Practicals Flashcards
Describe the 4 types of neuroglia and their broad functions:
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
What is the meaning of this anatomical terminology?
Rostral-caudal
Dorsal-ventral
Coronal
Sagittal
Rostral-caudal plane (caudal = towards tail)
Dorsal-ventral
Coronal section (=ear to ear)
Sagittal plane (medial line section)
Horizontal plane (long D-V line)
What do H&E and Nissl stains show?
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
What do lipid (e.g. LFB) and silver based stains show? What colours do they appear?
Lipid stains:
- Luxor fast blue (LFB)
- Show myelin sheath
- Do not stain cell bodies
Silver based (Golgi stain):
- Mark neurofilaments (dendrites)
- ‘Black reaction’
What are some ways that neuronal morphology can be quantified?
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
What are the principle layers of the hippocampus in CA1? Which cells are contained?
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)
What are the 6 layers of the cerebral cortex?
Pyramidal cells = excitatory; non-pyramidal (stellate) = inhibitory
- Molecular layer: axons/dendrites
- External granular layer: interneurons
- External pyramidal layer: small pyramidal cells. Axons project deeper and to other hemisphere via corpus callosum
- Internal granular layer: small stellate cells (particularly prominent in visual ‘striate’ cortex)
- Internal pyramidal layer: large pyramidal cells – corticofugal fibres to brainstem/spinal cord
- Multiform layer: both stellate and pyramidal cells and connects to thalamus
What is the main difference in cellular composition between the motor (M1) and somatosensory (S1) cortices?
- M1 contains giant pyramidal ‘Betz’ cells while somatosensory does not
What is the Stria of Gennari?
Prominent internal granular layer seen in the visual cortex (V1).
- Full of stellate cells
- Seen as darker staining region under Luxol stain
What is the role of immunohistochemistry? What are 3 benefits?
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
What are anterograde and retrograde transport?
Anterograde: moved from cell body to axon terminals
Retrograde: from axon to cell body
What is the CLARITY technique?
Studying intact structures with molecular resolution
- Making tissue ‘transparent’
- Removing fat and replacing with hydrogel matrix to support
What is the space constant? How is it calculated?
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
What order are somatosensory nerves lost during an ischemic nerve block?
- 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)
How can you measure pressure and resolution threshold for somatosensation?
Pressure:
- Von Frey hairs (detection threshold)
Resolution:
- Closest distinguishable distance
- Nyquist theory
What shape is the human visual field (for both eyes)? Think about representative diagram.
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
How could you work out the size of a retinal image based on the distance of the object focussed on?
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)
How many μm is a degree on the retina? How much is a cone worth?
1 degree = 60 minutes = 300μm on retina
Single cone = 30 seconds = 2.5μm
How many neurons, NMJs and chemical synapses does a C.Elegans have?
Neurons = 302
NMJs = 1500
Chemical synapses = 6400
What stimuli can zebrafish detect? How can these responses be adapted?
- Startle
- Light/dark preference
- Thigmotaxis
- Habituation
What sensory inputs and motor outputs can a C.elegans detect?
Inputs:
- Olfactory
- Gustatory
- Mechanical (touch, pain)
- Thermal
Outputs:
- Locomotion
- Feeding, defecation, egg-laying, mating
What is the role of Shh in development?
Setting up dorsal-ventral axis
- Highest concentration at dorsal
What is the role of radial glia in development?
- Provide surface for GCs to grow on
- Act as neural stem cells
What are the roles of neural crest cells?
- SNS
- PNS (e.g. sweating)
- Cartilage
- Teeth
- Glial cells
Which molecules set up the dorsal ventral notochord axis?
Ventral: BMPs
- Dorsalin
- Activin
Dorsal: Anti-BMPs:
- Chordin
- Noggin
- Follistatin
- (shh)
UV stops dorsal structures forming
Li stops ventral structures forming
What is the role of Agrin?
- Anti Dispersal factor for scaffold proteins forming NMJ
Name the main molecules providing a posterior-anterior identity:
Posterior = RA and FGF
What is the optokinetic reflex? How does this differ from VOR?
- Nystagmus ‘saw tooth’ pattern showing eyes drift to follow target then jump back
- For slower movements
- Use fewer feedforward mechanisms
How do you ensure experimentally that all muscle fibres are activated for a particular reflex?
- Gradually increase stimulating amplitude until response is no larger
- Suggests all fibres activated
How can conduction velocity be worked out?
- Plot latency as a function of distance
- Gradient is conduction velocity
- Roughly 49m/s for ulnar nerve
What is an H-wave and M-wave in a electromyogram? When does the H wave disappear?
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)
How does MRI work? What about fMRI?
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
How does a PET scan work?
- Tracer molecules labelled with positron emitting radionuclide
- Detected externally
How does MEG/EEG work?
Measures synchronous electrical/magnetic signals from many neurons
MEG more expensive but better spatial resolution
Name the 3 major sections of the hindbrain and 2 major forebrain sections:
Hindbrain:
- Medulla
- Pons
- Cerebellum
Forebrain:
- Diencephalon (hypothalamus, thalamus)
- Telencephalon (including BG, cerebral cortex)
What are the major defining sulci of the brain (3)
- Central sulcus
- Sylvian Fissure
- Longitudinal Fissure
What are the major layers of the retina from inside to outside?
- 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
What are the regions of the inner ear?
Organ of corti (bookended by tectorial and BM)
- Scala vestibuli
Reissner’s membrane - Scala media
- Scala tympani
Where is a likely lesion if someone has Broca’s aphasia? Wernicke’s aphasia?
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)
