BMS236 CSV Flashcards
1
Q
Being receptive; responsive and spontaneous Euglena show an example of a nervous system; T or F
A
T
2
Q
How do Euglena show aspects of possessing a nervous system
A
Exhibit spontaneous swimming activity; respond to light
3
Q
Water enters the sponge through the osculum; flows through the organism controlled by flagella and then leaves through the body wall; T or F
A
F – water enters via the body wall and leaves via the osculum
4
Q
What is the name given to the cells that control water flow in sponges
A
Myocytes
5
Q
Myocytes are neurons; T or F
A
F
6
Q
What type of cells were likely to be the first example of neurons
A
Sensorimotor cells
7
Q
Describe the type of nervous system seen in Hydra
A
Hydra are radially symmetrical and thus possess a nerve net rather than a central nervous system. The nerve net consists of a series on interconnected neurons but without a brain or any type of cephalisation. This does however allow Hydra to respond to physical contact as well as detect food and other chemicals
8
Q
Hydra show examples of motor and interneurons; T or F
A
T
9
Q
The nervous system seen in Hydra allows them to detect the source of a stimulus; T or F
A
F – they cannot detect the source
10
Q
Neuronal cells in Hydra are derived from what tissue
A
Skin ectoderm
11
Q
What type of body symmetry is seen in worms
A
Bilateral symmetry
12
Q
Segmented and non-segmented worms both show cephalisation; T or F
A
T
13
Q
Describe the nervous system seen in flatworms
A
Two nerve cords; one on each side of the body; gangliation; cephalisation and fasciculation seen at the anterior/rostral end. Commissures allow coordination of both sides of the body
14
Q
Name an example of a segmented worm
A
Annelids
15
Q
In flatworms suprapharyngeal ganglia are intimately associated with the mouth; T or F
A
T
16
Q
How many neuronal and glial cells are there in C. elegans
A
302 neurons; 56 glia
17
Q
Nematode worms possess dorsal; ventral; medial and lateral nerve cords; T or F
A
F – they possess dorsal; ventral and lateral
18
Q
Most neurons in the nematode are derived from EMS cells; T or F
A
F – they are derived from AB cells
19
Q
What is meant by the term delamination
A
In C.elegans the neural cells migrate into the blastoderm from the surface ectoderm
20
Q
Describe the major features of the adult Drosophila nervous system
A
Bristle-socket – consists of a sensory hair cell; a socket cell; a sheath cell and a sensory neuron
21
Q
Where is cephalisation seen in flatworms; segmented worms and insects
A
Anterior/rostral end; close to the pharynx
22
Q
In worms and insects; neural precursors induced in one part of the body migrate inwards from the surface later in development; what is this process called
A
Delamination
23
Q
Which gene network dictates dorsal and ventral sides of the body in insects and worms and are responsible for the developing neural regions
A
Dpp-sog network
24
Q
How do these two genes/gene products interact in order for cells to acquire a neural identity
A
Short gastrulation (sog) binds to dpp in the extracellular matrix and prevents its binding to receptors
25
Neural cells develop where dpp is inhibited by sog; T or F
T
26
What is the name of the vertebrate homologue of dpp
BMP4
27
What is the invertebrate homologue of BMP7
Screw
28
Which vertebrate gene is responsible for the cleavage of BMP4 and what is the name of its invertebrate homologue
BMP1 and Tolloid
29
The vertebrate short gastrulation homologue is called chordin; T or F
T
30
Where would you typically find the expression of BMP antagonists
Dorsal side of the embryo
31
What is the key difference between vertebrate and invertebrate neurulation
Invertebrates – individual neuroblasts delaminate and form neurons that cluster into ganglia. Vertebrates – entire dorsal cell sheet induced to neural identity known as the neural plate which rolls up to form the neural tube remaining attached to the ectoderm
32
What is the name of the structure in the Xenopus embryo that expresses transcription factors that lead to the expression of BMP antagonists in the dorsal side of the embryo
Spemann’s Organiser
33
Give examples of such transcription factors that lead to BMP antagonist expression
Goosecoid; Xnot and Xlim
34
Recall some of the BMP antagonists expressed in the dorsal side of the Xenopus embryo
Noggin; Chordin; Cb
35
How do these BMP antagonists act
Bind with higher affinity to BMP receptors or bind directly to BMP altering its conformation and preventing binding
36
BMP action will be inhibited in the dorsal region of the embryo; T or F
T
37
Cells inhibited by BMP antagonists will go onto to induce the formation of the neural plate; T or F
T
38
What is the name to the equivalent organiser structure found in Gallus gallus embryos
Hensen’s Node
39
Where does this structure develop in the embryo
Tip of the primitive streak
40
Recall the features of neural inducers
Expressed by organiser; overexpression in ectopic site leads to induction of secondary axis; inhibition of activity prevents axis formation.
41
What is the name of the structure that gives rise to the forebrain; midbrain; hindbrain and spinal cord
Anterior-posterior neuraxis
42
In what order are the forebrain; midbrain; hindbrain and spinal cord formed
Forebrain forms first then the Hindbrain and Spinal cord and the Midbrain forms last
43
Neural precursors are cells that can give rise to any neuron; T or F
F – they can give rise to any neuronal derived cell (i.e. glia ect)
44
What class of molecules released from the organiser induce neural plate formation
BMP antagonists
45
What structures does the organiser self-differentiate into
Prechordal mesoderm; notochord
46
Which of the structures that the organiser self-differentiates into is located most posteriorly and which is most anterior
Notochord – posterior; prechordal mesoderm – anteriorly
47
What can be said about the organiser as it self-differentiates with regards to its position
Involutes and extends underneath the induced neural plate
48
The posterior nervous system develops as the involuted node regresses posteriorly down the primitive streak; T or F
T
49
Axial mesoderm laid down in the wake of the posteriorly moving node induces the proliferation and growth of the back end of the neural tube; T or F
T
50
What is meant by the activation-transformation model
Neural inducing molecules initially released from early organiser cells induce and maintain the anterior/forebrain tissue. These molecules are only maintained in the prechord tissue once the organiser has differentiated. Other signals thus transform some of the prechord tissue into a more posterior fate.
