Understanding Electrical Signaling in Biology: Resting Potential, Action Potentials, and N, Study notes of Biology

Download Understanding Electrical Signaling in Biology: Resting Potential, Action Potentials, and N and more Study notes Biology in PDF only on Docsity! Lecture 2 October 2, 2007 Biology 140 Reading: Chapters 2&3 Electrical Signaling Signals recorded depend on recording techniques Galvani - 1791 Extracellular recording Injury potential - Bernstein - 1902 Intracellular recording The Resting Potential: -40 to -100 mV Intracellular impermeant anions (proteins) Selective permeability to cations (particularly K+) Asymmetry of permeable cations (particularly K+) Nernst equation; Nernst potentials Goldman-Hodgkin-Katz equation Na+/K+ pump Depolarization and Hyperpolarization By injection of current with microelectrodes positive in/ negative out - depolarization negative in/ positive out - hyperpolarization By Excitatory/Inhibitory synapses neurotransmitters open channels (ligand-gated channels) eg Glutamate – Na+ channels; GABA – Cl- channels The Action Potential Voltage-gated channels Na+ and Ca2+ (cause depol.) and K+ (cause hyperpol.) Threshold - an explosion of ionic current All-or-none; information in a neuron is digital No increase in size with increased stimulus strength Decrease in latency with increased stimulus strength Enables frequency coding: the larger the stimulus the higher the frequency of APs Refractory periods Absolute - Na+ channel inactivation Relative–long lasting K+ current > increased threshold The role of passive membrane properties in AP propagation The membrane as an RC circuit