cells of the nervous system Flashcards
what are neurones and what are their purpose
-excitable cells that conduct impulses
-Integrate and relay information within a neural circuit
-lead to neural circuits-> neural systems
what are glia and whats thaw purpose
-supporting cells - the ‘glue’
-keep neurones healthy
-Maintain homeostasis, protection, assist neural function
-lead to neural circuits-> neural systems
how many cells in neural system
-85 billion
whats nissl staining
-Allows us to distinguish between neurons and glia
-Nucleolus of all cells stained
-Neurons also have Nissl bodies
-Allows visualisation of variation in size, density and distribution of neurons
-cell bodies can be big or small, triangular or round
-fixitses- makes tissue hard and therefore easier to cut therefore you can add chemicals (staining ) to see whats in the tissue
whats the soma
-Aka cell body, perikaryon
-Nucleus
-Organelles for protein synthesis and processing:
=Ribosomes
=Rough Endoplasmic Reticulum
=Golgi apparatus
-Mitochondria- high density, neurones do a lot of AT so need lots of ATP
what are the 4 major compartments of neurones
1)Cell body, soma, perikaryon
Neurites:
2) Dendrites
3) Axons
4) Presynaptic terminal
-Golgi (Camillo) stain
=Silver chromate- binds to all the different bits in the neurone
=Small percentage-Santiago Ramón y Cajal- maps different bits of the brain
whats the cytoskeleton
-the internal scaffolding
-Microtubules:
=Longitudinally down neurites
=Hollow tube composed of polymers of tubulin
-Microfilaments
-Neurofilaments
what are axons
-Axon hillock- connects cell body to the rest of the axon
-Axon initial segment- comes just after hillock, specific and high density of iron channels
-Axon collaterals- ends I one synaptic neurone, signal can move on in different directions, not just one target due to branches
-Axon terminal or terminal bouton
-Features:
=No rough ER or fewer free ribosomes (?)
=Membrane composition different
=<1 mm to >1 m in length
=1 µm - 25 µm diameter
what is the axon initial segment
-Immunohistochemistry
Specific primary antibodies
Fluorescent secondary antibodies
what do axons really look like
-Thicker
-May be myelinated
-Axons with many collaterals
= high levels of divergence (signal spread out more)
what are presynaptic terminals
-Synapse ‘to fasten together’
-Specialisation of the terminal cytoplasm:
=No microtubules
=Synaptic vesicles
=Specialised proteins- fusing with membrane
=Mitochondria
-Synaptic cleft
-microtubules dont run right to the end of the terminal
what do presynaptic terminals look like
-Terminal arbour
-Boutons en passent (buttons in passing)
-slide 13
whats axoplasmic transport
-Slow axoplasmic transport
=Discovered by tying a knot!
-fast axoplasmic transport
=Radioactive amino acids
=1000 mm per day
=Microtubules, kinesin (carrying vesicles packed up with proteins) and ATP
=Anterograde transport
=Retrograde transport by dynein
what occurs with Manipulating axoplasmic transport to visualise cells
-Anterograde or retrograde labelling
-chemicals you can inject into muscle- taken up by presynapses
-dyenein brings it to spinal chord- Motor neurone
what are dendrites
-Dendritic branches together form dendritic trees (dendritic arbors)
-Structure to function relationship - convergence
-Can have thousand of synapses
-purkinje cell dendrites found in cerebellum
what are dendritic sines
-Isolate chemical reactions?
-Plastic - structure vs activity
-Abnormalities = cognitive impairment
-flexibility, appear and disappear, important in transport
what are the different methods of looking at cells
-Nissl stain - cresyl violet, neurons vs glia, cytoarchitecture
-Golgi stain - silver chromate, highlights some neurons, neuron doctrine
-Immunohistochemistry - fixed tissue, antibodies, fluorescent microscope
-Live imaging of fluorescent dye - genetic or injected
-Electron microscope - synapses and organelles
-Retrograde tracers - HRP - find cell body location
how can you classify neurones
-By structure:
=Number of neurites
=Dendritic geometry
=Connections - where do they project?
=Axon length - long, they project a long way
-By gene expression:
=Underlies structural differences
=Defines neurotransmitter expression
why do we have different types of neurones
-85 billion neurones in brain, can’t possibly go to each one to get an electrical recording
-hence can’t look at every single neurone therefore why we have different neurone types
Number of neurites - unipolar
-E.g. Dorsal root ganglion
-Peripheral process is part axon too
-Small area for receiving synaptic input = highly specialised function
-Reliable relay of information
-main function-> faithfully transmit a signal-> dont want too much modification to this signal therefore not integrated
-neurite coming off of the cell body
-psuedo-unipolar is different because has one neurone that comes out of the cell body and splits into 2 directions
-both directions initially on the axon but then at one end it turns to the dendrite
-one neurone comes out of axonal bit and goes towards spinal chord (dorsal)- NB sensory neurone
-dendrite goes to skin- sensory receptors
Number of neurites - bipolar
-E.g. retinal bipolar cells
-Small area for receiving synaptic input = highly specialised function
-Reliable relay of information
-the retina being an example
-faithfully transmit signal
-one signal from one area
-not a huge dendritic tree so not much integration in the retina
Number of neurites - multipolar
-Majority of neurons in the brain
-Large area for receiving synaptic input
-High levels of convergence
-Receives about 150,000 contacts
-multipolar are the vast majority
-one simple axon with multiple dendrites
-large area for receiving synaptic input
-they want to take in info from lots of different places
examples of multipolar neurons
-stellate
-pyramidal neurons
why do connections project
-Sensory- cranial nerves )straight to brain cells), dendritic: periphery, axonal: CNS
-Motor- cell body to CNS, presynaptic= periphery
-Interneuron - largest class:
-Relay or projection neurons
=Connect brain regions
-Local interneurons
=Short axons
=Process info in local circuits
