18 Questions
What is the primary function of voltage-gated calcium channels in nerve terminals?
To facilitate the diffusion of Ca2+ into the nerve terminal
What is the location of acetylcholine receptors in muscle fibers?
In the muscle fiber membrane, below the dense bar areas
What is the process by which acetylcholine is released from synaptic vesicles into the synaptic space?
Exocytosis
What is the effect of Ca2+ on acetylcholine vesicles in the nerve terminal?
It exerts an attractive influence on the vesicles, drawing them to the neural membrane
What is the approximate number of synaptic vesicles in the terminals of a single end plate?
300,000
What is the function of linear dense bars in the neural membrane?
To anchor protein particles that form voltage-gated calcium channels
What is the result of the sudden influx of sodium ions into the muscle fiber when the acetylcholine channels open?
An increase in the membrane potential of the muscle fiber
What is the minimum increase in membrane potential required to initiate an action potential in the muscle fiber?
20-30 mV
What is the primary mechanism by which the effect of acetylcholine binding is terminated?
Breakdown of acetylcholine by acetylcholinesterase
What is the result of stimulating the nerve fiber at rates greater than 100 times/second for several minutes?
Fatigue of the neuromuscular junction
What is the primary function of acetylcholinesterase in the synaptic cleft?
To break down acetylcholine into acetyl and choline
What is the name of the local potential created when the acetylcholine channels open?
End plate potential
What is the primary reason for the larger influx of sodium ions compared to potassium ions through the acetylcholine channel?
The higher concentration of sodium ions in the extracellular fluid
What is the primary effect of acetylcholine binding to its receptors on the muscle fiber membrane?
Allowing large numbers of sodium ions to pour into the muscle fiber
What is the outcome of the local positive potential change inside the muscle fiber membrane, also known as the end plate potential?
It initiates an action potential that spreads along the muscle membrane
Which ions are repelled by the negative charges in the mouth of the acetylcholine channel?
Chloride ions
What is the requirement for the acetylcholine channel to open and allow ions to pass through?
Two acetylcholine molecules attaching to the alpha subunit protein
What is the purpose of the negative potential on the inside of the muscle membrane?
It prevents the efflux of positively charged potassium ions
Learn about the brief duration of acetylcholine activity and its termination mechanisms, including the role of acetylcholinesterase and diffusion. Understand how ACh is broken down and becomes unavailable to activate the ACh receptor.
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