre of the field is excited by light, depolarize and increase bipolar neuron signalling
Surround is inhibit by light, hyperpolarize
Most respond when centre is filled with light, and surround is dark
225
What is off centre cells
Surround of the field is excited by light, depolarize and increase bipolar neuron signalling
Centre is inhibit by light, hyper polarize
Most respond when surround is filled with light, and centre is dark
226
What is mGluR6 cells.
Metabotropic bipolar cells
When bound to glutamate, it is hyperpolarized, so less excited
When light excite photoreceptor, less glutamate is released, so mGluR6 is excited, (less glutamate binding), and release more transmitter to ganglion cells
More AP firing, know centre has light
227
What is AMPA
Ionotropic bipolar cells
When bound to glutamate, it is depolarized, so more excited
When light excite photoreceptor, less glutamate is released, so AMPA is less excited, (less glutamate binding), and release less transmitter to ganglion cells
Less AP firing, know surround doesn't have light
228
Which is off centre and on centre? (AMPA and mGluR6)
mGlurR6= on centre
AMPA= off centre
229
What happen to bipolar cells when the light is uniform?
No responds, because there will be same effect on and off centre, cancel out
230
What does on and off centre bipolar cells best respond to
Contrast
231
Does bipolar cell fire AP
No, fire graded potential
232
How does bipolar cell project to retinal ganglion cells
Convert contras to signal code, trigger ganglion to fire AP that travel to the brain
233
What does the AP firing of retinal ganglion cells depend on
Contrast
Higher contrast= higher spike of firing
234
Does ganglion cell detect contrast?
Ganglion also have centre-surround receptive field, and they can also be on/off centre
so they do
235
What is the receptive field size of ganglion cells at different retina region
Fovea: only get input from a few cones, so smaller field size
Peripheral: get input from many rods, so larger field size
236
What is peripheral ganglion cells good with, and bad with
Light sensitive, good with dim light and motion detect
Poor with spatial detail, since it blends a lot of informations from many receptors
237
What is fovea ganglion cells good with, and bad with
Less light sensitive
Good with details, better spatial resolution, since it's getting information from a few cones
238
What is M cell
Large, magnocellular ganglion cells
Provide info about changes in movement of object, low resolution
~10%
239
Is M cell phasic or tonic
Phasic, good at detecting change in motion, stay phasic when stimulus is constant
240
What is P cells
Small, parvocellular ganglion cells
Provide high resolution info used to infer form/ fine details (texture, shape)
~70%
241
What is melanopsin ganglion cell
Photoreceptors with their own visual pigment
Project to brain master clock, help regulate circadian rythm (biological clock)
242
What is melanopsin
Visual pigment in melanopsin gangliong cell, detect ambient light without rods/ cones
243
What is suprachiasmatic nucleus
In hypothalmus, centre for circadian rhythms (master clocks)
244
What does visual information leaves the retina in
optic nerves, send out through blind spot
245
What is cranial nerve 2
The optic nerve
246
What is optic chiasm
When optic nerve reaches the optic chiasm, fibers of the nasal half( inner half) will cross to the other side, while the temporal half (outer half) wont cross, stay on same side
247
Why do optic nerve fibres cross
Ensure each brain hemisphere process visual input from each visual hemifield
Right visual hemifield info processed in left cerebral hemisphere
This is because most motor function are lateralized (right side control by left hemisphere), so this simplify visual input and motor action coordination
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What is optic tract
Nerve bundle, emerging from chiasm, carry information and end in LGN
One on each side, left optic nerve carry input from the right
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What is LGN
One on each side
Located in the thalamus
Organize and refine visual signal before sending it to cortex
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What is optic radiation
Tract that carry information from LGN to cortex
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What is V1
Primary visual cortex in brain
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How are visual areas in brain organized
Retinotopically, following retina as a map for location
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Why is visual areas in brain retinotopically organized
Allow consistence representation of the visual sense of world
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What is the area distribution of projection from fovea/ peripheral in the brain ( size of area covered by fovea/ peripheral)
Fovea project to large area in V1, although it is a small area in retina
This is because fovea has high density of photoreceptor that follow one to one convergence ration, carries a lot of information, that needs more area in the brain to process
Peripheral takes up large area in retina, but due to high convergence, smaller occupation in v1 (low spatial resolution)
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Does retinotropic map preserve area? (is the size of area distribution also consistent in the brain)
No
Fovea takes up small area in retina, but take up large area in brain
Vice versa for peripheral
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What does olor depends on
Wavelength of light
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What is the visible spectrum of wavelength
400 to 700
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What are the 3 types of cone that sense color
red, green and blue
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how does different cone sense different color
They have their own type of visual pigment, which is more sensitive to certain wavelength, prefer certain color
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What is trichomats (human)
Sense color with 3 type of cone
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What color does each cones prefer?
