The Nervous System

1. The Nervous System

2. I. General organization of nervous system • CNS 1. brain 2. spinal cord B. PNS 1. sensory 2. motor a. Somatic b. ANS -sympathetic -parasympathetic

3. II. Nervous Supporting Cells - neuroglia • Astrocytes • Connect to capillaries • Mopping up chemical environment of brain as far as potassium ions and neurotransmitters • Help to create blood brain barrier

4. B. Microglia • 1. spider-like phagocytes • 2. debris, dead brain cells, bacteria

5. C. Ependymal cells • 1. lines cavities in CNS • 2. beating of cilia moves cerebrospinal fluid • 3. fluid nourishes and cushions CNS • 4. creates CSF in the choroid plexi of the brain’s ventricles

6. D. Oligodendrocytes • 1. wrap axons of several nerve cells with fatty layer • 2. produces myelin sheath • 3. speeds conduction • 4. located with the CNS

7. E. Schwann cells • 1. located outside of CNS • 2. produce myelin sheath as do the oligodendrocytes • 3. takes several Schwann cells to produce the myelin sheath for one axon of one nerve cell

8. F. Glia cells in general • 1. resemble neurons • 2. not excitable • 3. supportive cells • 4. capable of repeated mitosis • 5. gliomas-glial tumors

9. III. NeuronsA. Structure • 1. cell body • 2. nissl bodies-rer • 3. dendrites • 4. axon • 5. axon hillock • 6. axon collateral • 7. axon terminals • 8. neurotransmitters • 9. synaptic cleft

10. B. Myelin sheath • 1. functions • 2. PNS-Schwann cell • 3. Node of Ranvier • 4. Can form a pathway for regrowth of damaged axon • 5. multiple sclerosis

11. C. Neurons classified by function • 1. afferent • 2. interneuron • 3. efferent • 4. ganglia • 5. nuclei • 6. gray matter • 7. white matter

12. D. Neurons classified by structure • 1. multipolar-most common • 2. bipolar-located in some sensory organs such as the eye • 3. unipolar-sensory neuron

13. IV. Neuron physiology • A. Membrane traits • 1. semipermeable • 2. Na/K ion pump • 3. Leak gates • 4. gated channels • a. Ligand-gated • b. Voltage-gated

14. B. Resting membrane characteristics • 1. semipermeable • 2. negative charged proteins • 3. relatively impermeable to Na and Cl ions • 4. bit more permeable to K ions • 5. due to action of Na/K ion pump notice separation of ions • 6. potassium ions leak out due to K ion leak channels

15. C. Resting membrane potential • 1. at rest, interior of cell possesses slightly negative charge • 2. -70 mV • 3. due to K ion movement mainly • 4. diffusion out • 5. electrical attraction in • 6. slightly more positive charge outside • 7.http://www.youtube.com/watch?v=YP_P6bYvEjE

16. D. Changing the resting membrane potential in a resting neuron • 1. depolarization • 2. hyperpolarization • 3. changes in extracellular K ions (hypokalemia) • 4. changes in extracellular Na ions • 5. changes in extracellular Ca ions • a. Ca ions are attracted to negative proteins of Na gated channels • b. If Ca ion concentration falls-fewer Ca ions attached to Na gated channels-causes channels to open-produces???hypocalcemia • c. If Ca ion levels rise-???

17. E. Graded potentials • 1. strictly local event • 2. caused by change in local ion gates • 3. change brought about by several possible stimulus sources • 4. chemical, voltage changes, temperature, mechanical stimulation • 5. may be excitatory or inhibitory • 6. conducted but in a decremental manner

18. F. Action potential • 1. produced by graded potentials • 2. threshold potential • 3. intiates series of membrane gate changes • 4. wave of depolarization • 5. repolarization • 6. hyperpolarization • 7. return to normal • 8. all-or-none • 9. https://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html

19. G. Refractory period • 1. definition • 2. absolute • 3. relative

20. H. Frequency carries information • 1. action potentials don’t vary in magnitude • 2. threshold stimulus produces one action potential • 3. submaximal stimuli produce increasing frequency of action potentials until • 4. maximal stimulus-lowest stimulus strength that produces maximum frequency of action potentials • 5. supramaximal stimulus

21. I. Propagation of action potentials • 1. concentration difference of ions on either side of membrane represents potential energy-kind of like of cocked gun • 2. stacked dominoes waiting to fall over • 3. one domino falling over initiates a wave of action potentials spreading out like the ripples in a pond • 4. each action potential is just as strong as the previous action potential • 5. strength does not diminish as nerve impulse moves down the axon • 6. http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter44/action_potential_propagation_in_an_unmyelinated_axon.html • 7. http://www.youtube.com/watch?v=DJe3_3XsBOg

22. V. Synapses A. Anatomy • 1. presynaptic membrane • 2. synaptic cleft • 3. postsynaptic membrane • 4. synaptic vesicles • 5. receptor sites for transmitter substance

23. B. Physiology of synapse • 1. action potential arrives • 2. Calcium ion channels open • 3. synaptic vesicles fuse with membrane • 4. transmitter substance released • 5. diffusion of transmitter substance • 6. binding to receptors • 7. creates a graded potential • 8. may bring postsynaptic membrane to threshold • 9. nerve gas-blocks cholinesterase • 10. IPSP or EPSP

24. C. You tube of synaptic events • http://www.youtube.com/watch?v=LT3VKAr4roo

25. D. Types of Synapses • 1. axo-dendritic • 2. axo-somatic • 3. axo-axonic • a. Presynaptic inhibition of enkephalins and endorphins in brain sensory neurons blocking Ca channels • b. Presynaptic facilitation due to serotonin release-causes Ca channels to open

26. E. Post synaptic fiber as a neural integrator • 1. temporal summation • 2. spatial summation • 3. neural integrator