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BMS236 - Toby > BMS236 CSV > Flashcards

BMS236 CSV Flashcards

1
Q

Being receptive; responsive and spontaneous Euglena show an example of a nervous system; T or F

A

T

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2
Q

How do Euglena show aspects of possessing a nervous system

A

Exhibit spontaneous swimming activity; respond to light

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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

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4
Q

What is the name given to the cells that control water flow in sponges

A

Myocytes

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5
Q

Myocytes are neurons; T or F

A

F

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6
Q

What type of cells were likely to be the first example of neurons

A

Sensorimotor cells

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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

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8
Q

Hydra show examples of motor and interneurons; T or F

A

T

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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

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10
Q

Neuronal cells in Hydra are derived from what tissue

A

Skin ectoderm

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11
Q

What type of body symmetry is seen in worms

A

Bilateral symmetry

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12
Q

Segmented and non-segmented worms both show cephalisation; T or F

A

T

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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

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14
Q

Name an example of a segmented worm

A

Annelids

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15
Q

In flatworms suprapharyngeal ganglia are intimately associated with the mouth; T or F

A

T

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16
Q

How many neuronal and glial cells are there in C. elegans

A

302 neurons; 56 glia

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17
Q

Nematode worms possess dorsal; ventral; medial and lateral nerve cords; T or F

A

F – they possess dorsal; ventral and lateral

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18
Q

Most neurons in the nematode are derived from EMS cells; T or F

A

F – they are derived from AB cells

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19
Q

What is meant by the term delamination

A

In C.elegans the neural cells migrate into the blastoderm from the surface ectoderm

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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

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21
Q

Where is cephalisation seen in flatworms; segmented worms and insects

A

Anterior/rostral end; close to the pharynx

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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

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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

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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

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25
Q

Neural cells develop where dpp is inhibited by sog; T or F

A

T

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26
Q

What is the name of the vertebrate homologue of dpp

A

BMP4

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27
Q

What is the invertebrate homologue of BMP7

A

Screw

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28
Q

Which vertebrate gene is responsible for the cleavage of BMP4 and what is the name of its invertebrate homologue

A

BMP1 and Tolloid

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29
Q

The vertebrate short gastrulation homologue is called chordin; T or F

A

T

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30
Q

Where would you typically find the expression of BMP antagonists

A

Dorsal side of the embryo

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31
Q

What is the key difference between vertebrate and invertebrate neurulation

A

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

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32
Q

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

A

Spemann’s Organiser

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33
Q

Give examples of such transcription factors that lead to BMP antagonist expression

A

Goosecoid; Xnot and Xlim

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34
Q

Recall some of the BMP antagonists expressed in the dorsal side of the Xenopus embryo

A

Noggin; Chordin; Cb

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35
Q

How do these BMP antagonists act

A

Bind with higher affinity to BMP receptors or bind directly to BMP altering its conformation and preventing binding

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36
Q

BMP action will be inhibited in the dorsal region of the embryo; T or F

A

T

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37
Q

Cells inhibited by BMP antagonists will go onto to induce the formation of the neural plate; T or F

A

T

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38
Q

What is the name to the equivalent organiser structure found in Gallus gallus embryos

A

Hensen’s Node

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39
Q

Where does this structure develop in the embryo

A

Tip of the primitive streak

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40
Q

Recall the features of neural inducers

A

Expressed by organiser; overexpression in ectopic site leads to induction of secondary axis; inhibition of activity prevents axis formation.

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41
Q

What is the name of the structure that gives rise to the forebrain; midbrain; hindbrain and spinal cord

A

Anterior-posterior neuraxis

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42
Q

In what order are the forebrain; midbrain; hindbrain and spinal cord formed

A

Forebrain forms first then the Hindbrain and Spinal cord and the Midbrain forms last

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43
Q

Neural precursors are cells that can give rise to any neuron; T or F

A

F – they can give rise to any neuronal derived cell (i.e. glia ect)

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44
Q

What class of molecules released from the organiser induce neural plate formation

A

BMP antagonists

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45
Q

What structures does the organiser self-differentiate into

A

Prechordal mesoderm; notochord

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46
Q

Which of the structures that the organiser self-differentiates into is located most posteriorly and which is most anterior

A

Notochord – posterior; prechordal mesoderm – anteriorly

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47
Q

What can be said about the organiser as it self-differentiates with regards to its position

A

Involutes and extends underneath the induced neural plate

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48
Q

The posterior nervous system develops as the involuted node regresses posteriorly down the primitive streak; T or F

A

T

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49
Q

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

A

T

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50
Q

What is meant by the activation-transformation model

A

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.

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51
Q

Posteriorising signals are antagonised by prechordal tissue; T or F

A

T

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52
Q

What classes of molecules lead to an induction of neural tissue that has an anterior character

A

BMP and Wnt antagonists

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53
Q

After gastrulation all of the regions of axial mesoderm are continuing to make BMP and Wnt inhibitors; T or F

A

F – only the bits of axial mesoderm that involuted first will continue to make BMP and Wnt inhibitors

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54
Q

Gives some examples of posteriorising signals

A

Wnt; FGF and retinoic acid

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55
Q

In the prospective hindbrain; BMP and Wnt inhibitors ensure that no posteriorising signals function; T or F

A

F – BMP and Wnt inhibitors prevents posteriorisation in the prospective forebrain

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56
Q

Retinoic is an example of a morphogen; T or F

A

T

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57
Q

What types of gene controls segment identity

A

Homeobox containing (Hox) genes

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58
Q

How are different domains of the hindbrain determined

A

Specific hox gene profile

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59
Q

Retinoic acid and wnt turn on different hox genes depending on their concentrations; T or F

A

T

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60
Q

Where are the highest concentrations of Wnt and RA found

A

Posterior end of the embryo

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61
Q

Explain how the midbrain is formed in the early embryo

A

Interaction at the border between the forebrain and hindbrain results in an induction of midbrain like tissue

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62
Q

What is the name of the border that forms at the neural-ectoderm boundary

A

Neural plate border

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63
Q

What causes the formation of this border at the neural-ectoderm boundary

A

Cells have received an intermediate level of BMP and have begun to go down but not fully towards a neural fate

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64
Q

What structures does the neural plate border give rise to

A

Peripheral nervous system; roof plate cells

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65
Q

What cells are involved in dorsal neural tube patterning/differentiation

A

Roof plate cells

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66
Q

Neural crest formation occurs during neurulation; T or F

A

T

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67
Q

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

A

T

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68
Q

What transcription factors upregulated by NBP and Wnt cause proliferation and multipotency and characterise neural crest cells