Red: yellow
Green: yellow-green
Blue: blue
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What makes a red cone "red"?
It is the most sensitive to red wavelength, absorb light toward the red end better than other cones
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How does brain infer colors
By comparing data from the 3 types of cones
All visible color is essentially a mix of red, green and blue
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How does a computer produce "yellow" image, when it only has red, green and blue light
By mixing red and green light, so it affects our cones in a pattern of activity that our brain infer as "yellow"
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What is spectral color
Colors that can be evoked by light of single wavelength, the rainbow color
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What is extraspectral colors
Color evoked by a mix of wavelength, a mix of more than 2 wavelength affecting cones
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What is the ganglion cell color signal made up of
A combo of cone signals
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What is R+G
Excited by both red and green light
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What is R-G
Excited by red, inhibited by green light
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What is red-green opponent channel
R-G and G-R
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What does opponent coding do
Ganglion cells excited by a color, and inhibit by the other color
helps detect subtle contrast
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how is afterimage formed? (eg, staring at a green image for a long time, look away at temporarily see red)
When one signalling pathway is fatigued and imbalanced, the opposite pathway will be more active and be in charge shortly
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What is the most common color blindness
Red-green color blindness, can't distinguish red and green
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What is Daltonism
red-green color blindness
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What is the cause of color blindness
X-linked recessive heritance
When both X chromosome is color blind gene, or XY, with one X chromosome color blind gene
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Why woman is less likely to be color blind
Color blind is due to recessive X-chromosome problem
A female will need both X-chromosome to code for faulty pigments, to get color blind
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What is "reflectance" (color)
Intrinsic color of a surface, reflect certain wavelength and absorb the others
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What is "color constancy"
Brain's ability to infer the "true" color on a objct, regardless of lighting color
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What is ear responsible for
Hearing and equilibrium
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What is the 3 main division of ear
External ear, middle ear, inner ear
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What is external ear consist of
Pinna, ear canal, eardrum
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What is middle ear connected to
Beyond ear drum, connect to pharynx by Eustachian tube
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What is the middle ear space filled by
Air
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What does the inner ear contain
Cochlea
Vestibular apparatus
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What does the Cochlea do
Detect sound and convert it to electrical signal
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What does the vestibular apparatus do
Maintain balance & spatial orientation
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What is the stimulus for hearing
Sound, which is pressure waves that can travel in air/ water, through solid surface
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When is the pressure high and low for a sound wave
High pressure: peak of the waves
Low pressure" Troughs of sound waves
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What is frequency of sound
Numbers of wave peak per second
It is the pitch of sound
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What is high VS low pitch
High VS low sound frequency
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What is amplitude of soundwave
Pressure difference between the peak and trough of wave
Determine loudness
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What makes a sound louder
Larger amplitude of soundwaves
Also depends on frequency
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What happen if a high amplitude sounds has a frequency beyond human hearing range
We cannot hear anything, no matter how large the amplitude is
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What is the initial step of transforming sound wave to mechanical energy (very first step of hearing)
Sound waves travel through ear canal, vibrate ear drum
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What are the ossicle chains?
MIS
Malleus, Incus, Stapes
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What does the ossicle chain do
Transmit vibration from eardrum to the oval window, which is a membrane between middle & inner ear, by pushing against it, creating a pressure wave into the inner ear
Amplify sound wave
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What does the oval window do
Leads the pressure wave from sound into the cochlea
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Where is auditory receptor cells located
In the cochlea, which is the in ear sound processor
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What is the mechanism of oval window triggering cochlea action
MIS pushed oval window, creating pressure wave that enter cochlea
Wave travel along cochlea, and stimulate the hair cells, which transmit mechanical energy into electrical signal that enter brain
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What is the structure of cochlea (what does it look like)
Fluid filled, look like cochlea
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What is the composition of cochlea
3 fluid filled duct, including vestibular, cochlear and tympanic duct
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Where is perilymph found?
Vestibular and tympanic ducts
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Where does vestibular and tympanic duct communicate
At the helicotrema, which perilymph flow between
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Where is cochlear duct located
Between vestibular and tympanic duct, and is completely sealed off from the two other ducts
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Where is endolymph found
In the cochlear duct
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What is endolymph rich in
K+ ion, which is essential for sensory cell function
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What happen in the cochlea, when waves is exert in by the oval window
Wave enter at the oval window, travel in the perilymph, and exit back into the middle ear through round window
The waves can travel through the helicotrema, circulate vestibular and tympanic duct
It can also shake the cochlear duct
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Where in the cochlea is the auditory cell located?
