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Electrochemical Impulse

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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  1. Electrochemical Impulse 9.2

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

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

  4. 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

  5. Neuron Membrane(Image from: http://www.columbia.edu/cu/psychology/courses/1010/mangels/neuro/neurosignaling/neurosignaling.html)

  6. 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

  7. Excitation of Neuron depolarization + repolarization + restoration of resting potential = actionpotential

  8. Depolarization (+40 mV)(Image from: http://www.lionden.com/nerve_animations.htm) • Na+ channels open • Na+ ions enter, causing charge reversal (depolarization)

  9. Repolarization (-70+ mV)(Image from: http://elysium.wustl.edu/LingleLab/general.htm) • Na+ channels shut • K+ channels open • K+ moves out of cell

  10. Repolarization (-70 mV)(Image from: http://student.ccbcmd.edu/~gkaiser/biotutorials/eustruct/sppump.html)

  11. Action Potential(Image from: http://jacobsussmanpsych100.blogspot.com)

  12. Animation… • 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

  13. From: http://commons.wikimedia.org/wiki/File:Action_potential_propagation_animation.gif

  14. Action Potential(Image from: http://jacobsussmanpsych100.blogspot.com) • refractory period (1-10 ms) • threshold level • all-or-none response

  15. What happens when the action potential reaches the axon terminals?

  16. Synaptic Transmission(Image from: http://cwx.prenhall.com/bookbind/pubbooks/morris5/chapter2/custom1/deluxe-content.html)

  17. 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

  18. 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

  19. Animations • 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

  20. 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)

  21. some related material from 9.4…

  22. 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

  23. Pain • substantiagelatinosa (SG) in the spinal cord interprets pain signals • produces neurotransmitter that transmits pain information to injured tissue or organ • more neurotransmitter = more pain

  24. 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

  25. Endorphins endorphin = endogenous morphine (http://dictionary.reference.com/browse/endorphin)

  26. 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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