A

C-Myc; Id and Snail

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69
Q

What cell types to the neural plate border cells form

A

Neural crest cells

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70
Q

All of the neural plate border cells form neural crest cells; T or F

A

F – some neural plate border cells are retained and form roof plate cells

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71
Q

What is the roles of roof plate cells

A

Important in the final step of neurulation and dorsal neural tube patterning

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72
Q

BMPs and Wnts released by the roof plate cells diffuse into dorsal neural tube and induce expression of which set of transcription factors

A

Pax6; 7; 3 and Lim1

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73
Q

What is the role of Pax3; 6; 7 and Lim1

A

Cause neural tube progenitors to acquire dorsal identities

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74
Q

What factors help determine which cell types neural progenitors differentiate into

A

Position or origin of neural crest cells; time of generation and migratory pathway

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75
Q

Dorsal character is achieved through Shh-mediated repression; T or F

A

T

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76
Q

BMPs that derive from the surface ectoderm initially induce their own expression in the immediately adjacent ventral spinal cord; T or F

A

F – they induce expression in cells of the roof plate in the dorsal spinal cord

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77
Q

BMPs act as morphogens; T or F

A

T – BMPs from the surface ectoderm/roof plate act as local morphogens to pattern other parts of the dorsal spinal cord

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78
Q

What three types of cells differentiate dorsally

A

Roof plate cells; neural crest cells; dorsal sensory relay neurons

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79
Q

The neural crest is sometimes referred to as the 4th germ layer because it differentiates in to so many types of cells; name them

A

Peripheral nervous system cells; epinephrine-producing cells of the adrenal gland; pigment containing cell and skeletal and connective tissue of the head

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80
Q

Trunk neural crest cells that have migrated into the axial mesoderm differentiate into the dorsal root ganglion; T or F

A

T

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81
Q

What is the fate of trunk neural crest cells that continue to migrate ventrally

A

They form sympathetic ganglia

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82
Q

Which cells migrate and generate the parasympathetic ganglia

A

Vagal and sacral neural crest cells

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83
Q

The neural tube forms under the influence of BMP; T or F

A

F – it forms under the influence of BMP antagonists

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84
Q

The neural plate border forms at the edges of BMP signalling; T or F

A

T

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85
Q

During neurulation what happens to the mediolateral axis

A

It becomes the dorsovental axis

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86
Q

What is the fate of the majority of neural plate border cells

A

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

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87
Q

What happens to the remaining neural plate border cells

A

Don’t migrate and form roof plate cells expressing BMP and Wnt morphogens in dorsal half of the embryo

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88
Q

What is the name given to the posterior neural tube

A

Notochord

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89
Q

What is the name given to the anterior neural tube

A

Prechordal mesoderm

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90
Q

What is the name of the structure that forms at the ventral midline of the neural tube

A

Floor plate

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91
Q

What is the morphogens secreted by the structure at the ventral midline of the neural tube

A

Sonic hedgehog

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92
Q

Where in the neural tube is Shh expressed in the neural tube

A

Notochord; floor plate

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93
Q

Shh is only expressed in the hindbrain; T or F

A

F – it is also expressed in the forebrain and midbrain

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94
Q

Where is the highest concentration of Shh found

A

Ventral neural tube

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95
Q

What is the result of Shh signalling in progenitor cells

A

Induces the expression of transcription factors that confer ventral neural tube identities and ultimate result in the differentiation of those cells into ventral neurons

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96
Q

Opposing gradients of Shh and which other morphogen act together to give the dorsal-ventral patterning of the notochord

A

BMP

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97
Q

Recall the sonic hedgehog signalling pathway

A

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

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98
Q

Roughly when does a daughter cell decide on its fate in the developing nervous system

A

Immediately after cell division

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99
Q

Neural cells are capable of giving rise to which cells

A

Neurons and glia

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100
Q

What type of signalling exists between pairs of cells in the proneural cluster

A

Juxtacrine

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101
Q

What are the names of the proneural genes being expressed by the proneural cluster and are needed for the expression of delta

A

Archaete; scute

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102
Q

Expression of proneural genes means that a cell is competent to become a neuron; T or F

A

T

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103
Q

Neuroblast cells are the simplest type of neurons found in Drosophila; T or F

A

T

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104
Q

What is the primary fate of cells in the proneural cluster

A

Neuroblasts

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105
Q

What is the secondary fate of cells in the proneural cluster

A

Epidermis

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106
Q

What is the name given to a group of cells that have equal potential

A

Equivalence group

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107
Q

Which process results in the formation of neuroblasts and neurectoderm from the proneural cluster cells

A

Lateral inhibition

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108
Q

How many of the 8 cells in the proneural cluster become neurons

A

1

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109
Q

Define lateral inhibition

A

Induction often used to make initially similar cells different from one another

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110
Q

What signalling pathway leads to the lateral inhibition in the proneural cluster

A

Delta-Notch signalling pathway

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111
Q

Which gene product in this lateral inhibition pathway acts as the inhibitory signal and directs cells to their primary fate

A

Delta

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112
Q

What is seen in delta and notch -/- mutants

A

All proneural cluster cells become neurons

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113
Q

The expression of which two transcription factors involved in the delta-notch signalling pathway leads to the downregulation of achaete and scute

A

Enhancer of split; suppressor of hairless

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114
Q

What is the result of a downregulation of achaete and scute

A

Downregulation in delta expression

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115
Q

What transcription factors are activated by achaete and scute that are involved in specifying neuronal differentiation

A

Neurogenin

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116
Q

The levels of which gene product signalling is responsible for controlling the levels of SuH and Espl

A

Notch signalling

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117
Q

Describe the delta-notch signalling pathway

A

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.

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118
Q

Where would you expect to find the highest concentrations of BMP and Wnt in the developing neural tube

A

Dorsally

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119
Q

Where would the GliA gradient be at its highest

A

Ventrally

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120
Q

The Shh and GliR gradient will be highest at the dorsal side of the embryo; T or F

A

F – The GliR gradient will be at its highest at the dorsal end but the Shh gradient is highest ventrally

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121
Q

What two types of cells do neuroepithelium in the ventricular zone give rise to

A

Neurons that move laterally; radial glia that are retained at the ventricular zone and extend lateral projections to the pial surface

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122
Q

Explain interkinetic nuclear migration

A

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

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123
Q

Neuroepithelial cells divide asymmetrically; T or F

A

F – they divide symmetrically generating two identical daughters

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124
Q

Radial glia divide asymmetrically; T or F

A

T

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125
Q

What do the daughter cell of radial glia become

A

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

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126
Q

Discuss the fates of the two daughter cells produced by the neuroepithelium

A

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

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127
Q

What developmental abnormality is the result of migration issues in the developing brain

