1. Inadequate calcium in the neuromuscular junction would directly affect which
ID: 3513148 • Letter: 1
Question
1. Inadequate calcium in the neuromuscular junction would directly affect which of the following processes?
a. Release of acetylcholine from the synaptic vesicles
b. Breakdown of acetylcholine by acetylcholinesterase
c. Depolarization of the junctional folds
d. Conduction of action potentials by the motor neuron
2. What structure most directly stimulates a skeletal muscle fiber to contract?
a. Voltage-gated calcium channels
b. Acetylcholinesterase
c. Synaptic cleft
d. Motor neuron
3. Indicate whether it is the neuromuscular junction at rest or active (in the process of transmitting a signal); neuromuscular junction at rest & neuromuscular junction active
- Na+ diffusion
- Calcium channels open
- More negative charges inside sarcolemma
- Calcium channels closed
- Chemically-gated channels open
- ACh in synaptic cleft
- No Na+ diffusion
- Less negative charges inside sarcolemma
- ACh in synaptic vesicles
- Chemically-gated channels closed
4. Match term to the appropriate definition.
Terms:
- Acetylcholine
- Synaptic vesicle
- Acetylcholinesterase
- Sodium channel
- Acetylcholine receptor
- Calcium channel
- Synaptic cleft
Definitions:
- Neurotransmitter that stimulates skeletal muscle contraction.
- Membranous sac located in the axon terminal that contains neurotransmitter.
- Enzyme located in the synaptic cleft that breaks down acetylcholine.
- A type of voltage-gated ion channel located on the axon terminal.
- The space between the axon terminal and junctional folds.
- A type of voltage-gated ion channel located on the sarcolemma of the muscle fiber.
- A type of chemically-gated ion channel located on the junctional folds of the muscle fiber.
5. Rank the sequence of events at the NMJ that initiate an action potential in the muscle fiber, from first to last.
- Action potential arrives at the axon terminal.
- Acetylcholine binds to its receptors on the junctional folds.
- Calcium ions enter the axon terminal.
- Synaptic vesicles fuse to membrane of axon terminal.
- Junctional folds become depolarized.
- Action potential is initiated on the sarcolemma.
- Acetylcholine is released into the synaptic cleft.
Explanation / Answer
1. Release of acetylcholine from synaptic vescicles
When the motor nerve action potential reaches the presynaptic nerve terminal, there will be an increase in the intracellular calcium concentration. This increased calcium concentration helps the acetylcholine vescicle to fuse the plasma membrane at the presynaptic membrane by a process called exocytosis. Finally acetylcholine release in to synapse.
Inadequate calcium level impair the acetylcholine vescicle exocytosis and release of acetylcholine from the synaptic vescicle
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