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BMS236 Building Nervous Systems > _ > Flashcards

_ Flashcards

1
Q

In what ways is the PNS classified?

A

How they connect to CNS - Cranial/Spinal nerves
Direction of propagation - Afferent/Efferent
Motor neurons’ target effectors - Somatic/Autonomic (symp/parasympathetic)

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2
Q

What has research shown us about fish brains?

A

= tube that carries nerve APs from distal parts of the body to a central point.
Mechanical and unconscious brain

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3
Q

What has research shown us about reptilian brains?

A

Nerves sorted into specialised modules (e.g. light-sensitive –> vision)
Mechanical and unconscious brain

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4
Q

What has research shown us about mammalian brains?

A

Hypothalamus - reaction to stimuli
Thalamus - integration of vision, smell + hearing
Limbic system - emotions (but unconscious)
Amygdala, hippocampus - crude memory

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5
Q

What has research shown us about human brains?

A
  • Enlargement of areas associated w/ thinking, planning + communicating
  • Larger cortex, pushing cerebellum to current position
  • Flat forehead due to skull bones pushed outwards
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6
Q

What are Brodmann’s areas of the brain?

A 
= systematic map of the brain based upon cell types. E.g.
Broca's area (44)
Wernicke's area (22)
Primary motor cortex (4)
Primary visual cortex (17)
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7
Q

What are Broca’s and Wernicke’s areas of the brain?

A

Broca’s area = produces speech by controlling muscles involved

Wernicke’s area = grammatical rules for language

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8
Q

What is anatomical modularity?

A

Connecting modules that work together to complete tasks/functions

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9
Q

Why are some parts of the brain hard-wired to become allocated to a specific task/function?

A

Evolution has made it essential that humans:

- Vision, - Ability to move precisely, - Speech

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10
Q

Why can humans perform tasks that have no evolutionary advantage (e.g. play music)?

A

Could be to attract opposite sex - reproduction to pass on genes

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11
Q

How does a musician’s brain differ?

A

Increased size - neurons sprout new connections to allow for complex movements involved
- Shows plasticity

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12
Q

What is brain plasticity?

A

Ability to produce new and destroy old connections between neurons in response to physical demands

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13
Q

Why is the human brain so powerful?

A

10^11 neurons, each w/ 1000-10,000 synapses. ~10^14 connections in the human brain

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14
Q

How do sponges show signs of an early NS?

A

Water flow regulated by myocytes = specialised muscle cells which respond to stretch

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15
Q

Characteristics of primordial NS?

A

Appearance of neurons - first neurons probably sensorimotor cells –> Began to differentiate down a nerve (neuronal) pathway instead of skin (epidermal) pathway

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16
Q

Characteristics of a hydra NS?

A

Derivation of diff types of neurons from ectoderm - MNs which receive inputs from sensory neurons
Interneurons which lie between sensory and MNs

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17
Q

Characteristics of a worm’s NS - how more complex vs. Hydra?

A
  • Gangliation
  • Cephalisation (formation of brain –> diff in A/P axis)
  • Bilateral symmetry
  • Fasciculation = nerves form bundles
  • Entire NS is internal
18
Q

How segmented worms’ NS evolved?

A

Fusion of longitudinal nerve cords

Brain evolved to regulate feeding - sense food and ability to grab it

19
Q

How C. Elegans NS has evolved?

A

Optic lobes
Beginning of proper brains
Formation of neuroblasts

20
Q

How vertebrates NS has evolved?

A
  • All have common body plan; early NS similar across all families
  • NS forms from ectoderm that would otherwise be epidermis
  • NS dorsal (vs. ventral in invertebrates); in evolution, head turned around so ventral things became dorsal
21
Q

Common features of vertebrate NS (e.g. Xenopus, chick, humans)?

A

Neural cells do not delaminate.

Stay together as layer = neuroepithelium = neural plate

22
Q

Cell differentiation definition?

A

= process by which cells become different from one another and acquire specialised properties.
Governed by gene expr. - can be changed in response to morphogens/t.f.s

23
Q

What is BMP?

