1. Fundamentals of the Nervous System Chapter 11 Dr Tamily Weissman, Department of Molecular and Cellular Biology, Harvard University

2. Functions of the Nervous System Master controller and communicator of the body Sensory input (to CNS) – External or internal sensors Integration – Immediate context – Experience Motor output (from CNS) – Muscle or gland response See yellow light Foot to brake or gas Process options

3. Nervous System Central Nervous System (CNS) BrainSpinal Cord Peripheral Nervous System (PNS) Motor (efferent) Autonomic (involuntary) SympatheticParasympathetic Somatic (voluntary) Sensory (afferent) Human Nervous System Divisions Integration & command Info in & out

4. http://images.google.com/imgres?imgurl=http://www.dmac c.edu/instructors/rbwollaston/Nervous_system/neuroglia_of _CNS.gif&imgrefurl=http://www.dmacc.edu/instructors/rbw ollaston/Chapter_8_Nervous_System.htm&usg=__2YxucQKr JmUKtfkBty- PZGw_y1A=&h=386&w=371&sz=9&hl=en&start=1&sig2=zDo9 CPoP08kpEikUtueyXw&um=1&tbnid=7Kr6pqq0qPkVQM:&tb nh=123&tbnw=118&prev=/images%3Fq%3Dneuroglia%26hl% 3Den%26sa%3DG%26um%3D1&ei=NGVTSvmkE8yjmQels_C gCQ Neuroglia CNS – Astrocytes Connect neurons to capillaries Guide growing neurons – Microglia: immune functions – Ependymal cells: circulate CSF – Oligodendrocytes: produce multiple myelin sheaths PNS – Schwann cells: produce myelin – Satellite cells: similar to astrocytes

5. Neurons http://www.pspnperak.edu.my/biologit5/Abd%20Razak%20b.%20Yaacob/Por tfolio/BBM/Audio/saraf/Neuron%208.gif Structural unit of the nervous system Cell body – Nissl bodies – Nuclei vs ganglia Processes – Dendrites Graded potentials – Axons Axon hillock Axon terminals Axolemma and axoplasm Myelin sheath and nodes of Ranvier White vs gray matter – Tracts vs nerves

6. Classification of Neurons http://www.unisanet.unisa.edu.au/Resources/101766/Online%20Brain%20Development%20course/Pics/Photo %201g.gif Structural classification – Multipolar: mainly in CNS – Bipolar: sense organs – Unipolar : mainly in PNS Functional classification – Sensory are afferents – Motor are efferents – Interneurons

7. Ion Channels Proteins spanning PM controlling flow – Leak channels – Gated channels Chemical (ligand) respond to NT Voltage respond to change in polarization Mechanical respond to physical change/deformation Ions move down an electrochemical gradient

8. Resting Membrane Potential Polarization creates potential energy Changes allow cellular communication – Current from flow of charge (ions) K + leaks out and Na + leaks in Na + /K + pump maintains – Resistance regulates

9. Graded Potentials Varies with stimuli – Short, localized, and decremental Depolarization (-70mV to -55mV) Hyperpolarization (-70mV to -100mV) – Summation can initiate action potentials (APs) http://www.colorado.edu/intphys/Class/IPHY3430-200/image/figure4-8.jpg

10. Action Potentials (AP’s) Depolarization – Positive feedback maintains – Threshold = all or nothing response Repolarization – Returning electrical conditions Hyperpolarization – Na + /K + pump returns ionic conditions Refractory periods – Absolute – Relative

11. Propagation of an Action Potential Unmyelinated Myelinated Self-generating Refractory period ensures one-way movement Conduction speed – Axon diameter – Degree of myelination Continuous conduction w/o myelin Saltatory conduction at nodes of Ranvier Multiple sclerosis

12. Synapses Types – Presynaptic neuron sends – Postsynaptic neuron receives Classification – Axodendritic – Axosomatic – Axoaxonic Function – Electrical synapses – Chemical synapses

13. Chemical Transmission AP reaches axon terminal Ca 2+ signals NT release NT binds postsynaptic neuron – EPSP (depolarize) – IPSP (hyperpolarize) Ending transmission – Degradation – Reuptake – Diffusion http://anthropologynet.files.wordpress.com/2008/01/neuron-synapse.png

14. Neurotransmitter Classes Acetylcholine (ACh): skeletal muscles Biogenic amines – Dopamine (DA) – Norepinephrine (NE) & epinephrine (Epi) – Serotonin (5-HT) – Histamine Amino acids – GABA – Glutamate Neuropeptides – Endorphins – Substance P Dissolved gases – NO: synthesized on demand; relaxation of smooth muscle (Viagra)