51
Posteriorising signals are antagonised by prechordal tissue; T or F
T
52
What classes of molecules lead to an induction of neural tissue that has an anterior character
BMP and Wnt antagonists
53
After gastrulation all of the regions of axial mesoderm are continuing to make BMP and Wnt inhibitors; T or F
F – only the bits of axial mesoderm that involuted first will continue to make BMP and Wnt inhibitors
54
Gives some examples of posteriorising signals
Wnt; FGF and retinoic acid
55
In the prospective hindbrain; BMP and Wnt inhibitors ensure that no posteriorising signals function; T or F
F – BMP and Wnt inhibitors prevents posteriorisation in the prospective forebrain
56
Retinoic is an example of a morphogen; T or F
T
57
What types of gene controls segment identity
Homeobox containing (Hox) genes
58
How are different domains of the hindbrain determined
Specific hox gene profile
59
Retinoic acid and wnt turn on different hox genes depending on their concentrations; T or F
T
60
Where are the highest concentrations of Wnt and RA found
Posterior end of the embryo
61
Explain how the midbrain is formed in the early embryo
Interaction at the border between the forebrain and hindbrain results in an induction of midbrain like tissue
62
What is the name of the border that forms at the neural-ectoderm boundary
Neural plate border
63
What causes the formation of this border at the neural-ectoderm boundary
Cells have received an intermediate level of BMP and have begun to go down but not fully towards a neural fate
64
What structures does the neural plate border give rise to
Peripheral nervous system; roof plate cells
65
What cells are involved in dorsal neural tube patterning/differentiation
Roof plate cells
66
Neural crest formation occurs during neurulation; T or F
T
67
The early border begins to express msx which acts with Wnt and FGF to turn on transcription factors Pax3; Zic1 and Pax7; T or F
T
68
What transcription factors upregulated by NBP and Wnt cause proliferation and multipotency and characterise neural crest cells
C-Myc; Id and Snail
69
What cell types to the neural plate border cells form
Neural crest cells
70
All of the neural plate border cells form neural crest cells; T or F
F – some neural plate border cells are retained and form roof plate cells
71
What is the roles of roof plate cells
Important in the final step of neurulation and dorsal neural tube patterning
72
BMPs and Wnts released by the roof plate cells diffuse into dorsal neural tube and induce expression of which set of transcription factors
Pax6; 7; 3 and Lim1
73
What is the role of Pax3; 6; 7 and Lim1
Cause neural tube progenitors to acquire dorsal identities
74
What factors help determine which cell types neural progenitors differentiate into
Position or origin of neural crest cells; time of generation and migratory pathway
75
Dorsal character is achieved through Shh-mediated repression; T or F
T
76
BMPs that derive from the surface ectoderm initially induce their own expression in the immediately adjacent ventral spinal cord; T or F
F – they induce expression in cells of the roof plate in the dorsal spinal cord
77
BMPs act as morphogens; T or F
T – BMPs from the surface ectoderm/roof plate act as local morphogens to pattern other parts of the dorsal spinal cord
78
What three types of cells differentiate dorsally
Roof plate cells; neural crest cells; dorsal sensory relay neurons
79
The neural crest is sometimes referred to as the 4th germ layer because it differentiates in to so many types of cells; name them
Peripheral nervous system cells; epinephrine-producing cells of the adrenal gland; pigment containing cell and skeletal and connective tissue of the head
80
Trunk neural crest cells that have migrated into the axial mesoderm differentiate into the dorsal root ganglion; T or F
T
81
What is the fate of trunk neural crest cells that continue to migrate ventrally
They form sympathetic ganglia
82
Which cells migrate and generate the parasympathetic ganglia
Vagal and sacral neural crest cells
83
The neural tube forms under the influence of BMP; T or F
F – it forms under the influence of BMP antagonists
84
The neural plate border forms at the edges of BMP signalling; T or F
T
85
During neurulation what happens to the mediolateral axis
It becomes the dorsovental axis
86
What is the fate of the majority of neural plate border cells
Express transcription factors and give rise to neural crest cells that migrate all over the body in turn giving rise to a variety of cells
87
What happens to the remaining neural plate border cells
Don’t migrate and form roof plate cells expressing BMP and Wnt morphogens in dorsal half of the embryo
88
What is the name given to the posterior neural tube
Notochord
89
What is the name given to the anterior neural tube
Prechordal mesoderm
90
What is the name of the structure that forms at the ventral midline of the neural tube
Floor plate
91
What is the morphogens secreted by the structure at the ventral midline of the neural tube
Sonic hedgehog
92
Where in the neural tube is Shh expressed in the neural tube
Notochord; floor plate
93
Shh is only expressed in the hindbrain; T or F
F – it is also expressed in the forebrain and midbrain
94
Where is the highest concentration of Shh found
Ventral neural tube
95
What is the result of Shh signalling in progenitor cells
Induces the expression of transcription factors that confer ventral neural tube identities and ultimate result in the differentiation of those cells into ventral neurons
96
Opposing gradients of Shh and which other morphogen act together to give the dorsal-ventral patterning of the notochord
BMP
97
Recall the sonic hedgehog signalling pathway
Sonic hedgehog is a signalling molecule that binds to and inhibits patched which in turn results in the repression of the inhibition of smoothened by patched. Smoothened is then free to signal resulting in the activation of the Gli II and Gli III. Gli II and III in the activated form are transcription factors that leads to gene transcription
98
Roughly when does a daughter cell decide on its fate in the developing nervous system
Immediately after cell division
99
Neural cells are capable of giving rise to which cells
Neurons and glia
100
What type of signalling exists between pairs of cells in the proneural cluster
Juxtacrine
101
What are the names of the proneural genes being expressed by the proneural cluster and are needed for the expression of delta
Archaete; scute
102
Expression of proneural genes means that a cell is competent to become a neuron; T or F
T
103
Neuroblast cells are the simplest type of neurons found in Drosophila; T or F
T
104
What is the primary fate of cells in the proneural cluster
Neuroblasts
105
What is the secondary fate of cells in the proneural cluster
Epidermis
106
What is the name given to a group of cells that have equal potential
Equivalence group
107
Which process results in the formation of neuroblasts and neurectoderm from the proneural cluster cells
Lateral inhibition
108
How many of the 8 cells in the proneural cluster become neurons
1
109
Define lateral inhibition
Induction often used to make initially similar cells different from one another
110
What signalling pathway leads to the lateral inhibition in the proneural cluster
Delta-Notch signalling pathway
111
Which gene product in this lateral inhibition pathway acts as the inhibitory signal and directs cells to their primary fate
Delta
112
What is seen in delta and notch -/- mutants
All proneural cluster cells become neurons
113
The expression of which two transcription factors involved in the delta-notch signalling pathway leads to the downregulation of achaete and scute
Enhancer of split; suppressor of hairless
114
What is the result of a downregulation of achaete and scute
Downregulation in delta expression
115
What transcription factors are activated by achaete and scute that are involved in specifying neuronal differentiation
Neurogenin
116
The levels of which gene product signalling is responsible for controlling the levels of SuH and Espl
Notch signalling
117
Describe the delta-notch signalling pathway
Elevation of notch signalling in one of the cells results in an upregulation of suppressor of hairless and enhancer of split in that cell. SuH and Espl result in the downregulation of achaete and scute in that cell which in turn downregulates delta expression. In the other cell; decreased activated notch receptors (due to decreased delta expression on the original cell) results in a decrease in SuH and Espl expression in that cell meaning that there is less inhibition of achaete and scute. With achaete and scute signalling increased; the cell expresses more delta. This cell will give rise to a neuron as achaete and scute transcriptionally active neurogenin.
