Transcript BLoA Neurotransmission

CNS and PNS
Striatum
The striatum is involved
in controlling thought
and action
It is also involved in
registering rewarding
events
Hippocampus
The hippocampus is
involved in memory –
people with hippocampus
damage often suffer from
amnesia
It seems to be particularly
involved in learning about
spaces – London cab
drivers have enlarged
hippocampi
Corpus Callosum
The corpus callosum is a
bundle of neurons that
links the two brain
hemispheres, which are
otherwise largely
separated
Some treatments for
epilepsy involved
cutting the corpus
callosum, which had
some very interesting
side-effects...
Amygdala
The amygdalae play a
primary role in
processing emotions
and in remembering
emotional events
The amygdalae are
particularly linked to
the emotion of fear
Hypothalamus
One function of the
hypothalamus is in
thermoregulation – it
serves as a thermostat
for the body
It also serves other
homeostatic functions
Specific areas of the
hypothalamus are
associated with hunger
and satiety
Neurotransmission
Overview of neurotransmission
1. Action potential (electrical impulse) passed
down presynaptic neuron
2. Vesicles move to the edge of synaptic button
3. Vesicles dump neurotransmitter into synapse
4. Neurotransmitter is taken up by receptors on
postsynaptic neuron
5. Postsynaptic neuron is either encouraged to
‘fire’ or not to fire
6. Neurotransmitter in synapse is either broken
down or transported back into presynaptic
neuron
Action potential
Now the presynaptic
neuron has a signal.
This stimulus is transmitted
as an action potential
electrically down the
neuron until it gets to the
bulge in the picture, the
synaptic button.
Vesicles
But the electrical signal cannot just
bounce on to the next neuron.
There’s too much space in
between the two neurons.
The change in potential is going to
affect little vesicles, little blobs of
membrane inside the
presynaptic neuron. These
vesicles contain the
neurotransmitters, which are
synthesized in the presynaptic
cell, and stored in the vesicles
until stimulated.
The synapse
So what are we looking at here?
That blue bulbous portion that
looks like a nose is the
presynaptic neuron.
The smiley below it in pink is the
postsynaptic neuron.
And neurotransmission is what
gets a signal from one side to
the other.
The distance between a
presynaptic and postsynaptic
neuron is about 20-40
nanometers!
Into the synapse
The electrical signal (via its
effects on calcium ions)
causes the vesicles to
begin to migrate to the
cell membrane.
Then they either dump all of
their neurotransmitter into
the synapse or just
release a little of it.
Reception
So now the neurotransitting
chemicals are in the synapse.
They float across the tiny space
in a random way, and in the
process, bump into receptors on
the other side.
The receptors here are important.
This is because there tend to be
many different types of receptor
for one type of neurotransmitter.
Depending on which receptor type
the neurotransmitter hits, the
result will usually be either
excitation or inhibition of the
postsynaptic neuron’s action
potential.
Breakdown/reuptake
So what happens then? You don’t want
to leave the neurotransmitter sitting
around in the synapse. Because
this means it will continue to bump
into receptors and pass signals on
to the post-synaptic neuron.
So the signal must be terminated.
Depending on the neurotransmitter
you’re dealing with, there are
various things that can happen.
An enzyme can break down the
neurotransmitter chemical into its
component parts, or the presynaptic
neuron can have transporters,
which suck the neurotransmitter up
back into the synaptic button, either
to be shoved back into vesicles, or
to be degraded.