This week's topics are:
Action potentials and synaptic transmission
Neurotransmitters, receptors and pathways
Neurotransmission defects and mental health; focus
on schizophrenia Hello,
welcome back.
BIOLOGICAL Week 3’s content will provide you with a detailed
look at how information is relayed within and
between neurons through a process called synaptic
transmission, and further will explore the role and
FOUNDATIONS
functions of specific neurotransmitters in normal
brain function and mental health.
OF MENTAL
HEALTH
Week Three
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,Learning Outcomes
Week 3: Learning Outcomes
By the end of Topic 1 you will be able to:
Explain how resting membrane potentials (RMP) are established
Explain how neurons integrate incoming signals
Understand how an action potential (AP) is generated in response to an appropriate stimulus
Describe how an AP is conducted along both myelinated and unmyelinated axons
Explain how a signal is transmitted to a postsynaptic cell via neurotransmitter release
By the end of Topic 2 you will be able to:
Give specific examples of neurotransmitters and the rate limiting enzymes for their synthesis
Outline the key features and mechanisms of action of ionotropic and metabotropic receptors classes
and understand how named neurotransmitters activate these receptors
Recognise that drugs can change the functional availability of neurotransmitters in the brain by
modifying their synthesis, storage, release, reuptake and degradation
By the end of Topic 3 you will be able to:
List some of the consequences of defects in neurotransmission
Describe the main symptoms and risk factors for schizophrenia
Outline the dopamine hypothesis of schizophrenia
Appreciate the involvement of other neurotransmitters in schizophrenia, such as glutamate
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,Topic One: Action Potentials and synaptic transmission - Part 1
Introduction
Phil Holland – primarily interested in headache disorders including migraine, for example, and what we do in
our laboratory is we use electrophysiological techniques to record the electrical impulses between nerves and
how they communicate with each other. Today’s topic is to talk about how the normal neurons set up their
resting membrane potential and how then they generate and transmit these potentials.
The membrane
All cells including neurons, have this membrane surrounding them, and that is this phospholipid bilayer. This is
a hydrophobic layer, so it allows the separation of aqueous ions between the extracellular space and the
intracellular space, allowing us to set up these ionic gradients.
We need to move ions across these membranes for this purpose we have proteins in the form of pumps, such as
the sodium-potassium ATPase on the left, and ion channels such as the sodium channels and the potassium
channels here in grey and purple.
These ion channels can be leak channels, that is they open and they allow ions to passively flux up and down
their concentration gradients. Or they can be gated in that they are closed at the resting condition and can
respond to an external stimuli be this electricity in the form of voltage-gated channel or a neurotransmitter, for
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, example in the form of a ligand-gated channel, causing this gate to open and allowing these channels to flux
ions across the membrane.
Resting Membrane potential: Leak channels
It is important to state that most membranes and neurons have a higher concentration of potassium leak
channels, and this important for setting up the resting membrane potential. Ni this, ration is 3 to 1, but this is just
representative. Inside the cell, we have these large, organic anions here in re, and these are negatively charged
ions large proteins. These are locked within the cell, so they can’t cross the membrane. And as you can see, this
puts a negative charge inside the cell in the intracellular space. This has the effect if drawing positively charged
sodium and potassium ions, sodium in the blue and potassium in the green here, towards the extracellular space
and repelling slightly negatively charged ions such as chloride ions here as can be seen. And that sets up a net
positive charge along the extracellular space.
And these are more potassium leak channels in the membrane. In response to this electrostatic charge this want
for the positive charged ions to be attracted towards the negative ions inside the cell, more potassium will enter
the cell, making a higher concentrations of potassium inside the cell.
Some sodium will also enter the cell, but because there are less sodium leak channels, this is relatively fewer
than the potassium. And we also have a low concentration of chloride ions within the cell, setting up this ionic
gradient across the membrane.
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