Question

What are the 9 steps of synaptic communication (excitation) at the neuromuscular junction?

a. Axon Terminal Depolarization, Muscle Fiber Excitation, Acetylcholine Release, Sodium Influx, Action Potential Propagation, Calcium Release, Troponin Binding, Crossbridge Formation, Muscle Contraction
b. Muscle Fiber Excitation, Calcium Release, Acetylcholine Release, Sodium Influx, Troponin Binding, Crossbridge Formation, Axon Terminal Depolarization, Action Potential Propagation, Muscle Contraction
c. Acetylcholine Release, Sodium Influx, Action Potential Propagation, Calcium Release, Troponin Binding, Crossbridge Formation, Muscle Fiber Excitation, Axon Terminal Depolarization, Muscle Contraction
d. Action Potential Propagation, Axon Terminal Depolarization, Calcium Release, Acetylcholine Release, Muscle Contraction, Troponin Binding, Sodium Influx, Crossbridge Formation, Muscle Fiber Excitation

Answer 1

The 9 steps of synaptic communication at the neuromuscular junction involve acetylcholine release, sodium influx, action potential propagation, calcium release, troponin binding, crossbridge formation, muscle fiber excitation, axon terminal depolarization, and muscle contraction.

Step-by-step explanation:

The 9 steps of synaptic communication (excitation) at the neuromuscular junction are:

1. Acetylcholine Release: Acetylcholine is released by the axon terminal of the motor neuron.
2. Sodium Influx: Acetylcholine binds to ACh receptors on the muscle fiber, opening ion channels and allowing sodium ions to enter the muscle fiber.
3. Action Potential Propagation: The influx of sodium ions causes depolarization of the muscle fiber, initiating an action potential.
4. Calcium Release: The action potential travels along the sarcolemma, triggering the release of calcium ions from the sarcoplasmic reticulum (SR).
5. Troponin Binding: The released calcium ions bind to troponin, causing a conformational change in the troponin-tropomyosin complex.
6. Crossbridge Formation: The conformational change in the troponin-tropomyosin complex exposes the binding sites on the actin filaments, allowing myosin heads to bind and form cross bridges.
7. Muscle Fiber Excitation: The cross bridges undergo a series of power strokes, resulting in the sliding of actin filaments over myosin filaments and muscle fiber contraction.
8. Axon Terminal Depolarization: The power strokes are powered by ATP, and the sarcomeres, myofibrils, and muscle fibers shorten to produce movement.
9. Muscle Contraction: The motor neuron impulses determine the strength and number of muscle fibers that contract.