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What roles do the DHP and ryanodine receptors play in muscle contraction?
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They are involved in the voltage-gated release of calcium from the sarcoplasmic reticulum.
Describe the role of acetylcholine esterase.
Acetylcholine esterase breaks down acetylcholine in the synaptic cleft, stopping the transmission of the signal.
How does the number of muscle fibers in a motor unit differ between large muscles and small muscles?
Large muscles, like those in the back, have motor units that supply more muscle fibers, while small muscles, like in the hand or eye, have motor units that supply fewer muscle fibers.
What is the function of the sliding filament model in muscle contraction?
It describes the process involving myosin heads binding to actin, ATP hydrolysis, and the movement of actin and myosin filaments.
What constitutes a motor unit?
A motor neuron and the skeletal muscle fibers it innervates.
How does an action potential in a motor neuron affect the muscle fibers it innervates?
All the muscle fibers in the motor unit contract.
What is the role of calcium in muscle contraction?
Calcium binds to troponin, moving tropomyosin away from binding sites on actin, allowing myosin heads to form cross-bridges.
Describe the recruitment process of motor units during increasing muscle contraction force.
The recruitment starts with smaller motor units and progresses to larger ones to achieve greater tension.
What effect does curare have on neuromuscular signaling?
Curare binds to acetylcholine receptors, preventing muscle contraction as it is not broken down by acetylcholine esterase.
List the key components of the neuromuscular junction (NMJ).
Nerve endings, vesicles containing acetylcholine, Schwann cells, synaptic cleft, and acetylcholine receptors.
How does acetylcholine facilitate muscle contraction at the NMJ?
Acetylcholine binds to receptors, opening ligand-gated sodium channels and potentially initiating action potential in the muscle fiber if the threshold is reached.
Identify the uses of ATP in muscle contraction.
Sodium-potassium ATPase pump, calcium ATPase pump in sarcoplasmic reticulum, myosin heads for cross-bridge cycling, and releasing myosin from actin.
Explain the role of calcium in the neuromuscular junction.
Calcium enters the neuron upon action potential arrival, facilitating the exocytosis of acetylcholine.
How do organophosphates affect neuromuscular signaling?
They inhibit acetylcholine esterase, causing excessive muscle contraction.
What are the antidotes for organophosphate poisoning?
Pralidoxime (prevents action of nerve gas) and Atropine (blocks receptors).
What is the motor end plate?
The area where the nerve meets the muscle fiber at the neuromuscular junction (NMJ).
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