118
Where would you expect to find the highest concentrations of BMP and Wnt in the developing neural tube
Dorsally
119
Where would the GliA gradient be at its highest
Ventrally
120
The Shh and GliR gradient will be highest at the dorsal side of the embryo; T or F
F – The GliR gradient will be at its highest at the dorsal end but the Shh gradient is highest ventrally
121
What two types of cells do neuroepithelium in the ventricular zone give rise to
Neurons that move laterally; radial glia that are retained at the ventricular zone and extend lateral projections to the pial surface
122
Explain interkinetic nuclear migration
During G1 and S phases the cell body of the neuroepithelium is located at the mantle but during cytokinesis the lateral attachment to the pial surface is lost and then reforms
123
Neuroepithelial cells divide asymmetrically; T or F
F – they divide symmetrically generating two identical daughters
124
Radial glia divide asymmetrically; T or F
T
125
What do the daughter cell of radial glia become
One remains as a radial glia (stem) cell; the other differentiates into a neuron and migrates laterally along the projection of the radial glia cell
126
Discuss the fates of the two daughter cells produced by the neuroepithelium
One cell remains at the ventricular zone; undifferentiated and radial glia-like (stem cell); the other migrates along the projection of the radially glia and terminally differentiates into a neuron
127
What developmental abnormality is the result of migration issues in the developing brain
Lissencephaly – caused by radial glia not forming the scaffold or by the neuron not migrating properly
128
What is the equivalent structure to the lumen of the spinal cord in the brain
Ventricles/ventricular zone
129
What structure do early post-mitotic cells in the cerebral cortex form
Pre-plate
130
What cell types make up the early structure in the developing cortex
Cajal-Retzuis cells and subplate cells
131
What structure later forms in development of the brain that provides the basis for the layers that define the cortex
Proper cortical plate
132
Cajal-Retzuis cells are the first post-mitotic cells; T or F
T
133
Cajal-Retzuis cells project long vertical projections; T or F
F – long sideways projections
134
What large protein is secreted by the Cajal-Retzuis cells and what is its role
Reelin – role in causing/preventing neuronal migration
135
Newly born layers of the cortex are formed deeper in; closer to their progenitors; T or F
F – newly born cells of the cortex form on the outside
136
The retention of stem-like progenitor cells at the lumen of the brain; particularly the cortex explains why humans possess such complex nervous systems; T or F
T
137
Early cell migration is along the scaffolding provided by the radial glia but later in development; some cells migrate tangentially; T or F
T
138
Where does the cerebellum form
At the root of the 4th ventricle
139
Daughters of which cells remain in the hindbrain and become neurons of the cerebellum
Rhombic lip cells
140
At the same time as rhombic lip cells are giving rise to cells of the external granular layer Purkinje cells progenitors form from the ventricular zone; T or F
T
141
Purkinje cells are a type of radial glia; T or F
T – they send long projections towards to lumen
142
Purkinje cells secrete BMP and Wnt which cause the EGL cells to proliferate; T or F
F – they secrete Shh which has that effect
143
Around birth cells in the EGZ start it differentiate into neurons but migrate inwards along the Purkinje cells scaffold; T or F
T
144
Which cells that once migrated out from the ventricular zone give rise to the entire peripheral nervous system
Neural crest cells
145
What type of sensory receptors can be found in C.elegans
Mechanoreceptors for gentle and harsh body touch
146
In C.elegans; where can we see clustering of ganglia
Pharyngeal region
147
What type of cell is recepsonsible for mechanoreception in C.elegans
Touch cell
148
Discuss the touch cell lineage
Q cells give rise to Q1a and Q1p cells. Q1p cells give rise to touch cell and an interneuron
149
Which transcription factors are needed to induce a touch cell fate
UNC-86 and MEC-3
150
Which touch cell specific genes are switched on by the activity of these transcription factors
Protofilaments for microtubules; proteins for a specialised extracellular matrix
151
Touch cell differentiation is an example of cell-autonomous differentiation; T or F
T
152
What are the components of the adult Drosophila nervous system
Socket cell; hair cell; sheath cell; sensory neuron
153
What which cells are cells of the bristle-socket derived from
Sensory organ precursors
154
The differentiation of cells in the Drosophila nervous system is an example of multiple binary decision making by the cells; T or F
T
155
Initial inhibition of Notch signalling in the SPII cell results in which fate
Sensory neuron fate
156
SOP divide symmetrically; T or F
F – asymmetrically
157
Which cytoplasmic factor is unevenly distributed between SPIIa and SPIIb and what is its function
Numb – inhibits Notch signalling pathway resulting in the cell achieving a neural fate
158
```
Match up the sensory cell names with their equivalent nervous system structure
Sensory Neuron
Bristle Cell
Socket Cell
Sheath Cell
Trichogen
Toromogen
Sensory neuron
Thecogen
```
Thecogen - Sheath Cell
Trichogen - Hair Cell
Tormogen - Socket Cell
Sensory Neuron - Sensory Neuron
159
What is the name of the repeating unit found in the Drosophila eye
Ommatidia
160
How many of these repeating units are found in the Drosophila eye
800
161
What are the constituent parts in each repeating unit found in the Drosophila eye
Rhabdomeres 1-8; 12 accessory cells
162
What causes rhabdomeres to begin differentiating
R8 is induced by Hh coming from the morphogenic furrow. R8 then signals to instruct neighbours to acquire their fates
163
What is the fate of the 1st proliferating cells that comes in to contact with Hh signalling in the developing ommatidia
Rhabdomere 8
164
Which transcription factor does this first cells to receive Hh signal express
Atonal
165
Pax6 is required for development of the vertebrate eye; T or F
T
166
Recall the pathway in which photoreceptive information reaches the brain
Rods/ConesàBipolar CellsàGanglion CellsàOptic NerveàBrain
167
In the forebrain; the eyes develop at a ventricular zone; T or F
T
168
Each neuronal cell type involved in photoreception have their own ventricular progenitor; T or F
F – they all derive from the same progenitors
169
Neurogenesis of the neurons involved in photoreception occurs in the order in which they receive information; T or F
T
170
Dorsal root ganglia are derived from neural crest cells; T or F
T
171
The ear; lens and olfactory epithelium are derived from placodes; T or F
T
172
What structures do the head placodes give rise to
Otic placodes and nasal placodes
173
From which placode does the ear develop
Otic placode
174
The spinal accessory nerve is placodal; T or F
T
175
Hair cells development is regulated by cell-cell interactions whereby high amount of notch activation results in the hair cell fate whereas low notch activity determines a supporting cell fate; T or F
F – vice versa
176
How do we overcome the problem of having only 20;000 genes in the human genome but the need to create 1014 connections between neurons during development
Genes have to be used in combination
177
Explain the Wiess resonance theory when trying to explain axon guidance
Cell body of neurons sends out random and diffuse neuronal projections to all targets followed by the elimination of non-functional connections
178
Explain Sperry’s chemoaffinity hypothesis
Neurons undergo directed and specific outgrowth through axons following individual identification tags
179
Explain the projections seen in the retinotectal pathway
