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Neurobiology > Practicals > Flashcards

Practicals Flashcards

1
Q

Describe the 4 types of neuroglia and their broad functions:

A

Astrocytes: anchor neurons and capillaries together; form BBB and regulate homeostatic environment

Microglia: specialised phagocytes to engulf dead tissue

Oligodendrocytes: produce myelin sheaths (wrap around)

Ependymal cells: line ventricles and involved in CSF secretion

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2
Q

What is the meaning of this anatomical terminology?
Rostral-caudal
Dorsal-ventral
Coronal
Sagittal

A

Rostral-caudal plane (caudal = towards tail)

Dorsal-ventral

Coronal section (=ear to ear)

Sagittal plane (medial line section)

Horizontal plane (long D-V line)

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3
Q

What do H&E and Nissl stains show?

A

H&E stain (principle in histology but not the best for brain):
- Haematoxylin = stains nuclei blue
- Eosin = stains cytoplasm pink

Nissl stains (including Cresyl violet):
- Stain nucleic acid (RNA)
- Show RER and ribosomes
- Do not stain axons

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4
Q

What do lipid (e.g. LFB) and silver based stains show? What colours do they appear?

A

Lipid stains:
- Luxor fast blue (LFB)
- Show myelin sheath
- Do not stain cell bodies

Silver based (Golgi stain):
- Mark neurofilaments (dendrites)
- ‘Black reaction’

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5
Q

What are some ways that neuronal morphology can be quantified?

A

Extent of dendritic tree:
- Sholl analysis (number of interactions between concentric circles and dendrites counted)

Number/size of dendritic spines:
- Minute analysis

Arborisation pattern:
- Size and distribution of branching

Sparse labelling in technicolour:
- Fluorescent colour specific to a circuit

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6
Q

What are the principle layers of the hippocampus in CA1? Which cells are contained?

A

3 main layers (unlike neocortex 6):
- Stratum oriens = pyramidal cells and cell bodies of inhibitory interneurons
- Stratum pyramidale = cell bodies of pyramidal cells
- Stratum radiatum = Shaffer collaterals (incoming fibres)

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7
Q

What are the 6 layers of the cerebral cortex?

A

Pyramidal cells = excitatory; non-pyramidal (stellate) = inhibitory

  1. Molecular layer: axons/dendrites
  2. External granular layer: interneurons
  3. External pyramidal layer: small pyramidal cells. Axons project deeper and to other hemisphere via corpus callosum
  4. Internal granular layer: small stellate cells (particularly prominent in visual ‘striate’ cortex)
  5. Internal pyramidal layer: large pyramidal cells – corticofugal fibres to brainstem/spinal cord
  6. Multiform layer: both stellate and pyramidal cells and connects to thalamus
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8
Q

What is the main difference in cellular composition between the motor (M1) and somatosensory (S1) cortices?

A
  • M1 contains giant pyramidal ‘Betz’ cells while somatosensory does not
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9
Q

What is the Stria of Gennari?

A

Prominent internal granular layer seen in the visual cortex (V1).
- Full of stellate cells
- Seen as darker staining region under Luxol stain

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10
Q

What is the role of immunohistochemistry? What are 3 benefits?

A

Allows ability to stain for a specific molecule or antigen.
- Uses primary antibody
- Secondary antibody with stain attached (e.g. fluorescing molecule)

Allows co-localisation of different proteins in the same neuron at the same time

Can be conducted live:
- Map transport
- Map circuitry

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11
Q

What are anterograde and retrograde transport?

A

Anterograde: moved from cell body to axon terminals

Retrograde: from axon to cell body

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12
Q

What is the CLARITY technique?

A

Studying intact structures with molecular resolution
- Making tissue ‘transparent’
- Removing fat and replacing with hydrogel matrix to support

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13
Q

What is the space constant? How is it calculated?

A

Distance over which steady state potential decays to 1/e
- λ = sqrt(Rm/Ri)
- Affected by capacitance of membrane; diameter of axons; conductivity of fluid and temperature

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14
Q

What order are somatosensory nerves lost during an ischemic nerve block?

A
  • Order of loss = strength, touch, vibration, proprioception, pain and temp.
  • Aα lost first, then Aβ, then Aδ
  • Last to go are C fibres
  • When only C fibres active labelled line coding shown (hot and cold both feed hot)
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15
Q

How can you measure pressure and resolution threshold for somatosensation?

A

Pressure:
- Von Frey hairs (detection threshold)

Resolution:
- Closest distinguishable distance
- Nyquist theory

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16
Q

What shape is the human visual field (for both eyes)? Think about representative diagram.

A

X-axis = degrees azimuth
y-axis = degrees in vertical plane

  • Blind spots in the centre
  • Nose blocks opposite side for each eye
  • Eyebrows obscure top
17
Q

How could you work out the size of a retinal image based on the distance of the object focussed on?

