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Nerves, Hormones &
Homeostasis
Stephen Taylor
i-Biology.net
Schwan
cell
The Motor Neuron
Diagram from: http://commons.wikimedia.org/wiki/File:Anatomy_and_physiology_unlabeled_neuron.jpg
http://bcs.whfreeman.com/thelifewire/content/chp44/4402s.swf
-70mV
Membrane 50 times more
permeable to K+ ions than
Na+
Proteins inside the nerve fiber are negatively charged which increases the charge
imbalance.
http://www.blackwellpublishing.com/matthews/channel.html
From McGraw Hill: http://goo.gl/tI2MD
http://www.blackwellpublishing.com/matthews/actionp.html
http://outreach.mcb.harvard.edu/animations/synaptic.swf
Acetylcholine
• Neurotransmitter in many synapses
• Produced in pre-synaptic neuron, loaded into
vesicles & released into synaptic cleft during
synaptic transmission.
• Receptors located in post-synaptic membrane
• While bound, one action potential is initiated.
• After transmission it breaks down.
Threshold potential
• Action potentials only initiated if threshold
potential is reached
• At synapse, the amount of neurotransmitter
secreted following depolarization of the presynaptic membrane may not be enough to cause
t.p. to be reached in post-synaptic membrane.
• Depolarization does not take place. Returns to
resting potential
• Neurons in brain & spinal cord have many presynaptic neurons. Often multiple must secrete
neurotransmitters at same time.
neonicotinoids
• Synthetic compounds similar to nicotine
• Bind to acetylcholine receptor in the central
nervous system of insects.
• Binding is irreversible, permanently blocking
receptors resulting in paralysis and death
• Advantage in pesticides: not toxic to humans
or mammals.
• Disadvantages: effects on honeybees and
other beneficial insects.
@IBiologyStephen
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