Cochlear duct
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Where is the organ of corti
cochlear duct, sits on the basilar membrane, under the tectorial membrane
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What is hair cell, and where is it precisely found
Mechanoreceptor/ auditory receptor, convert vibration to electrical signal
Found in the organ of corti
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What type of cell is hair cell
epithelial cell
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What is stereocilia
"stiff" hair found in hair cells, which extent to tecotrial membrane
Bend when waves in the perilymph deform basilar/ tectorial membrane
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How does hair cell act upon waves
Waves in the perilymph shake the tectorial/ basilar membrane, which which bend the stereocilia "hair", trigger the transduction to electrical signal
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When does hair cell excites neuron?
When the stereocilia bend toward the longest cilium, hair cell is depolarized, open ion channel, release neurotransmitter and activate the primary sensory neuron
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What is cranial nerve 8
Auditory nerve/ cochlear nerve, formed by the axons of the primary sensory neurons activate by hair cell
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What happen when cilia bend toward the shorter stereocilium
Opposite direction of activation
Hair cell hyperpolarize, release less transmitter, excite less neurons
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How does hair cell act as "gate keeper" for signalling
Hair can modulate the intensity and frequency of signal, based on the direction and strength of waves induced bending
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What are the two ends of basilar membrane
Narrow and stiff end, near the oval/ round window
Wide and flexible end, near the helicotrema
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Which part of the basilar membrane is the most sensitive to high/ low frequency soundwave
High frequency: narrow end
Low frequency: wide end
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How can the brain deduce the sound frequency, using basilar membrane
Each region of the basilar membrane correspond to a specific frequency
All the hair cells are positioned on the basilar membrane
Frequency can be decoded, by looking at which regions has the most active hair cell
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What is frequency mapping
Relationship between frequency, and the vibration pattern of membrane
Certain frequency has the most vibration motion at certain location on the basilar membrane
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How does auditor signal travel from cochlea to brain
Signal input to cochlear nuclei of the medulla, then bilateral and transport to both sides of the brain
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How does cochlear nuclei receive signal
Each nucleus only get input from one side of the ear, then bilateral after the cochlear nuclei
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Which side of ear does the brain receive signal from?
From both ears, this helps accurate localization of sound by comparing input of both ears
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What does the medial geniculate nucleus do
MGN process auditory signal
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What is the auditory cortex
NEar temporal lube, interpret sound signal and give it meaning
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Where is MGN located
Thalamus
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What is A1
The primary auditory cortex, crucial for processing sound, to get audio/ language info
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How is A1 organized
Tonotopically organized
Different cortex region correspond to different frequency, so it can decode different sound features, recognize music/ speech
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What does A2 do
Handle more complex auditory task, such as understand language, voice distinguish
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How does the brain localize sounds? (base on what)
loudness and timing
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How does brain localize a sound base on loudness
If a sound is louder at one side than the other, the louder side will have higher neuron firing frequency, and the brain can compare firing frequency between both ear
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What does a louder sound do to sensory neurons firing
Louder sound make neurons fire at a higher rate
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How does the timing help sound localize
The sound will reach one side first then the other
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What are the 3 kinds of hearing loss
Conductive
Sensorineural
Central
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What is conductive hearing loss
Sound can be transport through the external to middle ear, due to blockage/ ear drum damage or MIS ossicles problem
Difficult in hearing softer sound
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What is sensorineural hearing loss
Damage to hair cell/ inner ear
Dead hair cell cannot be replaced in mammal
Permanent
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What is presbycusis
Hearing loss in elderly, sensorineural
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What is central hearing loss
Damage to the cortex/ pathway from cochlea to cortex (brain problem)
Patient have trouble recognizing/ interpreting the sound, able to detect the sound (auditory processing problem)
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What is the Rinne test
Hold tuning fork aginst mastoid bone and beside ear
If sound is louder through ear canal, normal
If sound is louder through the bone, conductive hearing loss problem
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What is weber test
Hold tuning fork against forehead, and see which ear hear louder sound
If good ear hear louder sound= sensorineural hearing loss
If bad ear is louder= conductive loss
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Why conductive loss patient hear a loud noise in their bad ear?
Bad ear cannot pick up ambient noise, so less sound compete to enter ear canal
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What is stapedius reflex
Protect ear from loud noise, but it needs longer time to activate, so it cannot protect ear from sudden loud noise
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What is the utricle and saccule?
Sensory organ in vestibular apparatus
Fluid filled
Have otoliths, which is a small crystal that shift by gravity/ motion, when head tilt
Otoliths shifting will bend the hair cell, activate sensory neurons and send signal to brain
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What is semicircular canals
Fluid filled loops in vestibular apparatus
detect head rotation
When head turn right, fluid in the tube sloshes left, activate hair cell, send signal too brain
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Where does semicircular canals, utricle and saccule send signal to
Send sensory signal to brain stem, then to cerebellum
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Where in the brain process equilibrium signal and maintain balance
Cerebellum
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What is vestibular-occular reflex
coordination of eye movement with head motion
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What is the vestibular nerve part of
Cranial nerve 8
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What is vestibular nerve activated by
Vestibular hair cell
