Brain and Behaviour 2 Flashcards
(200 cards)
1
Q
What is the only output from the basal ganglia?
A
PMC
2
Q
How does the basal ganglia interact with motor control?
A
Suppresses unwanted movements, generally initiates and terminates movement, establishes normal level of tone
3
Q
What structures comprise the subcortical motor control loop?
A
Basal ganglia, cerebellum, PMC
4
Q
How does the cerebellum interact with motor control?
A
Similar to basal ganglia, monitors differences in intended and actual movements
5
Q
What are the two types of of UMN?
A
Direct and indirect
6
Q
What do direct UMN input to?
A
LMN from axons extending directly from cerebral cortex
7
Q
What do indirect UMN input to?
A
LMN from motor centres in brainstem, basal ganglia, cerebellum and cortex
8
Q
What reflex is studied in aplysia?
A
Gill and siphon withdrawal
9
Q
In what organism is the gill and siphon withdrawal reflex studied?
A
Aplysia
10
Q
What is the gill and siphon withdrawal reflex?
A
Touch to siphon elicits gill withdrawal
11
Q
What is habituation?
A
Repeated stimuli results in reduced reflex
12
Q
Where does habituation of the gill and siphon withdrawal reflex in the aplysia occur?
A
Abdominal-ganglion synapse
13
Q
What is the cellular basis of habituation?
A
A result of reduced synaptic strength, and reduced transmitter release
14
Q
What is sensitisation?
A
Increased reflex response by association with simultaneous second stimulus
15
Q
What does sensitisation involve?
A
Pre-synaptic input from sensory neurons - serotinergic and GP action
16
Q
What is associative learning?
A
Association of one stimulus with another, resulting with the response to the original stimulus also being evoked by the second stimulus
17
Q
What was the famous example of associative learning?
A
Pavlovian dogs
18
Q
Outline various models of sensitisation or learning
A
Multiple intracellular signalling pathways, varied activation thresholds, pre and post-synaptic modulation, long term involves nucleus
19
Q
What does NSP stand for?
A
Non-synaptic plasticity
20
Q
What is NSP?
A
Experience-dependent changes to synaptic efficacy not based directly on synaptic changes
21
Q
What is Hebbian synapse modification?
A
Coordinated activity of a presynaptic terminal and a postsynaptic neuron strengthen the synaptic connection between them
22
Q
Outline the hippocampal LTP circuit
A
Entorhinal cortex - dentate gyrus - CA3 - CA1 - fornix and subiculum
23
Q
What are the three neuronal connections in the hippocampal LTP circuit?
A
Perforant fibres, mossy fibres, Schaffer collaterals
24
Q
Where do perforant fibres connect in the hippocampal LTP circuit?
A
Entorhinal cortex to dentate gyrus
25
Where do mossy fibres connect in the hippocampal LTP circuit?
Dentate gyrus to CA3
26
Where are Schaffer collaterals?
CA3 and CA1
27
What does LTP stand for?
Long term potentiation
28
Where does LTP usually occur?
Before CA3 and CA1 synapses
29
What does HFS stand for?
High frequency stimulus
30
What causes LTP?
HFS
31
What does HFS resemble?
Human theta rhythm
32
Characterise LTP.
Specific - only increases sensitivity from HFS inputs; co-operative - two converging pathways can both be strengthened if they fire together
33
What is the MOA of LTP?
Could be pre-synaptic, but evidence suggests often a post-synaptic Ca involvement
34
How might NMDA receptors be involved in LTP?
Blocked by Mg, it needs dislodging before Ca can enter - pre-stimulation required
35
What two phases can LTP be split into, and what are their differences?
Early - don't need protein synthesis; late - may need protein synthesis
36
How does early LTP occur?
Through NMDAR - allows Ca in
37
What are NMDAR also known as?
Glutamate receptors
38
How does early LTP passage of Ca into the cell cause LTP?
Activates CaMKII, PSD and constant activation of autophosphorylation by multiple catalytic subunits
39
What does CaMKII stand for?
