1 BASIC NEUROSCIENCE. Basic Neuroscience

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1 1 BASIC NEUROSCIENCE QUESTION ONE An excitatory signal is received at the dendrite of a pyramidal glutamate neuron. When the signal is released from the incoming presynaptic dopaminergic axon, it is received as an inhibitory signal. However, this signal is not integrated properly with other incoming signals to that neuron. Which is the most likely site at which the error of integrating this signal with other incoming signals occurred? A. Dendritic membrane B. Soma C. Axonal zone D. Presynaptic zone 1

2 Answer to Question One The correct answer is B. Choice Peer Answers A. Dendritic membrane 21% B. Soma 47% C. Axonal zone 9% D. Presynaptic zone 22% A Incorrect. Dendritic membrane is the site of signal detection; signal integration does not occur here. B Correct. Soma is the site that integrates chemical encoding of signal transduction from all incoming signals; improper signal integration is most likely at this site. C Incorrect. Axonal zone is the site of signal propagation; signal integration does not occur here. D Incorrect. Presynaptic zone is the site of signal output; signal integration does not occur here. References Schatzberg AF, Nemeroff CB. Textbook of psychopharmacology, fourth edition. Washington, DC: American Psychiatric Publishing, Inc.; (Chapter 2) Stahl SM. Stahl s essential psychopharmacology, third edition. New York, NY: Cambridge University Press; (Chapter 1) 2

3 QUESTION TWO A receptor synthesized with an erroneous amino acid sequence is sent via fast anterograde transport to its axonal destination. If you want to find the original site of error, which organelle would you elect to observe? A. Free polysome B. Golgi apparatus C. Mitochondria D. Rough endoplasmic reticulum 3

4 Answer to Question Two The correct answer is D. Choice Peer Answers A. Free polysome 5% B. Golgi apparatus 12% C. Mitochondria 14% D. Rough endoplasmic reticulum 69% A Incorrect. Free polysomes, or nonmembrane-bound ribosomes, are the site of peripheral protein (e.g. microtubules, neurofilaments) synthesis. B Incorrect. Golgi apparatus is the place to which integral proteins are sent for modification after synthesis. C Incorrect. Mitochondria, the cell s powerhouses, are important energy sources to fuel cellular transport but will not reveal underlying causes of errors in protein synthesis. D Correct. The rough endoplasmic reticulum, or membrane-bound ribosomes, is the site of integral protein (e.g. receptors, enzymes, ion channels) synthesis; such proteins are destined for membrane insertion and travel via fast transport. References Schatzberg AF, Nemeroff CB. Textbook of psychopharmacology, fourth edition. Washington, DC: American Psychiatric Publishing, Inc.; (Chapter 2) Stahl SM. Stahl s essential psychopharmacology, third edition. New York, NY: Cambridge University Press; (Chapter 1) 4

5 QUESTION THREE A discarded receptor being transferred through the neuron is most likely moving: A. From the axon to the soma at a max speed of 100 mm/day B. From the soma to the axon at a max speed of 200 mm/day C. From the axon to the soma at a max speed of 2 mm/day D. From the soma to the axon at a max speed of 4 mm/day 5

6 Answer to Question Three The correct answer is A. Choice A. From the axon to the soma at a max speed of 100 mm/day B. From the soma to the axon at a max speed of 200 mm/day C. From the axon to the soma at a max speed of 2 mm/day Peer Answers 44% 19% 26% D. From the soma to the axon at a max speed of 4 mm/day 10% A Correct. Discarded proteins and organelles, among other materials, are transported to the soma via fast retrograde transport, where they are masticated by lysosomes. B Incorrect. Fast anterograde transport (soma to axon) has a max speed of 200 mm/day but this is not generally the direction of transport for discarded proteins. C and D Incorrect. Slow transport, on the other hand, travels from axon to soma at a max speed of 2 mm/day but this is not generally the mechanism by which discarded proteins are transported. References Schatzberg AF, Nemeroff CB. Textbook of psychopharmacology, fourth edition. Washington, DC: American Psychiatric Publishing, Inc.; (Chapter 2) Stahl SM. Stahl s essential psychopharmacology, third edition. New York, NY: Cambridge University Press; (Chapter 1) 6

7 QUESTION FOUR You are looking at a cell from the prefrontal cortex. It has three branched dendrites and one axon terminal. The initial segment of its axon receives an inhibitory signal from a chandelier axon terminal. Which type of cell are you most likely looking at? A. Basket cell B. Chandelier neuron C. Pyramidal cell D. Purkinje cell E. Double bouquet cell 7

8 Answer to Question Four The correct answer is C. Choice Peer Answers A. Basket cell 5% B. Chandelier neuron 9% C. Pyramidal cell 73% D. Purkinje cell 12% E. Double bouquet cell 2% A Incorrect. Basket cells are interneurons with wide-reaching dendritic trees shaped like baskets. Their several axon terminals spread horizontally to make inhibitory connections with the soma of other neurons in the cortex. B Incorrect. Axon terminals of chandelier neurons form inhibitory axoaxonal contacts with pyramidal cells. C Correct. Pyramidal cells have a triangular cell body, three branched dendrites, two of which are shorter than the third, and a single axon originating from between the two shorter basal dendrites; these make up the majority of the neurons in the prefrontal cortex. D Incorrect. Purkinje cells are found mainly in the cerebellum and have extensively branched dendritic trees. E Incorrect. Double bouquet cells have a tight bundle of vertically oriented axons that make inhibitory connections with other neurons in the cortex, including other double bouquet cells. References Schatzberg AF, Nemeroff CB. Textbook of psychopharmacology, fourth edition. Washington, DC: American Psychiatric Publishing, Inc.; (Chapter 2) Stahl SM. Stahl s essential psychopharmacology, third edition. New York, NY: Cambridge University Press; (Chapter 1) 8

9 QUESTION FIVE Which of the following pairs is most likely to form an axoaxonal connection? A. Two double bouquet cells B. A double bouquet cell and a pyramidal neuron C. A basket neuron and a pyramidal neuron D. A chandelier neuron and a pyramidal neuron 9

10 Answer to Question Five The correct answer is D. Choice Peer Answers A. Two double bouquet cells 11% B. A double bouquet cell and a pyramidal neuron C. A basket neuron and a pyramidal neuron D. A chandelier neuron and a pyramidal neuron 8% 13% 68% A Incorrect. Two double bouquet cells form mostly axodendritic connections. B Incorrect. A double bouquet cell and a pyramidal neuron form mostly axodendritic connections. C Incorrect. A basket neuron and a pyramidal neuron form mostly axosomatic connections. D Correct. A chandelier neuron and a pyramidal neuron form mostly axoaxonic connections. References Schatzberg AF, Nemeroff CB. Textbook of psychopharmacology, fourth edition. Washington, DC: American Psychiatric Publishing, Inc.; (Chapter 2) Stahl SM. Stahl s essential psychopharmacology, third edition. New York, NY: Cambridge University Press; (Chapter 1) 10