A

Lissencephaly – caused by radial glia not forming the scaffold or by the neuron not migrating properly

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128
Q

What is the equivalent structure to the lumen of the spinal cord in the brain

A

Ventricles/ventricular zone

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129
Q

What structure do early post-mitotic cells in the cerebral cortex form

A

Pre-plate

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130
Q

What cell types make up the early structure in the developing cortex

A

Cajal-Retzuis cells and subplate cells

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131
Q

What structure later forms in development of the brain that provides the basis for the layers that define the cortex

A

Proper cortical plate

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132
Q

Cajal-Retzuis cells are the first post-mitotic cells; T or F

A

T

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133
Q

Cajal-Retzuis cells project long vertical projections; T or F

A

F – long sideways projections

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134
Q

What large protein is secreted by the Cajal-Retzuis cells and what is its role

A

Reelin – role in causing/preventing neuronal migration

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135
Q

Newly born layers of the cortex are formed deeper in; closer to their progenitors; T or F

A

F – newly born cells of the cortex form on the outside

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136
Q

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

A

T

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137
Q

Early cell migration is along the scaffolding provided by the radial glia but later in development; some cells migrate tangentially; T or F

A

T

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138
Q

Where does the cerebellum form

A

At the root of the 4th ventricle

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139
Q

Daughters of which cells remain in the hindbrain and become neurons of the cerebellum

A

Rhombic lip cells

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140
Q

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

A

T

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141
Q

Purkinje cells are a type of radial glia; T or F

A

T – they send long projections towards to lumen

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142
Q

Purkinje cells secrete BMP and Wnt which cause the EGL cells to proliferate; T or F

A

F – they secrete Shh which has that effect

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143
Q

Around birth cells in the EGZ start it differentiate into neurons but migrate inwards along the Purkinje cells scaffold; T or F

A

T

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144
Q

Which cells that once migrated out from the ventricular zone give rise to the entire peripheral nervous system

A

Neural crest cells

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145
Q

What type of sensory receptors can be found in C.elegans

A

Mechanoreceptors for gentle and harsh body touch

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146
Q

In C.elegans; where can we see clustering of ganglia

A

Pharyngeal region

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147
Q

What type of cell is recepsonsible for mechanoreception in C.elegans

A

Touch cell

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148
Q

Discuss the touch cell lineage

A

Q cells give rise to Q1a and Q1p cells. Q1p cells give rise to touch cell and an interneuron

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149
Q

Which transcription factors are needed to induce a touch cell fate

A

UNC-86 and MEC-3

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150
Q

Which touch cell specific genes are switched on by the activity of these transcription factors

A

Protofilaments for microtubules; proteins for a specialised extracellular matrix

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151
Q

Touch cell differentiation is an example of cell-autonomous differentiation; T or F

A

T

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152
Q

What are the components of the adult Drosophila nervous system

A

Socket cell; hair cell; sheath cell; sensory neuron

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153
Q

What which cells are cells of the bristle-socket derived from

A

Sensory organ precursors

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154
Q

The differentiation of cells in the Drosophila nervous system is an example of multiple binary decision making by the cells; T or F

A

T

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155
Q

Initial inhibition of Notch signalling in the SPII cell results in which fate

A

Sensory neuron fate

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156
Q

SOP divide symmetrically; T or F

A

F – asymmetrically

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157
Q

Which cytoplasmic factor is unevenly distributed between SPIIa and SPIIb and what is its function

A

Numb – inhibits Notch signalling pathway resulting in the cell achieving a neural fate

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158
Q 
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
A

Thecogen - Sheath Cell
Trichogen - Hair Cell
Tormogen - Socket Cell
Sensory Neuron - Sensory Neuron

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159
Q

What is the name of the repeating unit found in the Drosophila eye

A

Ommatidia

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160
Q

How many of these repeating units are found in the Drosophila eye

A

800

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161
Q

What are the constituent parts in each repeating unit found in the Drosophila eye

A

Rhabdomeres 1-8; 12 accessory cells

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162
Q

What causes rhabdomeres to begin differentiating

A

R8 is induced by Hh coming from the morphogenic furrow. R8 then signals to instruct neighbours to acquire their fates

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163
Q

What is the fate of the 1st proliferating cells that comes in to contact with Hh signalling in the developing ommatidia

A

Rhabdomere 8

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164
Q

Which transcription factor does this first cells to receive Hh signal express

A

Atonal

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165
Q

Pax6 is required for development of the vertebrate eye; T or F

A

T

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166
Q

Recall the pathway in which photoreceptive information reaches the brain

A

Rods/ConesàBipolar CellsàGanglion CellsàOptic NerveàBrain

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167
Q

In the forebrain; the eyes develop at a ventricular zone; T or F

A

T

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168
Q

Each neuronal cell type involved in photoreception have their own ventricular progenitor; T or F

A

F – they all derive from the same progenitors

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169
Q

Neurogenesis of the neurons involved in photoreception occurs in the order in which they receive information; T or F

A

T

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170
Q

Dorsal root ganglia are derived from neural crest cells; T or F

A

T

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171
Q

The ear; lens and olfactory epithelium are derived from placodes; T or F

A

T

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172
Q

What structures do the head placodes give rise to

A

Otic placodes and nasal placodes

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173
Q

From which placode does the ear develop

A

Otic placode

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174
Q

The spinal accessory nerve is placodal; T or F

A

T

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175
Q

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

A

F – vice versa

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176
Q

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

A

Genes have to be used in combination

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177
Q

Explain the Wiess resonance theory when trying to explain axon guidance

A

Cell body of neurons sends out random and diffuse neuronal projections to all targets followed by the elimination of non-functional connections

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178
Q

Explain Sperry’s chemoaffinity hypothesis

A

Neurons undergo directed and specific outgrowth through axons following individual identification tags

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179
Q

Explain the projections seen in the retinotectal pathway

A

Connections are flipped – anterior neurons of retina project to posterior tectum; temporal neurons project to posterior tectum. Dorsal and ventral information is also flipped

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180
Q

Recall Sperry’s 1963 experiment

A

Cut optic nerve and removed temporal retina allowing only nasal axons to regrow

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181
Q

Does the regrowth of nasal retinal axons to the correct tectal location prove that axons are guided by specific cues during development

A

No – because the axons were growing over existing axonal debris during a regeneration; this cant be assumed to be the case in development

