CSB332H1 Lecture Notes - Lecture 8: Tight Junction Protein 1, Gap Junction, Neurotransmission
14 May 2018
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Lecture 8(a): Role of Ca2+
Neurotransmission:
• Neurons are not physically in contact with each other – they are
separated by a small gap between them known as a synaptic cleft
• AP will travel toward the pre-synaptic neuron triggering the release
of neurotransmitters
o Neurotransmitters will travel along the synaptic cleft and
bind onto different receptors found on post-synaptic neuron which will further have
downstream effects
Synapse:
• Synapse – point of contact between a nerve cell and a target cell; site of information transfer
• Two different types of synapses:
a. Electrical Synapse:
§ Current flows directly from
pre-synaptic to post-synaptic
§ Tightly linked together via
gap junction channels: Zona
Oxxludens-1 (ZO-1)
b. Chemical Synapse:
§ Arrival of AP at the
presynaptic neuron triggers for
neurotransmitter release
which will diffuse toward the post-synaptic and bind to specific receptors
Improving Propagation:
• Propagation can be improved by increasing the length constant/space constant (
l
)
o
l
is a measure of the speed of conduction of a current down an axon
§ Length constant & resistance = cable properties of a neuron
ð Length constant is directly proportional to conduction velocity
o Conduction velocity – measures action potential propagation
o Length constant – measures current propagation
Ca2+ and Excitation:
• Neurons have VG-Ca2+ channels; resemble other VG channels (i.e. + charged S4 domain)
o Ca2+ influx during an AP in the presynaptic neuron is critical for the secretion (release)
of neurotransmitters in chemical synapses
ð Conductance of Ca (gCa2+) is regenerative – similar to gNa+
o More depolarization = more channels become opened = influx of Ca2+ |(+ feedback)
Document Summary
Synapse: synapse point of contact between a nerve cell and a target cell; site of information transfer, two different types of synapses, electrical synapse: Current flows directly from pre-synaptic to post-synaptic. Tightly linked together via gap junction channels: zona. Arrival of ap at the presynaptic neuron triggers for neurotransmitter release which will diffuse toward the post-synaptic and bind to specific receptors. Improving propagation: propagation can be improved by increasing the length constant/space constant (l, l is a measure of the speed of conduction of a current down an axon. Length constant & resistance = cable properties of a neuron. Length constant is directly proportional to conduction velocity: conduction velocity measures action potential propagation, length constant measures current propagation. Ca2+ and excitation: neurons have vg-ca2+ channels; resemble other vg channels (i. e. + charged s4 domain, ca2+ influx during an ap in the presynaptic neuron is critical for the secretion (release) of neurotransmitters in chemical synapses.
