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Systems Neuroscience > CNS development And Structure > Flashcards

CNS development And Structure Flashcards

1
Q

What does the brain do

A

Senses environment and integrates information
Some things hardwired - breathing
Some aren’t - eg run to the train?

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2
Q

Brain function

A

Neuronal computation > output > real world interactions > input > neuronal computation

Adjust responses through learning

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3
Q

Hardwired example

A

Patella reflex
Hammer tap, tendon stretch, stretches sensory receptors in leg extensor muscle
Sensory neuron excites motor neurone in spinal cord and spinal interneuron, interneuron synapse inhibit motor neurone to flexor muscle
Motor neurone conducts AP to synapse on extensor muscle fibres causing contraction, flexor muscle relaxes due to inhibition
Leg extends

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4
Q

Sperrys experiment (1940s)

A

Frog: retinotopic map from retina
Direct connection optic tectum to motor cortex
Amphibians can regrow optic nerve if cut
Cut and rotate eye by 180, map did not reflect new sight as hard wired, inverted image and could not catch fly
Innate and based on initial distribution of chemical markers in the brain

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5
Q

Plastic circuits

A

Learnt behaviours
Usually during critical period for easier learning
Neurodegenerative diseases effect learning and memory so related to plasticity

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6
Q

Are receptors different during development and adulthood

A

Yes
Biophysical properties different
Activated for different times, different processing
Activation threshold (long term potentiation) for memory formation

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7
Q

System development: Nature and nurture

A

Nature- hardwired eg migration, differentiation etc usually overshoot and then defined

Nurture- plasticity. Some synapses maintained and strengthened some lost based on experience

Experiences are key

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8
Q

Neuroscience core concepts

A

1) NS controls and responds to body functions and direct behaviour
2) NS structure and function are determined by both genes and environment throughout life
3) the brain is the foundation of the mind
4) research leads to essential understanding for therapies

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9
Q

NS system structure and function determined by both genes and environment throughout life

A

Genetically determined circuits are foundations of NS
Experiences change the NS

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10
Q

Experimental approach to systems neuroscience

A

What is the sensory stimulus? Complex or minimalistic?
What is the neuronal processing? Single cell resolution, cells of same type or neuronal networks?
What is the output? Motor output, neuronal firing, recall?

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11
Q

Visual perception

A

Neurone detects position
System will interstate all different inputs
Processing of image details

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12
Q

Key areas of research related to systems neuroscience

A

Life long health
Nutrition for health
Biotech for health
Mental health
Neurodegenerative
Insight into living human brain

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13
Q

Types of evidence

A

Correlation
Causation

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14
Q

Key elements of research

A

Grand question?
Model system?
Stimulus?
Outcome measure?
Correlation vs causation?
Remaining questions?

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15
Q

System

A

A group of cells with a concerted function
In neuroscience_= info processing
Smell, heating, touch, memory etc

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16
Q

Every function of NS is underpinned by circuit

A

Sensing changes in environment
Deciding what to do based on instinct and experience
Response

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17
Q

Early stages of brain development of vertebrates (frog)

A

Blastula
Blastocoele
Gastrula
Blastophore
Mesoderm
Neural plate

Great similarities in embryonic development across vertebrates
Time course differences tho (xenopus 6hrs humans 2 weeks)

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18
Q

Neurogenesis

A

Notochord, floorplate, and roofplate are transient structures essential for instructing nervous system formation

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19
Q

Neurogenesis and differentiation

A

When and where neuron is born determines it’s fate
Morphogen gradients drive differentiation

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20
Q

3 primary brain vesicles in development

A

Prosencephalon (forebrain)
Mesencephalon (midbrain)
Rhombencephalon (hindbrain)

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21
Q

Adult derivatives

A

3 segments further differentiate to 5 secondary brain vesicles
Telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon
Further separate

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22
Q

How do brain vesicles differentiate

A

Morphogenetic bind to receptors ti activate or repress sets of TFs
TFs (Hox genes) control programmes of gene expression
Gene expression profiles determine identity

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23
Q

Cranial nerve development

A

Develop from inner neural tube but part of PNS (except optic nerve as it remains in CNS)
Intermediate targets
Guidance cues (attractive/repulsive)
Fasciculation
Growth cone