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182
Q

Axon pathways are highly stereotyped; T or F

A

T

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183
Q

What evidence is there to suggest the axonal growth cues are located on axons

A

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

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184
Q

Name the earliest source of axon guidance cues

A

Pioneer axons – form an axon scaffold on which later axons project

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185
Q

Pioneer axons do not show stereotyped paths; T or F

A

F

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186
Q

What are the main distinguishing features of the growth cone

A

Filopodia – long projections; lamellae – web-like fanning between projections

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187
Q

What is the difference in actin arrangement in the structures of the growth cone

A

F-actin is bundled together in a polarised fashion in filopodium whereas in the lamellae they are cross-linked to form a net

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188
Q

Explain the actin treadmilling that is seen in the resting growth cone

A

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

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189
Q

Growth cones can turn; T or F

A

F – they don’t turn they reorganise

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190
Q

What happens when the growth cone comes into contact with an attractive cue

A

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

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191
Q

When a growth promoting cue is encountered; two key components lead to filopodial extension; what are these

A

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

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192
Q

What causes neurons to fasciculate only with their own kind

A

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

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193
Q

What inhibitory guidance cue family of molecules are responsible for the collapse of differing growth cones

A

Semaphorins

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194
Q

Inhibitory guidance cue molecules can be membrane-bound or secretory; T or F

A

T

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195
Q

What are the four forces of axon guidance

A

Contact attraction; contact repulsion; chemoattractants; chemorepellents

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196
Q

What is the other name for contact repellent substrate

A

Non-permissive substrates

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197
Q

What is the other term for a permissive substrate

A

Contract attractant

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198
Q

Growth cones cannot adhere to non-permissive substrates; T or F

A

F

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199
Q

Axons can’t grow where they can’t adhere; T or F

A

T

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200
Q

Although growth cones adhere better to collagen than they do to laminin; they grow substantially more on laminin than collagen; T or F

A

T

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201
Q

Permissive factors both allow growth cone attachment and stimulates the growth of the axon; T or F

A

T

202
Q

Permissive factors both define a substrates path in the developing embryo and dictate the direction of axon growth; T or F

A

F – cannot dictate direction

203
Q

Discuss the influence of laminin concentration on axon growth

A

Laminin concentration has no effect on the direction of axon growth although growth only occurs within a particular range of laminin concentrations

204
Q

Semaphorins are permissive factors; T or F

A

F – they are non-permissive

205
Q

Semaphorins are contact repellent forces; T or F

A

T

206
Q

Semaphorin knockout model organisms exhibit several inappropriate axon projections rather than just innervating one target cell; T or F

A

T

207
Q

Growth cones can be kept out of where they aren’t supposed to grow by contact repulsive factor; T or F

A

T

208
Q

Axons can use non-permissive factors alone to grow and reach the target cell; T or F

A

F – they rely on permissive factors too; it’s a balance between permissive and non-permissive factors

209
Q

Permissive and non-permissive factors can tell a growth cone which direction to grow in; T or F

A

F – chemoattractants/chemorepellents provide directional information

210
Q

Growth cones require permissive substrates in which to grow on; T or F

A

T

211
Q

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

A

Ephrins and ephs (receptors)

212
Q

Ephs and ephrins are used to keep axons out of specific areas; what is another role they play

A

Compartmentalise the embryo into discrete domains – i.e. Rhombomeres

213
Q

What is the name of the molecule that is secreted by the floor plate to direct axon growth towards it

A

Netrin

214
Q

What type of axon is guided by the floor plate

A

Commissural sensory relay neurons

215
Q

What is the name of the chemorepellent secreted by the roof plate to direct axon growth away from it

A

BMP7

216
Q

Chemorepellents can induce growth cone collapse; T or F

A

T

217
Q

Give examples of early patterning molecules that are later used to direct axon growth

A

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
Q

How do we create tissue specific knockouts

A

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
Q

What phenomena does the growth cone exhibit that adds the number of different connections it can make without increasing the number of genes

A

Changes its sensitivity to different molecules

220
Q

What happens to commissural sensory relay neurons after they have crossed the midline in the hindbrain

A

Loose their responsivity to chemoattractive Netrins

221
Q

What is the name given to a structure at which axon reprograming occurs

A

Choice point

222
Q

What is seen when commissural sensory relay neurons cross the midline in the spinal cord and why

A

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
Q

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

A

Semaphorins and slits

224
Q

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

A

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
Q

What are the two type of neurons seen in the ventral nerve cord of Drosophila

A

Commissural neurons and longitudinal neurons

226
Q

In the developing Drosophila ventral nerve cord; you can observe commissural and longitudinal neurons; what factor is being secreted by the midline glia cells

A

Netrins

227
Q

What two unusual phenotypes are produced by genetic screens in Drosophila that exhibit problems with the neurons of the ventral nerve cord

A

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
Q

What is the role of robo

A

Robo is a cell surface receptor for the inhibitory protein; slit

229
Q

Where is robo expressed

A

Expressed at high levels in the axons that don’t cross the midline

230
Q

Robo is expressed at high levels at all times in commissural axons; T or F

A

F – it is initially not expressed in high levels in commissural neurons. Only expressed in high levels after crossing the midline

231
Q

What is seen in robo mutants

A

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
Q

Commissureless is only expressed in the commissural neurons; T or F

A

T

233
Q

Commissureless is expressed both before and after crossing the midline; T or F

A

F – after crossing the midline comm is no longer expressed

234
Q

What is seen in comm mutants

A

Robo protein is expressed at high levels in all cells that would normally cross the midline but which now project their axons longitudinally

235
Q

What happens if comm expression is forced in all the neurons in the ventral nerve cord of Drosophila

A

Robo protein expression is lost everywhere resulting in a phenotype identical to that of the robo mutant

236
Q

Explain how comm; robo and slit interact in the invertebrate embryo

A

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
Q

Comm is a transcriptional regulator protein; T or F

A

F – commissureless is a post-transcriptional control protein

238
Q

There is no comm homolog in vertebrates but instead there are 3 robo homologs; T or F

A

T

239
Q

What causes the change in behaviour of axons crossing the midline in vertebrates

A

Robo3/Rig1 inhibits robo1 from acting until the axon crosses the midline

240
Q

In vertebrates; knockout of robo1 leads to a phenotype similar to the netrin knockout; T or F

A

T

241
Q

Pioneer axons establish an axons scaffold on which follower axons later project; T or F

A

T

242
Q

What process allows both axons to stick to the axon scaffold but also allows them to get off when they have reached their targets

A

Control of fasciculation

243
Q

What does fasciculation involve

A

Homophilic binding by cell adhesion molecules

244
Q

What is seen in FasII mutants

A

Defasciculated axons

245
Q

What is seen as a result of FasII overexpression

A

Novel/overfasciculation

246
Q

Levels of fasciclin II are able to influence the amount of fasciculation in the ventral nerve cord of insects; T or F

