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The Muscular System: Neuromuscular Junction

1.What insulates each muscle cell? __________endomysium_______________

2.Synaptic vesicles in the axon terminal of a motor neuron contain what

neurotransmitter? __________acetylcholine_______________

3.An action potential in the axon terminal of a motor neuron opens what type

of ion channels? ____________Voltage-gated Calcium_____________

4.By what means of membrane transport does the neurotransmitter leave the

axon terminal? ____________exocytosis_____________

5.Binding of neurotransmitter to the receptors on the motor endplate open

what type of ion channels? ___________chemically-gated______________

6.Opening of these channels leads to ______depolarization_________ of the motor endplate.

7.How is the neurotransmitter removed from the synaptic cleft?

Acetylcholine diffuses away from the receptor and is broken down by acetylcholinesterase

8.As a result of question 6, an action potential is propagated along the

________sarcolemma_________ of the muscle cell and down the _______T tubules________

into the cell.

9.The result of this action potential releases what ion from the terminal

cisternae? ____Ca²⁺____

10.a. What effect did molecule “X” in the quiz have on the muscle contraction?

Molecule x blocked the ion channel receptor site so acetylcholine could not attach therefor not allowing the muscle to ultimately contract.

b. Explain its mechanism of action.

When the secretory vesicles opened to allow acetylcholine to enter the synaptic cleft Molecule X rushed into the synaptic cleft. Molecule X moved faster than Acetylcholine therefore binding to the receptor sites first.

c. What drug did molecule “X” act like? _______curare________

11.a. What effect did molecule “Y” have on the muscle contraction?

Molecule Y prevented break down of acetylcholine and generated more muscle contractions than action potentials

b. Explain its mechanism of action.

Molecule Y blocks off the acetylcholinesterase which prevents the break down of acetylcholine

c. What drug did molecule “Y” act like? _______neostigmine________

12.a. What effect did molecule “Z” have on the muscle contraction?

Molecule Z prevented chemically-gated ion channel to close and caused more muscle contractions than action potentials

b. Explain its mechanism of action.

Molecule Z rushes to attach to the receptor of the chemically-gated ion channels and does not break down with acetylcholinesterase

c. What drug did molecule “Z” act like? ________nicotine_______

The Muscular System: Sliding Filament Theory

1.a. The thick filament is composed of what molecule?

__________myosin_____________

b. Flexing the head of this molecule provides what is known as the

____________power stroke_____________.

2.The cross bridge (myosin head) contains binding sites for what two molecules?

a. ATP

b. actin

3.Three molecules make up the thin filament.

a. Which molecule has a binding site for myosin cross bridges?

____________Actin_________________

b. Which molecule covers this binding site?

_______________Tropomyosin__________________________________

c. Which molecule has a binding site for calcium ions?

________________Troponin______________________

4.What molecule must bind to the cross bridge in order for it to disconnect with

actin? ____________ATP_____________

5.Hydrolysis of the molecule in question 4 returns the myosin molecule to the

____________high-energy_____________ confirmation.

6.Binding of the cross bridges sequentially prevents _________sliding____________

of the thin filament.

7.Name three roles for...
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