14 12 2012 09 35 00 Lever System Cannot have both high mechanical advantage and velocity ratio High Mechanical advantage o Increase speed by increased muscle length High Velocity Ratio o Increase force production by increased Cross sectional area ME KE PE Nervous System Control System o Homeostatic Loop Stimulus Sensory Structure Comparator with Preset reference value Error Signal Effector Organ o Closed loop output affects input Negative Feedback Output offsets or negates input Central Nervous System vs Peripheral Nervous System Think A comes before E CNS PNS SENSORY AFFERENT INTER NEURON MOTOR EFFERENT EFFECTOR GANGLION Membrane Potential Vm Difference in electrochemical gradient inside and outside of cell Sodium in Potassium out Use Nernst Equation to approximate Vm E Ion R T ln Ion 1 z F Ion 2 R gas constant 1 987 cal mol deg T degrees K F Faraday s Constant 23 062 cal V mol z ion valence 37 degrees RT F 61 5 mammals 20 degrees RT F 58 Use V IR and I VG where G is conductance to determine voltage DG RTln Xi Xo zFVm set DG equal to 0 and solve for Vm Goldman Equation takes into account permeabilities Vm RT ln PK Ko PNa Nao PCl Cli F PK Ki PNa Nai PCl Clo The Action Potential 1 stimulus arrives at dendrites o induces EPSPs or IPSPs o summation of EPSPs depolarization 2 Opening of voltage gated Na channels o positive feedback loop o rapid depolarization o rising phase of AP 3 Na channel inactivation K channel activation o voltage gated Na start to close end of rising phase o voltage gated K channels start to open peak to trough 4 after hyperpolarization o tome course of K channels causes undershoot o closing o drift back to resting Vm 5 chemical synapses o opening of voltage gated Ca channels o release of neurotransmitter from vesicles Channel inactivation often occurs after it is opened due to Voltage Difference across membrane Vm Sodium Channel Possesses an inactivation gate Resting Membrane potential gate is closed Depolarization gate is opened Repolarization gate is inactivated Neurons Unmyelinated Myelinated system o Membrane of a Schwan cell in vertebrate peripheral nervous o Relatively solid membrane o Few membrane proteins or ion channels o Insulator to prevent current leak o Bare membrane between sections of myelin Nodes of Ranvier o Increases conduction velocity Nodes of Ranvier possess a lot of Sodium Channels so the charge Synaptic Transmission AP frequency determines Amount of Ca entering neuron terminal which determines Amount of neurotransmitter released which determines Magnitude of post synaptic response EPSP EPSP Depolarization Threshold Action Potential Excitation Of Post Synaptic Structure IPSP IPSP Hyperpolarization Inhibition Information carried by a nerve is proportional to the frequency of jumps here action potentials Signal Molecule Receptors Trans membrane protein Specificity Also binds exogenous agonists antagonists Transducer converts signal molecule binding to intracellular response Histamine Receptors Histamine released to initiate inflamatory or allergic response Take chlorpheneramine a histaminergic antagonist Axonal Agents Tetrodoxin TTX prevents opening of Na channels Saxitoxin STX blocks Na channels Iberiotoxin is scorpion toxin blocking K channels 14 12 2012 09 35 00 14 12 2012 09 35 00
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