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Download Name________________________ Midterm #1 Biology 3330, Fall
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Name________________________ Midterm #1 Biology 3330, Fall 2014 1. (6 pts) Explain (one sentence), in the space provided on the right, the effects of a lesion in the following structures: Structure Effects of Lesion a) Cerebellum b) Substantia Nigra c) Reticular Formation d) Frontal Lobe e) Hippocampus / Temporal lobe f) Amygdala 2) (6pts) A transformation in the representation of visual information occurs between the LGN and visual cortex. As a result, simple-type cells in visual cortex are selective for what stimulus features? Describe the mechanism that underlies this selectivity; in your answer, explain how intracellular recordings have revealed this mechanism (use a diagram). 3) (9 pts) Choose the correct answer: Photoreceptor cells are (depolarized/hyperpolarized) in response to light. Photoreceptors release (more/less) glutamate when stimulated by light ON bipolar cells are (excited/inhibited) by glutamate OFF bipolar cells are (excited/inhibited) by glutamate The peripheral retina has more (rods/cones) The peripheral retina is (more/less) sensitive to light than the fovea The fovea has (higher/lower) acuity than the peripheral retina Color vision is produced by (rods/cones) (Horizontal/amacrine/ganglion) cells connect to photoreceptors and to bipolar cells 4. (6 Pts) The figure below shows the responses of a ganglion cell to a visual stimulus. Using this figure answer the questions that follow. a. Using the stimulus-response characteristics of the ganglion cell, can you explain and identify which type of ganglion cell this is? b. By summoning your knowledge of the retinal organization could you explain the activity of such ganglion cell? Use (draw) a simple circuit to illustrate how the above response characteristics arise. 5). (13 pts) Identify, on the pictures below, the location of the listed brain structures; put letters in boxes. a) OL: Occipital Lobe PL: Parietal Lobe FL: Frontal Lobe TL: Temporal Lobe Cb: Cerebellum CS: Central Sulcus b) VC: Visual Cortex PC: Parietal Cortex AC: Auditory Cortex MC: Primary Motor Cortex PMC: Premotor Cortex SS: Somatosensory Cortex PFC: Prefrontal Cortex c) SN: Substantia Nigra Put: Putamen (Basal ganglia) GP: Globus Pallidus “ “ CC: Corpus Callosum Thal: Thalamus AM: Amygdala CN: Caudate Nucleus d) MP: Medullary pyramidal tract ML: Medial lemniscus VCN: Ventral Cochlear N. IO: Inferior Olivary N. DC: Dorsal Column Nuclei RF: Reticular Formation 6) (8 pts) Matching: ___ AMPA-type glutamate receptor ___ GAD (Glutamic acid decarboxylase ___ Glutamate ____ GABA-A type receptor a) Has voltage-dependent ion channels that conduct Ca+2 b) Enzyme for GABA synthesis c) Primary excitatory neurotransmitter d) Ionotropic receptor, mediates fast excitatory transmission e) Binding site of benzodiazepines and purines ____ NMDA-type receptor b) What 3 criteria must be satisfied to prove that a chemical is a neurotransmitter? 7) (3 pts) Properties of sensory systems: a) Using a diagram and 1-2 sentences, illustrate the principle of Range Fractionated/population coding, as it applies to color vision. 8) (4 Pts) Circle the correct choices. a. At threshold voltage the relative ionic permeability of the membrane favors potassium/ sodium. b. An action potential can be fired even during the absolute/relative refractory period by forcing enough positive current into the cell. c. When cell membrane is strongly depolarized, there is a huge driving force on K+ / Na+ ions. d. Action potentials are triggered at the axon hillock/dendritic spine. 9( 6 Pts) Using figure 1 and the concepts you have learned, answer the following questions: Level 1 Level 2 Level 3 Membrane voltage Figure1: An illustration of an experimental stimulation of a neuron using different levels of injected current. Top trace shows the levels of current injected into the cell, bottom trace shows the changes in membrane voltage due to current injection. a. (2 pts) When zero current is being injected the membrane voltage is at -65mV, explain why a sudden increase in positive current injection results in a ‘curved/slow’ change in membrane potential as indicated in the red dotted circle? b. (2 pts) Write down the ‘law’ that governs the relationship between a neuron’s membrane voltage and injected current. Which variable remains constant in this equation w.r.t. the manipulations in figure 1? c. (2 pts) Can you explain the type of neuronal coding behavior seen in figure 1 using a biological example that you have come across in this course 10) (8 pts) Matching: ___ ___Bitter ___ ___Sweet ___ Sour ___ Salt ___ ___ Odorant (Olfaction) ___ ___Light (Vision) a) Proton-mediated closure of K channels b) G-protein-mediated increase in IP3 c) G-protein-mediated increase in cAMP d) G-protein-mediated decrease in cGMP e) Ions directly pass through amiloridesensitive channels f) Phospholipase C activated g) Adenylyl cyclase activated h) Phosphodiesterase activated b) Describe the actions of the 2nd messengers (cAMP, cGMP, IP3) in the sensory transduction shown above. In your answer describe the effects of these 2nd messengers on particular ion channels. Action cAMP cGMP IP3 11. (6pts) Chemosensory (taste and olfaction): Fill in the blanks. The main organ of taste is the tongue on which the tip is sensitive to _________, the back is sensitive to __________, and the sides are sensitive to _______. On the tongue surface, there are small projections called _________, and each have hundreds of ______________ with several (50-150) ______________, which are responsive to chemicals indicating tastes. When these cells are exposed to appropriate tastant chemicals, there are membrane potential changes, called ____________. The majority of these cells are relatively _________ (qualitative answer) to chemical sensing. The taste information is then carried by _________ (afferent/efferent) nerves to the _____________. Axons here make synapses on neurons of the ____________, which projects to the _______________ of the cerebral cortex. This pathway is presumed to mediate conscious perception of taste 12. (6 pts) Neurotransmitter systems & Synaptic Transmission Thien identifies a rare form of familial tremor, in which patients have involuntary tremors and cardiac irregularities. An undergraduate chemist working with Thien reported that patients have elevated levels of epinephrine in their blood samples. Thien thought “Aha! This must involve a malfunction in a rate-limiting step of the epinephrine synthesis!” So he looked at the epinephrine synthesis pathway. a). What is the precursor to epinephrine (and DOPA, Dopamine, or norepinephrine) called? What kind of molecule is it? b). Above each arrow, give individual names to the molecules catalyzing these reactions (depending on the reaction). Hint: they are named for the chemical modifications they produce. c). What is the step that is rate-limiting in this synthesis? d). Thien thinks that the molecule that catalyzes this rate-limiting step is overexpressed in a particular set of neurons. What is the name of the brain region where these neurons are found? __________ e). Thien has access to mouse models of this disease, and their nervous systems. Describe how he could identify these neurons. 13. (6 pts) You are recording from a neuron that receives inputs from neurons A and B. The postsynapse at A contains ligand-gated Cl- channels and has a reversal potential of 60 mV (below threshold for spike initiation). The neuron being recorded has a resting membrane potential of -70 mV. a) If only neuron A is stimulated, what will the change in membrane potential look like? Draw below. (2 pts) b) When only neuron B is stimulated, there is a depolarization of 30 mV. Draw what the change in membrane potential would look like if both neurons A and B are stimulated. (2 pts) c) Is synapse A excitatory or inhibitory? Explain your answer. (2 pts) 14.(Total: 6 pts) Using figure 2 answer the questions below: _________ ___________ ___________ ____________ Figure 2: Different states of a voltage gated Sodium channel. Each state of the channel is represented by a number below the channel. a. Name each state of the channel indicated in figure 2: b. Explain the transition of the voltage-gated sodium channel from state 1 to state 2. Which part of the sodium channel is essential for such transition? c. Generalized epilepsy with febrile seizures is a common inherited disorder. One of the causes of this disorder is a mutation in the voltage-gated sodium channel. Could you name which state transition is affected by such mutation and how? How does this mutation affect the action potential? (Hint: Batrachotoxin has a similar effect on the channel function as this mutation.) 15. (Total: 6 Pts) Answer the following questions: a. (4 pts) Use a simple diagram to explain the projection of neurons/information from the retina to the lateral geniculate nucleus of the thalamus. In this answer explain the functional specializations of the 6 layers of the LGN. b. (1 pt) What is retinotopy? c. (1 pt)Visual space is not uniformly sampled in the retina. What effect does this have on the organization of visual field in the striate/V1 cortex? 13. (11pts) You have learned that 2nd messenger systems are important in synaptic transmission. These 2nd messenger pathways are also important in stimulus transduction in the visual, gustatory and olfactory systems. Complete the chart showing how sensory stimuli are transduced by filling the blanks. Each blank can have more than one answer, and the answers can be used more than once. A. Adenylyl cyclase B. Increase Ca2+ release C. Ca2+ channels open D. Depolarization E. Increased IP3 F. Phosphodiesterase G. Decreased cGMP H. Hyperpolarization I. Na+ channels close J. Cyclic nucleotide gated channels open K. PKA phosphorylates K+ channel, closing it L. PKC phosphorylates K+ channel, closing it M. PLC N. Decreased Na+, Ca2+ entry O. Increased cAMP Matching: ___ Bitter ___ Sweet ___ Sour ___ Salt ___ Odorant (Olfaction) ____ Light (Vision) i) Proton-mediated closure of K channels j) G-protein-mediated increase in IP3 k) G-protein-mediated increase in cAMP l) G-protein-mediated decrease in cGMP m) Ions directly pass through amiloridesensitive channels n) Phospholipase C activated o) Adenylyl cyclase activated p) Phosphodiesterase activated b) Describe the actions of the 2nd messengers (cAMP, cGMP, IP3) in the sensory transduction shown above. In your answer describe the effects of these 2nd messengers on particular ion channels. Action cAMP cGMP IP3 7) (8 pts) a) What is the function of the synapse (1-2 sentences)? (2 pts) b) Label the key components of the synapse indicated on the image below. Also, label the presynaptic side and postsynaptic side of the synapse. (6 pts) 8. (3 pts) a) For each of the following receptor properties, write I for ionotropic, M for metabotropic, B for both, or N for neither: ___ Triggers a fast postsynaptic response ___ Is important in neuromodulation ___ Binds neurotransmitters such as somatostatin and vasopressin ___ Triggers a slow postsynaptic response ___ Binds acetylcholine ___ Acts via a G-protein mediated cascade