Lecture 2 - cells of the nervous system Flashcards
What are the 2 types of cells in the nervous system?
- Neurons
- Glia
What are neurons?
excitable cells that conduct impulses
What are the purpose of neurons?
integrate & relay information within a neural circuit
What are glia cells?
supporting cells - the ‘glue’
What is the purpose of glia cells?
maintain homeostasis, protection, assist neural function - assist in rapid transmission
How many neurons and glia cells are there?
85 billion of each cell type
What are neurons & glia cells both?
part of the neural circuits that make up the neural system
What does Nissl staining do?
- allows us to distinguish between neurons & glia
- nucleolus of all cells stained - this is because staining binds to negatively-charged molecules (RNA in the nucleolus)
Do neurons have Nissl bodies?
Yes, as well as a stained nucleolus
Do glia have Nissl bodies?
No, but they do have a stained nucleolus
How large are cell bodies?
Up to 50um
What is the purpose of Nissl staining?
allows visualisation of variation in size, density & distribution of neurons
What is the soma?
cell body (perikaryon)
What organelles are used for protein synthesis & processing?
- ribosomes
- rough ER
- Golgi apparatus
What is the function of mitochondria in neurons?
found in high quantity used by neurons to affect membrane potential
What are the 4 compartments of the neurons?
- Cell body, soma, perikaryon
- Dendrites
- Axons
- Presynaptic terminal
What are the neurites?
term for any process coming off neuronal body:
- dendrites
- axons
What is the Golgi (Camillo) stain?
this stain showed that neurones are more than just cell bodies, however doesn’t pick up all neurones
- silver chromate
- small%
Who used the golgi stain?
Santiago Ramon y Cajal - used Golgi stain and did drawings of the brain of different neurons.
What doesn’t the Golgi stain show?
synaptic terminal
Describe the cytoskeleton of a neuron
Microtubules - longitudinally down neurites & a hollow tube composed of polymers of tubulin
What is the axon hillock?
where the cell body transitions into the axon
What is the axon initial segment?
important for generation of action potentials (specialised area for action potentials)
What are axon collaterals?
(branches - often at right angles) - each collateral ends with a terminal
Describe the features of an axon
- no rough ER or free ribosomes (which is why it doesn’t appear when stained)
- membrane composition is different - important in transmission of action potentials, as well as ensuring unidirectional flow of action potential
- 1<mm>1m</mm>
- 1um - 25um diameter (width)
- inter neurons - small neurons
Why are there a lot of voltage-gated sodium channels in the AIS - axon initial segment?
as they are needed for action potential generation
How can we use immunohistochemistry to observe the axon initial segment?
primary antibodies can be used to locate sodium channels, by attaching to them. Fluorescent secondary antibodies can then be used to show where sodium channels are located
What is immunohistochemistry?
specific primary antibodies & fluorescent secondary antibodies
What do axons look like?
- may be myelinated
- axons may have many collateral = high levels of divergence
What are uses of collaterals?
the spreading of signals further and wider
How is the terminal cytoplasm specialised?
- no microtubules
- synaptic vesicles
- specialised proteins
- mitochondria - high levels of energy-requiring processes
What do presynaptic terminals look like?
- collaterals can have their own terminals
- axons may have a terminal along their axon (boutons en passent)
Describe axoplasmic transport
- fast axoplasmic transport
- radioactive amino acids
- 1000mm per day
- microtubules, kinesin & ATP
- anterograde by dynein
What does Kinesin do?
carries vesicles down to the presynaptic terminal (ATP-requiring)
What is anterograde?
forward movement from the cell body to the terminal
What type of movement does dyenin use?
retrograde (opposite of anterograde)
How can you manipulate axoplasmic transport to visualise cells?
anterograde or retrograde labelling
What do dendritic branches together form?
dendritic trees (dendritic arbors)
Why is it useful that one cell body can have many dendrites?
integration of information from thousands of synapses into 1 cell body (can have thousands of synapses)
What can abnormalities in dendritic spines lead to?
cognitive impairment
Why is it useful that dendritic spines are plastic (dynamic)?
may be lost due to lack of activity or grow due to high levels of activity
