EXAM II - DAPY 701 November 6, 2006 Version A Name 1. A 60-year-old man visits his physician complaining of double vision, eyelid droop, difficulty chewing and swallowing and general weakness in his limbs. He is diagnosed with Myasthenia gravis. What is the most likely basis for the symptoms described in this patient? *a. autoimmune response b. overexertion c. depletion of voltage-gated Ca channels in certain motor neurons d. development of large motor units following recovery from polio e. botulinum toxicity 2. Which of the following has been used as a treatment for bruxism? a. tetrodotoxin b. nicotine *c. botulinum toxin d. dendrotoxin e. none of the above 3. Decreasing the level of phospholamban in cardiac muscle cells works to a. increase SR Ca uptake activity b. activitate SERCA by removing phospholamban's inhibition c. facilitate relaxation of the heart d. increase the force of contraction *e. all of the above 4. Which one of the following can occur in smooth muscle cells? a. action potentials b. spike potentials c. pacemaker potentials d. hyperpolarization *e. all of the above 5. Which of the following muscle types uses oxidative metabolism as a means to meet energy demands associated with contraction? a. skeletal b. cardiac c. smooth *d. all of the above e. a and b 6. Which of the following can be used as a stimuli for calcium entry into smooth muscle cells? a. nerve stimulation b. hormonal stimulation c. stretch of the fiber d. change in the chemical environment of the fiber *e. all of the above 7. Calcium binds to which of the following troponin subunits? a. troponin I b. troponin T *c. troponin C d. none of the above 8. Calmodulin is most closely related functionally to which of the following proteins? a. G-actin b. Troponin I *c. Troponin C d. Tropomyosin e. Myosin light chain 9. Which of the following is always excitatory to smooth muscle? a. acetylcholine b. epinephrine c. norepinephrine d. glycine *e. none of the above 10. Which of the following structures permit the electrical coupling observed in cardiac muscle cells? a. fascia adherens b. desmosomes *c. gap junctions d. all of the above e. none of the above 11. Which of the following would cause (indirectly) acetylcholine receptors to remain open for longer periods of time? *a. physostigmine b. curare c. bungarotoxin d. a and c e. a, b and c 12. Which component of the actin filament does the myosin head bind to in skeletal muscle? a. tropomyosin b. troponin-C c. troponin-T d. troponin-I *e. none of the above 13. Which of the following mechanisms work to increase cytosolic calcium in smooth muscle cells? a. SERCA pumps b. sarcolemmal Ca pumps c. Na-Ca antiporters *d. Ca flux via ryanodine receptors e. all of the above 14. Prior to contraction in skeletal muscle (in the "Cocked State"), what is bound to the myosin head? *a. ADP and inorganic phosphate b. ATP c. creatine d. phosphocreatine e. cGMP 15. Tetanic contraction of a skeletal muscle fiber results from a cumulative increase in the intracellular concentration of which of the following? a. Na b. K c. Troponin d. ATP *e. Ca 16. Smooth muscle tissue lacks which of the following? a. actin b. ryanodine receptors *c. troponin d. dense bodies e. myosin light chain kinase 17. Which of the following are physiological responses following administration of nitroglycerine? a. coronary artery vasoconstriction b. decreases in cGMP in smooth muscle *c. decreases in myosin light-chain phosphorylation d. activation of β1-adrenergic receptors e. decreases in the amplitude of the end-plate potential 18. Your patient received a muscle relaxant before oral surgery but soon developed massive spontaneous contractions and increased heart rate. The patient began to hyperventilate and experienced a dramatic increase in body temperature. The physician administered dantrolene, a blocker of SR Ca channels, which reversed the condition. The massive contractions were likely to have been caused by which of the following? a. hyperexcitability of the alpha motor neurons b. inhibition of acetylcholinesterase c. hyperexcitability of calcium channels in the sarcolemma *d. hyperexcitability of calcium channels in the SR e. increased calcium sensitivity of the thin filaments 19. Gap junctions are consisted of complementary *a. connexons b. desmosomes c. fascia adherens d. intercalated discs e. actin filaments 20. The portion of the myofibril that lies between two Z discs is called the a. sarcolemma *b. sarcomere c. sarcoplasm d. dense body e. none of the above 21. Which of the following is electrogenic, characterized by a depolarizing current in cardiac muscle cells? *a. 3Na-1Ca antiporter b. sarcolemmal Ca pumps c. voltage-gated K channels d. the Na-K pump e. all of the above 22. The participation of calcium in the contraction of skeletal muscle is facilitated or associated with which of the