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Cellular and Molecular Neuroscience > Neuronal Networks > Flashcards

Neuronal Networks Flashcards

1
Q

Connectomics

A

study of the brain’s structural and functional connections between cells

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2
Q

Allen Brain Atlas

A

Brain maps of gene expression in human and mouse brains
serves as dataset for further research to compare
10,000 different brain cell types

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3
Q

Neuronal complexity

A

complexity is related to the requirements of the organism

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4
Q

Caenorhabditis elegans

A

Transparent nematode
unsegmented pseudocoelomate and lacks respiratory or circulatory systems
302 neurons
basic organism + behaviours e.g. chemo/thermotaxis and mechanotransduction

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5
Q

Vision in forager ants

A

Detect polarised light to find their way home

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6
Q

Rhabdomeric receptors

A

contains visual pigment
structure is tubules of rolled up membrane (microvilli)
upward dorsal rim receptors match w celestial e-vector pattern

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7
Q

ocelli

A

small eyes next to apposition eyes that detect polarised light

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8
Q

apposition compound eyes

A

type of compound eye found in ants

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9
Q

ommatidia

A

unit of compound eye

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10
Q

e-vector

A

electrical/euclidean vector

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11
Q

Polarised light

A

light waves in which the vibrations occur in a single plane

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12
Q

Sherrington study 1950s

A

It was the introduction of electron
microscopy that led to two groups
describing the anatomical basis of synapses
in the mid-1950s

Both groups described the small vesicles
close to the broadening of the presynaptic
element 20–60 nm in diameter and the
extracellular space between the two
swollen membranes of some 20 nm

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13
Q

Katz et al. 1960s

A

experiment of neurotransmitter presence in synapse as form of transmission
miledi used tetrodoxin to stop APs on either side of synapse
still a response(small) - release of transmitter

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14
Q

Steps of chemical synaptic transmission

A
  1. AP initiation
  2. Depolarisation of terminal
  3. Fusion of vesicles to membrane
  4. Diffusion
  5. Binding to receptors
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15
Q

role of calcium in vesicle fusion

A

When an action potential reaches the presynaptic terminal, voltage-gated calcium channels on the plasma membrane of the terminal open, allowing calcium ions to flow into the cell. This influx of calcium triggers a series of events that ultimately leads to the fusion of synaptic vesicles with the plasma membrane, releasing their contents into the synaptic cleft.

Specifically, calcium ions bind to a protein called synaptotagmin, which is located on the surface of the synaptic vesicle. This binding causes synaptotagmin to undergo a conformational change, which in turn triggers the recruitment of other proteins involved in the fusion process, such as SNAP-25 and synaptobrevin. These proteins work together to form a complex that brings the synaptic vesicle into close proximity with the plasma membrane, leading to the fusion of the vesicle with the membrane and the release of neurotransmitters into the synaptic cleft.

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16
Q

astrocyte

A

type of glial cell
wrap around synapse to limit outer diffusion
containers transporters to clear neurotransmitters e.g. glutamate, GABA
Contain glucose/glycogen to fuel neurons in shortages
synaptic modulation

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17
Q

long term potentiation

A

a process involving persistent strengthening of synapses that leads to a long-lasting increase in signal transmission between neurons

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18
Q

release probability

A

low and high release probability synapses
more VDCCs = higher probability

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19
Q

kiss and run model

A

More likely to be involved in neurotransmitter transmission
Partially empty vesibles present in EM
Porosomes present in synaptic bulbs

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20
Q

full fusion collapse model

A

complete fusion/collapse into membrane
slow dilation possibly for small molecules to be released quickly
Thoreson et al. (salamander photoreceptors)
Larger fusion pores - for bigger molecules/peptides

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21
Q

Diffusion equation

A

t = (Δx^2)/2D
t = diffusion time
x = distance across the cleft
D = diffusion coefficient for the transmitter

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22
Q

Porosomes

A

Permanent structures that act as a dock for transient vesicles
SNARE proteins involved

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23
Q

SNAREs

A

Proteins involved with membrane fusion at neural synapses
t and v SNARE complexes work together

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24
Q

Synaptic conductance (Gsyn)

A

The degree to which the synapse conducts electricity, calculated as the ratio of the current which flows to the potential difference present
Determined by 3 things: Number of channels(Nc), Single channel conductance(g), open probability (Popen)
Gsyn = g(Nc x Popen)

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25
Q

Duration of Gsyn determined by?

A

Transmitter profile - how long transmitter stays in cleft
Channel Kinetics

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26
Q

SM proteins

A

Work with SNARE to promote membrane fusion
Coagonist of SNARE
Sec1/Munc18 protein

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27
Q

Excitatory post-synaptic potentials

A
  • Makes it more likely to fire an AP
  • temporary depolarisation of postsynaptic membrane
  • flow of positive ions into cell
  • ligand gated ion channels responsible for this
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28
Q

Inhibitory post-synaptic potentials

A
  • Makes it less likely for AP to fire
  • inhibitory neurotransmitters bind to postsynpatic membrane
  • induced change in permeability
  • flow of negative ions into cell/positive ions out
  • negative potential increasess = closer to HYPERPOLARISATION
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29
Q

Spatial Summation

A

Spatial summation, on the other hand, is a process by which the strength of a signal is enhanced by the combined activity of multiple neurons that are spatially close to each other. In the context of brain waves, spatial summation refers to the phenomenon where the amplitude or power of a brain wave is increased by the simultaneous activity of multiple neuronal populations that are spatially close to each other.

