Depolarization of the Triad

What initiates the depolarization of the muscle cell at the neuromuscular synapse?

The release of acetylcholine from the innervating neuron.

The influx of which ion is responsible for the depolarization of the muscle cell?

Sodium (Na+).

What initiates the depolarization of the muscle cell at the neuromuscular synapse?

The release of acetylcholine from the innervating neuron.

The influx of which ion is responsible for the depolarization of the muscle cell?

Sodium (Na+).

Fill in the blank: Acetylcholine opens ___________ channels in the postsynaptic membrane.

ligand-gated.

What is the localized depolarization of the muscle membrane called?

Sarcolemma.

What type of channels facilitate the spreading of depolarization along the sarcolemma?

Voltage-gated sodium channels.

Fill in the blank: The extracellular space around the synaptic cleft and transverse tubules contains __________ concentrations of sodium.

high.

What is the cytoplasmic environment of the muscle cell primarily characterized by in terms of sodium concentration?

Lower sodium levels.

What does the influx of sodium ions trigger in the muscle cell?

The opening of voltage-gated calcium channels.

Where are the voltage-gated calcium channels located that respond to sodium influx?

In the terminal cisternae of the sarcoplasmic reticulum.

What is released from the sarcoplasmic reticulum when calcium channels open?

Calcium ions.

Fill in the blank: The release of calcium ions from the sarcoplasmic reticulum initiates __________ contraction.

muscle.

What ultimate role does calcium release play in muscle physiology?

It initiates muscle contraction.

What is the mechanism by which muscle contractions are activated at the neuromuscular junction?

Sodium influx leading to calcium release.

What type of signaling event occurs at the neuromuscular junction?

Chemical signaling via neurotransmitter release.

Fill in the blank: The process of sodium influx causing depolarization is crucial for __________ function.

muscle.

What structure does the sodium influx cause depolarization to spread into after the sarcolemma?

Transverse tubules.

Fill in the blank: The synaptic cleft separates the __________ from the muscle cell.

innervating neuron.

What is the term for the fluid within muscle cells where calcium is released from the sarcoplasmic reticulum?

Sarcoplasm.

What is the primary ion responsible for causing depolarization in muscle action?

Sodium.

Fill in the blank: The interaction between sodium and calcium at the neuromuscular synapse illustrates the critical interplay of __________ concentrations for muscle function.

ionic.

How does the depolarization of the muscle cell ultimately affect myofibrils?

It activates myofibrils to contract.

Fill in the blank: The neuromuscular synapse is vital for the communication between __________ and muscle cells.

neurons.

What roles do the transverse tubules serve in muscle cell function?

They help propagate depolarization.

How does the sodium influx affect the concentration gradient across the muscle cell membrane?

It reduces the sodium concentration gradient.

What leads to propagation of action potentials in muscle cells?

The influx of sodium and subsequent depolarization.

What occurs to sodium channels after a muscle cell has depolarized?

They become inactive, preventing further sodium influx.

What is the result of the interaction between sodium and calcium in muscle cells?

Initiation of muscle contraction.

Fill in the blank: The combination of sodium influx and calcium release is essential for muscle __________.

contraction.

Where does depolarization in muscle cells primarily begin at the neuromuscular junction?

Near the postsynaptic membrane.

Fill in the blank: The relationship between sodium and calcium is termed __________ in muscle physiology.

interdependent.

What initiates the chain of events leading to muscle contraction at the neuromuscular junction?

Acetylcholine release.

What is maintained within the sarcoplasmic reticulum, crucial for muscle contraction?

High calcium concentration.

Fill in the blank: The release of calcium ions into the sarcoplasm is a key trigger for __________.

muscle contraction.

What role does acetylcholine play at the neuromuscular synapse?

It acts as a neurotransmitter that opens ion channels.

Fill in the blank: An __________ leads to a cascade effect in muscle contraction following the depolarization.

action potential.