2112022 Title Anat Phys 111006 Objectives To learn

2/11/2022 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, February 11, 2022 7: 41 PM 1

2/11/2022 Class Assignments What • Read 240 -270 • Nervous System Test By When 11/16/06 • Due this class period • Due next class period • Due in the future 2

2/11/2022 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 3

2/11/2022 • Cell body – cytoplasm, nucleus (with nucleolus), and organelles Neuron Parts • 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 4

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2/11/2022 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 6

2/11/2022 Resting Membrane Potential (cont. ) • Ions most often found – Na+, K+ – More sodium outside and potassium inside – this imbalance is kept by the sodiumpotassium pump • uses energy to move the ions out/in the cell 7

2/11/2022 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 8

2/11/2022 • 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 m. V (millivolts) • Very small amount – A D battery has about 1. 5 volts 9

2/11/2022 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 – 70 m. V to +30 m. V – Changes the charge inside the cell from negative to positive 10

2/11/2022 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) 11

2/11/2022 Conduction of a nerve impulse • The action potential moves quickly along a nerve fiber – Propagated by the electrical gradient – Figure 9 -8 (p. 248) 12

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2/11/2022 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 14

2/11/2022 Animations • Action potential – http: //www. blackwellscience. com/matthews/act ionp. html • Channel gating – http: //www. blackwellscience. com/matthews/ch annel. html • Other links – http: //www. psych. ufl. edu/~rowland/neurochem 1 +2/sld 031. htm – http: //bio. rpi. edu/HB/Universal%20 Files/Le ctures/L 40 Nerve. AP. html 15