12 Questions
Which component is vital for initiating muscle contraction?
ATP
What process involves the hydrolysis of Creatine Phosphate to generate ATP?
Substrate Phosphorylation
Which energy storage compound is found in high-energy using tissues like the brain, heart, and skeletal muscle?
Creatine Phosphate
What is the primary function of Acetylcholine at the neuromuscular junction?
Initiating muscle fiber depolarization
What is the term used to describe the phenomenon where impulses fail to pass into the muscle fiber due to diminished acetylcholine vesicles?
Neuromuscular fatigue
Which protein found at triads on T-tubules is voltage-sensitive and activated by the action potential?
Dihydropyridine receptor
What causes about three times as much end plate potential at the neuromuscular junction as required to stimulate the muscle fiber?
Safety factor
Which neurotransmitter is synthesized by the nerve cell body and packaged into secretory vesicles for release at the presynaptic terminal?
Acetylcholine
What is the main function of Acetylcholinesterase in the neuromuscular junction?
To break down Acetylcholine
Which positive ions can move easily through the opened acetylcholine channel at the neuromuscular junction?
Ca++ and K+
What is the role of the END PLATE POTENTIAL in muscle contraction?
Initiating action potential that spreads along the muscle membrane
Which event directly precedes the activation of Ligand-gated Ach channels at the neuromuscular junction?
Secretion of NT Ach into the synaptic cleft
Study Notes
- Excitation-Contraction Coupling is a process involved in muscle contraction.
- Sliding Filament Theory requires six components for muscle contraction: ATP, Ca2+, thick filaments, thin filaments, tropomyosin, and troponin.
- ATP is essential for muscle contraction and is used in three processes: disconnecting myosin from actin, pumping Ca from cytosol back into SR, and generating a high energy state of myosin.
- Creatine Phosphate is a means of storing energy and is found in high energy using tissues like brain, heart, and skeletal muscle. It generates ATP through a process called Substrate Phosphorylation, and its phosphate pool is four times the size of the ATP pool. Creatine is used by athletes and bodybuilders to increase energy reserves and attract water into muscle fibers.
- The neuromuscular junction has a high safety factor, meaning each impulse that arrives at the junction causes about three times the required end plate potential. However, excessive stimulation can result in fatigue and impulse failure.
- Excitation-Contraction Coupling: an action potential travels from the motor end plate into the muscle fiber via T-tubules, activating dihydropyridine receptor (DHP) and ryanodine receptor (RR) proteins, which physically associate and change conformation to pump Ca2+ from SR into the cytosol.
- The opened acetylcholine (Ach) channel has a diameter of about 0.65 nanometers and allows important positive ions like Na+, K+, and Ca++ to move through.
- The neuromuscular junction functions as follows: an action potential reaches the presynaptic terminal, causing the exocytosis of Ach-containing secretory vesicles, followed by Ach crossing the synaptic cleft to activate ligand-gated Ach channels, allowing Na+ influx and the initiation of the end plate potential (EPP), which spreads as an action potential and causes muscle contraction.
- Acetylcholinesterase breaks down Ach in the synaptic cleft into Acetyl CoA and choline.
Test your knowledge on the components required for muscle contraction according to the Sliding Filament Theory, such as ATP, Ca2+, thick filaments, thin filaments, tropomyosin, and troponin. Learn a mnemonic 'ACT-4 Muscle Metabolism' to remember these components and understand their roles in muscle contraction.
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