Lecture 2 – CELLULAR ORGANISATION OF THE NERVOUS SYSTEM Flashcards
1
Q
Golgi and the Reticular Theory
A
- Reduced silver strain that was invented which allowed the staining of entire neurons
- Golgi believed that neurites were fused together to form a network which we now know is not the case, although this was the beginning of the idea that the brain was linked to a collection of cells
2
Q
Cajal and the Neuron Doctrine
A
- Each neuron is a discrete cell known as the neuron doctrine
- Cajal argued that neurons are not fused together but are distinct cells which communicate by contact
- Principle of dynamic polarisation – neurons have a preferred direction in which they transmit information
- Principle of connectional specificity – contact only certain other neurons and even then, only specialised structures on that neuron
3
Q
The development of the electron microscope
A
- Human eye resolution: 0.1mm
- Light microscope resolution: 0.1μm
- Electron microscope resolution: 0.1nm
4
Q
cell ultrastructure
A
- shows how things work
- Confirmed the existence of synapses which was done by EM and gave more details about cells structure
5
Q
Disadvantages of electron microscopy
A
cells must be fixed/ dead so cannot see any movement and its very difficult to see individual molecules
6
Q
development of fluorescence labelling methods
A
- determines protein distribution in cell as it absorbs one light and emits enough due to ligand tags
7
Q
disadvantages of fluorescence labelling methods
A
- limited by range of antibodies available as very specific to protein of interest
8
Q
Development of confocal microscopes
A
- include lasers, high sensitivity cameras and imaging software which can examine live cells and the physiology
9
Q
disadvantages of confocal microscopes
A
- modest resolution of 0.1μm
10
Q
Neurons
A
- neuron stained with MAP-2 and is red and is an individual cell
- nervous system has not internal connect tissue for support
11
Q
Glia
A
- Outnumber neurons in some brain regions
- 17:1 in the thalamus – predominant cell type in some areas of the brain
- 1:1 in the cerebral cortex
- may mediate some signalling in the brain
- primary role is to support neurons – physically and physiologically important
- can divide which neurons can’t do
12
Q
Glia – astrocytes
A
- majority of glia
- star-shaped cells
- fill space between neurons – need tissue for support of neurons
- regulate composition of extracellular fluid – contains ions
- new research shows that astrocytes can play an important role in directing the proliferation and differentiation of neural stem cells
13
Q
Oligodendrocytes/ Schwann Cells
A
- myelinated axons of neurons
- Oligodendrocytes is the CNS with many axons
- Schwann cells are in the PNS with a single axon and form a sheath to insulate it (both) and if removed will not be able to function properly
- Diagram in black in white is myelinated optic nerve fibres
14
Q
Microglia
A
- act as the brain scavengers:
1. Phagocytic/ immune function
2. They can migrate and are very diverse
15
Q
Ependymal cells
A
- Line ventricles – fluid filled spaces
- Direct migration during the development of the brain
- Type of glia
- Have cilia and structure looks a bit like epithelial cells
Important role in production of CSF
16
Q
The Prototypical Neuron
A
- beginnings of polarity in epithelial cells which have specialised functions
- Cilia are specialised so only need to be on one end of the cell
- Neurons have several specialised structures: cell body, dendrites and axons
17
Q
Neuronal Structure:
A
- Common with all cells:
- Cell body with cytosol and organelles including a nucleus
- Cell membrane (plasma lemma) - Unique to neuronal cells:
- Cannot reproduce
- Can trigger action potentials - Cytosolic organelles: stay in cytoplasm
- Peroxisomes
- Mitochondria
- Ribosomes
- Vacuolar apparatus (secretory pathway/ endocytic pathway) which includes the ER, secretory vesicles, Golgi complex, endosomes, lysosomes - Division at axon hillock includes the synaptic vesicles, mitochondria and smooth ER
18
Q
dendrites
A
- Ca 2+ channels
- Ligand-gated ion channels (Glutamate receptors)
- G-Protein coupled receptors
- MAP2 staining makes nuclei blue and the dendrites green
19
Q
Axon
A
- G-Protein coupled receptors (terminals)
- Ca2+ channel terminals
- Na+ and K+ channels (axon shafts)
- MAP2 staining makes the axon terminals orange
20
Q
How does the polar structure of neurons arise?
A
- Targeting of components to axons or dendrites
- Neuronal cytoskeleton
- Structural support – shape and calibre of axons and dendrites
- Transport cargo to and from axons and dendrites
- Tethering of components at membrane surface
21
Q
Microtubules
A
- Run along longitudinally down axons and dendrites
- Big, 20nm wide and tubulin polymers
- Polymerisation/depolymerisation changing the shape
- Microtubule associated proteins (MAP2 and Tau)
- Role: structural and transport
- Kinesin (motor protein) that moves cargo enclosed in vesicles down the microtubule towards the axon terminal and Dynein which moves stuff back from the terminal to the cell body
22
Q
Neuro-filaments
A
- 10nm wide
- Filamentous protein threads
- Role: Mechanical strength
23
Q
Microfilaments
A
- 5nm wide
- Actin polymers
- Tethered to membrane
- Role: mediate shape change
24
Q
distinct populations of neurons with different shapes
A
UNIPOLAR, BIPOLAR AND MULTIPOLAR
25
Q
neuronal classification
A
- Sensory (afferent; somatic or visceral) neurons originate from sensory receptors to the processor
- Motor (efferent; somatic and visceral) neurons conduct signals that originated in the CNS
- Interneurons are between sensory and motor neurons
- Can also be divided by a functional level – diversity of neurons in hippocampus
26
Q
Alzheimer’s
A
green is viable/ live cells, red are dead cells
27
Q
SUMMARY
A
- Golgi and Cajal together revealed neuronal structures
- Glia are the non-excitable cells of the CNS and the support neurons
- Neurons are very polarised and their structure reflects this
The cytoskeleton is made of different structural elements – problems can lead to disease
