Nmj Test With Complete Solution

NMJ TES T W ITH COMPLE TE SOLUT ION Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine? - ANSWER Acetylcholine is degraded by acetylcholinesterase//Acetylcholinesterase is an enzyme that degrades acetylcholine. This degradation results in a rapid cessation of the acetylcholine signal and a swift removal from the cleft. The neuromuscular junction is a well-studied example of a chemical synapse. Which of the following statements describes a critical event that occurs at the neuromuscular junction? - ANSWER Acetylcholine is released by axon terminals of the motor neuron.//Acetylcholine is released into the synaptic cleft via exocytosis. Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________. - ANSWER extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber//The cell bodies of motor neurons to muscles in the head and neck are located in the brain. The cell bodies of motor neurons to the rest of our muscles are located in the spinal cord. Calcium entry into the axon terminal triggers which of the following events? - ANSWER Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.//When synaptic vesicles fuse to the plasma membrane, acetylcholine is released via exocytosis. Acetylcholine binds to its receptor in the sarcolemma and triggers __________. - ANSWER the opening of ligand-gated cation channels// These channels permit sodium ions to diffuse inward and potassium ions to diffuse outward. Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why? - ANSWER The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.// The resting membrane potential of all cells is negative (inside compared to outside). Therefore, given the direction of the chemical and electrical gradients, more sodium ions diffuse inward than potassium ions diffuse outward. Inadequate calcium in the neuromuscular junction would directly affect which of the following processes? - ANSWER Release of acetylcholine from the synaptic vesicles//Calcium ions enter the axon terminal when voltage-gated calcium channels open in response to the arrival of an action potential. The presence of calcium causes synaptic vesicles to release acetylcholine into the synaptic cleft.