Calmodulin kinase II
40
What does PSD stand for?
Post-Synpatic Density (protein)
41
Characterise late LTP.
Needs protein synthesis, takes effect approx 1 hour after initiation, cAMP signalling may be critical
42
How is LTP linked to memory?
Inhibition of LTP inhibits some memory formation, drugs that enhance memory also enhance LTP
43
What is the name given to memory enhancing drugs?
Nootropics
44
Why isn't LTP everything about memory?
LTP is no sufficient to create all memories
45
What does LTD stand for?
Long term depression
46
What is LTD?
Actively evoked, long lasting reduction in synaptic efficacy
47
What is LTP?
Actively evoked, long lasting increase in synaptic efficacy
48
What are the two main types of LTD?
Depotentiation - removal of previous potentiation; LTD denovo - no previous potentiation
49
What two forms can LTD take?
Hebbian - monosynaptic; non-hebbian - heterosynaptic not requiring pre-synaptic activity
50
What are the general mechanisms for LTD induction?
NMDAR, LFS, Ca influx, diffuse transmitters - neuro-modulators
51
What kind of drug is anandamide?
Endocannabinoid
52
What are the cerebellar LTD inputs?
Positive mossy fibres and climbing fibres
53
What are the cerebellar LTD output?
Purkinje fibres
54
What are the two cerebellar LTD pathways to Purkinje cells?
Mossy fibres - granule cells - Purkinje cells; climbing fibres - Purkinje cells
55
What causes LTD at Purkinje cells?
Paired PF and CF inputs to a single Purkinje cell
56
Cerebellar LTD MOA?
Not NMDAR - Glu-R/AMPA-R/Ca-v
57
Outline the cerebellar LTD cascade.
PF activates AMPA+GPCR - Ca influx - PKC activation - receptors pulled from surface - reduced strength of synapse
58
What evidence is there for the current cerebellar LTD cascade?
Endocytosis inhibition prevents LTD
59
What is does the BCM theory stand for?
Bienenstock, Cooper, Monroe theory
60
What is the BCM theory?
Synapses that are active when the rest of the cell isn't get weakened
61
Where does hippocampal LTD occur?
CA3-CA1 synapse
62
What determines the probability of inducting LTP and LTD?
Degree of NMDA receptor activation - low = LTD, high = LTP
63
Does LTP+LTD=memory?
No - memory = distributed, structural changes
64
What is the key role of the hippocampus in memory?
Formation of new associations and passing on for storage if appropriate
65
What focuses the inverted image on the retina?
Cornea and lens
66
What is the name given to the aperture of the eye?
Pupil
67
How many classes of photoreceptor are on the eye?
2
68
How can the retina be described, and why?
Duplex retina - two types of photoreceptor
69
What are the two types of photoreceptor?
Rods and cones
70
What is the number of the two types of photoreceptor?
5million cones, 100 million rods
71
What is photopic vision?
Daylight vision
72
What is scotopic vision?
Night vision
73
What is mesopic vision?
Dusk vision
74
What is another term for night vision?
Scotopic vision
75
What is another temr for dusk vision?
Mesopic vision
76
What is another term for daylight vision?
Photopic vision
77
What photoreceptors are responsible for mesopic vision?
Rods
78
What photoreceptors are responsible for scotopic vision?
Rods
79
What photoreceptors are responsible for photopic vision?
Cones
80
What is the term given to the region of retina with macimum resolution?
Fovea
81
Why does the fovea convey our most acute vision?
Highest density of cones
82
What are photoreceptors generally processed by?
Retinal interneuons
83
Where is the photoreceptor signal output to after retinal interneurons?
Ganglion cells in the optic nerve
84
How many ganglion cells are there?
1.5 million
85
Name the 'thalamic relay station' in conscious image perception.
LGN - lateral geniculate nucleus
86
What does LGN stand for?
Lateral geniculate nucleus
87
What are the five key projection destinations in the visual system?