Connections are flipped – anterior neurons of retina project to posterior tectum; temporal neurons project to posterior tectum. Dorsal and ventral information is also flipped
180
Recall Sperry’s 1963 experiment
Cut optic nerve and removed temporal retina allowing only nasal axons to regrow
181
Does the regrowth of nasal retinal axons to the correct tectal location prove that axons are guided by specific cues during development
No – because the axons were growing over existing axonal debris during a regeneration; this cant be assumed to be the case in development
182
Axon pathways are highly stereotyped; T or F
T
183
What evidence is there to suggest the axonal growth cues are located on axons
Experiment in grasshopper embryo – ablation of 1 of the 5 neurons results in a change in projection of another axon in the nerve tract. This is not seen be ablation of the other neurons. Proves that cue on the originally ablated neuron influences the guidance of the other neuron
184
Name the earliest source of axon guidance cues
Pioneer axons – form an axon scaffold on which later axons project
185
Pioneer axons do not show stereotyped paths; T or F
F
186
What are the main distinguishing features of the growth cone
Filopodia – long projections; lamellae – web-like fanning between projections
187
What is the difference in actin arrangement in the structures of the growth cone
F-actin is bundled together in a polarised fashion in filopodium whereas in the lamellae they are cross-linked to form a net
188
Explain the actin treadmilling that is seen in the resting growth cone
F-actin subunits are added at the peripheral zone; move through the microfilament and are removed at the central zone. Tubulin is sporadically dragged into the filopodia
189
Growth cones can turn; T or F
F – they don’t turn they reorganise
190
What happens when the growth cone comes into contact with an attractive cue
F-actin treadmilling slows down and F-actin begins to accumulate which stabilises the filopodia. A molecular clutch engages the extension over the substrate and an actin-tubulin link pulls the microtubules into the wake of the extending filopodium
191
When a growth promoting cue is encountered; two key components lead to filopodial extension; what are these
A molecular clutch is engaged and rearward actin treadmilling slows down. Next an actin-tubulin links pull the microtubules into the wake of the extending filopodium
192
What causes neurons to fasciculate only with their own kind
Repulsive cues triggered when the neurons come into contact with each other induce growth cone collapse by destabilising the F-actin between axons of differing neurons
193
What inhibitory guidance cue family of molecules are responsible for the collapse of differing growth cones
Semaphorins
194
Inhibitory guidance cue molecules can be membrane-bound or secretory; T or F
T
195
What are the four forces of axon guidance
Contact attraction; contact repulsion; chemoattractants; chemorepellents
196
What is the other name for contact repellent substrate
Non-permissive substrates
197
What is the other term for a permissive substrate
Contract attractant
198
Growth cones cannot adhere to non-permissive substrates; T or F
F
199
Axons can't grow where they can't adhere; T or F
T
200
Although growth cones adhere better to collagen than they do to laminin; they grow substantially more on laminin than collagen; T or F
T
201
Permissive factors both allow growth cone attachment and stimulates the growth of the axon; T or F
T
202
Permissive factors both define a substrates path in the developing embryo and dictate the direction of axon growth; T or F
F – cannot dictate direction
203
Discuss the influence of laminin concentration on axon growth
Laminin concentration has no effect on the direction of axon growth although growth only occurs within a particular range of laminin concentrations
204
Semaphorins are permissive factors; T or F
F – they are non-permissive
205
Semaphorins are contact repellent forces; T or F
T
206
Semaphorin knockout model organisms exhibit several inappropriate axon projections rather than just innervating one target cell; T or F
T
207
Growth cones can be kept out of where they aren’t supposed to grow by contact repulsive factor; T or F
T
208
Axons can use non-permissive factors alone to grow and reach the target cell; T or F
F – they rely on permissive factors too; it’s a balance between permissive and non-permissive factors
209
Permissive and non-permissive factors can tell a growth cone which direction to grow in; T or F
F – chemoattractants/chemorepellents provide directional information
210
Growth cones require permissive substrates in which to grow on; T or F
T
211
What is the name of the non-permissive factor found on the cell surface and its receptor that are used in early patterning as well as later to guide axons and show a reciprocal expression pattern in the mammalian embryo
Ephrins and ephs (receptors)
212
Ephs and ephrins are used to keep axons out of specific areas; what is another role they play
Compartmentalise the embryo into discrete domains – i.e. Rhombomeres
213
What is the name of the molecule that is secreted by the floor plate to direct axon growth towards it
Netrin
214
What type of axon is guided by the floor plate
Commissural sensory relay neurons
215
What is the name of the chemorepellent secreted by the roof plate to direct axon growth away from it
BMP7
216
Chemorepellents can induce growth cone collapse; T or F
T
217
Give examples of early patterning molecules that are later used to direct axon growth
BMP7 initially involved in dorsalisation of the neural tube later directs commissural sensory relay neurons away from the roof plate. Shh used to specify ventral neuronal fates in the embryo is also sued to guide neurons to the floor plate
218
How do we create tissue specific knockouts
Created a model system in which loxP sites have been introduced either side of the target knockout gene. Cross this organism with another that has cre-recombinase; the enzyme that works on the loxP sites; under the control of a promoter that directs expression of genes only in the target tissue. The progeny produced will have a normally functioning target gene except in the target tissue
219
What phenomena does the growth cone exhibit that adds the number of different connections it can make without increasing the number of genes
Changes its sensitivity to different molecules
220
What happens to commissural sensory relay neurons after they have crossed the midline in the hindbrain
Loose their responsivity to chemoattractive Netrins
221
What is the name given to a structure at which axon reprograming occurs
Choice point
222
What is seen when commissural sensory relay neurons cross the midline in the spinal cord and why
Once they have crossed the midline the commissural sensory relay neurons turn. This is because they lose sensitivity to chemoattractive Netrins but also gain sensitivity to chemorepulsive molecules released by the floor plate
223
Recall the inhibitory molecules released by the floor plate that contribute to the guiding of commissural relay neurons after they have crossed the midline of the spinal cord
Semaphorins and slits
224
Commissural sensory relay neurons are initially attracted to the floor plate of the developing neural tube but then once having crossed it; they are repelled by the floor plate; what are the guidance cue molecules involved in this phenomena
Netrins released by the floor plate initially act as chemoattractive guidance cues to direct axon growth towards it. Once the axon crosses the midline it loses all sensitivity to netrins and becomes sensitive to inhibitory guidance cues in the form of semaphorins and slits expressed by the floor plate which repel axon growth away from it.
