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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
Duration of Gsyn determined by?
Transmitter profile - how long transmitter stays in cleft Channel Kinetics
26
SM proteins
Work with SNARE to promote membrane fusion Coagonist of SNARE Sec1/Munc18 protein
27
Excitatory post-synaptic potentials
- 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
28
Inhibitory post-synaptic potentials
- 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
29
Spatial Summation
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.
30
Glutamate
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
31
Ionotropic receptors
Ligand gated ion channels Open to allow ions such as sodium, potassium and calcium Specialised for fast excitation
32
Metabotropic
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
33
NMDA receptor
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
34
AMPA receptor
Tetramer with each subunit having a binding site for glutamate Opens to allow cations through when activated
35
Kainate receptor
Heterotetramer Permeable to sodium and potassium ions Slight permeability to Ca2+ Metabotropic (G-protein cascades) and ionotropic
36
Agonist
Compound that can bind to and cause activation of a receptor, thus mimicking an endogenous ligand or neurotransmitter
37
GABA
Main inhibitory neurotransmitter gamma-aminobutyric acid Synthesised by precursor glutamate
38
GABA receptors
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
GABAergic neurons
Neurons that produce GABA as their output
40
GABA in immature and mature neurons
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
Benzodiazapines
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
Types of basic network motifs
Feedforward Feedback Disinhibition
43
Cerebellum
Made up of orderly repeating microcircuits Geometric array Involved in sensory motor control + eyes
44
Purkinje cells
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
Granule cells
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
Parallel fibres
Granule cell axons
47
Mossy fibres
48
Basket cells
49
Stellate cells
50
Golgi cells
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
alpha6 beta2 delta GABAA receptors
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
Tonic conductance
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
Glomerular synapse in cerebellum
54
Brainbow study
55
Why is dense and strong coding of mf inputs most likely in the cerebellum?
The arrangement favours robust receptive fireld mapping
55
Why is dense and strong coding of mf inputs most likely in the cerebellum?
The arrangement favours robust receptive fireld mapping
56
Mindscope
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
Split/binocular vision
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
How long does it take for visual inputs to be processed by our brains?
0.25s
59
What is the order of cells that light passes through in the retina?
Photoreceptors > horizontal + bipolar > amacrine > ganglia
60
Ganglion cell
61
Rod cells
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
Cone cells
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
Rhodopsin(OPN2)
Opsin + retinal attached lines membrane shelves in rod cells
64
What neurotransmitter do photoreceptor cells release?
Glutamate to inhibit bipolar cells and
65
OPN1LW
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
OPN1MW
Middle Wavelength Sensitive Opsin λmax in the green region (534 nm).
67
OPN1SW
Short Wavelength Sensitive Opsin λmax in the blue region (420 nm).
68
Melanopsin (OPN4)
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
ipRGC
intrinsically photosensitive retinal ganglion cells found in inner plexiform layer
70
tetradodoxin
sodium channel blocker inhibits APs
71
rod amacrine cell
Inhibitory interneuron Lateral inhibition Can be GABAergic or Glutaminergic
72
what neurotransmitter do OFF Bipolar cells release in the retina?
Dopamine
73
what neurotransmitter do ON Bipolar cells release in the retina?
Glutamate
74
Function of horizontal cells
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
Centre-surround receptive field
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
Size of receptive field
density of photoreceptors
77
Spatial frequency
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
Small receptive fields
high spatial frequencies, fine detail.
79
Large receptive fields
Low spatial frequencies, coarse detail
80
What are the 3 thalamic regions that receive retinal input?
dorsal lateral geniculate nucleus (dLGN) ventral lateral geniculate nucleus (vLGN) & intergeniculate leaflet (IGL)
81
dLGN
Primary visual relay – involved in conscious visual processing
82
IGL
Input from melanopsincontaining retinal ganglion cells – role in circadian rhythm generation
83
vLGN
Integration of sensorimotor information
84
Types of memory
Explicit Procedural Sensory Short-term Long-term
85
Procedural/Implicit memory
Memories that dont directly involve consciousness such as physical actions and skills
86
Model of synaptic plasticity
Donald Hebb 1949 Strength of connections change during learning and memory
87
Long term potentiation
When a synapse is repeatedly activated this increases efficiency of synaptic transmission connections between neurons enhanced
88
LTP at molecular level
Changes in number of channels at synapses and volume of neurotransmitter released
89
Hebb's postulates
Hebbian learning Cell assembly Phase sequence
90
Hebbian learning
Connections between neurons increase in efficacy in proportion to the degree of correlation between pre and post-synaptic activity
91
Cell assembly
Group of neurons that will tend to fire together
92
Phase sequence
Thinking is the sequential activation of sets of cell-assemblies.

Cellular and Molecular Neuroscience (10 decks)

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