A

T

247
Q

What are the effects of FasII overexpression on defasciculation

A

Motor axons fail to defasciculate and so miss their target muscles

248
Q

What is meant by dependent synaptogenesis

A

Where the developing structure requires innervation/sensory input in order to drive differentiation

249
Q

Give an example of a structure which shows dependent development

A

Muscle spindles

250
Q

What is meant by independent synaptogenesis

A

Structures develop without the need for innervation/sensory input

251
Q

Give an example of a structure that shows independent development

A

Merkel cells

252
Q

What morphological changes are required by the growth cone and the target postsynapse in order for a synapse to form

A

Growth cones forms a presynapse and the postsynaptic cell develops specialisations in order for a synapse to form

253
Q

What two features can dictate synaptic site formation

A

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
Q

How can the complexity and number of individual synapses be accounted for with only limited cell adhesion molecules

A

Using specific combinations of multiple different cell adhesion molecules together can dictate the specificity needed to form each synapse

255
Q

The neuromuscular junction initially is innervated by multiple neurons before being reduce to single innervation; T or F

A

T

256
Q

What type of receptor is found at the neuromuscular junction

A

nAchR

257
Q

How many subunits does the neuromuscular junction receptor have

A

5 – ?; ?; ? and ?

258
Q

In development the nAchRs are initially diffusely distributed; T or F

A

T

259
Q

What is the term that describes the localisation of nAchRs in the developing neuromuscular junction

A

Focussed distribution

260
Q

How is the localisation of nAchRs achieved in the development neuromuscular junction

A

Transcription of the receptors is upregulated in the nuclei adjacent to the neuromuscular junction whilst down regulated in the peripheral nuclei

261
Q

Gephrin is a cell adhesion molecule; T or F

A

F – it’s a clustering protein

262
Q

What is the role of AchR receptor-inducing activity protein (ARIA)

A

ARIA is released by motorneurons and increases AchR synthesis; in particular the ? subunit. This leads to maturation and clustering of the receptors

263
Q

What is the name of the molecule that stimulates receptor clustering

A

Agrin

264
Q

During development agrin is only expressed in the motor neuron growth cone; T or F

A

F – it is expressed by the motor neuron and by its target muscle

265
Q

Agrin contains multiple regions for interactions with the extracellular matrix and cell adhesion molecules; T or F

A

T

266
Q

What is MuSK and what does it do

A

Muscle-specific kinase is a protein that aids in receptor clustering in the developing neuromuscular junction

267
Q

Explain the mechanism of agrin in receptor clustering

A

Agrin binds to MuSK. MuSK is linked to the AchRs by rapsyn

268
Q

What is seen in agrin knockout mice

A

Death due to malformed neuromuscular junctions causing asphyxia

269
Q

What happens as a result of MuSK knockout

A

Insensitivity to agrin

270
Q

Rapsyn is essential for clustering to occur; without it no clustering occurs; T or F

A

T

271
Q

What are the names of the scientists credited with the discovery of the first neurotrophin

A

Viktor Hamburger and Rita Levi-Montalcini

272
Q

Lots of synapses and neurons fail during development; T or F

A

T

273
Q

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

A

At a later stage in development DRGs at the limb regions are much larger than those in the interlimb regions

274
Q

What is the effect of removal of a chick limb bud on the development of the nervous system

A

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
Q

What is the result of ectopic limb bud grafting in the chick embryo during development

A

Increased survival of synapses and motor neurons in that regions

276
Q

Define neurotrophic

A

A factor that promotes/feeds neurons

277
Q

Define neurotropic

A

A factors that dictates direction of neuronal growth

278
Q

What was the name of the first discovered neurotrophin

A

Nerve Growth Factor

279
Q

Where was NGF isolated from and what is the active subunit

A

Isolated from the submandibular gland – ? active subunit

280
Q

How is ?-NGF secreted

A

As a dimer

281
Q

NGF is only important for the survival of neurites; T or F

A

F – it is also important for survival of the soma and can guide growth cones in vitro

282
Q

What happens once NGF binds to receptors in the periphery

A

The NGF and its receptors are internalised and transported towards the soma via retrograde transport

283
Q

What are the name of the receptors that NGF binds to

A

TrkA and P75-NTR

284
Q

Which receptor does NGF bind to with high affinity

A

TrkA

285
Q

Which receptor does NGF bind to with low affinity

A

P75-NTR

286
Q

What class of receptor is the receptor that NGF binds to with high affinity

A

Tyrosine Kinase Receptor

287
Q

Which receptor that binds NGF can promote cell death or cell survival depending on its context

A

P75-NTR

288
Q

Why aren’t neurotrophins abundant in the developing embryo

A

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
Q

What are the three other main neurotrophins that have been identified

A

Brain-Derived Neurotrophic Factor (BDNF); NT3 and NT4/5

290
Q

Different combinations of neurotrophins are required for the survival of different neurons; T or F

A

T

291
Q

Different populations of neurons are affected by loss of different neurotrophin receptors; T or F

A

T

292
Q

Only some neurotrophins can bind to P75-NTR because of its low affinity for them; T or F

A

F – all neurotrophins can bind to P75-NTR

293
Q

Newly born neurons are always dependant on neurotrophins in order to survive; T or F

A

F – some may have no dependency

294
Q

Arrival of a neuron at its target often coincides with new expression of a particular neurotrophin by the target; T or F

A

T

295
Q

Neurons can change which neurotrophin they need in order to survive throughout development; T or F

A

T

296
Q

All animals require neurotrophins at some point in development; T or F

A

F – Drosophila and C.elegans do not

297
Q

Name three other families of survival factors other than neurotrophins

A

Cytokines; Glia-Derived Neurotrophic Factors (GDNF) and Testosterone

298
Q

Neurons themselves can also synthesise neurotrophins as well as their targets; T or F

A

T

299
Q

What is the primary determinant of neuronal/synaptic survival

A

Electrical activity pre and post-synaptically

300
Q

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

A

T

301
Q

What converts electrical activity into neuronal survival

A

The more active a synapse the more neurotrophin it takes up and thus the more likely to survive

302
Q

The greater the target tissue mass the more neurotrophin that is available to a neuron; T or F

A

T

303
Q

Motor neurons still exhibit cell death despite the fact that the mass of the target tissue is increasing; T or F

A

T

304
Q

Neuronal cell death tends to only occur postsynaptically during development; T or F

A

F – occurs both pre and postsynaptically

305
Q

By what type of cell death do neurons die during development

A

Apoptosis

306
Q

The process of cell death seen in neural development is an active process; T or F