225
What are the two type of neurons seen in the ventral nerve cord of Drosophila
Commissural neurons and longitudinal neurons
226
In the developing Drosophila ventral nerve cord; you can observe commissural and longitudinal neurons; what factor is being secreted by the midline glia cells
Netrins
227
What two unusual phenotypes are produced by genetic screens in Drosophila that exhibit problems with the neurons of the ventral nerve cord
Roundabout mutants – show no longitudinal neurons and are the result of robo mutation. Commissurless mutants – show no neurons crossing the midline and is due to comm mutation
228
What is the role of robo
Robo is a cell surface receptor for the inhibitory protein; slit
229
Where is robo expressed
Expressed at high levels in the axons that don’t cross the midline
230
Robo is expressed at high levels at all times in commissural axons; T or F
F – it is initially not expressed in high levels in commissural neurons. Only expressed in high levels after crossing the midline
231
What is seen in robo mutants
Insensitivity to slit so all the commissural neurons go back and forth across the midline forming roundabouts of neurons – they are constantly attracted to the Netrins produced by the midline glia cells and not repelled by the action of slit
232
Commissureless is only expressed in the commissural neurons; T or F
T
233
Commissureless is expressed both before and after crossing the midline; T or F
F – after crossing the midline comm is no longer expressed
234
What is seen in comm mutants
Robo protein is expressed at high levels in all cells that would normally cross the midline but which now project their axons longitudinally
235
What happens if comm expression is forced in all the neurons in the ventral nerve cord of Drosophila
Robo protein expression is lost everywhere resulting in a phenotype identical to that of the robo mutant
236
Explain how comm; robo and slit interact in the invertebrate embryo
Slit binds to robo. Comm encodes a trafficking protein that prevents the vesicles containing robo from reaching the cell surface of the neurons. This in turn prevents the slit inhibitory signal from being received. After the axon crosses the midline; comm expression is turned back off and robo-containing vesicles can reach the cell surface allowing the growth cone to respond to the inhibitory slit signal and thus change direction
237
Comm is a transcriptional regulator protein; T or F
F – commissureless is a post-transcriptional control protein
238
There is no comm homolog in vertebrates but instead there are 3 robo homologs; T or F
T
239
What causes the change in behaviour of axons crossing the midline in vertebrates
Robo3/Rig1 inhibits robo1 from acting until the axon crosses the midline
240
In vertebrates; knockout of robo1 leads to a phenotype similar to the netrin knockout; T or F
T
241
Pioneer axons establish an axons scaffold on which follower axons later project; T or F
T
242
What process allows both axons to stick to the axon scaffold but also allows them to get off when they have reached their targets
Control of fasciculation
243
What does fasciculation involve
Homophilic binding by cell adhesion molecules
244
What is seen in FasII mutants
Defasciculated axons
245
What is seen as a result of FasII overexpression
Novel/overfasciculation
246
Levels of fasciclin II are able to influence the amount of fasciculation in the ventral nerve cord of insects; T or F
T
247
What are the effects of FasII overexpression on defasciculation
Motor axons fail to defasciculate and so miss their target muscles
248
What is meant by dependent synaptogenesis
Where the developing structure requires innervation/sensory input in order to drive differentiation
249
Give an example of a structure which shows dependent development
Muscle spindles
250
What is meant by independent synaptogenesis
Structures develop without the need for innervation/sensory input
251
Give an example of a structure that shows independent development
Merkel cells
252
What morphological changes are required by the growth cone and the target postsynapse in order for a synapse to form
Growth cones forms a presynapse and the postsynaptic cell develops specialisations in order for a synapse to form
253
What two features can dictate synaptic site formation
Site availability – glial cells such as astrocytes may cover the cell body and restrict the number of sites to which a growth cones can attach. Pre-preparation of sites – cells may have prepared sites which contain cell adhesion molecules to dictate synapse formation at specific points
254
How can the complexity and number of individual synapses be accounted for with only limited cell adhesion molecules
Using specific combinations of multiple different cell adhesion molecules together can dictate the specificity needed to form each synapse
255
The neuromuscular junction initially is innervated by multiple neurons before being reduce to single innervation; T or F
T
256
What type of receptor is found at the neuromuscular junction
nAchR
257
How many subunits does the neuromuscular junction receptor have
5 – ?; ?; ? and ?
258
In development the nAchRs are initially diffusely distributed; T or F
T
259
What is the term that describes the localisation of nAchRs in the developing neuromuscular junction
Focussed distribution
260
How is the localisation of nAchRs achieved in the development neuromuscular junction
Transcription of the receptors is upregulated in the nuclei adjacent to the neuromuscular junction whilst down regulated in the peripheral nuclei
261
Gephrin is a cell adhesion molecule; T or F
F – it’s a clustering protein
262
What is the role of AchR receptor-inducing activity protein (ARIA)
ARIA is released by motorneurons and increases AchR synthesis; in particular the ? subunit. This leads to maturation and clustering of the receptors
263
What is the name of the molecule that stimulates receptor clustering
Agrin
264
During development agrin is only expressed in the motor neuron growth cone; T or F
F – it is expressed by the motor neuron and by its target muscle
265
Agrin contains multiple regions for interactions with the extracellular matrix and cell adhesion molecules; T or F
T
266
What is MuSK and what does it do
Muscle-specific kinase is a protein that aids in receptor clustering in the developing neuromuscular junction
267
Explain the mechanism of agrin in receptor clustering
Agrin binds to MuSK. MuSK is linked to the AchRs by rapsyn
268
What is seen in agrin knockout mice
Death due to malformed neuromuscular junctions causing asphyxia
269
What happens as a result of MuSK knockout
Insensitivity to agrin
270
Rapsyn is essential for clustering to occur; without it no clustering occurs; T or F
T
271
What are the names of the scientists credited with the discovery of the first neurotrophin
Viktor Hamburger and Rita Levi-Montalcini
272
Lots of synapses and neurons fail during development; T or F
T
273
In early development a large number of synapses and neurons are seen throughout the neuraxis with DRGs of the same size throughout the body plan; how is this different in later development
At a later stage in development DRGs at the limb regions are much larger than those in the interlimb regions
274
What is the effect of removal of a chick limb bud on the development of the nervous system
Removal of a limb bud results in fewer motor neurons and synapses in the regions where the limb bud was removed due to higher levels of cell death
275
What is the result of ectopic limb bud grafting in the chick embryo during development
Increased survival of synapses and motor neurons in that regions
276
Define neurotrophic
A factor that promotes/feeds neurons
277
Define neurotropic
A factors that dictates direction of neuronal growth
278
What was the name of the first discovered neurotrophin
Nerve Growth Factor
279
Where was NGF isolated from and what is the active subunit
Isolated from the submandibular gland – ? active subunit
280
How is ?-NGF secreted
As a dimer
281
NGF is only important for the survival of neurites; T or F
F – it is also important for survival of the soma and can guide growth cones in vitro
282
What happens once NGF binds to receptors in the periphery
The NGF and its receptors are internalised and transported towards the soma via retrograde transport
283
What are the name of the receptors that NGF binds to
TrkA and P75-NTR
284
Which receptor does NGF bind to with high affinity
TrkA
285
Which receptor does NGF bind to with low affinity
P75-NTR
286
What class of receptor is the receptor that NGF binds to with high affinity
Tyrosine Kinase Receptor
287
Which receptor that binds NGF can promote cell death or cell survival depending on its context
P75-NTR
288
Why aren’t neurotrophins abundant in the developing embryo
Because they specify regional areas of cell survival and dictate a selection process. Too many neurotrophins would result in too many neurons and synapses surviving
289
What are the three other main neurotrophins that have been identified
Brain-Derived Neurotrophic Factor (BDNF); NT3 and NT4/5
290
Different combinations of neurotrophins are required for the survival of different neurons; T or F