following? *a. Calcium release from sarcoplasmic reticulum. b. Calcium binding to the myosin heads. c. Active transport of calcium out of longitudinal tubules. d. Uptake of calcium by T-tubules. e. Binding of calcium to troponin I 23. Why don't negatively charged ions pass through the pore of acetylcholine gated channels? *a. negative amino acids that line the pore b. bound too tightly to large, intracellular proteins c. too large to pass through d. the electrical gradient e. all of the above 24. After seeing the bill for your dental services, a patient experiences an asthma attack. His treatment will include which of the following? a. activation of B1-adrenergic receptors with an agonist b. blocking B2-adrenergic receptors with an antagonist c. increases in phospholamban d. administration of nitroglycerine *e. inhibition of myosin light-chain phosphorylation 25. Which statement about the end plate potential (EPP) is true? *a. The EPP is caused by increased sodium and potassium conductances of the postjunctional membrane. b. In the presence of an inhibitor of acetylcholinesterase, the EPP will be the same amplitude as in the absence of the inhibitor. c. In health, The EPP is sometimes too small to elicit an action potential. d. In myasthenia gravis, EPPs may be larger amplitude. 26. Defects in what protein can result in Familial Cardiomyopathic Hypertophy? a. myosin b. troponin c. tropomyosin *d. all of the above 27. Which of the following best describes dystrophin? a. connects to actin filaments b. connects to beta-dystroglycan c. provides structural support to the muscle fiber d. defects in dystrophin result in muscular dystrophy *e. all of the above 28. In what way does visceral smooth muscle differ from skeletal muscle? *a. visceral smooth muscle can contract in response to stretch b. visceral smooth muscle does not contain actin filaments c. visceral smooth muscle does not contain myosin filaments d. contraction of visceral smooth muscle is ATP dependent e. the rate of cross-bridge cycling in visceral smooth muscle is approximately 100 times faster than that in skeletal muscle 29. Force of contraction can be increased in cardiac muscle by a. increasing the number of motor units recruited b. frequency summation c. tetanization *d. modulation of L-type Ca channels e. none of the above 30. Which of the following muscle types uses a balance between MLCK phosphorylation and dephosphorylation as a means to regulate the amount of force generated? a. skeletal b. cardiac *c. smooth d. all of the above e. a and b 31. In which part of a neuron are non-peptide neurotransmitters (such as acetylcholine) synthesized and transported into synaptic vesicles? *a. axon terminal b. endoplasmic reticulum c. golgi apparatus d. axon hillock e. synaptic cleft 32. Which of the following neurotransmitters are employed at neuromuscular junctions in smooth muscle? a. acetylcholine b. norepinephrine c. glutamate d. all of the above *e. a and b 33. In which location would you be most likely to find intercalated discs? *a. left ventricle b. aorta c. ureter d. tongue e. gastrointestinal tract 34. Which of the following work to decrease cytosolic calcium levels in smooth muscle cells? a. voltage gated Ca channels b. InsP3-gated Ca channels c. ryanodine receptors *d. SERCA pumps e. all of the above 35. Which of the following compounds have similar effects on the muscle fiber membrane as acetylcholine? a. methacholine b. nicotine c. carbachol *d. all of the above 36. During a routine medical checkup, a 25-year-old man is found to have an enlarged heart. He is a professional athlete and does not have high blood pressure or high cholesterol level, and he is otherwise in good health. He mentions that his father and paternal grandfather had both died at an early age of apparent heart attacks. A few months after the medical checkup, he died suddenly of an apparent heart attack. DNA analyses indicate mutations in a gene for cardiac myosin. Analysis of the heart showed that many cardiac sarcomeres were in disarray, which was probably due to which of the following? a. effects of his physical training b. decreased ATP production by cardiac mitochondria c. development of an arrhythmia d. myocardial infarction *e. development of familial cardiac hypertrophy 37. Which of the following muscle types can have the longest twitch duration? a. skeletal b. cardiac *c. smooth d. all have equal twitch durations 38. Calcium that enters the cell during smooth muscle excitation binds with which of the following? *a. calmodulin b. inactive myosin kinase c. troponin d. myosin e. actin 39. Which of the following is the most likely cause of the "Staircase Effect" observed in skeletal muscle? a. increased blood flow b. increased ATP production from mitochondria *c. increased residual calcium levels in the cytosol d. genetic disorder e.