A

T

307
Q

Antinomycin D and cyclohexamide inhibit cell death; T or F

A

T

308
Q

How is the debris produced by neuronal cell death cleared up

A

Macrophage removal and neurotic disintegration

309
Q

By what two pathways can the cell death seen in neuronal development take

A

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
Q

What are the key pro-apoptotic genes

A

Ced 3 and Ced 4

311
Q

What are the key anti-apoptotic genes

A

Ced 9

312
Q

What is the gene responsible for initiation of apoptosis

A

EGL-1

313
Q

What is the name given to the class of mammalian homologues of EGL-1

A

BH3-only proteins

314
Q

The caspases are homologues of the Ced 9 gene; T or F

A

F – caspases are homologues of Ced 3

315
Q

The caspases are pro-apoptotic; T or F

A

T

316
Q

Which caspase is particularly important in development of the nervous system

A

Caspase 3

317
Q

What three things does caspase 3 break down

A

Poly ADP-ribose polymerase; Lamin A and Huntingdin

318
Q

What are the two triggers of developmental apoptosis

A

Lack of trophic support; absence of depolarising stimulus

319
Q

NGF deprival is a likely cause of developmental apoptosis; T or F

A

T

320
Q

Neurotrophins are synthesised and released in a pro form; T or F

A

F – synthesised in a prepro form

321
Q

What does the pre form of neurotrophins do

A

Signal peptide to direct transport

322
Q

The pro portion of neurotrophins is cleaved after release; T or F

A

T

323
Q

ProNGF strongly activates TrkA; T or F

A

F – strongly activates P75-NTR

324
Q

Neurotrophins are mainly released from the apical membrane; T or F

A

F – they are released basally

325
Q

What can trigger the release of neurotrophins

A

Ca2+ levels due to depolarisation or ligand binding

326
Q

Neurotransmitters can act as neurotrophins; T or F

A

T

327
Q

Developmental plasticity comes from our understanding of the plasticity in the mature brain that underlies memory and learning; T or F

A

T

328
Q

Developmental plasticity can be explained by mechanisms similar to that seen in memory and learning; T or F

A

T

329
Q

There is only a loss of synapses during development; T or F

A

F – new synapses are also formed but there is a net loss

330
Q

Coordinated activity of a presynaptic terminal and postsynaptic neurons strengthens the synaptic connections between them; T or F

A

T

331
Q

When two neurons fire at the same time the connection between becomes stronger and they become more likely to fire again; T or F

A

T

332
Q

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

A

F – initially many neurons innervate muscle fibres but this decreases to only a single neuron later in development

333
Q

Explain how we can see the decreasing innervation in skeletal muscle throughout development

A

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
Q

What assumptions does measuring the postsynaptic potential as a result of quantal increase of afferent stimulation require

A

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
Q

The climbing fibres are another example of decreasing convergence seen in development; T or F

A

T

336
Q

To which cells do the climbing fibres of the cerebellum project

A

Purkinje neurons

337
Q

In the mature cerebellum how many climbing fibres synapse with each Purkinje cell

A

1

338
Q

Where in the early stages of development are most of the synaptic connections made

A

At the soma

339
Q

Where are the mature connections between climbing fibres and Purkinje cells made

A

In the dendrites

340
Q

What is significant about the innervation of the eye in the mature layer IV of the visual cortex

A

Striated appearance of alternating innervation by the right and left eye

341
Q

What is the result in sensory deprivation of one particular eye during development

A

Loss of synaptic function in the monocular layer in the regions ipsilateral to the deprived eye

342
Q

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

A

T

343
Q

What occurs as a result of sensory deprivation of both eyes during development

A

Maintenance of binocular and monocular connections from both eyes

344
Q

Synapses from each eye compete with each other for strengthening; T or F

A

T

345
Q

What is meant by silent synapses

A

Intact synapses that are non-functional where stimulation doesn’t result in chemical signalling

346
Q

Where are silent synapses mainly seen

A

Glutamatergic system

347
Q

What is meant by a tetanus; in the brain

A

High frequency stimulus

348
Q

Describe what is meant by paired long-term potentiation

A

Coincident stimulation of a pathway and depolarisation of the target cell leads to a strengthening of the synapse.

349
Q

Long-depression is classically studied in the cerebellum; T or F

A

T

350
Q

How does LTP occur at the cellular level

A

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
Q

What is the most abundant excitatory neurotransmitter in the nervous system

A

Glutamate

352
Q

What is the most abundant inhibitory neurotransmitter in the nervous system

A

GABA

353
Q

Give some examples of modulatory neurotransmitters

A

Neuropeptide (endorphin; encephalin); ATP and opiates

354
Q

Where are glutamate receptors more often found

A

Distal dendrites/dendritic spines

355
Q

Where are the GABA receptors more often found on neurons

A

Proximal dendrites/soma

356
Q

Most receptors are synthesised and inserted into the membrane after synaptogenesis; T or F

A

F – most receptors are made prior to synapse assembly and are stored in transport vesicles before insertion

357
Q

Excitatory neurotransmitters cause hyperpolarisation of neurons; T or F

A

F – they cause depolarisation

358
Q

Opening of Na+ in mature neurons causes depolarisation; T or F

A

T

359
Q

What happens to the magnitude and polarity of the resting potential during development

A

Magnitude increases as it gets more negative – shifts towards hyperpolarisation

360
Q

What causes the resting membrane potential to shift negatively during development

A

New channel and pump expression

361
Q

Astrocytes increase and causes a decrease in the [K+]EC during development; T or F

A

T – this accounts for the negative shift in resting membrane potential

362
Q

What causes the decrease in the input resistance of neurons during development

A

More current (ions) can flow across the membrane due to the synthesis and insertion of new channels

363
Q

What is meant by the neuronal membrane time constant

A

The membrane time constant is a measure of how quickly the potential of the membrane can change and spread.

