Bisc 421 Module I Review QuestionsChapter 1: Studying the Nervous System1. Is the size of an organism’s genome a good predictor of the organism’s complexity? Explain your answer.No it is not. Total number of genes encoded in the genome of an organism does not generally correlate with complexity, as demonstrated by worms having 19,000genes compared to humans with 24,000; some plants encode hundreds of thousands of genes! Rather, organismal complexity is determined by sophisticated control of gene expression, splice variants, post-transcriptional mechanisms, and other factors. 2. Diagram a neuron and label its components. In what ways are neurons specialized for communication? Do these specializations distinguish neurons from other types of cells?Neurons are polarized cells with specialized structures including dendrites and axons. Synapses are junctions between a presynaptic axon terminal and a postsynaptic cell; this structure is specialized to convert electrical information (action potential) into chemical information (release of neurotransmitter) which is converted back into electrical information.3. Describe 2 technologies that can be used to manipulate neural activity experimentally? Discuss the pros and cons of each.Voltage clamp: Technology used to manipulate voltage in a cell and record the ion fluxes that emerge. Very powerful and very high resolution information is pro.Con is very invasive, time is limited, and on a small number of cells can be recorded from at a single time.Optogenetics: Transgenically express ion channels that are inducible by light; can be used to activate or inhibit activity. Pro is large numbers of neurons can be manipulated in vivo. Con is do not monitor electrical activity. Chapter 2: Electrical Signals of Nerve Cells1. Draw a typical action potential. Label the axes and each phase of the action potential.Describe the key events that underlie each phase:Rising phase: Na permeability >> KOvershoot phase: Na permeability = KFalling phase: K permeability > NaUndershoot phase: K permeability >> all other ions (due to perdurance of VG K+ channels)Bisc 421 Module I Review Questions2. Suppose you are recording a neuron’s resting membrane potential. If you add KCl to the external medium, what will happen to the resting potential? Compare this to what will happen if you add the same amount of NaCl. What can you conclude from this comparison?Add KCl: resting potential become less negative (depolarizes). Add NaCl: No significant change. K is the main contributor to resting potential.3. What is the magnitude of a typical neuron’s resting membrane potential? Why do neurons and other cells have a negative resting membrane potential?-65mV. Cells establish ion concentration gradient across the membranes and the membranes are permeable to the ions. K ions play dominant role in establishing resting membrane potential and its concentration inside the cell is higher than the outside which makes the inside of the cell more negative. 4. In what situation would you use the Goldman equation as opposed to the Nernst equation?When there are more than one ions contributing to the membrane potential.5. Which of the following best describes nerve cells?a. Nerve cells are exceptionally good conductors of electricity (much better than copper wires).b. Nerve cells are similar in their electrical conduction properties to copper wires.c. In comparison to copper wires, nerve cells are relatively poor conductors of electricity.d. Nerve cells are unable to conduct electricity under any circumstances.e. Nerve cells are electron sinks: they absorb many electrons, but no electricity comes out of them.Answer: cTextbook Reference: Overview, p. 25Chapter 3: Voltage-Dependent Membrane Permeability1. Does current flow from positive to negative or from negative to positive? Which way does current flow across the membrane during the rising phase of the action potential? Which way does current flow across the membrane during the falling phase?Current flow from positive to negative. During rising phase current flows into the cell (Na flow in), during falling phase current flows out of the cell (K flow out).2. Suppose you are recording action potentials from a neuron. How will the action potential be affected if you remove Na+ from the external medium? How will the action potential be affected if you remove external K+?Bisc 421 Module I Review QuestionsRemove Na: there will be no action potential.Remove K: peak of action potential will sill reach the same level, but resting potential will become more negative (hyperpolarized)3. What prevents action potentials from turning around and going back up the axon?Inactivation of voltage-gated Na channel in the path action potential just travelled.4. In an experiment using a series of voltage steps to study the two different ionic currents associated with the action potential (as shown in Figure 3.2), it was found thata. both currents had the exact same voltage dependence.b. both currents increased monotonically with increasingly large voltage steps.c. both currents decreased with increasingly large voltage steps.d. the early current increased initially, but then it decreased in size as the voltage step was increased.e. the late current increased initially, but then it decreased in size as the voltage step was increased.Answer: dTextbook Reference: Two Types of Voltage-Dependent Ionic Current, pp. 43–455. Which of the following was shown to eliminate the early inward current in squid giant axons?a. Removal of external sodiumb. Doubling of external sodiumc. Removal of external potassiumd. Doubling of external potassiume. Removal of all external cationsAnswer: aTextbook Reference: Two Types of Voltage-Dependent Ionic Current pp. 43–45Chapter 4: Ion Channels and Transporters1. Compare the responses of voltage-gated Na+ and K+ channels to depolarization. Howwould you expect these channel properties to affect the shape, duration and frequency of action potentials?Shape and duration are affected by how fast voltage-gated Na channel inactivate and how fast voltage-gated K channel become open in response to above-threshold voltage.Frequency is affected by how long the voltage-gated Na channel remain inactivated after an action potential.Bisc 421 Module I Review Questions2. What is meant by the statement that ion channels and active transporters have complementary functions?Ion channels let ions flow down their concentration gradient while active