Visual cortex, LGN, superior colliculus, pretectal region, hypothalamus
88
What do pathways projecting to the superior colliculus do?
Control eye movements
89
What do pathways projecting to the pretectal region do?
Control pupil
90
What do pathways projecting to the hypothalamus do?
Entrain circadian rhythms
91
What is the range of visible light?
400-700nm
92
What are the four key variables of light?
Intensity, wavelength, space and time
93
Light from a source is quantified as what?
Illuminance
94
Light reflected from objects is quantified as what?
Luminance
95
What is illuminance a measure of?
Light from a source
96
What is luminance a measure of?
Light reflected from an object
97
What is the unit of illuminance?
Lux
98
What is the unit of luminance?
cd/m^2
99
What is the range of light intensity in the environment?
10^10
100
Why is the massive range of light intensity found in the environment an issue for the eye?
It must adapt to cover this range
101
By how much does the reflectance of natural objects vary?
20 fold
102
Reflectance is independent of what?
Illuminance
103
What measure of stimulus strenght is used?
Relative intensity - contrast
104
What is relative intensity also known as?
Contrast
105
What is contrast also known as?
Relative intensity
106
Define the formula of contrast.
Difference in intensity / mean background intensity
107
What range of luminance is photopic vision?
10^10 - 10^0
108
What range of luminance is mesopic vision?
10^0 - 10^-3
109
What range of luminance is scotopic vision?
10^-3 - 10^-6
110
What does the diffraction limit mean for optics?
Even with a perfect lens, the image of a point source is a round blur
111
What is the formula for the blur diameter as a result of the diffraction limit?
SEE PAD 28
112
What three lens aberrations further affect the image on the retina?
Spherical, chromatic, glare
113
Characterise spherical aberrations.
For a spherical surface, rays towards the edge are more strongly refracted
114
Characterise chromatic aberrations.
Different colours focus at different depths
115
Characterise glare.
Small particles in the optical media scatter light, reducing the contrast
116
What colour is the human eye well focused for?
Green
117
What colour is the human eye poorly focused for?
Blue
118
Draw a spherical aberration
SEE PAD 29
119
Draw a chromatic aberration
SEE PAD 30
120
Draw glare
SEE PAD 31
121
What is the term given to the eye if an object at infinity is sharply focused?
Emmetropic
122
What does emmetropic mean?
Describes the eye if an object at infinity is sharply focused
123
What is the term given to the eye if an object at infinity is NOT sharply focused?
Ametropic
124
What does ametropic mean?
Describes the eye if an object at infinity is NOT sharply focused
125
What is short-sightedness also known as?
Myopia
126
What is myopia also known as?
Short-sightedness
127
What is the incidence of myopia?
20%
128
What is long-sightedness also known as?
Hypermetropia
129
What is hypermetropia also known as?
Long-sightedness
130
What is the incidence of hypermetropia?
30%
131
Draw refraction in a myopic eye.
SEE PAD 32
132
Draw refraction in a hypermetropic eye
SEE PAD 33
133
What type of lens correct myopia?
Diverging lens
134
What type of lens corrects hypermetropia?
Converging lens
135
What is a diverging lens also known as?
Concave lens
136
What is a converging lens also known as?
Convex lens
137
Draw converging lens correction of hypermetropia
SEE PAD 34
138
Draw diverging lens correction of myopia
SEE PAD 35
139
What does myopia predispose you to?
Retinal detachment, degeneration and glaucoma
140
When does myopia combine with presbyopia?
Later in life
141
What treats myopia and presbyopia?
Bifocal lenses
142
Why would you need bifocal lenses?
If you had myopia and presbyopia
143
What is presbyopia?
Decrease in lens elasticity with age, leading to hypermetropia
144
What is the eye's two point resolution break down point?
0.5 arc min
145
What is the linespread function?
Definition of optical performance - intensity distribution in the image of point or line
146
What is the key variable in the detail of an optical image?
Grain - photoreceptor spacing
147
What is the ideal receptor spacing?
Half the width of the linespread function
148
Why is the ideal grain of the eye half the width of the linespread function?
