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Exam #3 W 4/2 in class Review T 4/1 from 5-7pm in PAI 3.02 Before Exam #3: the nervous system, movement and the immune system Two ways to think about the world: Reductionism atoms molecules organelles cells tissues organs systems organisms environment Two ways to think about the world: Reductionism atoms molecules organelles cells tissues organs systems organisms Wholism environment Sensing and reacting to the environment is critical Failure to properly sense and react to the environment can be fatal Nerves allow us to perceive the environment while the brain integrates the incoming signals to determine an appropriate response. CB 48.3 Neurons: cells specialized for transmitting signals CB 48.5 Parts of a neuron Axon Signals In the brain neurons are shorter and highly interconnected CB 48.7 CB 48.5 Neurons: signals move through neurons electrically and between neurons chemically Nervous System Signaling Stimulus Transduction Transduction Response Ionic gradients in neurons plasma membrane CB 48.10 Na+/K+ pump Na+ ATP–>ADP K+ At rest, the Na+/K+ gradient is maintained CB 48.13 Depolarization occurs with the opening of Na+ channels CB 48.13 An action potential starts when the local depolarization causes other Na+ channels to open CB 48.13 Action potentials only occur when the initial depolarization is above the threshold CB 48.12 An action potential starts when the local depolarization causes other Na+ channels to open CB 48.13 CB 48.13 Repolarization is achieved via closing Na+ and opening K+ channels the Na+/K+ pump reestablishes the resting state CB 48.13 Depolarization of one part of the membrane opens Na+ channels further along so the signal travels from one end to the other CB 48.14 Myelination: allows the depolarization to travel faster CB 48.8 Myelination: allows the depolarization to travel faster…it jumps CB 48.15 Neurons: signals move through neurons electrically and between neurons chemically CB 48.5 At the end of the neuron, neurotransmitters are released signaling the next neuron to depolarize CB 48.17 Neurotransmitters can be excitatory or inhibitory (+) CB tbl 48.1 (–) (–) (+) (+/–) (–) At the synapse the electrical signal is converted to a chemical signal electrical at synapse chemical electrical Neurons are commonly connected to many other neurons, and the effect of the different incoming signals determines what the neuron will do. CB 48.16 Neurons are commonly connected to many other neurons, and the effect of the different incoming signals determines what the neuron will do. CB 48.18 Incoming signals move through neurons. Only signals above the threshold are transmitted along the neuron. Neuron videos: http://www.youtube.com/watch?v=YwN9aCobCy8 http://www.blackwellpublishing.com/matthews/actionp.html http://www.blackwellpublishing.com/matthews/nmj.html The brain and the central nervous system integrate the various incoming signals CB 48.19