T
291
Different populations of neurons are affected by loss of different neurotrophin receptors; T or F
T
292
Only some neurotrophins can bind to P75-NTR because of its low affinity for them; T or F
F – all neurotrophins can bind to P75-NTR
293
Newly born neurons are always dependant on neurotrophins in order to survive; T or F
F – some may have no dependency
294
Arrival of a neuron at its target often coincides with new expression of a particular neurotrophin by the target; T or F
T
295
Neurons can change which neurotrophin they need in order to survive throughout development; T or F
T
296
All animals require neurotrophins at some point in development; T or F
F – Drosophila and C.elegans do not
297
Name three other families of survival factors other than neurotrophins
Cytokines; Glia-Derived Neurotrophic Factors (GDNF) and Testosterone
298
Neurons themselves can also synthesise neurotrophins as well as their targets; T or F
T
299
What is the primary determinant of neuronal/synaptic survival
Electrical activity pre and post-synaptically
300
Initially multiple motor neurons innervate a single muscle fibre during development but later on this is decreased so that one motor neuron innervates a single muscle fibre; T or F
T
301
What converts electrical activity into neuronal survival
The more active a synapse the more neurotrophin it takes up and thus the more likely to survive
302
The greater the target tissue mass the more neurotrophin that is available to a neuron; T or F
T
303
Motor neurons still exhibit cell death despite the fact that the mass of the target tissue is increasing; T or F
T
304
Neuronal cell death tends to only occur postsynaptically during development; T or F
F – occurs both pre and postsynaptically
305
By what type of cell death do neurons die during development
Apoptosis
306
The process of cell death seen in neural development is an active process; T or F
T
307
Antinomycin D and cyclohexamide inhibit cell death; T or F
T
308
How is the debris produced by neuronal cell death cleared up
Macrophage removal and neurotic disintegration
309
By what two pathways can the cell death seen in neuronal development take
Extrinsic pathway – killing of the cell via cells of the immune system; indirect activation of caspases via DISC. Intrinsic pathway – cytochrome c release by the mitochondria binding to APAF1 and Caspase 9 activating the caspase cascade
310
What are the key pro-apoptotic genes
Ced 3 and Ced 4
311
What are the key anti-apoptotic genes
Ced 9
312
What is the gene responsible for initiation of apoptosis
EGL-1
313
What is the name given to the class of mammalian homologues of EGL-1
BH3-only proteins
314
The caspases are homologues of the Ced 9 gene; T or F
F – caspases are homologues of Ced 3
315
The caspases are pro-apoptotic; T or F
T
316
Which caspase is particularly important in development of the nervous system
Caspase 3
317
What three things does caspase 3 break down
Poly ADP-ribose polymerase; Lamin A and Huntingdin
318
What are the two triggers of developmental apoptosis
Lack of trophic support; absence of depolarising stimulus
319
NGF deprival is a likely cause of developmental apoptosis; T or F
T
320
Neurotrophins are synthesised and released in a pro form; T or F
F – synthesised in a prepro form
321
What does the pre form of neurotrophins do
Signal peptide to direct transport
322
The pro portion of neurotrophins is cleaved after release; T or F
T
323
ProNGF strongly activates TrkA; T or F
F – strongly activates P75-NTR
324
Neurotrophins are mainly released from the apical membrane; T or F
F – they are released basally
325
What can trigger the release of neurotrophins
Ca2+ levels due to depolarisation or ligand binding
326
Neurotransmitters can act as neurotrophins; T or F
T
327
Developmental plasticity comes from our understanding of the plasticity in the mature brain that underlies memory and learning; T or F
T
328
Developmental plasticity can be explained by mechanisms similar to that seen in memory and learning; T or F
T
329
There is only a loss of synapses during development; T or F
F – new synapses are also formed but there is a net loss
330
Coordinated activity of a presynaptic terminal and postsynaptic neurons strengthens the synaptic connections between them; T or F
T
331
When two neurons fire at the same time the connection between becomes stronger and they become more likely to fire again; T or F
T
332
Early in development only a single axon innervates a muscle fibre and this in maintained despite increasing numbers of neurons throughout the course of development; T or F
F – initially many neurons innervate muscle fibres but this decreases to only a single neuron later in development
333
Explain how we can see the decreasing innervation in skeletal muscle throughout development
Gradually increase stimulation of the afferents innervating a target muscle and record the postsynaptic potential until a maximum response in reached. Repeat these measurements throughout development and a decrease in the maximum response will be seen indicating a decrease in innervation by the afferents.
334
What assumptions does measuring the postsynaptic potential as a result of quantal increase of afferent stimulation require
The smallest size of response seen in the target muscle corresponds to the innervation by a single afferent. Linear relationship between the stimulus size and the postsynaptic response
335
The climbing fibres are another example of decreasing convergence seen in development; T or F
T
336
To which cells do the climbing fibres of the cerebellum project
Purkinje neurons
337
In the mature cerebellum how many climbing fibres synapse with each Purkinje cell
1
338
Where in the early stages of development are most of the synaptic connections made
At the soma
339
Where are the mature connections between climbing fibres and Purkinje cells made
In the dendrites
340
What is significant about the innervation of the eye in the mature layer IV of the visual cortex
Striated appearance of alternating innervation by the right and left eye
341
What is the result in sensory deprivation of one particular eye during development
Loss of synaptic function in the monocular layer in the regions ipsilateral to the deprived eye
342
Sensory deprivation of the eye results in altering of the competition between the monocular synaptic connections from each eyes resulting in a loss of synaptic connections between the layer IV cells and the deprived eye; T or F
T
343
What occurs as a result of sensory deprivation of both eyes during development
Maintenance of binocular and monocular connections from both eyes
344
Synapses from each eye compete with each other for strengthening; T or F
T
345
What is meant by silent synapses
Intact synapses that are non-functional where stimulation doesn’t result in chemical signalling
346
Where are silent synapses mainly seen
Glutamatergic system
347
What is meant by a tetanus; in the brain
High frequency stimulus
348
Describe what is meant by paired long-term potentiation
Coincident stimulation of a pathway and depolarisation of the target cell leads to a strengthening of the synapse.
349
Long-depression is classically studied in the cerebellum; T or F
T
350
How does LTP occur at the cellular level
Tetanic stimulation removes the Mg2+ block in the NMDA receptors allowing Ca2+ influx. This leads to the insertion of AMPA receptors into the membrane at the dendritic spines and thus an increased response to subsequent stimulation. AMPAfication
351
What is the most abundant excitatory neurotransmitter in the nervous system
Glutamate
352
What is the most abundant inhibitory neurotransmitter in the nervous system
GABA
353
Give some examples of modulatory neurotransmitters
Neuropeptide (endorphin; encephalin); ATP and opiates
354
Where are glutamate receptors more often found
Distal dendrites/dendritic spines
355
Where are the GABA receptors more often found on neurons
Proximal dendrites/soma
356
Most receptors are synthesised and inserted into the membrane after synaptogenesis; T or F
F – most receptors are made prior to synapse assembly and are stored in transport vesicles before insertion
357
Excitatory neurotransmitters cause hyperpolarisation of neurons; T or F
F – they cause depolarisation
358
Opening of Na+ in mature neurons causes depolarisation; T or F
T
359
What happens to the magnitude and polarity of the resting potential during development
Magnitude increases as it gets more negative – shifts towards hyperpolarisation
360
What causes the resting membrane potential to shift negatively during development
New channel and pump expression
361
Astrocytes increase and causes a decrease in the [K+]EC during development; T or F
T – this accounts for the negative shift in resting membrane potential
362
What causes the decrease in the input resistance of neurons during development
More current (ions) can flow across the membrane due to the synthesis and insertion of new channels
363
What is meant by the neuronal membrane time constant
The membrane time constant is a measure of how quickly the potential of the membrane can change and spread.