364
Q

What happens to the neuronal membrane time constant during development and why

A

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
Q

What is meant by neuronal membrane capacitance

A

The ability of the membrane to store charge

366
Q

Why does the capacitance increase during development

A

Increased size of the neurons

367
Q

Action potentials appear early in development; T or F

A

T

368
Q

What is significant about the duration of the action potential in early development

A

It has quite a long duration

369
Q

What ion channel underpins depolarisation and is thus responsible for the early action potential and how is this different to the mature neuron

A

In early development Ca2+ channels underpin the action potential as opposed to the Na+ channels that dictate it later

370
Q

Tetrodotoxin is an inhibitor of voltage-gated Ca2+ channels; T or F

A

F – it inhibits voltage-gated Na+ channels

371
Q

What is the difference seen in the action potentials that are Ca2+ and Na+ dependent

A

The Na+ action potentials are much shorter

372
Q

What are delayed rectifier potassium channels and how do they influence the generated action potentials

A

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
Q

Different neurons refine the way they respond to synaptic activity by incorporation of different channels into the membrane; T or F

A

T

374
Q

High voltage activated Ca2+ channels appear first in development; T or F

A

F – Low voltage activated Ca2+ channels appear first

375
Q

Where do high and low voltage activated Ca2+ channels tend to be located

A

Lva Ca2+ channels are often found on the soma whereas hva Ca2+ channels are more commonly found at axon terminals

376
Q

Lva T-currents tend to control membrane excitability whereas hva N and L-currents control neurotransmitter release; T or F

A

T

377
Q

Later in development lva currents tend to disappear; T or F

A

T

378
Q

Lva currents exhibit the property of rapid inactivation; they open and close quickly; T or F

A

T

379
Q

What changes can occurs to receptors through the course of development

A

Changes in subunit composition; localisation; efficacy and also changes in types of receptor populations expressed

380
Q

Where on the axon are glutamate receptors more commonly found

A

On the dendritic spines

381
Q

Where on the axon are GABA receptors more commonly found

A

On or near to the soma

382
Q

What are the two types of GABA receptor and what is the main difference

A

GABAA – ionotropic; localised to the soma. GABAB – GPCR that ends up at the axon terminal

383
Q

Which GABA receptor controls neurotransmitter release

A

GABAB

384
Q

Which GABA receptor controls transcription

A

GABAA

385
Q

How is it that GABA receptors act as excitatory receptors in early development

A

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
Q

What causes the switching of GABA signalling from excitatory to inhibitory

A

Insertion of NKCC2 channel into the membrane decreases intracellular Cl- concentration via efflux from the neurons

387
Q

Which classes of animals have an increased regeneration capacity

A

Amphibia and reptiles

388
Q

What causes Xenopus tadpole tail regeneration during the critical refractory period

A

Triggered by BMP signalling

389
Q

Organisms that show regeneration capacity all use similar mechanisms to do so; T or F

A

F – each organism uses a different strategy to regenerate

390
Q

Regeneration can occur independent of innervation; T or F

A

F – regeneration of tissue is dependent on nerve regeneration

391
Q

What are the two main types of nerve injury

A

Crush injury; severing injury

392
Q

Which type of nerve injury tends to be easier to repair and why

A

Crush injuries are usually easier to repair as the basal lamina and extracellular matrix is usually still intact

393
Q

If injury to a neuron occurs near to the soma the neuron is more likely to die; T or F

A

T

394
Q

What happens if an injury to a neuron occurs in the proximal axon

A

Reorganisation and re-expression of immature features such as tubulins

395
Q

What is the name of the process commonly seen in response to damage to the distal axon; in particular; trauma

A

Wallerian degeneration

396
Q

Denervation of a muscle will result in atrophy; T or F

A

T

397
Q

What happens to the receptors on muscle if it becomes denervated

A

They reverse to embryonic types

398
Q

Level of muscle-specific kinase rapidly drop in response to muscle denervation; T or F

A

F – they increase

399
Q

How can atrophy of a muscle be prevent should it become denervated

A

External electrical input

400
Q

Regeneration of a neuron involves the mitosis of Schwann cells and the supply of growth factors; T or F

A

T

401
Q

What is the name of the structure formed by rows of Schwann cells that guides axon regrowth

A

Bands of Bunger

402
Q

What is meant by sprouting and how can this contribute to regeneration

A

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
Q

The basal lamina and extracellular matrix usually remains intact in crush injuries; T or F

A

T

404
Q

Why do sutured nerves no regrown accurately

A

Disruption of the basal lamina and extracellular matrix

405
Q

Why are spinal cord injuries difficult to treat

A

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
Q

What is the name of the family of inhibitory proteins present in myelin that prevent axon regrowth

A

NOGO

407
Q

Where is nogo-a commonly found

A

Oligodendrocytes and developing neurons

408
Q

What is the result of nogo-a knockout

A

Partial decrease in inhibition of axon regrowth

409
Q

Antibodies to nogo improves regeneration of the spinal cord; T or F

A

T

410
Q

If inflammation is minimised from an early period in a damaged motor neuron there is an increased chance of regeneration; T or F

A

T

411
Q

Which cell types are responsible for the limitations in regeneration of neurons

A

Glia – astrocytes

412
Q

Name a class of secreted inhibitory molecule other than nogo that prevents regeneration

A

Chondroitin sulphate proteoglycans

413
Q

Which nerve is commonly used as a spinal cord bridge to bypass lesions

A

Sural nerve

414
Q

Stem cell transplant can also be used to aid in the regeneration of nervous tissue; T or F

A

T

415
Q

Which brain structure provides the highest level of motor control

A

Primary motor cortex

416
Q

What structure do the corticospinal tracts project to from the spinal cord

A

Primary motor cortex

417
Q

Which structure represents the middle level of motor control

A

Brainstem

418
Q

Which region(s) of the brainstem controls parts of the distal limb

A

Lateral descending brainstem

419
Q

The brainstem is important in goal orientated movements of the hand and arm; T or F

A

T

420
Q

The lowest level of motor control comes from which central nervous system structure

A

Spinal cord

421
Q

What is the most common type of reflex

A

Polysynaptic reflexes

422
Q

Name an example of each type of reflex

A

Monosynaptic – knee-jerk reflex. Polysynaptic – stretch reflex

423
Q

The spinal cord contains the neuronal circuits involved in mediation of reflexes; T or F

A

T

424
Q

What is the simplest type of reflex

A

Monosynaptic – contain just sensory and motor neurons

425
Q

Electrical stimulation of the primary motor cortex results in complex coordinated movements; T or F

A

F

426
Q

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

A

T

427
Q

What two other centres coordinate the response of the primary motor cortex and lead to complex movements

A

Basal Ganglia and Cerebellum

428
Q

What is the main difference between the two centres that coordinate motor information from the primary motor cortex

A

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
Q

Error correction signals sent directly to the muscled from the cerebellum only occur in emergency situations; T or F

A

T

430
Q

What are the 4 brain areas that constitute to the basal ganglia

A

Caudate nucleus; putamen (striatum); substantia nigra and subthalamic nucleus

431
Q

The cerebellum accounts for 40% of the neurons in the nervous system; T or F

A

T

432
Q

Via what structure do the basal ganglia project through to pass information to the motor cortex

A

Thalamus

433
Q

How do the basal ganglia and cerebellum influence output from the primary motor cortex

A

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
Q

What is meant by the subcortical loop

A

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
Q

How was the motor cortex initially discovered

A

Electrical stimulation experiments revealed certain regions of the brain that once stimulated lead to certain actions in the patient