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30
Q

Glutamate

A

Main excitatory neurotransmitter
Dianion amino acid
2 types of receptors: Ionotropic and metabotropic
Ionotropic: AMPA, NMDA, Delta and Kainate
Metabotropic: Groups 1,2 and 3 e.g mGlur

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31
Q

Ionotropic receptors

A

Ligand gated ion channels
Open to allow ions such as sodium, potassium and calcium
Specialised for fast excitation

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32
Q

Metabotropic

A

Second messneger system
Slow, sustained excitatory response
G-protein couple receptors
they are involved in learning, memory, anxiety, and the perception of pain. They are found in pre- and postsynaptic neurons in synapses of the hippocampus, cerebellum and the cerebral cortex

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33
Q

NMDA receptor

A

NMDA is its agonist
Blocked by Mg2+ and Zn2+ ions
Glutamate binding receptor
Heterotetramer

Activation of NMDA receptors results in the opening of the ion channel that is nonselective to cations

NMDARs require the binding of two molecules of glutamate or aspartate and two of glycine

More permeable to Ca2+ to cause activation of genes

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34
Q

AMPA receptor

A

Tetramer with each subunit having a binding site for glutamate
Opens to allow cations through when activated

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35
Q

Kainate receptor

A

Heterotetramer
Permeable to sodium and potassium ions
Slight permeability to Ca2+
Metabotropic (G-protein cascades) and ionotropic

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36
Q

Agonist

A

Compound that can bind to and cause activation of a receptor, thus mimicking an endogenous ligand or neurotransmitter

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37
Q

GABA

A

Main inhibitory neurotransmitter
gamma-aminobutyric acid
Synthesised by precursor glutamate

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38
Q

GABA receptors

A

GABAA in which the receptor is part of a ligand-gated ion channel complex - allow flow of chloride ions into cell e.g. alpha, beta, gamma, delta, pi, rho and theta subunits

GABAB metabotropic receptors, which are G protein-coupled receptors that open or close ion channels via intermediaries (G proteins) e.g. GABABR1/2 subunits

39
Q

GABAergic neurons

A

Neurons that produce GABA as their output

40
Q

GABA in immature and mature neurons

A

Depolarises immature neurons as 2Cl- in and 1Cl- out with sodium and potassium being let in as well

Inhibits mature neurons by maintaining Cl- concentration at equilibrium - therefore can’t depolarise

Close to hyperpolarisation but doesn’t quite get there

DEVELOPMENTALLY REGULATED

Cl- can alter day night cycle in certain nuclei

41
Q

Benzodiazapines

A

benzodiazepine binding acts as a positive allosteric modulator by increasing the total conduction of chloride ions across the neuronal cell membrane when GABA is already bound to its receptor. This increased chloride ion influx hyperpolarizes the neuron’s membrane potential.

42
Q

Types of basic network motifs

A

Feedforward
Feedback
Disinhibition

43
Q

Cerebellum

A

Made up of orderly repeating microcircuits
Geometric array
Involved in sensory motor control + eyes

44
Q

Purkinje cells

A

Soma diameter 50-80 μm
1 -2 primary dendrites, but hundreds of
secondary and tertiary branches.
100-300,000 granule cell axons synapse
onto a single Purkinje cell.

45
Q

Granule cells

A

Soma diameter ~10 μm
3 – 4 dendrites. Each only ~15 μm in length
Each granule cell sends a single axon into the
Purkinje cell dendritic tree.

46
Q

Parallel fibres

A

Granule cell axons

47
Q

Mossy fibres

A
48
Q

Basket cells

A
49
Q

Stellate cells

A
50
Q

Golgi cells

A

Soma diameter ~30 μm
Ascending dendrites branch within the
molecular layer and the axonal plexus
arborists within the granule cell layer. Each
Golgi cell inhibits thousands of granule cells.

51
Q

alpha6 beta2 delta GABAA receptors

A

Only found outside of synapses
Delta has a higher affinity for GABA
Resting ambient [GABA] by having an equilibrium w GABA transporters
Generates tonic conductance

52
Q

Tonic conductance

A

Tonic conductance refers to the baseline level of ion conductance through the cell membrane of a neuron or other electrically excitable cell. It is the level of ion flow that exists in the absence of any external stimuli or synaptic input

53
Q

Glomerular synapse in cerebellum

A
54
Q

Brainbow study

A
55
Q

Why is dense and strong coding of mf inputs most likely in the cerebellum?

A

The arrangement favours robust receptive fireld mapping

55
Q

Why is dense and strong coding of mf inputs most likely in the cerebellum?