364
What happens to the neuronal membrane time constant during development and why
During development the membrane time constant decreases. The time constant is dependent on the resistance and capacitance of the membrane and thus the increased capacitance that is seen during development is responsible for this increase
365
What is meant by neuronal membrane capacitance
The ability of the membrane to store charge
366
Why does the capacitance increase during development
Increased size of the neurons
367
Action potentials appear early in development; T or F
T
368
What is significant about the duration of the action potential in early development
It has quite a long duration
369
What ion channel underpins depolarisation and is thus responsible for the early action potential and how is this different to the mature neuron
In early development Ca2+ channels underpin the action potential as opposed to the Na+ channels that dictate it later
370
Tetrodotoxin is an inhibitor of voltage-gated Ca2+ channels; T or F
F – it inhibits voltage-gated Na+ channels
371
What is the difference seen in the action potentials that are Ca2+ and Na+ dependent
The Na+ action potentials are much shorter
372
What are delayed rectifier potassium channels and how do they influence the generated action potentials
Delayed rectifier K+ channels are channels that only open sometime after their voltage threshold has been reached and let K+ out of the cell preferentially to letting K+ in. They play a role in shortening the duration of the action potential
373
Different neurons refine the way they respond to synaptic activity by incorporation of different channels into the membrane; T or F
T
374
High voltage activated Ca2+ channels appear first in development; T or F
F – Low voltage activated Ca2+ channels appear first
375
Where do high and low voltage activated Ca2+ channels tend to be located
Lva Ca2+ channels are often found on the soma whereas hva Ca2+ channels are more commonly found at axon terminals
376
Lva T-currents tend to control membrane excitability whereas hva N and L-currents control neurotransmitter release; T or F
T
377
Later in development lva currents tend to disappear; T or F
T
378
Lva currents exhibit the property of rapid inactivation; they open and close quickly; T or F
T
379
What changes can occurs to receptors through the course of development
Changes in subunit composition; localisation; efficacy and also changes in types of receptor populations expressed
380
Where on the axon are glutamate receptors more commonly found
On the dendritic spines
381
Where on the axon are GABA receptors more commonly found
On or near to the soma
382
What are the two types of GABA receptor and what is the main difference
GABAA – ionotropic; localised to the soma. GABAB – GPCR that ends up at the axon terminal
383
Which GABA receptor controls neurotransmitter release
GABAB
384
Which GABA receptor controls transcription
GABAA
385
How is it that GABA receptors act as excitatory receptors in early development
In immature neurons the intracellular concentration of Cl- is extremely high. This means that opening of the GABA receptors causes Cl- efflux from the neurons which in turn causes the opening of voltage-gated Na+ and Ca2+ channels and thus depolarisation
386
What causes the switching of GABA signalling from excitatory to inhibitory
Insertion of NKCC2 channel into the membrane decreases intracellular Cl- concentration via efflux from the neurons
387
Which classes of animals have an increased regeneration capacity
Amphibia and reptiles
388
What causes Xenopus tadpole tail regeneration during the critical refractory period
Triggered by BMP signalling
389
Organisms that show regeneration capacity all use similar mechanisms to do so; T or F
F – each organism uses a different strategy to regenerate
390
Regeneration can occur independent of innervation; T or F
F – regeneration of tissue is dependent on nerve regeneration
391
What are the two main types of nerve injury
Crush injury; severing injury
392
Which type of nerve injury tends to be easier to repair and why
Crush injuries are usually easier to repair as the basal lamina and extracellular matrix is usually still intact
393
If injury to a neuron occurs near to the soma the neuron is more likely to die; T or F
T
394
What happens if an injury to a neuron occurs in the proximal axon
Reorganisation and re-expression of immature features such as tubulins
395
What is the name of the process commonly seen in response to damage to the distal axon; in particular; trauma
Wallerian degeneration
396
Denervation of a muscle will result in atrophy; T or F
T
397
What happens to the receptors on muscle if it becomes denervated
They reverse to embryonic types
398
Level of muscle-specific kinase rapidly drop in response to muscle denervation; T or F
F – they increase
399
How can atrophy of a muscle be prevent should it become denervated
External electrical input
400
Regeneration of a neuron involves the mitosis of Schwann cells and the supply of growth factors; T or F
T
401
What is the name of the structure formed by rows of Schwann cells that guides axon regrowth
Bands of Bunger
402
What is meant by sprouting and how can this contribute to regeneration
Sprouting is the process by which intact functioning axons near to the site of damage send projections to the denervated muscle to cover the damage
403
The basal lamina and extracellular matrix usually remains intact in crush injuries; T or F
T
404
Why do sutured nerves no regrown accurately
Disruption of the basal lamina and extracellular matrix
405
Why are spinal cord injuries difficult to treat
Cysts and glial scars from that makes recovery of connections difficult. The myelin produced contains inhibitory proteins such as nogo-a that inhibits axon regrowth
406
What is the name of the family of inhibitory proteins present in myelin that prevent axon regrowth
NOGO
407
Where is nogo-a commonly found
Oligodendrocytes and developing neurons
408
What is the result of nogo-a knockout
Partial decrease in inhibition of axon regrowth
409
Antibodies to nogo improves regeneration of the spinal cord; T or F
T
410
If inflammation is minimised from an early period in a damaged motor neuron there is an increased chance of regeneration; T or F
T
411
Which cell types are responsible for the limitations in regeneration of neurons
Glia – astrocytes
412
Name a class of secreted inhibitory molecule other than nogo that prevents regeneration
Chondroitin sulphate proteoglycans
413
Which nerve is commonly used as a spinal cord bridge to bypass lesions
Sural nerve
414
Stem cell transplant can also be used to aid in the regeneration of nervous tissue; T or F
T
415
Which brain structure provides the highest level of motor control
Primary motor cortex
416
What structure do the corticospinal tracts project to from the spinal cord
Primary motor cortex
417
Which structure represents the middle level of motor control
Brainstem
418
Which region(s) of the brainstem controls parts of the distal limb
Lateral descending brainstem
419
The brainstem is important in goal orientated movements of the hand and arm; T or F
T
420
The lowest level of motor control comes from which central nervous system structure
Spinal cord
421
What is the most common type of reflex
Polysynaptic reflexes
422
Name an example of each type of reflex
Monosynaptic – knee-jerk reflex. Polysynaptic – stretch reflex
423
The spinal cord contains the neuronal circuits involved in mediation of reflexes; T or F
T
424
What is the simplest type of reflex
Monosynaptic – contain just sensory and motor neurons
425
Electrical stimulation of the primary motor cortex results in complex coordinated movements; T or F
F
426
The primary motor cortex is said to oversee and make important decisions but can't functions meaningfully without input from other centres; T or F
T
427
What two other centres coordinate the response of the primary motor cortex and lead to complex movements
Basal Ganglia and Cerebellum
428
What is the main difference between the two centres that coordinate motor information from the primary motor cortex
Basal Ganglia can only feed information back to the motor cortex before it is sent to the muscles whereas the cerebellum can send signals down the brainstem and spinal cord straight to the muscles without feedback to the motor cortex
429
Error correction signals sent directly to the muscled from the cerebellum only occur in emergency situations; T or F
T
430
What are the 4 brain areas that constitute to the basal ganglia
Caudate nucleus; putamen (striatum); substantia nigra and subthalamic nucleus
431
The cerebellum accounts for 40% of the neurons in the nervous system; T or F
T
432
Via what structure do the basal ganglia project through to pass information to the motor cortex
Thalamus
433
How do the basal ganglia and cerebellum influence output from the primary motor cortex
