Psio 201 Exam 3 Study 2024 Solved 100% Correct

Neuromuscular junction Relaxation {Ans: Relaxation - Sequestration of Ca2+1. When Action Potentials stop arriving at the NMJ, the 'trigger' to release Ca2+ from the SR stops 2. Active Ca2+ transporters in the SR membrane pumpCa2+ back into the SR 3. Cytoplasmic [Ca2+] decreases 4. As [Ca2+]cyto falls, Ca2+ comes off troponin - the myosin binding sites on actin get covered by tropomyosin 5. Crossbridge cycling stops and tension drops 6. Titin brings the sarcomere back to resting position}muscle development {Ans: Myoblasts form the muscle fibers after birth fibers can only grow by hypertrophy}Excitation Contraction Coupling {Ans: Triggers release of Ca2+ from SR}Cross bridge cycling steps {Ans: 1) Myosin binding sites on actin become exposed whenCa2+ binds to troponin 2) Myosin heads bind to actin forming cross bridges 3) Myosin heads pivot toward the center of the sarcomere (power stroke) 4) ATP binds to the myosin head → detachment of myosin head from actin (cross bridges break) 5) ATP is hydrolyzed and the energy released is used tore-energize the myosin head back to its start position('cocked') so a new crossbridge can form 6) The contraction cycle repeats until the myosin binding sites on actin are no longer