Muscle Contraction Mechanisms at the Neuromuscular Junction

The video explains skeletal muscle contraction, focusing on the neuromuscular junction, excitation-contraction coupling, and the sliding filament theory. It details the role of calcium in muscle contraction, cross-bridge cycling, and muscle relaxation. Energy sources for contraction, muscle fatigue, and oxygen debt are also discussed.

What is the primary role of the neuromuscular junction in muscle contraction?

• To store calcium ions

• To connect muscle fibers to bones

• To transmit signals from motor neurons to muscle fibers

• To provide energy for muscle contraction

Which neurotransmitter is released at the neuromuscular junction to stimulate muscle contraction?

• Norepinephrine

• Acetylcholine

• Serotonin

• Dopamine

What initiates the excitation-contraction coupling process in muscle fibers?

• Formation of cross-bridges

• Release of calcium from the sarcoplasmic reticulum

• Binding of acetylcholine to receptors on the sarcolemma

• Breakdown of ATP

According to the sliding filament theory, what happens to the I-bands during muscle contraction?

• They lengthen

• They disappear

• They shorten

• They remain unchanged

Who first proposed the sliding filament theory of muscle contraction?

• Isaac Newton

• Marie Curie

• Albert Einstein

• Hugh Huxley

What role does calcium play in muscle contraction?

• It provides energy for the contraction

• It binds to troponin, causing tropomyosin to expose myosin binding sites

• It inhibits the binding of myosin to actin

• It breaks down ATP

What enzyme is responsible for breaking down acetylcholine in the neuromuscular junction?

• Phosphorylase

• ATPase

• Lipase

• Acetylcholinesterase

Which of the following is NOT a pathway for ATP regeneration in muscle cells?

• Aerobic cellular respiration

• Photosynthesis

• Anaerobic cellular respiration

• Coupled reaction with creatinine phosphate

What causes muscle fatigue during intense exercise?

• Increased calcium levels

• Excessive oxygen supply

• Accumulation of lactic acid

• High levels of ATP

What is the primary cause of heat production during muscle contraction?

• Breakdown of glucose

• Release of calcium ions

• Energy released from ATP hydrolysis

• Formation of cross-bridges