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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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Electrochemical Impulse

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Electrochemical impulse

Electrochemical Impulse


Electrochemical impulse

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)

Electrochemical impulse

(Image from:http://www.thenutritionpost.com/tag/brain-scans)

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

Electrochemical impulse

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

What happens when the action potential reaches the axon terminals

What happens when the action potential reaches the axon terminals?

Electrochemical impulse

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)

Some related material from 9 4

some related material from 9.4…

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

Electrochemical impulse


  • 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

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