Lecture Objectives for Unit 3 Fall 2021, Bio 312-02 Following lectures and in association with the assigned readings, students should be able to: NERVOUS TISSUES, COMPONENTS 1. Describe essential differences between the endocrine system and nervous system in terms speed, duration of action, and mode of chemical communication. 2. Draw an organizational chart that identifies the major divisions and subdivisions of the nervous system. 3. Define the primary physiological role of each of the major divisions and subdivisions of the nervous system. 4. Contrast the type of effector organs that are innervated by the autonomic nervous system with respect to those innervated by the somatic nervous system. 5. Distinguish neurons from glia in terms of general properties of these two classes of nervous system cells. 6. List the 6 classes of glial cells according to their primary functions and locations – how they are integrated into the network of neurons and other glial cells. 7. Describe the contacts between astrocytes and neurons, capillaries, and ependymal cells. 8. List the major components of a neuron and tell what the general role of each major part is with respect to communication of information. 9. Describe how myelin is created in the PNS and in the CNS. 10. Distinguish between the contacts made by Schwann cells and axons that are myelinated, versus axons that are unmyelinated. 11. Describe the essential characteristics of the 3 morphological classes of neurons: multipolar, bipolar and unipolar. 12. Define the functions and anatomical distributions of the three physiological (functional) classes of neurons: sensory neurons, interneurons, and motor neurons. 13. Describe the movement of transmitter molecules and organelles along axon microtubules and filaments in retrograde and anterograde directions at differing speeds. 14. Apply these movements to circumstances of axon development and regeneration (PNS neurons) and the work of R. Levi-Montalcini. ELECTRICAL MEMBRANE POTENTIALS (review and brief, quantitative expansion) 15. Explain why membrane potentials depend upon which ion channels are open at any given moment in time. 16. Distinguish ‘leak channels’ from gated channels. 17. Recognize the relationships and assumptions that are included in the Nernst Equation, and use the Nernst Equation to describe how a change in an intracellular or extracellular concentration of an ion (electrolyte) may change membrane potential. 18. Note how changes in graded (local) potentials and action potentials are created by temporarily changing the relative permeability of a cell membrane to selected ions. 19. Recognize how the relative permeability of the cell membrane to ions is embedded in the Goldman Equation, and why momentary membrane potentials never become more negative than Em for K+ or more positive than Em for Na+ in normal, physiological conditions. GATED CHANNELS AND SIGNALING IN/BETWEEN NEURONS 20. Differentiate between each of the three types of channel gates: ligand- sensitive, voltage-sensitive, mechano-sensitive. (recap from earlier lectures)21. Describe the primary differences between graded potentials and action potentials in terms of: a. The types of gated channels that typically produce them. b. The locations where these channels are found in a neuron. c. Variability of signal amplitude. d. Suitability for long-distance or short-distance communication. 22. Tell how a graded potential spreads, and how much time it takes to spread. 23. Note the degradation of graded potentials over distance. 24. Define: depolarization, hyperpolarization, repolarization, resting potential. 25. Tell which direction each of the following will flow (net movement) when an appropriate channel opens in a membrane that is at resting potential: Na+, Cl-, Ca2+, K+. (Use table in slides for reference. The Nernst Equation can help provide a specific answer.) 26. Explain whether hyperpolarization or depolarization occurs in each case listed in the previous objective, and why. 27. Explain the concepts of ‘subthreshold’ and ‘suprathreshold’ graded potentials and correlate these with the all-or-none nature of action potentials. 28. List the primary properties for the voltage-gated Na+ and voltage-gated K+ channels that are part of action potential activity. 29. Tell whether the number of ions crossing the membrane in a single AP are enough to significantly change ion concentrations in ICF or ECF. 30. Note the role of the Na+/K+ pump in recovery to resting potential. 31. Describe the triggers for opening voltage-gated Na+ and K+ channels, and the reasons why these channels close. 32. Describe the interaction of local currents and voltage-gated channels in propagating APs down axonal segments in an unmyelinated axon. 33. Tell how myelinated axons differ from unmyelinated axons anatomically. ------------------------------ 34. Describe the interaction of local currents and voltage-gated channels in propagating APs down axonal segments in a myelinated axon. 35. Explain how myelinated axons make use of graded potentials to speed the progress of APs. 36. List the steps of the AP cycle (“Hodgkins cycle”) with respect to changes in membrane potential, channel open/close states, and ion permeabilities. 37. Tell which physical characteristics are important in producing faster propagation of action potentials. 38. Classify axons (Types A,B,C) and give appropriate descriptions of the use of each class. 39. Tell whether axons can be myelinated to different degrees, correlate myelination with nerve impulse propagation characteristics, and describe how myelin might improve an axon’s electrical properties. 40. Define what is meant by ‘refractory period’, and the two parts of this period, the absolute and relative refractory periods. 41. Describe the relationship between the absolute refractory period and the maximum ‘firing rate’ for APs in a neuron. 42. Explain why it is that a sustained depolarization can produce multiple action potentials. 43. Explain why a more intense sustained depolarization produces action potentials at a higher rate than does a less intense