Download Nervous System

Nervous System
Group 2
Eric Pinsker-Smith, Ian Kinney,
George Hatzipetrou
Chemical Synapses
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Are specialized junctions where neurons
signal
to each other and non-neuronal cells
Connect
neurons to form
circuits within
the nervous
system
Allow nervous
system to
interact with
other systems of
the body
(4. Starr, Taggart Textbook)
http://upload.wikimedia.org/wikipedia/commons/3/30/Chemi
cal_synapse_schema_cropped.jpg
Neurotransmitters
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Are molecules that transmit signals to cells
through synapses
Two examples are histamine, which is part
of the immune system and triggers
inflammatory responses all throughout the
body, and acetylcholine, which triggers
action potentials in muscles, glands, spinal
cord, and brain (4. Starr, Taggart Textbook).
http://en.wikipedia.org/wiki/File:Histamine3d.png
http://upload.wikimedia.org/wikipedia/commons/2/26/
Acetylcholine.png
How Electrical Signals Transform
into Chemical signals and why they
do this
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Neurons always have a negative charge. (-70
millivolts) evenly distributed throughout the
neuron. The charge is carried by sodium ions
When a neuron is pressed or pulled, the cells
movement redistributes the ions, making it
charged.
If a sufficient charge is reached, it will trigger a
release of sodium ions. This energy release is
powerful, lasts for 1 milli second and sends a
strong electric current down the axon.
Source: Principles of Neural Science
How Electrical Signals Transform
into Chemical signals and why they
do this
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This electronic signal reaches the neurotransmitters
stored in the end of the axon.
The electricity excites them and starts their exocytosis,
in which they leave the neuron, trigger receptors in the
adjacent neuron, then diffuse back into the neuron in
which it started.
psychology.about.com/od/bi
opsychology/f/neuron01.htm
Why is this conversion necesary?
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This is important because electricity can't
cross the synaptic cleft, only chemicals can.
This allows for the transportation of signals
between neurons.
http://en.wikipedia.org/wi
ki/Principles_of_Neural_
Science
http://images.google.com
/imgres?q=chemical+syn
apses&num=10&hl=en&
biw=1202&bih=591&tbm
How neurotransmitters cross the neural membrane
and how that signal is then received by an adjacent
neuron
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Synapses serve as the means to
allow neurons to pass signals to
another cell.
When a cell has a voltage
disturbance, (one side more
positively charged than the other)
this is known as an action
potential, in which an electrical
current is released. An action
potential is the local voltage
change across the cell wall as a
nerve impulse is transmitted.
Each neuron has a different
charge. Gated channels for
calcium ions span the presynaptic
cell's membrane, and they open
once action potential occurs.
http://img.tfd.com/mk/S/X2604-S-70.png
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Cont...
Neurons carry a negative charge, and thus are filled
with sodium ions. The calcium ions on the outside hold
a positive charge, and they therefore diffuse into the
neuron.
This intake of calcium stimulates a release of sodium
ions in the form of an electric current.
This current excites the neurotransmitters which are in
vesicles, and they undergo exocytosis and leave the
neuron.
The neurotransmitters then diffuse into the postsynaptic
cell, where they stimulate receptors.
Bibliography
1. Bullock, T.H., Bennett, M.V.L., Johnston, D., Josephson, R., Marder, E.,
Fields R.D. 2005. The Neuron Doctrine, Redux, Science, V.310, p. 791–
793.
2. Kandel E.R., Schwartz, J.H., Jessell, T.M. 2000. Principles of Neural
Science, 4th ed., McGraw-Hill, New York.
3. Peters, A., Palay, S.L., Webster, H, D., 1991 The Fine Structure of the
Nervous System, 3rd ed., Oxford, New York
4. Starr, Cecie, and Ralph Taggart. Biology: The Unity and Diversity of Life.
Ninth ed. Pacific Grove: Brooks/Cole, 2001. Print.
5. "What Is a Neuron." Psycology.net. N.p., n.d. Web. 3 Nov. 2012.
<psychology.about.com/od/biopsychology/f/neuron01.htm>.