DEV2011 Lecture Notes - Lecture 13: Peripheral Nervous System, Myocyte, Oligodendrocyte
25 May 2018
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Lecture 13 – The Nervous System
Cellular Diversity
• Neurone
o Fundamental unit of nervous systems
o Formed of a cell body from which extend processes
o Lots of dendrites but single axon
▪ Axon transports nervous
message from cell body
▪ Dendrites receive
connections from other
neurones and transport
electrical impulse to cell
body
o Neurons connect through synapses
• Synapse
o Conversion: electric signal → chemical
energy
o Release of neurotransmitter by pre-synaptic
element
o Binds to specific receptors on post-synaptic
of synapse
o Triggers new electrical impulse in post-
synaptic neurone
o Synapses are not always between two
neurones
▪ Neuro-musuclar junction where
neurone connects with muscle fibre to initiate the contraction
o Post synaptic elements: contain receptors → send messages to cell
body
• Nerves
o Axon group together forming a bundle: nerve
o To accelerate transmission of message nerve fibres are covered with
insulating sheath: myelin
o Conduction speed can also be increased by increasing axon diameter
o Without myelin, would take 5 mins for information to go from our
brain to leg
• Oligodendrocytes and Myelin
o Electrical impulse jumps between myelinated
segments – region called Node of Ranvier
o Myelin supports axon which can be damaged if
myelin is removed
▪ More wraps – more insulation
o One oligodendrocytes can myelinate multiple
segments on or distinct axons establishing a
network between them
▪ In peripheral nervous system, myelinating
cells are Schwan cells – can only myelinate
a single fibre at a time
▪ Or can wrap across different axons of the
same bundle → forming network
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