1. 9.5-9.9 Notes https://www.youtube.com/watch?v= XdCrZm_JAp0

2. Biology 21/15 HW-finish reading guide for Friday Agenda: Action Potentials -notes first -online activity next 1.Take out 9.5 reading guide 2.Take out online activity.

3. Cell Membrane Set-up Membrane is polarized. -large amounts of negative charges on the inside of the membrane -large amounts of positive charges on the outside of the cell Overall makes inside the cell negatively charged- THIS IS POLARIZED Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

5. Ions move during Rest Time Channels in membranes are permeable – Potassium moves easier than sodium More potassium moving out that sodium coming in – Move through diffusion Helps create negative charge inside Sodium Potassium Pump-ATP is used to pump sodium and potassium ions across membrane – Maintains polarization Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

6. Resting Potential Active Transport allows for potassium to move out faster than sodium moving in. This separation of charge, or potential difference, is called the resting potential. Cell is at -70 millivolts Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

7. Things happen to the membrane: When a neurotransmitter is picked up by a dendrite, it will stimulate the membrane. An action potential can occur: 2 things must happen – Repolarization – Depolarization

8. Depolarization Inside of the membrane becomes less negative (insides becomes more positive)- increase in volts Sodium channels open and potassium channels close Stimulation must reach a certain point (threshold) before the neuron continues on.

9. Repolarization potassium channels open and sodium closes Inside of the membrane becomes negative Refractory period-time when the neuron cannot respond to a second stimulus (time when the graph dips below resting potential)

10. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

11. Dip in graph after repolarization: Hyperpolarization (at refractory period time)-a deep below the -70 mv occurs because gates are closed and chlorine comes into the cell. So the cell negativity drops more. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

14. Impulse Conduction MYELINATED VS UNMYELINATED Unmyelinated fibers conduct impulses over their entire membrane surface-SLOW Myelinated fibers conduct impulses from node of Ranvier to node of Ranvier, a phenomenon called saltatory conduction. – Saltatory conduction is many times faster than conduction on unmyelinated neurons. http://www.blackwellpublishing.com/matthews/a ctionp.html http://www.blackwellpublishing.com/matthews/a ctionp.html AXON DIAMETER The greater the diameter, the faster it travels. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

15. All-or-None Response If a nerve fiber responds at all to a stimulus, it responds completely by conducting an impulse (all-or-none response). Greater intensity of stimulation triggers more impulses per second, not stronger impulses. Complete depolarization must take place for a neuron to travel along the axon How does an action potential move from one neuron to the next? http://www.execulink.com/~ekimmel/mixed_flash.htm Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

16. The Synapse http://outreach.mcb.harvard.edu/animations/synap tic.swf The junction between two communicating neurons is called a synapse There exists a synaptic cleft between them across which the impulse must be conveyed. Presynaptic neuron-carries pulse Postsynaptic neuron-receives it When the impulse reaches the synaptic knobs (also known as axon terminal), neurotransmitters must be released from synaptic vesicles into the synaptic cleft. The nts are released because of the influx of calcium. Recycled, deactivated, or attach to receptors Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

17. LABEl

20. Excitatory and Inhibitory Actions Neurotransmitters that increase postsynaptic membrane permeability to sodium ions may trigger impulses and are excitatory. – Acetylcholine, epinephrine, norepinephrine, serotonin, amino acids Decrease membrane permeability to sodium ions, reducing the chance that it will reach threshold, and are inhibitory. – GABA, dopamine Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

21. Impulse Processing How impulses are processed is dependent upon how neurons are organized in the brain and spinal cord. Neuronal Pools – Neurons within the CNS are organized into neuronal pools with varying numbers of cells. – Each pool receives input from afferent nerves and processes the information according to the special characteristics of the pool. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

22. Facilitation A particular neuron of a pool may receive excitatory or inhibitory stimulation; if the net effect is excitatory but subthreshold, the neuron becomes more excitable to incoming stimulation (a condition called facilitation). Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

23. Convergence A single neuron within a pool may receive impulses from two or more fibers (convergence), which makes it possible for the neuron to summate impulses from different sources. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

24. Divergence Impulses leaving a neuron in a pool may be passed onto several output fibers (divergence), a pattern that serves to amplify an impulse. Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

26. Reflex Arc Sensory neuron---interneuron in spinal cord---motor neuron Autonomic Homeostasis and survival (withdraw reflex)