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24
Q

Early development summary

A

Fertilised egg (zygote) divides
Morula forms
Blastocyst
Gasrelation - movement of cells towards midline creating primitive streak
Production of endoderm, mesoderm, ectoderm
NS develops from ectoderm, thickens and becomes neural plate
Neural groove due to uneven rates of cell division creasing midline of embryo
Forms neural tube which becomes cerebral ventricles of the brain and central canal with the spinal cord

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25
Q

Early development - neural cells

A

Progenitor cells of neural tube are precursor cells aka neural stem cells
First step of neurogenesis
Undifferentiated cells undergo mitotic divisions to produce stem cells or neural blasts that will differentiate into neurones
Dividing precursor cells form ventricular zone
Some leave ventricular zone and form marginal zone
As it grows an intermediate zone forms where cells differentiate into neurones and glia
2nd stage - Greater distances so cell migration occurs via radial glia
3rd stage - differentiation into neurones
4th - process outgrowth

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26
Q

Prenatal brain development

A

Largely genetic control
But nutrition and toxins can impact

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27
Q

Postnatal brain development

A

Experience depending
Gene environment interactions

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28
Q

Are all connections worth keeping

A

No
Overshoot
Neurotrophic and electrical activity determine final pattern of contacts
Compete for neurotropins and electrical input

29
Q

Example of experience dependent development

A

Critical period of column dominance in visual system
Input from eyes reaches the primary visual cortex (striate cortex) via LGN
Layer 4 first intermingled and then ocular dominance columns during development
One eye deprived - columns of good eye expands, bad eye columns shrink

30
Q

Congenital cataract

A

Needs to be treated quickly

31
Q

Amblyopia

A

Cover eye to make lazy eye work
Earlier detected better treatment
Untreated causes poor or blurry vision

32
Q

Central nervous system

A

Brain and spinal cord

Integration and analysis of info

33
Q

Peripheral nervous system

A

Cranial nerves
Spinal nerves

Sensory and motor components

34
Q

Cranial nerves

A

1 olfactory
2 optic
3 oculomotor
4 trochlear
5 trigeminal
6 abducens
7 facial
8 vestibulocochlear
9 glossopharyngeal
10 vagus
11 accessory
12 hypoglossal

35
Q

Somatosensation

A

Receptor endings pick up stimulus
Pain and temp afferent fibres make connection
Mechanosensory enters dorsal root and joins dorsal column

36
Q

Somatic sensory systems

A

Body
Mechanical stimuli: dorsal column medial lemniscal system

Face and anterior head
Trigeminal somatic sensory system

37
Q

The thalamus

A

Relay station
Contains complete representation of somatic sensory periphery

38
Q

Cortical maps of sensory surface

A

Sensory map exaggerates certain regions according to number/type of peripheral givers innervating a region

Hands and face have the most/greatest
Seen in animals too eg mouse whisker pad

39
Q

Cortical integration and signalling

A

Thalamic input mainly layer 4 of cortex
Cortex sends projections to limbic structures such as amygdala and hippocampus
Cortex also sends descending signals (thalamus, brainstem and spinal cord)

Eg ocular dominance columns in monkeys
Barrels in primary somatic sensory cortex of ray of rat

40
Q

Broadmann areas

A

Subdivided cortex into distinct regions based on gross anatomy and cytoarchitectural studies

Imaging studies - characteristics reflected systems contributing to specific functions

41
Q

Human brain

A

Neuronal and non neuronal cells in the brain proportionate

Brain tissues - neurones (excitatory and inhibitory), glia (astrocytes, microglia, Oligodendrocyte, NG+ cells)
Other influences - EMC, vasculature, ependymal cells

42
Q

Tripartite synapse

A

Pre synapse
Post synapse
astrocyte - buffers k+, recycle glutamate

43
Q

Barrel cortex development

A

P0-2 thalamic axons invade layer 4
P3-5 barrels become evident
P7 local inhibitor projections formed
P7-14 reduction in LTP in corticothalamic synapses

44
Q

Glial cell development matches development of neural circuits

A

First neurones
Then glial cells

45
Q

Barrel cortex somatotropic map

A

Whisker pad matches barrels in the brain (each whisker is one barrel)

46
Q

Whisker signalling pathway (ascending)

A

Mechanogated ion channels in nerve endings of sensory neurons Innervate hair follicle
AP fires in sensory neurones trigeminal nerve
Sensory neurons make excitatory glutamatergic synapse in trigeminal nuclei of the brain stem
Trigeminithalamic neurones in principle trigeminal nucleus organised into barralettes - each receiving strong input from a single whisker