A

= bone morphogenetic protein found in vertebrates; causes cascade that will cause differentiation of ectoderm into skin. Been conserved through evolution

24
Q

What is chordin?

A

= BMP antagonist (inhibits BMP signalling). Found in vertebrates

25
Q

How does the neurogenic region arise?

A

BMP signalling is inhibited by chordin (vertebrates)

26
Q

What is the homologue of BMP and chordin in insects (invertebrates)?

A 
Dpp = BMP
Sog = Chordin

Sog inhibits Dpp, causing the cells to become the neurogenic region.

27
Q

Where in the embryo does the neurogenic region dev?

A

Chordin and BMPs diffuse from opp. ends - where they meet is where the n.t. develops

28
Q

What is the pathway for ectoderm differentiating into epidermis?

A
  1. BMP binds to BMP R, leading to a 2ndary signal causing SMAD(1) phosphorylation
  2. SMAD translocates to nucleus and upregulates epidermalising t.f.s (Msx1, GATA1, Vent)
  3. Epidermalising t.f.s act on further promoters which activate genes (e.g. LEF1) leading to epidermal differentiation [Sox not repressed]
29
Q

What is the pathway for ectoderm differentiating into neural [plate] tissue?

A
  1. BMP inhibited (due to antagonist)
  2. No SMAD phosphorylation
  3. Upregulation of diff - neuralising t.f.s (e.g. Pou, SoxD)
    that further activate other t.f.s (e.g. Neurogenin, NeuroD)
  4. Neural differentiation pathway —> neural plate cell
30
Q

What is neurulation?

A

= when the neural plate rolls up to form the neural tube

31
Q

What is the Spemann organiser?

A

= specialised part of the mesoderm that expr. t.f.s (Gsc) expr. antagonists of BMPs (e.g. chordin), which diffuse into the ectoderm and bind w/ BMP to inhibit it —> formation of neural plate in ectoderm neighbouring the organiser

32
Q

What decides the location of the organiser in the mesoderm?

A

Low [nodal protein] leads to ventral mesoderm

High [nodal protein] gives the organiser

33
Q

What happens to organiser cells in the mesoderm?

A
  • Differentiate into: 1. Anterior endoderm 2. Prechordal mesoderm 3. Notochord (= chordamesoderm)
  • Involutes, intercalates and undergoes convergent extension
  • Forms the midline of the neural plate
34
Q

Give experimental evidence for neural induction?

A
  1. A donor organiser was grafted onto a host newt
  2. Found that a “twinned” embryo developed - w/ a 2ndary neural axis
  3. 2ndary neural tube was derived from host tissue, therefore it was induced from the host ectoderm in response to signals from the donor organiser
  4. The prechordal mesoderm and notochord were donor-derived, so they are formed from the donor organiser
35
Q

How were BMP inhibitors discovered?

A
  1. Extracted all mRNA from organiser cells
  2. Reverse transcription from mRNA to cDNA
  3. cDNA tested to look for protein (coded) that mimics organiser’s ability to induce a 2ndary neural plate
36
Q

Give experimental evidence for the fate of the organiser (Henson’s node)?

A
  1. Cut the node and culture
  2. Node develops into long, rod shape - i.e. the notochord (at posterior end) and prechordal mesoderm develops at anterior end
37
Q

What is the activation-transformation model?

A

= idea that neural-inducing molecules, e.g. BMP inhibitors (e.g. chordin) and Wnt inhibitors only remain in the prechordal mesoderm - i.e. the part of organiser that involuted first.
Later Node expr. Wnt, FGF and RA which posterialise initially anterior tissue

38
Q

When establishing A/P axis (regional identity) in neural plate, what is expr. on anterior side?

A

BMP and Wnt antagonists

39
Q

When establishing A/P axis (regional identity) in neural plate, what is expr. on posterior side?

A

Wnt, FGF and RA = promote posterior identity and growth

40
Q

Developing invertebrate NS vs. vertebrate NS position and name? What do they have in common?

A

Invertebrate = ventral nerve cord
Vertebrate = dorsal neural tube
Specialised midline in common.

BMS236 Building Nervous Systems (1 decks)

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