1. What you should know The parts of the nerve What an action potential is How nerve cells are insulated and the function of this How nerve cells communicate

2. Bellwork: Label the neuron

3. Fig. 48-4 Dendrites Stimulus Nucleus Cell body Axon hillock Presynaptic cell Axon Synaptic terminals Synapse Postsynaptic cell Neurotransmitter

4. Introduction to Information Processing Nervous systems process information in three stages: sensory input, integration, and motor output

5. Fig. 48-9 Stimuli +50 Stimuli 00 Membrane potential (mV) –50 Threshold Resting potential Resting potential Hyperpolarizations –100 0 123 4 5 Time (msec) (a) Graded hyperpolarizations Time (msec) (b) Graded depolarizations Depolarizations 0 1 234 5 Strong depolarizing stimulus +50 0 Membrane potential (mV) –50 Threshold Resting potential –100 Time (msec) 01 2 3 4 56 (c) Action potential Action potential Action Potential – enough stimulus to send the signal (all or nothing)

6. Conduction Speed The speed of an action potential increases with the axon’s diameter In vertebrates, axons are insulated by a myelin sheath, which causes an action potential’s speed to increase Myelin sheaths are made by glia— oligodendrocytes in the CNS and Schwann cells in the PNS

7. Fig. 48-12a Axon Myelin sheath Schwann cell Nodes of Ranvier Schwann cell Nucleus of Schwann cell Node of Ranvier Layers of myelin Axon

8. Importance of Myelin Sheath http://www.youtube.com/watch?v=qgySDmRRz xYhttp://www.youtube.com/watch?v=qgySDmRRz xY

9. Fig. 48-13 Cell body Schwann cell Depolarized region (node of Ranvier) Myelin sheath Axon

10. Neurons communicate with other cells at synapses At electrical synapses, the electrical current flows from one neuron to another At chemical synapses, a chemical neurotransmitter carries information across the gap junction Most synapses are chemical synapses

11. Fig. 48-15 Voltage-gated Ca 2+ channel Ca 2+ 1 2 3 4 Synaptic cleft Ligand-gated ion channels Postsynaptic membrane Presynaptic membrane Synaptic vesicles containing neurotransmitter 5 6 K+K+ Na +

12. Activity Go to http://www.emc.maricopa.edu/faculty/farabee/ BIOBK/BioBookNERV.html and complete the worksheet http://www.emc.maricopa.edu/faculty/farabee/ BIOBK/BioBookNERV.html

13. Muscles and how they contract

14. Muscles work because they are anchored to bonesMuscles work because they are anchored to bones

16. Muscles are made of actin and myosin Actin and myosin move past each other, they do not shorten Myosin heads “walk” along the actin

21. The tropomyosin covers the myosin-binding sites Calcium causes the tropomyosin to shift positions so myosin heads can bind

22. How the neuron sends a signal

24. Video on muscle contraction