Monitor commands coming from the motor cortex and make sure they are appropriate for the situation. If commands aren’t appropriate they calculate correction signals which are sent back to the motor cortex or directly to the muscles
434
What is meant by the subcortical loop
The loop consisting of motor output from the motor cortex to the basal ganglia and the feedback of the basal ganglia to the motor cortex
435
How was the motor cortex initially discovered
Electrical stimulation experiments revealed certain regions of the brain that once stimulated lead to certain actions in the patient
436
Which structure is also referred to as Brodmann’s area 4
Primary motor cortex
437
Where is the primary motor cortex located and thus what can it be referred to as
Lies anterior to the central sulcus and is thus sometimes called the precentral gyrus
438
The regions found by Wilder Penfield that when stimulated lead to no observable response were later determined to be what
Supplementary areas that support primary regions of the brain
439
What is meant by the motor homunculus
Proportional representation of the anatomical structures based on the amount of motor cortex occupied
440
Which anatomical structures represent the largest proportional innervation by the motor cortex
Fingers; hands and face
441
Why is the control of the hands by the motor cortex spread out over large areas
So that localised neuronal damage to the motor cortex minimises the loss of function to the hands
442
What happens to the area in the spinal cord associated to a region of the motor cortex that suffers legions or damage
Subsequent degeneration is also seen in the area of the spinal cord
443
Electrical stimulation of the primary motor cortex can result in the production of complex or learnt movements; T or F
F – requires inputs from many different centres
444
What are the first neurons in the motor cortex
Upper motor neurons
445
Which motor neurons are the longest
Upper motor neurons
446
What is meant by decussation and where do the upper motor neurons do this
Decussation is where the neurons cross the midline and occurs at the pyramids in the brainstem
447
Which motor neurons do upper motor neurons synapse with
Lower motor neurons
448
Interneurons often link the upper and lower motor neurons; T or F
T
449
What is the role of the upper motor neurons
Panning; initiating and directing movements
450
Some upper motor neurons originate from higher motor centres; which are these
Nucleus ruber; vestibular nucleus; superior colliculus and the reticular formation
451
What four features do upper motor neurons regulate
Muscle tone; postural muscles; maintenance of balance and the orientation of the head and body
452
What is the name of the pathway established by the lower motor neurons and is the one that is responsible for the muscle contraction/movement
Final common pathway
453
As the LMN pathways are the only ones that lead to muscle contraction these are the only pathways that lead to action potential generation; T or F
F – both pathways leads to action potential generation
454
With what two structures does the basal ganglia interact with in order to regulate motor control
Provides input to UMNs and connects with the motor cortex
455
The cerebellum connects to the cortex via the thalamus as well as connecting to the brainstem; T or F
T
456
What is the basal ganglia’s influence on motor control
Helps to initiate and terminate movement whilst supressing inappropriate movement
457
The basal ganglia help to establish the normal level tone; T or F
T
458
Tourette’s syndrome has been linked to damage to the basal ganglia; T or F
T
459
The cerebellum controls the activity of UMNs; T or F
F – it controls UMN activity
460
How does the cerebellum respond if there is a difference in intended and actual movements
Sends an error signal either to the motor cortex or to the muscle itself to reduce the discrepancy.
461
Rod cells are used in central vision and are photopic; T or F
F – cone cells detect the wavelength of light; rod cells are primarily involved in peripheral vision and are concentrated in the outer edges of the retina
462
List some distinguishing features of rod cells.
(High) convergence and sensitivity; low resolution and visual acuity and function best in low intensities
463
What are the four types of retinal neurons
Bipolar; ganglion; horizontal and amacrine cells
464
Are ganglion cells 1st or 2nd order neurons
2nd order
465
Are bipolar cells 1st or 2nd order neurons
1st order
466
What is the main role of horizontal cells
Enhance contrast and intensity
467
What is meant by duplicity theory
Cant have high sensitivity and high resolution in single receptor
468
Rod cells contract ganglion cells directly; T or F
F – they are connected via amacrine and horizontal cells
469
What are the two main photoreceptive pigments and in which photoreceptors are they found
Rhodopsin – rods Photopsin – cones
470
In the dark the rod cell is depolarised causing and inhibition of the bipolar cells; T or F
T
471
In photoreception; glutamate acts as an excitatory neurotransmitter; T or F
F – glutamate is normally an excitatory neurotransmitter but in photoreception; it’s release from a depolarised rod cell in response to darkness causes an IPSP in the bipolar cell ultimately resulting in no signal.
472
What are the two types of bipolar cells and the differences
ON Bipolar – Glutamate inhibits; hyperpolarised in dark; light causes loss of inhibition; metabotropic and OFF Bipolar – Glutamate excites; depolarised in dark; light causes loss of excitation; ionotropic
473
What three types of stimuli is the visual system adapted to recognise
Food stimuli; predators and mates
474
What are the three levels of processing in the visual system
Positive feedforward; negative feedback and negative feedforward
475
What is meant by the optic nerve being an information bottleneck
The optic nerve cannot transmit all of the information it receives from the retina to the visual cortex and so decides on what types of information are transmitted
476
Put these centres in order to show the pathway taken by visual information - a) Laternal geniculate nucleus b) eyes c) optic radiator d) primary visual cortex e) pulvinar nucleus f) superior colliculus
b; e; a; f; c; d
477
The right hemifield of vision activates the right side of the brain and vice versa; T or F
F – the right hemifield activates the left side of the brain
478
What is the main function of the retina
Image acquisition
479
Although the majority occurs in the visual cortex; what is the name of the other brain centre that processes visual information
Lateral geniculate nucleus
480
What are the two different visual pathways in the brain and what are the differences between them
Ventral visual pathway processes information about what the object is and is located inferiorly and temporally. One the other hand the dorsal visual pathway is located posteriorly and parietally and processes the spatial information
481
What is the function of the pupil
Regulate the amount of light that falls on the retina
482
What is the role of the lens
To focus light on the fovea
483
The fovea is the region of the retina with the highest visual acuity; T or F
T
484
The majority of the retina consists mostly of rods; T or F
T
485
What are the two types of photoreceptors
Rods; cones
486
How many layers of synapses are present in the visual cortex and what are their names
Inner plexiform layer; outer plexiform layer
487
Which type of photoreceptor is most active in dim light
Rods
488
Which type of photoreceptor is most active in bright light
Cones
489
Stimulation by light results in a hyperpolarisation of the photoreceptors; T or F
T
490
What is the name of the synapses formed in the visual system that allows permanent glutamate release
Ribbon synapses
491
Photoreceptors usually trigger action potentials; T or F
F – they don’t spike and have graded responses
492
In the dark the photoreceptors are constantly releasing glutamate; T or F
T
493
Horizontal cells inhibit photoreceptors; T or F
T
494
Rod cells connect directly to ganglion cells; T or F
F – they connect via bipolar and amacrine cells
495
What is significant about ganglion cell dendritic fields and how this implements their ability to process fine detail and movement
Ganglion cells with dense dendritic fields are better tuned to process fine detail whereas ganglion cells with sparse dendritic fields are better at processing movement
496
Visual neurons can either be saturated or not sensitive enough; T or F
T
497
What happens at high contrast if there was no visual adaptation
All the neurons would be saturated
498
What happens at low contrast is the was no visual adaptation
All the neurons wouldn’t fire
499
What are the strategies used by visual neurons to avoid saturation
Desensitisation; hyperpolarisation
500
Adaptation to changes in temporal contrast is very fast; T or F
F – it is slow