A

The arrangement favours robust receptive fireld mapping

56
Q

Mindscope

A

Attempting to understand the computations that lead from photons to
behaviour by observing and modelling the physical transformations of signals in the visual
brain of behaving mice for one perception-action cycle
aims to catalogue all the building blocks (over 100 distinct cell types) of the
mouse visual system (e.g. neurons of the retina, thalamus, colliculus, cortex) and model
their dynamics.

57
Q

Split/binocular vision

A

Split vision, also known as binocular vision, is a type of vision where an organism’s eyes are positioned in a way that allows them to see two different images simultaneously, which are then fused together by the brain to create a single three-dimensional image.

58
Q

How long does it take for visual inputs to be processed by our brains?

A

0.25s

59
Q

What is the order of cells that light passes through in the retina?

A

Photoreceptors > horizontal + bipolar > amacrine > ganglia

60
Q

Ganglion cell

A
61
Q

Rod cells

A

Photoreceptor cells responsible for vision in low light (work best in low)

Optimized for detecting changes in light intensity over a wide range of levels.

More sensitive to light than rod cells

62
Q

Cone cells

A

3 opsin types - S, M, and L –> trichromatic
Densely packed in fovea
Work best in bright light
Response time to stimuli faster than rod cells

63
Q

Rhodopsin(OPN2)

A

Opsin + retinal attached
lines membrane shelves in rod cells

64
Q

What neurotransmitter do photoreceptor cells release?

A

Glutamate to inhibit bipolar cells and

65
Q

OPN1LW

A

Long Wavelength Sensitive Opsin
λmax in the red region (564 nm) of the electromagnetic
spectrum. Despite its name, this receptor has a secondary
response in the violet high frequencies.

66
Q

OPN1MW

A

Middle Wavelength Sensitive Opsin
λmax in the green region (534 nm).

67
Q

OPN1SW

A

Short Wavelength Sensitive Opsin
λmax in the blue region (420 nm).

68
Q

Melanopsin (OPN4)

A

λmax in the blue region (488 nm) but broader then the other
opsins. This opsin is found in ipRGCs and mediates
circadian rhythms and pupillary reflex but is not involved in
image-forming.

69
Q

ipRGC

A

intrinsically photosensitive retinal
ganglion cells

found in inner plexiform layer

70
Q

tetradodoxin

A

sodium channel blocker
inhibits APs

71
Q

rod amacrine cell

A

Inhibitory interneuron

Lateral inhibition

Can be GABAergic or Glutaminergic

72
Q

what neurotransmitter do OFF Bipolar cells release in the retina?

A

Dopamine

73
Q

what neurotransmitter do ON Bipolar cells release in the retina?

A

Glutamate

74
Q

Function of horizontal cells

A

Lateral inhibition between adjacent photoreceptors

Lateral inhibition helps to sharpen the contrast and enhance the spatial resolution of visual information transmitted to the brain.

75
Q

Centre-surround receptive field

A

Allows ganglion cells to transmit information not merely about whether photoreceptor cells are exposed to light, but also about the differences in firing rates of cells in the center and surround. This allows them to transmit information about contrast.

Central excitatory region + inhibitory surround region

76
Q

Size of receptive field

A

density of photoreceptors

77
Q

Spatial frequency

A

The number of cycles of a visual pattern that occur within a given unit of visual space.

A cycle refers to a complete repetition of the visual pattern, such as a sine wave or a bar.

78
Q

Small receptive fields

A

high spatial frequencies, fine detail.

79
Q

Large receptive fields

A

Low spatial frequencies, coarse detail

80
Q

What are the 3 thalamic regions that receive retinal input?

A

dorsal lateral geniculate nucleus (dLGN)
ventral lateral geniculate nucleus (vLGN)
& intergeniculate leaflet (IGL)

81
Q

dLGN

A

Primary visual relay – involved in
conscious visual processing

82
Q

IGL

A

Input from melanopsincontaining
retinal ganglion cells – role in
circadian rhythm generation

83
Q

vLGN

A

Integration of sensorimotor
information

84
Q

Types of memory

A

Explicit
Procedural
Sensory
Short-term
Long-term

85
Q

Procedural/Implicit memory

A

Memories that dont directly involve consciousness such as physical actions and skills

86
Q

Model of synaptic plasticity

A

Donald Hebb 1949
Strength of connections change during learning and memory

87
Q

Long term potentiation

A

When a synapse is repeatedly activated
this increases efficiency of synaptic transmission
connections between neurons enhanced

88
Q

LTP at molecular level

A

Changes in number of channels at synapses and volume of neurotransmitter released

89
Q

Hebb’s postulates

A

Hebbian learning
Cell assembly
Phase sequence

90
Q

Hebbian learning

A

Connections between neurons increase in efficacy in proportion to the degree of correlation between pre and post-synaptic activity

91
Q

Cell assembly

A

Group of neurons that will tend to fire together

92
Q

Phase sequence

A

Thinking is the sequential activation of
sets of cell-assemblies.

Cellular and Molecular Neuroscience (10 decks)

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