BMS1052 Lecture Notes - Lecture 2: Myelin, Peptide, Motor Neuron
30 May 2018
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Week 1. Neurons and Glia cells & Action potential
generation
NEURONS AND GLIA CELLS
• Two major specialisations found in neurons:
o Neurites = neuronal process = axons and dendrites (specialised structure)
o A range of proteins specialised for electrical and chemical transmission (specialised
function)
• Two classes of cells in NS:
o Neurons (~10%): information processing
Important components:
Neuronal membrane (separates intra-and extracellular space)
Ribosomes
Rough endoplasmic reticulum and mitochondria (only in cell body)
o Glia (~90%): supporting roles
• Axons transmit information away from the cell body
• Dendrites transmit information towards the cell body
• Neuronal cytoskeleton forms the scaffolding of the neuron and maintains its shape and controls
its movements:
-neuron shape is dynamic
Microtubules
o Longitudinal down neurites
o Mediate intracellular transport
o Assembly and function regulated by MAPs (microtubule-associated
proteins)
Neurofilaments
o Provide structural support
o Regulate diameter of axons
(diameter determines the size of conduction eg. increasing diameter
will increase conduction)
Microfilaments
o Linked to microtubules and membrane
o Comprised of actin molecules (same protein in muscles)
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• Important parts of Axon:
o Axon hillock (beginning): generating action potentials
o Axon proper (middle)
o Axon terminal (end)
• ER does not extend into axon (no protein synthesis)
• Axon contains specialised proteins:
o Ion channels and ion pumps to allow electrical communication
• Material (proteins, neurotransmitters, metabolites)is transported in two ways in axon:
Slow axoplasmic transport
o Simple diffusion
o Some material diffuses through cytoplasm or along
membrane
o 1-10mm/day
Fast axoplasmic transport
o Active transport (requires energy)
o Proteins synthesised in soma are actively transported
o Metabolic signals from synapse are communicated to
cell body
o 1m/day
o Can be hijacked by viruses
• Direction:
o Anterograde: forward/towards synapse
o Retrograde : backwards/away from synapse
• Axon terminals:
o No microtubules
o Internal vesicles containing neurotransmitters
o Membrane is protein-dense
o Lots of mitochondria
• Synapse:
1. Electrical signal travels down axon
2. Presynaptic membrane: releases vesicles containing neurotransmitters
3. Synaptic cleft
4. Postsynaptic membrane: neurotransmitter binds to specialised proteins and is converted
into an electrical signal
5. Dendritic spin receives information: its density and length depends on environment and
development i.e. fewer spines = less potential for learning
• Neurons vary in:
Number of neurites
o Unipolar is found exclusively in invertebrates
o Bipolar: single axon and dendrite directly connected to cell body
o Multipolar: typically one axon and multiple dendrites
find more resources at oneclass.com
find more resources at oneclass.com