So image detail is not sacrificed
149
Where in the eye is the ideal grain achieved?
Fovea
150
How is the ideal grain achieved in the fovea?
Small separation distances and precise mosaic to maximise packing
151
What is the power or strength of the lens expressed as?
Dioptres
152
What are dioptres?
The units used to measure the of power or strength of a lens
153
What formula defines a dioptre?
SEE PAD 36
154
What is the power and refractive index of the front of the cornea?
48.7 and 1.376
155
What is the power and refractive index of the back of the cornea?
minus 5.9 and 1.336
156
What is the power of the relaxed lens front?
7
157
What is the power of the accommodated lens front?
13.2
158
What is the refractive index of the lens front?
1.41
159
What is the refractive index of the lens back?
1.336
160
What is the power of the accommodated lens back?
13.2
161
What is the power of the relaxed lens back?
11.7
162
Does the power of the cornea change with acommodation?
No - it doesn't accommodate
163
How thick is the cornea?
650 micrometers
164
What does the cornea consist of?
Stroma sandwiched between an epithelium and endothelium
165
What is the corneal stroma?
Thick layer of transparent collagen fibrils
166
What is the lens made from?
Long ribbon-like cells, added from the periphery
167
The lens is added to from the periphery over time - what does this mean about it's structure?
Denser in the middle, thus corrects spherical aberration
168
What is a cataract?
Clouding of the lens
169
What does the lens absorb?
UV, and increasingly over time, blue
170
How is transparency of the cornea and lens assured?
Avascular
171
What provides nutrients to the cornea and lens?
Aqueous humour
172
What secretes the aqueous humour?
Epithelium of the ciliary body
173
What drains the aqueous humour?
Trabecular meshwork and Canal of Schlemm
174
What is glaucoma?
Increased pressure in the eye as a result of a reduction in rate of outflow of aqueous humour
175
What is meant by accommodation?
Changes in the lens' focal length to focus on objects and different distances
176
How is accommodatio brought about?
Combination of radial and elastic ligaments - suspensory ligaments and circular ciliary muscle
177
What are the suspensory ligaments also known as?
Zonule
178
When is the lens relaxed?
When unaccommodated
179
Describe the optical power of the relaxed lens.
Low
180
Describe the optical power of the accommodated lens.
Higher
181
When is the lens accommodated?
When objects are closer - ciliary muscles contract
182
What controls the ciliary muscle?
PSS
183
What nerve supplies the ciliary muscle?
Oculomotor
184
What is accommodation associated with, and why?
Constriction of the pupil to improve depth of focus; convergence of the eyes to fixate on new target
185
What is convergence of the eyes known as?
Near reflex
186
What is the response to focussing on a near object known as, and why?
Triple response - accommodation, pupil constriction and convergence
187
What does the iris comprise of?
Two antagonisic smooth muscles under ANS control
188
What are the to iris smooth muscles, and what controls them?
Sphincter - PSS; dilator - SS
189
What mainly determines pupil diameter?
Sphincter
190
Describe the control circuit for pupil constriction/dilation control.
Projection from retina - pretectum (midbrain) - bilateral projection to preganglionic PSS neurons (Edinger-Westphal nucleus) - occulomotor nerve - ciliary ganglion - sphincter muscle
191
What does the bilateral projection in pupillary control result in?
Increased intensity in one eye (direct) causes constriction in both (consensual)
192
What photoreceptor is concentrated in the fovea?
Cones
193
In which layer are the photoreceptors?
The one furthest from the light
194
What do the layers on top of the photoreceptors contain?
Interneurons
195
What do the layers on top of the photoreceptors do to the light?
Scatter it - causing glare
196
What is different about the layers in the fovea?
Interneurons are pushed to one side
197
What is the foveola?
Point with the highest acuity
198
How large is the foveola?
260 micrometers
199
What is the composition of the foveola?
Avascular and rod free
200
What is the cone spacing in the foveola?
0.5 min of an arc (3 micrometres)