47
Q

Whisker signalling from periphery to barrel cortex

A

Principle trigeminal neurones to ventral posterior medial nucleus of the thalamus
VPM neurones respond rapidly and precisely to whisker deflection with one principal whisker evoking stronger responses that others
VPM neurone to primary somatosensory neocortex
Target = layer 4 barrel map

48
Q

Primary function of neocortex

A

Generate associations of different sensory inputs which are processed in highly context dependent manner

49
Q

Fgm8 - morphagen

A

Control - normal barrel field
Anterior- move barrel field
Posterior - expand structure

50
Q

Barrel cortex is plastic (development)

A

Lesion of whisker follicles before day 4 prevents formation of corresponding barrels, changing the anatomical map in new born mouse

51
Q

Arrival of axons in whisker pad development

A

WP first
TG
PrV
VPM
S1 last

And then everything refunded basically post nataly

52
Q

When is the map of whisker pad fixed?

A

Within a few days of birth
Lesions have little effect after on map
So early critical period

Refinement of maps guided by activity dependent mechanism
Experiences influence physiological properties of neurones

53
Q

Cortical integration and signalling

A

Thalamic input predominately layer 4 recieved by spiny stellate and pyramidal neurones (excitatory)

Descending outputs outnumber ascending ones

54
Q

L4 dendrites

A

Input from thalamus
Excitatory and inhibitory

55
Q

L4 axons

A

Innervate layer 2/3 dendrites and axons

56
Q

Interneurons

A

Inhibitory neurones
Grouped by morphology, connectivity, mastheads and intrinsic properties
Loads of cross talk so categories difficult
Some have electrical synapses
Close proximity and junctions needed
Fast spiking cells that are most prominent inhibitory neurones in cortex and control AP generation

57
Q

Cortical interneurons

A

Have different origin
Born in ganglionic eminences and migrate tangentially and populate layers

58
Q

P7

A

Local inhibitory projections are formed

59
Q

P14

A

Feedforward inhibition and low intracellular cl concentrations

So inhibitory projections match more to glial system development

60
Q

GABAa receptors are selective for cl-

A

Early in development cl- concentrations are higher inside neeurones
Neurons mature KCC2 synporter expressed and lowers cl- concentrations
So during development GABA are actually excitatory due to concentrations

61
Q

Inhibition helps to localise them integration of signals into columnar fashion

A

Voltage sensitive dye imaging
Confinded to column
L4 dendrites to Axon to L2/3 dendrites yo axons

62
Q

How is thalamicirtical feedforward inhibition in spiny Stellate cells mediated

A

Small number of fast spiking interneurons that dampen activity

Reduced subsequent excitation so synchronisation
so changes charge in cell and probability that it will be excited again
So depol and hyperpolerisation at the same time so integrates info

63
Q

Inhibitory neurons essential in all neural networks

A

Visual system to V1
Both excitatory and inhibitory inputs shape response to stimuli

64
Q

Modifying GABAnergic inhibition impacts critical period plasticity in mice

A

Plasticity can be delayed by preventing maturation of GABA mediated transmission
Critical period brought forward by enhancing GABA transmission (eg with benzodiazepines)

65
Q

Sensory perception

A

Subjective
Created by neuronal activity eg vase vs 2 faces, light and dark etc

66
Q

Experimental investigation of sensory perception in humans

A

Sensory stimulus (vase vs faces)
Neuronal computation if sensory perceptive
Behaviour report by motor output i saw 2 faces etc” so correlated

67
Q

Experimental investigation of sensory perception in animals

A

Whisker detection task
Model organism for brain studying
Immobilised on magnetic platform
Activate whiskers and measure brain activity
C2 Whisker activated, tongue out, reward and trained with this
Membrane potential correlates perception (correlation)

Opogenetic programming of behaviour
Activate that area induces linking don’t need to stimulate whisker

S1 is necessary for detection of task
Control, injection, recovery
Inhibit it kill response, block glutamate receptors (is activation needed if inhibitors necessary) (causation)

68
Q

Late depol contributes to perception

A

Causation

Inhibit late or early response
Inhibit early then block response
Inhibit early block response
So causation

Systems Neuroscience (5 decks)

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