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28 Cards in this Set

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impulses from the motor neurons
What causes skeletal muscle cells to contract?
neuromuscular junction
What is the place called where a motor neuron stimulates a muscle cell?
by endomysium
How are skeletal muscle cells are electrically insulated from each other?
motor neuron
A single nerve cell that extends from the brain or spinal cord to a muscle or gland and carries movement instructions to muscle. An efferent neuron.
The axon. A elongated portion of the neuron
What part of the motor neuron carries impulses to the muscle? Describe its structure.
T-tubules
Invaginations of the sarcolemma penetrating deep into the interior of the muscle cell.
Synaptic cleft
The space between the axon terminal and the motor end plate.
Axon terminal
swollen distal end of the motor neuron axon.
Sarcolemma
The muscle cell membrane.
Synaptic vesicles
Structures within the axon terminal that contain the neurotransmitter acetylcholine.
Sarcomere
The contractile unit of the muscle cell that extends from one Z line to the next.
S.R. & terminal cisternae
Structures within skeletal muscle cells that serve as reservoirs of calcium ions.
Motor end plate
A folded region of the sarcolemma at the neuromuscular junction.
polarized membrane
A condition in which a difference in electrical charge exist across a cell membrane.
It is when the + & - sign indicate a polarized condition. More + on outside & more - on inside.
Describe the resting membrane potential with respect the neuromuscular junction?
They are polarized
Describe the T Tubules when they are at resting membrane potential.
_____ e. An action potential arrives at the axon terminal

_____ c. Acetyl choline is released from the axon terminal into the synaptic cleft.

_____ a. The motor end plate is depolarized.

_____ d. The depolarization triggers an action potential which propagates along the sarcolemma and the T tubules.

_____ b. The sarcomeres contract.
List the following events in the order they occur:

_____ a. The motor end plate is depolarized.

_____ b. The sarcomeres contract.

_____ c. Acetyl choline is released from the axon terminal into the synaptic cleft.

_____ d. The depolarization triggers an action potential which propagates along the sarcolemma and the T tubules.

_____ e. An action potential arrives at the axon terminal
The voltage change of the membrane opens voltage-regulated Ca++ channels, allowing Ca++ ions to enter the axon terminal.
What happens at the neuromuscular junction when the action potential arrives at the axon terminal?
causes synaptic vesicles to fuse w/the membrane of the axon terminal.
What is the effect of the presence of calcium ions inside the axon terminal?
1. Ach is liberated (released) by exocytosis into the synaptic cleft.
2. Ca++ is pumped out of the axon terminal.
What two events happen after the synaptic vesicles fuse with the membrane of the axon terminal?
It binds to receptor sites of the chemically-regulated ion channels on the motor end plate.
What happens to acetylcholine after it is released into the synaptic cleft?
Cause channel to open, permitting an influx of Na+ ions and a small flux of K+ ions. This causes a local depolarization of motor end plate.
What happens after the acetylcholine binds to the acetylcholine receptor on the motor end plate?
when Ach diffuses away from the receptor.
When does the chemically regulated ion channel on the motor end plate close?
It is degraded by acetylcholinesterase.
What happens to the acetyl choline after it diffuses away from its receptor on the motor end plate?
it initiates an action potential which propagates along the sarcolemma all directions and down the T-tubules.
The movement of the sodium ions through the chemically regulated ion channel initiates a depolarization of the motor end plate. What happens after this depolarization is generated?
it causes the release of Ca++ ions from the terminal cisternae into the cytosol.
What happens as the action potential moves down the T Tubules?
it contracts
What happens when calcium ion is present in the cytosol of the muscle cell?
F, J, C, A, H, D, E, B, G, I.
Place the following events in their proper sequence:

_____ a. Acetyl choline is released into the synaptic cleft.

_____ b. Action potential propagates along the sarcolemma and down the T Tubules.

_____ c. Synaptic vesicles fuse to membrane of axon terminal.

_____ d. Motor end plate becomes depolarized.

_____ e. Action potential is initiated on the sarcolemma.

_____ f. Action potential arrives at the axon terminal.

_____ g. Calcium ions are released from the terminal cisternae.

_____ h. Acetylcholine binds to receptor sites on the motor end plate.

_____ i. The muscle cell contracts.

_____ j. Calcium ions enter the axon terminal.