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Electrochemical Impulse. 9.2. Nerve Impulses (Image on previous slide: http://scientopia.org/blogs/scicurious/2011/05/04/science-101-the-neuron/). there are about 100 billion neurons in the human brain neurons can transmit 1000 nerve impulses per second

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Nerve Impulses(Image on previous slide: http://scientopia.org/blogs/scicurious/2011/05/04/science-101-the-neuron/)
  • there are about 100 billion neurons in the human brain
  • neurons can transmit 1000 nerve impulses per second

(Source: http://virtuallabs.stanford.edu/tech/images/ReactionTime.SU-Tech.pdf)

potential difference image from http people eku edu ritchisong 301notes2 htm
Potential Difference(Image from: http://people.eku.edu/ritchisong/301notes2.htm)
  • caused by relative concentrations of positive ions (Na+ and K+) on either side of the membrane
Neuron Membrane(Image from: http://www.columbia.edu/cu/psychology/courses/1010/mangels/neuro/neurosignaling/neurosignaling.html)
resting potential 70mv
Resting Potential -70mV
  • the resting membrane is about 50 times more permeable to K+ ions than Na+
  • more K+ out than Na+ in
  • polarized membrane
excitation of neuron
Excitation of Neuron


+ repolarization

+ restoration of resting potential

= actionpotential

depolarization 40 mv image from http www lionden com nerve animations htm
Depolarization (+40 mV)(Image from: http://www.lionden.com/nerve_animations.htm)
  • Na+ channels open
  • Na+ ions enter, causing charge reversal (depolarization)
repolarization 70 mv image from http elysium wustl edu linglelab general htm
Repolarization (-70+ mV)(Image from: http://elysium.wustl.edu/LingleLab/general.htm)
  • Na+ channels shut
  • K+ channels open
  • K+ moves out of cell
repolarization 70 mv image from http student ccbcmd edu gkaiser biotutorials eustruct sppump html
Repolarization (-70 mV)(Image from: http://student.ccbcmd.edu/~gkaiser/biotutorials/eustruct/sppump.html)
action potential image from http jacobsussmanpsych100 blogspot com
Action Potential(Image from: http://jacobsussmanpsych100.blogspot.com)
  • Neat interactive animation of action potential; worth spending the time to go through:
  • http://outreach.mcb.harvard.edu/animations/actionpotential.swf
  • The dry but informative McGraw-Hill narrated animation & quiz:
  • http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html
from http commons wikimedia org wiki file action potential propagation animation gif
From: http://commons.wikimedia.org/wiki/File:Action_potential_propagation_animation.gif
action potential image from http jacobsussmanpsych100 blogspot com1
Action Potential(Image from: http://jacobsussmanpsych100.blogspot.com)
  • refractory period (1-10 ms)
  • threshold level
  • all-or-none response
Synaptic Transmission(Image from: http://cwx.prenhall.com/bookbind/pubbooks/morris5/chapter2/custom1/deluxe-content.html)
synaptic transmission
Synaptic Transmission
  • nerve impulse in presynapticneuron causes calcium channels to open
  • Ca2+ ions flow in and cause the release of neurotransmitters (such as acetylcholine) into the synaptic cleft
synaptic transmission 2
Synaptic Transmission 2
  • neurotransmitter (e.g. acetylcholine) binds to receptors in dendrites of post-synaptic neuron
  • acetylcholine (excitatory) causes Na+ channels to open, propagating the action potential
  • Quick McGraw-Hill narrated animation with quiz:
  • http://highered.mcgraw-hill.com/sites/0072943696/student_view0/chapter8/animation__chemical_synapse__quiz_1_.html
  • Narrated animation with quiz (a bit more detailed):
  • http://bcs.whfreeman.com/thelifewire/content/chp44/4403s.swf
other neurotransmitters
Other Neurotransmitters
  • dopamine - regulates motor skills, emotional response, ability to express pleasure and pain
  • serotonin - helps with sleep, calms anxiety, relieves depression
  • histamine - allergic reactions
  • norepinephrine (noradrenaline)
  • epinephrine (adrenaline)
anti anxiety drugs image from http www mxmcreation com medicine generic forms of valium html
Anti-anxiety drugs(Image from: http://www.mxmcreation.com/medicine/generic-forms-of-valium.html)
  • depressants such as diazepam (Valium) act by increasing the amount of inhibitory neurotransmitters at synapses
  • substantiagelatinosa (SG) in the spinal cord interprets pain signals
  • produces neurotransmitter that transmits pain information to injured tissue or organ
  • more neurotransmitter = more pain
natural painkillers
Natural Painkillers
  • endorphins and enkephalins are produced by the pituitary and hypothalamus
  • released in times of pain (and also during exercise, etc.)
  • bind to receptors on SG cells so that neurotransmitter is not produced


= endogenous



artificial painkillers image from http www drugrehabscalifornia org about the drugs opiates
Artificial Painkillers(Image from: http://www.drugrehabscalifornia.org/about-the-drugs/opiates)
  • opiates such as heroin, codeine, morphine mimic the action of endorphins
  • depressants don’t act on SG cells exclusively, but cause inhibitory