The Nervous System:Neurotransmitters

By Josephina, Ben, Andrew, and Jacob

Photo: http://total-body-psychology.com.au/wp-content/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&source=images&cd=&docid=Li8YVDJMckV3cM&tbnid=5WoEACCv3HccsM:&ved=0CAIQjBw&url=http%3A%2F%2Ftotal-body-psychology.com.au%2Fwp-content%2Fuploads%2F2012%2F07%2Fneurotransmitter.gif&ei=lhd3UtOoE9as4AOYw4DwBg&bvm=bv.55819444,d.cWc&psig=AFQjCNGi47hO8noNSO-uL5slBG3aXKwxqA&ust=1383622930610294

• At the chemical synapse a neuron stores neurotransmitters in synaptic vesicles in the cytoplasm (3)

Where are neurotransmitters stored?

Photo: http://www.brainfacts.org/~/media/Brainfacts/Article%20Multimedia/Brain%20Basics/Cell%20Communication/Neurotransmitters_.ashx

Synaptic vesicles!

• 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)

Step 1: Action Potential

• 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)

Release of Neurotransmitters Step 2: Calcium Ion Release

Photo: http://scientopia.org/img-archive/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 membraneo 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/img-archive/scicurious/img_373.png

The release of synaptic vesicles is an example of what type of transport?

Active Transport - Exocytosis!

• The neurotransmitters then diffuse across the synaptic region (3)

Step 4: Crossing the Synapse

Photo: www.maddgraphix.com/images/lightbox/DMAE Boosting Neurotransmitters.jpghttp://faculty.washington.edu/chudler/chnt1.html

• Postsynaptic cell membrane → has protein receptors on gated channel proteins that bind specific neurotransmitterso 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)

How are neurotransmitters received by an adjacent neuron?

(Step 5: Protein receptors)

www.daviddarling.info/encyclopedia/N/neurotransmitter.html

• 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

Protein receptor analogy: Lock and Key

Photos:http://www.ablongman.com/html/psychplace_acts/synapse/images/lockkey.gif http://biowiki.ucdavis.edu/@api/deki/files/690/=08neurotranskinase.gif

• Neuron input area has excitatory and inhibitory graded potentials (short distance signals) reaching it all at onceo Synaptic integration → combining postsynaptic signals

that determines the output of the thousands of signals (3)

• Allows signals to be weakened or increasedo 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)

Step 6: Signals in The Postsynaptic Neuron

Photo: http://classes.midlandstech.edu/carterp/Courses/bio210/chap11/Slide23.JPG

• Can be either (10)

o 1. broken down by enzymeso 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)

(What happens to the “used” neurotransmitters?)

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) (8).

• Involved in many processes including movement, emotion, reward, memory, behavior and cognition, attention, inhibition of prolactin production, sleep, learning, pain processing, and nausea. (8)

http://www.cs.stedwards.edu/chem/Chemistry/CHEM43/CHEM43/NeuroT/Dopamine.htm

Neurotransmitters in action

Animation: http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__transmission_across_a_synapse.html

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 & Paste10. Starr, Cecie, and Ralph Taggart. Biology: the unity and diversity of life. 6th ed. Belmont, Calif.: Wadsworth Pub. Co., 1992. Print.

References