Neuromuscular Junction Mechanisms

The video explains how nerve impulses, or action potentials, travel from the brain or spinal cord to trigger skeletal muscle contraction. It details the process at the neuromuscular junction, a chemical synapse where motor neurons excite muscle fibers. The transmission involves seven steps, including the release of acetylcholine and the opening of ligand-gated cation channels. The video also covers how neural transmission ceases when acetylcholine is removed from the synaptic cleft, either by diffusion or breakdown by acetylcholine esterase.

What is another term for nerve impulses?

• Neural signals

• Action potentials

• Muscle contractions

• Synaptic transmissions

Where does an action potential travel to trigger muscle contraction?

• Heart

• Lungs

• Digestive system

• Skeletal muscle fiber

What is the neuromuscular junction?

• A chemical synapse between a motor neuron and a muscle fiber

• A type of muscle fiber

• A type of nerve cell

• A part of the brain

What happens when voltage-gated calcium channels open?

• Sodium ions enter the terminal

• Calcium ions diffuse into the terminal

• Acetylcholine is synthesized

• Potassium ions exit the terminal

What is released into the synaptic cleft during step 3?

• Acetylcholine

• Potassium ions

• Sodium ions

• Calcium ions

What occurs when acetylcholine binds to its receptors?

• Ligand-gated cation channels open

• Potassium ions enter the muscle fiber

• Voltage-gated calcium channels open

• Sodium ions exit the muscle fiber

What causes the membrane potential to become less negative?

• Outward flux of acetylcholine

• Inward flux of calcium ions

• Greater outward flux of potassium ions

• Greater inward flux of sodium ions

What happens once the membrane potential reaches a threshold value?

• An action potential propagates along the sarcolemma

• Potassium ions enter the muscle fiber

• Calcium ions are released

• Acetylcholine is synthesized

How is acetylcholine removed from the synaptic cleft?

• It diffuses away from the synapse

• Both A and B

• It is broken down by acetylcholine esterase

• It is transported into the muscle fiber

What happens to choline after acetylcholine is broken down?

• It diffuses away from the synapse

• It binds to acetylcholine receptors

• It is transported into the axon terminal for resynthesis

• It is excreted from the body