Class Topics

1. Nervous System Review "Honor is like an island, rugged and without a beach; once we have left it, we can never return." Nicholas Boileau Despreaux To learn about the nervous system. Title: Anat & Phys 11/16/06 Class Topics Objectives: Saturday, January 4, 20201:59 AM

2. Class Assignments What By When • Read 240-270 11/16/06 • Nervous system test 11/20/06 • Due this class period • Due next class period • Due in the future

3. Review

5. Animations • Action potential • http://www.blackwellpublishing.com/matthews/actionp.html • Channel gating • http://www.blackwellpublishing.com/matthews/channel.html

6. Saltatory Conduction • Movement of action potential along myelinated fibers • Impulse moves from node of Ranvier to node of Ranvier • Moves much faster due to the fact that the impulse jumps over the myelinated areas • Can jump up to 3 mm sections • 130 m per second compared to 10 m per second for unmyelinated

7. Problems • Speed = Distance/time • Myelinated fibers can carry an action potential 150 m/s • Unmyelinated fibers can carry an action potential 10 m/s • How long does it take for an action potential to travel from the toe to the brain of a 1.8 m individual for each fiber?

9. All-none-response • If a stimulus causes an action potential it will be sent the length of the neuron at maximum speed • threshold stimulus • minimum stimulus needed to send an action potential • Summation • a series of subthreshold stimuli that eventually add up to a stimulus

10. Anatomy of a synapse • Presynaptic neuron • Synaptic end bulb • Synaptic vesicles • Contain neurotransmitters • Chemicals released to relay impulse • Postsynaptic neuron • Concave surface • Synaptic cleft • Space between the two neurons

12. Physiology of a synapse • Nerve impulse enters synaptic end bulb • Ca2+ ions enter bulb from outside • Synaptic vesicles fuse with cell membrane • Exocytosis of neurotransmitters • Chemicals diffuse between cells • Contact postsynaptic neuron (receptor protein) • Can excite neuron or inhibit neuron • Depends on what neurotransmitter is released • Excited neurons open Na+ ion channels • Neurotransmitter is immediately inactivated • By enzymes (ex. acetylcholinesterase)

14. Neurotransmitters • Acetylcholine (Ach) • neuromuscular junction • prominent in PNS • Dopamine • brain processes that control movement, emotional response, and ability to experience pleasure and pain. • Norepinephrine & Epinephrine • also called adrenaline • sympathetic branch of autonomic system

15. Neurotransmitters • Serotonin • found in brain • Melatonin • brain - used in sleep • Endorphins • inhibit the transfer of pain impulses • opiates bond to same receptors • morphine, heroin, codeine

16. Neurotransmitter actions • Inhibitory • hyperpolarizes the cell membrane • below resting potential • unable to conduct an action potential • Excitatory • depolarizes the cell membrane • action potential is sent to next neuron

17. Good Links • http://www.zerobio.com/central/actionpotential.htm • http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookNERV.html • http://emile-21.com/VRML/membPotMain.html • http://www.accessexcellence.org/RC/VL/GG/ecb/propagation_action_potential.html • http://www.ship.edu/~cgboeree/theneuron.html • http://www.dls.ym.edu.tw/ol_biology2/ultranet/ExcitableCells.html • http://web.lemoyne.edu/~hevern/psy340/lectures/psy340.02.2a.neur.impulse.html • http://www.ucl.ac.uk/~sjjgsca/NerveRestingPot.html • http://www.columbia.edu/cu/psychology/courses/1010/mangels/neuro/neurosignaling/neurosignaling.html • http://academic.kellogg.cc.mi.us/vrugginkf/biol202/bio202obj/nervous_system.htm • http://www.cptc.ctc.edu/library/Bio%20118%20Lecture%20Notes%20Rev%200105.htm • http://trc.ucdavis.edu/biosci10v/bis10v/week10/06potential.html