436
Q

Which structure is also referred to as Brodmann’s area 4

A

Primary motor cortex

437
Q

Where is the primary motor cortex located and thus what can it be referred to as

A

Lies anterior to the central sulcus and is thus sometimes called the precentral gyrus

438
Q

The regions found by Wilder Penfield that when stimulated lead to no observable response were later determined to be what

A

Supplementary areas that support primary regions of the brain

439
Q

What is meant by the motor homunculus

A

Proportional representation of the anatomical structures based on the amount of motor cortex occupied

440
Q

Which anatomical structures represent the largest proportional innervation by the motor cortex

A

Fingers; hands and face

441
Q

Why is the control of the hands by the motor cortex spread out over large areas

A

So that localised neuronal damage to the motor cortex minimises the loss of function to the hands

442
Q

What happens to the area in the spinal cord associated to a region of the motor cortex that suffers legions or damage

A

Subsequent degeneration is also seen in the area of the spinal cord

443
Q

Electrical stimulation of the primary motor cortex can result in the production of complex or learnt movements; T or F

A

F – requires inputs from many different centres

444
Q

What are the first neurons in the motor cortex

A

Upper motor neurons

445
Q

Which motor neurons are the longest

A

Upper motor neurons

446
Q

What is meant by decussation and where do the upper motor neurons do this

A

Decussation is where the neurons cross the midline and occurs at the pyramids in the brainstem

447
Q

Which motor neurons do upper motor neurons synapse with

A

Lower motor neurons

448
Q

Interneurons often link the upper and lower motor neurons; T or F

A

T

449
Q

What is the role of the upper motor neurons

A

Panning; initiating and directing movements

450
Q

Some upper motor neurons originate from higher motor centres; which are these

A

Nucleus ruber; vestibular nucleus; superior colliculus and the reticular formation

451
Q

What four features do upper motor neurons regulate

A

Muscle tone; postural muscles; maintenance of balance and the orientation of the head and body

452
Q

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

A

Final common pathway

453
Q

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

A

F – both pathways leads to action potential generation

454
Q

With what two structures does the basal ganglia interact with in order to regulate motor control

A

Provides input to UMNs and connects with the motor cortex

455
Q

The cerebellum connects to the cortex via the thalamus as well as connecting to the brainstem; T or F

A

T

456
Q

What is the basal ganglia’s influence on motor control

A

Helps to initiate and terminate movement whilst supressing inappropriate movement

457
Q

The basal ganglia help to establish the normal level tone; T or F

A

T

458
Q

Tourette’s syndrome has been linked to damage to the basal ganglia; T or F

A

T

459
Q

The cerebellum controls the activity of UMNs; T or F

A

F – it controls UMN activity

460
Q

How does the cerebellum respond if there is a difference in intended and actual movements

A

Sends an error signal either to the motor cortex or to the muscle itself to reduce the discrepancy.

461
Q

Rod cells are used in central vision and are photopic; T or F

A

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
Q

List some distinguishing features of rod cells.

A

(High) convergence and sensitivity; low resolution and visual acuity and function best in low intensities

463
Q

What are the four types of retinal neurons

A

Bipolar; ganglion; horizontal and amacrine cells

464
Q

Are ganglion cells 1st or 2nd order neurons

A

2nd order

465
Q

Are bipolar cells 1st or 2nd order neurons

A

1st order

466
Q

What is the main role of horizontal cells

A

Enhance contrast and intensity

467
Q

What is meant by duplicity theory

A

Cant have high sensitivity and high resolution in single receptor

468
Q

Rod cells contract ganglion cells directly; T or F

A

F – they are connected via amacrine and horizontal cells

469
Q

What are the two main photoreceptive pigments and in which photoreceptors are they found

A

Rhodopsin – rods Photopsin – cones

470
Q

In the dark the rod cell is depolarised causing and inhibition of the bipolar cells; T or F

A

T

471
Q

In photoreception; glutamate acts as an excitatory neurotransmitter; T or F

A

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
Q

What are the two types of bipolar cells and the differences

A

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
Q

What three types of stimuli is the visual system adapted to recognise

A

Food stimuli; predators and mates

474
Q

What are the three levels of processing in the visual system

A

Positive feedforward; negative feedback and negative feedforward

475
Q

What is meant by the optic nerve being an information bottleneck

A

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
Q

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

A

b; e; a; f; c; d

477
Q

The right hemifield of vision activates the right side of the brain and vice versa; T or F

A

F – the right hemifield activates the left side of the brain

478
Q

What is the main function of the retina

A

Image acquisition

479
Q

Although the majority occurs in the visual cortex; what is the name of the other brain centre that processes visual information

A

Lateral geniculate nucleus

480
Q

What are the two different visual pathways in the brain and what are the differences between them

A

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
Q

What is the function of the pupil

A

Regulate the amount of light that falls on the retina

482
Q

What is the role of the lens

A

To focus light on the fovea

483
Q

The fovea is the region of the retina with the highest visual acuity; T or F

A

T

484
Q

The majority of the retina consists mostly of rods; T or F

A

T

485
Q

What are the two types of photoreceptors

A

Rods; cones

486
Q

How many layers of synapses are present in the visual cortex and what are their names

A

Inner plexiform layer; outer plexiform layer

487
Q

Which type of photoreceptor is most active in dim light

A

Rods

488
Q

Which type of photoreceptor is most active in bright light

A

Cones

489
Q

Stimulation by light results in a hyperpolarisation of the photoreceptors; T or F

A

T

490
Q

What is the name of the synapses formed in the visual system that allows permanent glutamate release

A

Ribbon synapses

491
Q

Photoreceptors usually trigger action potentials; T or F

A

F – they don’t spike and have graded responses

492
Q

In the dark the photoreceptors are constantly releasing glutamate; T or F

A

T

493
Q

Horizontal cells inhibit photoreceptors; T or F

A

T

494
Q

Rod cells connect directly to ganglion cells; T or F

A

F – they connect via bipolar and amacrine cells

495
Q

What is significant about ganglion cell dendritic fields and how this implements their ability to process fine detail and movement

A

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
Q

Visual neurons can either be saturated or not sensitive enough; T or F

A

T

497
Q

What happens at high contrast if there was no visual adaptation

A

All the neurons would be saturated

498
Q

What happens at low contrast is the was no visual adaptation

A

All the neurons wouldn’t fire

499
Q

What are the strategies used by visual neurons to avoid saturation

A

Desensitisation; hyperpolarisation

500
Q

Adaptation to changes in temporal contrast is very fast; T or F

A

F – it is slow

BMS236 - Toby (1 decks)

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