Final Answer:
During synaptic transmission at the motor end plate, an action potential arrives at the axon terminal of the motor neuron, leading to the release of acetylcholine (ACh) into the synaptic cleft.
Step-by-step explanation:
ACh binds to receptors on the motor end plate, causing depolarization and the generation of an action potential in the muscle fiber.
Synaptic transmission at the motor end plate is a critical process for muscle contraction.
When an action potential reaches the axon terminal of a motor neuron, voltage-gated calcium channels open, allowing calcium ions to enter the terminal. The increase in calcium concentration triggers the exocytosis of synaptic vesicles containing acetylcholine (ACh) into the synaptic cleft.
Once released, ACh binds to nicotinic receptors on the motor end plate, which is the specialized region of the muscle fiber membrane. This binding results in the opening of ion channels, allowing an influx of sodium ions into the muscle fiber. This influx causes depolarization of the muscle fiber membrane, leading to the generation of an action potential that propagates along the sarcolemma and into the T-tubules.
The action potential then travels deep into the muscle fiber, reaching the sarcoplasmic reticulum. This triggers the release of calcium ions from the sarcoplasmic reticulum into the cytoplasm, where they bind to troponin, initiating the contraction of the muscle fibers. The entire process, from the arrival of the action potential to the activation of the muscle fiber, is crucial for the precise and coordinated contraction of skeletal muscles.