A

x/d = y/e where:
x = vertical height of object (or dtan(α))
d = distance from focus point (lens) to object
y = height of image
e = Distance from focus point to retina (normally =17mm in human)

18
Q

How many μm is a degree on the retina? How much is a cone worth?

A

1 degree = 60 minutes = 300μm on retina

Single cone = 30 seconds = 2.5μm

19
Q

How many neurons, NMJs and chemical synapses does a C.Elegans have?

A

Neurons = 302
NMJs = 1500
Chemical synapses = 6400

20
Q

What stimuli can zebrafish detect? How can these responses be adapted?

A
  • Startle
  • Light/dark preference
  • Thigmotaxis
  • Habituation
21
Q

What sensory inputs and motor outputs can a C.elegans detect?

A

Inputs:
- Olfactory
- Gustatory
- Mechanical (touch, pain)
- Thermal

Outputs:
- Locomotion
- Feeding, defecation, egg-laying, mating

22
Q

What is the role of Shh in development?

A

Setting up dorsal-ventral axis
- Highest concentration at dorsal

23
Q

What is the role of radial glia in development?

A
  • Provide surface for GCs to grow on
  • Act as neural stem cells
24
Q

What are the roles of neural crest cells?

A
  • SNS
  • PNS (e.g. sweating)
  • Cartilage
  • Teeth
  • Glial cells
25
Q

Which molecules set up the dorsal ventral notochord axis?

A

Ventral: BMPs
- Dorsalin
- Activin

Dorsal: Anti-BMPs:
- Chordin
- Noggin
- Follistatin
- (shh)

UV stops dorsal structures forming
Li stops ventral structures forming

26
Q

What is the role of Agrin?

A
  • Anti Dispersal factor for scaffold proteins forming NMJ
27
Q

Name the main molecules providing a posterior-anterior identity:

A

Posterior = RA and FGF

28
Q

What is the optokinetic reflex? How does this differ from VOR?

A
  • Nystagmus ‘saw tooth’ pattern showing eyes drift to follow target then jump back
  • For slower movements
  • Use fewer feedforward mechanisms
29
Q

How do you ensure experimentally that all muscle fibres are activated for a particular reflex?

A
  • Gradually increase stimulating amplitude until response is no larger
  • Suggests all fibres activated
30
Q

How can conduction velocity be worked out?

A
  • Plot latency as a function of distance
  • Gradient is conduction velocity
  • Roughly 49m/s for ulnar nerve
31
Q

What is an H-wave and M-wave in a electromyogram? When does the H wave disappear?

A

M-wave = direct response of muscle due to stimulation of efferent motor fibres

H-wave = reflex response due to activation of afferent sensory fibres (muscle spindle)

H wave disappears when efferent fibre refractory period coincides with efferent stimulation (due to large depolarisation)

32
Q

How does MRI work? What about fMRI?

A

MRI:
- Hydrogen nuclei in water become aligned with direction of field
- Can differentiate grey and white matter

fMRI:
- Detects blood oxygenation and flow in response to neural activity
- Difference in magnetisation between oxy and deoxy haemoglobin
- Different BOLD signal

33
Q

How does a PET scan work?

A
  • Tracer molecules labelled with positron emitting radionuclide
  • Detected externally
34
Q

How does MEG/EEG work?

A

Measures synchronous electrical/magnetic signals from many neurons

MEG more expensive but better spatial resolution

35
Q

Name the 3 major sections of the hindbrain and 2 major forebrain sections:

A

Hindbrain:
- Medulla
- Pons
- Cerebellum

Forebrain:
- Diencephalon (hypothalamus, thalamus)
- Telencephalon (including BG, cerebral cortex)

36
Q

What are the major defining sulci of the brain (3)

A
  • Central sulcus
  • Sylvian Fissure
  • Longitudinal Fissure
37
Q

What are the major layers of the retina from inside to outside?

A
  • Choroid
  • Pigmented layer
  • Outer nuclear layer (rods/cones)
  • Outer plexiform layer
  • Inner nuclear layer (amacrine, horizontal and bipolar)
  • Inner plexiform layer (ganglion)
  • Ganglion cell layer
38
Q

What are the regions of the inner ear?

A

Organ of corti (bookended by tectorial and BM)

  • Scala vestibuli
    Reissner’s membrane
  • Scala media
  • Scala tympani
39
Q

Where is a likely lesion if someone has Broca’s aphasia? Wernicke’s aphasia?

A

Broca’s: motor association cortex of frontal lobe = good comprehension; poor, afluent speech

Wernicke’s: posterior temporal lobe = poor comprehension but fluent speech (though nonsensical)

Neurobiology (7 decks)

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