The Nervous System
By Nate Levin, Cedric White,
and Andrew Boon
Chemical Synapse
 Chemical synapses are specialized
areas through which neurons (nerve
cells) signal each other.
 A junction that permits a neuron to
pass a chemical signal to another
cell.
 A space in between two neurons(1).
Chemical Synapse
Animation
QuickTime™ and a
decompressor
are needed to see this picture.
QuickTime™ and a
decompressor
are needed to see this picture.
Neurotransmitter
 Neurotransmitters are chemicals
created within the cells that transmit
signals from a neuron to a cell
across a synapse(2).
 Neurotransmitter Animation
QuickTime™ and a
decompressor
are needed to see this picture.
QuickTime™ and a
decompressor
are needed to see this picture.
Acetylcholine
 Acetylcholine (ACh) is a neurotransmitter
that has inhibitory and excitatory effects
on the brain, spinal cord, glands, and
muscles.
 ACh is released from the motor neuron,
diffused across the cleft, and binds to
receptors on the muscle cell
membrane(3).
Dopamine
 Dopamine is a neurotransmitter
present in the brain that functions by
activating the five types of
Dopamine receptors.
 It is produced in the brain.
Crossing the Neural
Membrane
 An electrical impulse called an action
potential travels along the axon in the
pre-synaptic neuron toward the axon
terminal. The action potential can not
cross the synaptic space because
electrical signals can not cross gaps. The
vesicle holding the neurotransmitters then
moves to the end of the pre-synaptic
neuron.
Crossing the Neural
Membrane
 The neurotransmitters released move
across the synaptic space to receptors on
the post-synaptic neuron. The binding of
the neurotransmitter to the receptors
triggers an action potential within the
post-synaptic neuron. At this point, the
neurotransmitters release and either are
degraded by enzymes in the synaptic
space or move back into the vesicles in
the pre-synaptic space through
transporter proteins.
Electrical to Chemical
 Question: Why do the electrical signals (action
potential) need to be converted to chemical
signals (neurotransmitter) to be transported
across the membrane?
 Answer: The electrical signals are unable to cross
the synaptic space without direct contact to the
post-synaptic neuron. (Think plugging into a
socket. It must be fully plugged in to work)
Because the electrical signals are unable to
cross the synaptic space, the actions that must
be relayed would be stuck in the pre-synaptic
membrane.
Electrical to Chemical
 Due to the electrical signal’s inability
to cross the synaptic space, the
signal is relayed through
neurotransmitter in the form of
chemical energy.
 Without this conversion, it would be
impossible for the message to move
from neuron to neuron.
Now, watch the animation
again and pay close attention
to how neurotransmitters cross
the synaptic space and the
importance of converting
electrical signals to chemical.
Review of Neurotransmission
Alzheimer’s
 The lead cause for Alzheimer’s, doctors
believe, is that the neurotransmitter
acetylcholine is becoming useless,
making it impossible for neurons to
interact.
 There are no known medicines for
Alzheimer’s because doctors can not
stimulate the now-useless
neurotransmitters(4).
References

1. McGraw-Hill. "Animation: Chemical Synapse (Quiz 1)." Animation: Chemical
Synapse. 2006. Web. 04 Nov. 2010. <http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter14/animation__chemical_synapse__qu
iz_1_.html>.
 2. "The Brain - Lesson 2 - How Neurotransmission Works." The Brain: Understanding
Neurology. 2000. Web. 04 Nov. 2010.
<http://science.education.nih.gov/supplements/nih2/addiction/activities/lesson2_neurotr
ansmission.htm>.

3. "Acetylcholine - Chemistry Encyclopedia - Structure, Reaction." Chemistry:
Foundations and Applications. 2008. Web. 04 Nov. 2010.
<http://www.chemistryexplained.com/A-Ar/Acetylcholine.html>.
 4. "Alzheimer's Association - What Is Alzheimer's." Alzheimer's Association. 1 Nov.
2010. Web. 05 Nov. 2010.
<http://www.alz.org/alzheimers_disease_what_is_alzheimers.asp>.