The Nervous System:
Neurotransmitters
By Josephina, Ben, Andrew, and Jacob
Photo: http://total-body-psychology.com.au/wpcontent/uploads/2012/07/neurotransmitter.gif
What are Neurotransmitters and Chemical
Synapses?
•
•
Neuron → Nerve Cell (3)
Neurotransmitters → Signaling molecules which carry nerve
impulses between neurons by diffusing across Chemical (3)
Synapses → A narrow cleft between a neuron's’ output area
and the input end of another cell (7)
o Neuron - neuron or neuron - other cell (e.g. muscle) (10)
Photo:
http://www.google.com/url?sa=i&rct=j&q=&esrc=s&so
urce=images&cd=&docid=Li8YVDJMckV3cM&tbnid=
5WoEACCv3HccsM:&ved=0CAIQjBw&url=http%3A%
2F%2Ftotal-body-psychology.com.au%2Fwpcontent%2Fuploads%2F2012%2F07%2Fneurotransm
itter.gif&ei=lhd3UtOoE9as4AOYw4DwBg&bvm=bv.55
819444,d.cWc&psig=AFQjCNGi47hO8noNSOuL5slBG3aXKwxqA&ust=1383622930610294
Where are neurotransmitters
stored?
•
At the chemical synapse a neuron stores neurotransmitters
in synaptic vesicles in the cytoplasm (3)
Synaptic
vesicles!
Photo: http://www.brainfacts.org/~/media/Brainfacts/Article%20Multimedia/Brain%20Basics/Cell%20Communication/Neurotransmitters_.ashx
Step 1: Action Potential
•
Action potential → a change in the electrical gradient of a cell
membrane b/c of a signal which reaches the neuron, causing
changes in ion concentration, making the inside temporarily
positive (8)
Release of Neurotransmitters Step 2: Calcium
Ion Release
•
Calcium channels (made of protein)
span the membrane of the neuron (1)
o These channels open in response
to an action potential(10)
o More calcium ions (Ca2+)
outside → concentration gradient
→ calcium ions flow into the cell
and bind to receptors inside
membrane (2)
Photo: http://scientopia.org/imgarchive/scicurious/img_374.png
•
Step 3: Converting Electrical Signals into Chemical
Signals
Calcium ion flow induces currents
which cause the synaptic vesicles to
move toward the plasma membrane
o Vesicles fuse with the plasma
membrane and either
 1. Release neurotransmitters
into the chemical synapse (8)
(What type of transport is this?)
 2. Open briefly, release some
neurotransmitter then return to
interior (“kiss and run”) (3)
Photo: http://scientopia.org/imgarchive/scicurious/img_373.png
The release of synaptic vesicles is an
example of what type of transport?
Active Transport - Exocytosis!
Step 4: Crossing the Synapse
•
The neurotransmitters then diffuse across the synaptic
region (3)
Photo: www.maddgraphix.com/images/lightbox/DMAE Boosting Neurotransmitters.jpg
http://faculty.washington.edu/chudler/chnt1.html
•
How are neurotransmitters received by an
adjacent neuron?
(Step 5: Protein receptors)
Postsynaptic cell membrane → has
protein receptors on gated channel
proteins that bind specific neurotransmitters
o Protein receptors change shape, creating
a passageway into the inside of the cell
(what type of diffusion is this?) (9)
o Ions flow into the postsynaptic cell by
diffusing through this passage - starts
process again (3)
www.daviddarling.info/encycloped
ia/N/neurotransmitter.html
Protein receptor analogy: Lock and Key
•
Receptors on postsynaptic cell are
important - many different receptors
for one type of neurotransmitter,
affect how cell reacts to signal (3)
o Analogy: for a neurotransmitter to
have an effect on the
postsynaptic neuron, must bind to
a receptor with the right shape
Photos:http://www.ablongman.com/html/psychplace_acts/synapse/images/lockkey.gif
http://biowiki.ucdavis.edu/@api/deki/files/690/=08neurotranskinase.gif
Step 6: Signals in The Postsynaptic Neuron
•
Neuron input area has excitatory and inhibitory graded
potentials (short distance signals) reaching it all at once
o Synaptic integration → combining postsynaptic signals
that determines the output of the thousands of signals (3)
•
Allows signals to be weakened or increased
o EPSP (excitatory postsynaptic potential) → depolarizing
effect (drives membrane close to threshold) (10)

Cycle repeated: Synapse empty, vesicles filled,action
potential, calcium ready to flow back in
o IPSP (inhibitory postsynaptic potential) (10)
Photo:
http://classes.midlandstech.edu/carterp/
Courses/bio210/chap11/Slide23.JPG
(What happens to the “used”
neurotransmitters?)
