EEOB 4550 Exam 1 and 2 Questions for Final Exam

Based on Question 5: Know the typical electrical and concentration/chemical gradients that exist across the plasma membrane of a neuron for Na+, K+ and Cl-. Based on these gradients, be able to state what direction each ion moves across the membrane - -[Na+]out [Na+]in -[K+]out [K+]in -Differences maintained by Na+ K+ ATPase pump; 3 Na+ ions out, 2 K+ ions in, creates a net loss of positive ions -resting membrane potential is -50 to -80 mV -for K+ and Cl-, concentration and electrical gradients are equal and opposite (electrochemical equilibrium) What is the difference between a mechanically-gated channel and a voltage-gated channel in terms of where each is located in a neuron, which direction Na+ or K+ move if a channel is open, and what happens to membrane potential when Na+ vs. K+ channels open. Also note that all ion channels are SPECIFIC for a given ion, i.e. only Na+ moves through a Na+ channel - -Opening a mechanically-gated ion channel in a sensory neuron results in hyperpolarization of Vm if the channel is a K+ channel, depolarization of Vm if the channel is a Na+ channel -Voltage-gated channel: opens in response to change in voltage, closed at rest. Change away from opening voltage causes them to close -Mechanically-gated channel: membrane proteins that open in response to physical change in the cell Review the similarities and differences between graded and action potentials; would also be good to understand what the passive properties of a neuronal membrane are. Know that graded potentials do NOT change the passive properties, but action potentials do - similarities -Vm changes -time is required for Vm to change differences -propagation, GP is passive, and AP is active -distance, GP dies out with distance and APs do not degrade -size, GPs are small, APs are large -duration, GPs last longer, APs are brief -refractory period, GPs have no refractory periods but APs do Recognize that 10-50 Hz is NOT a frequency of sound that stimulates moth auditory neurons......10-50 kHz is, i.e. understand that bats produce ultrasonic (very high frequency) sounds and that moths need to hear pulses of sound, not continuous sound. - -10-30 pulses per second is the feature of sound appropriate for stimulating moth auditory neurons -Moths hear ultrasonic bat cries, but their sensory (auditory) neurons do NOT encode frequency or pitch of a sound Question 12 / Choice Question 1: Explain the meaning of Tinbergen's survival value and evolution questions - what do those questions ask? Be able to answer those questions for either gull chick pecking behavior or graylag goose egg retrieval behavior. - Proximate causes -Ontogeny - how does the behavior develop during the animal's lifetime? -Causation - what are the stimuli that produce the response? Ultimate causes -Evolution - how did the behavior arise in the species? -Survival value - how does the behavior contribute to the animal's survival and reproductive success? You will not be asked to do any calculations but review the electrical model of the membrane (circuit problems) so that you understand what happens to membrane voltage when the permeability to a given ion increases. - -When permeability to a given ion increases, conductance increases and resistance decreases -[X+] out [X+] in = + end facing inside -[X+] out [X+] in = - end facing inside -Current always flows from - to + -The total voltage lost across the resistors has to equal the amount of voltage gained by the battery -Membrane voltage tends to be close to the equilibrium potential to whichever ion has the greatest permeability Most did well on the lambda/length constant parts of this question, but not so well with tau/time constant....what does tau represent, why is related to membrane capacitance and can you approximate a value of tau (hint: it will be some number of msec) for each of the curves labeled A, B, C and D in the figure with this question? - -Tau (T) describes time required for the voltage change to reach its maximum (plateau)