Do what you can, with what you have, where you are. 9/21/2018 Title: Anat & Phys 11/10/06 Objectives: To learn about the nervous system. Class Topics PMI Review Skeletal System Test Nervous System Do what you can, with what you have, where you are. Theodore Roosevelt Friday, September 21, 2018 7:11 PM

Class Assignments Read 240-270 11/16/06 Nervous System Test 11/16/06 9/21/2018 Class Assignments What By When Read 240-270 11/16/06 Nervous System Test 11/16/06 Due this class period Due next class period Due in the future

9/21/2018 Neuroglia (Figure 9-2) Oligodendrocytes - CNS - used to speed up action potentials Schwann cells - found in PNS - aids in conduction of action potential and helps large neurons

Neuron Parts Cell body Dendrites Axon 9/21/2018 Cell body cytoplasm, nucleus (with nucleolus), and organelles organelles including Nissl bodies (like RER) and lacking mitotic spindles Dendrites numerous conduct action potential towards cell body Axon single conduct action potential away from cell body Neuron Parts

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Resting Membrane Potential 9/21/2018 Resting Membrane Potential Difference in charge on inside and outside of plasma membrane unequal distribution of ions Ion channels integral proteins that regulate ion movement in cell membrane not only in nerve cells

Resting Membrane Potential (cont.) 9/21/2018 Resting Membrane Potential (cont.) Ions most often found Na+, K+ More sodium outside and potassium inside this imbalance is kept by the sodium- potassium pump uses energy to move the ions out/in the cell

Sodium-Potassium Pump 9/21/2018 Sodium-Potassium Pump Forces Na+ out and K+ in the cell Creates a concentration gradient Na+ diffuses in and K+ diffuses out Pump doesn’t work evenly 3 Na+ for every 2 K+ Creates an electrical gradient with more positive charges on the outside K+ diffuses more readily than Na+ Increases the electrical gradient

Cell is at resting potential 9/21/2018 Inside the cell Negatively charged Lack of positive ions and presence of Cl- ions Cell is at resting potential Ready to go at stimulus POLARIZED Voltage About –70 mV (millivolts) Very small amount A D battery has about 1.5 volts

Action Potential Excitability 9/21/2018 Action Potential Excitability Ability to respond to a stimulus A stimulus changes the permeability of the cell membrane Na+ ions are able to diffuse through the cell membrane (sodium ion channels) DEPOLARIZED Changes the electrical potential from –70mV to +30 mV Changes the charge inside the cell from negative to positive

Action Potential (cont) 9/21/2018 Action Potential (cont) REPOLARIZED Sodium ion channels close Potassium ion channels open Diffusion of K+ ions begins Cell is back at resting potential Very small amount of ions moved Time taken is minimal (milliseconds)

Conduction of a nerve impulse 9/21/2018 Conduction of a nerve impulse The action potential moves quickly along a nerve fiber Propagated by the electrical gradient Figure 9-8 (p. 248)

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9/21/2018 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

Animations Action potential Channel gating Other links 9/21/2018 Animations Action potential http://www.blackwellscience.com/matthews/actionp.html Channel gating http://www.blackwellscience.com/matthews/channel.html Other links http://www.psych.ufl.edu/~rowland/neurochem1+2/sld031.htm http://bio.bio.rpi.edu/HB/Universal%20Files/Lectures/L40NerveAP/L40NerveAP.html