•
Can be either (10)
o 1. broken down by enzymes
•
o 2. presynaptic neuron transporters take it back in to be
degraded or reused
However the neurotransmitter can become stuck inside the cleft - e.g. cocaine blocks the intake
of dopamine (3)
Examples of Neurotransmitters:
Epinephrine
Epinephrine- Another term for adrenaline.
Both a hormone and a neurotransmitter, the
difference in the two being that the hormones are
released into the bloodstream by the adrenal gland,
while neurotransmitters cross between the chemical
synapses between neurons and the receiving cell.
•
•
(4)
When in danger crosses synapses, which increases
heart rate and turns on the body and mind’s “Fight
or Flight” mode.
Photo: http://sd.keepcalm-o-matic.co.uk/i/keep-calm-and-carry-epinephrine.png
Another Neurotransmitter Example:
Dopamine
Dopamine
Acts as a neurotransmitter in the substantia
nigra and the ventral tegmental area (parts
of the brain)
Involved in many processes including
movement, emotion, reward, memory,
behavior and cognition, attention, inhibition
of prolactin production, sleep, learning,
pain processing, and nausea. (8)
•
•
(8).
http://www.cs.stedwards.edu/chem/Chem
istry/CHEM43/CHEM43/NeuroT/Dopami
ne.htm
Neurotransmitters in action
Animation: http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter14/animation__transmission_across_a_synapse.html
References
1. "Animation: Transmission Across a Synapse." Animation: Transmission Across a Synapse. N.p., n.d. Web. 4 Nov. 2013.
<http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__transmission_across_a_synapse.html>.
2. Augustine, George J. "How Does Calcium Trigger Neurotransmitter Release." Columbia University.
Elsevier Science, n.d. Web. <http://www.columbia.edu/cu/biology/courses/g6002/2003/
Augustine.pdf>.
3. Brookshire, Bethany. "Back to Basics 1: Neurotransmission." Sciencetopia. Sciencetopia, n.d. Web. 3
Nov. 2013. <http://scientopia.org/blogs/scicurious/2010/08/23/
back-to-basics-1-neurotransmission/>.
4. "Can It Ever Be Too Much? The effects of epinephrine on the brain." Serendip Studio. Serendip, n.d. Web. 3 Nov. 2013.
<http://serendip.brynmawr.edu/exchange/node/430>.
5. "Dopamine." St. Edwards University. St. Edwards University, n.d. Web. 3 Nov. 2013.
<http://www.cs.stedwards.edu/chem/Chemistry/CHEM43/CHEM43/NeuroT/Dopamine.htm>.
6. "Epinephrine." University of Delaware. U of Delaware, n.d. Web. 3 Nov. 2013. <http://www.udel.edu/
chem/C465/senior/fall00/Performance1/epinephrine.htm.html>.
7. Ophardt, Charles E. "Nervous System Overview." Virtual ChemBook. Ed. Charles E. Ophardt. Elmhurst
College, n.d. Web. <http://www.elmhurst.edu/~chm/vchembook/661nervoussys.html>.
8. Mandal, Ananya, Dr. Md. "Dopamine Functions." Ed. April Cashin-Garbutt. News Medical. AZo, n.d. Web.
<http://www.news-medical.net/health/Dopamine-Functions.aspx>.
9. "Neurotransmitter Postsynaptic Receptors." 3. Neurotransmitter Postsynaptic Receptors. N.p., n.d. Web. 4 Nov. 2013.
<http://web.williams.edu/imput/synapse/pages/III.html>.
Copy & Paste
10. Starr, Cecie, and Ralph Taggart. Biology: the unity and diversity of life. 6th ed. Belmont, Calif.: Wadsworth Pub. Co., 1992. Print.