A&p1 Neuromuscular Junction Review

Front 1

What causes skeletal muscle cells to contract?

Back 1

Impulses from motor neurons

Front 2

What is the place called where a motor neuron stimulates a muscle cell?

Back 2

A neuromuscular junction

Front 3

How are skeletal muscle cells are electrically insulated from each other?

Back 3

By endomysium

Front 4

A nerve cell which extends from the brain or spinal cord to the muscle, where it can stimulate several skeletal muscle cells

Back 4

Motor neuron

Front 5

What part of the motor neuron carries impulses to the muscle? Describe its structure.

Back 5

The axon, which is an elongated process that extends from the brain or spinal cord to the muscle.

Front 6

________________________ a. Invaginations of the sarcolemma penetrating deep into the interior of the muscle cell.

Back 6

T tubule

Front 7

________________________ b. The space between the axon terminal and the motor end plate.

Back 7

Synaptic cleft

Front 8

________________________ c. The swollen distal end of the motor neuron axon.

Back 8

Axon terminal

Front 9

________________________ d. The muscle cell membrane.

Back 9

Sarcolemma

Front 10

________________________ e. Structures within the axon terminal that contain the neurotransmitter acetylcholine.

Back 10

Synaptic vesicles

Front 11

________________________ f. The contractile unit of the muscle cell that extends from one Z line to the next.

Back 11

Sarcomere

Front 12

________________________ g. Structures within skeletal muscle cells that serve as reservoirs of calcium ions.

Back 12

Terminal cisternae & Sarcoplasmic reticulum

Front 13

________________________ h. A folded region of the sarcolemma at the neuromuscular junction.

Back 13

Motor end plate

Front 14

A membrane that has more positive charge on one side and more negative charge on the other side

Back 14

Polarized membrane

Front 15

Describe the T Tubules when they are at resting membrane potential.

Back 15

There is more positive charge in the interior of the T tubule and more negative charge inside the cell.

Front 16

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

Back 16

e, c, a, d, b

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

Front 17

What happens at the neuromuscular junction when the action potential arrives at the axon terminal.

Back 17

The voltage change of the membrane opens the voltage-regulated calcium channels, allowing calcium ions to enter the axon terminal.

Front 18

What is the effect of the presence of calcium ions inside the axon terminal?

Back 18

The calcium ions cause several synaptic vesicles to fuse with the membrane of the axon terminal.

Front 19

What two events happen after the synaptic vesicles fuse with the membrane of the axon terminal?

Back 19

The neurotransmitter acetylcholine is released by exocytosis into the synaptic cleft and calcium ions are pumped out of the axon terminal.

Front 20

What happens to acetylcholine after it is released into the synaptic cleft?

Back 20

The neurotransmitter acetylcholine is released by exocytosis into the synaptic cleft and calcium ions are pumped out of the axon terminal

Front 21

What happens after the acetylcholine binds to the acetylcholine receptor on the motor end plate?

Back 21

It binds to receptor sites on chemically regulated ion channels on the motor end plate.

Front 22

When does the chemically regulated ion channel on the motor end plate close?

Back 22

The chemically regulated ion channel opens allowing sodium ions to diffuse from the synaptic cleft to the inside of the muscle cell and potassium ions to diffuse from the inside of the muscle cell into the synaptic cleft. This action causes a depolarization of the membrane within the motor end plate.

Front 23

What happens to the acetyl choline after it diffuses away from its receptor on the motor end plate?

Back 23

When the acetylcholine diffuses away from its receptor site

Front 24

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?

Back 24

It is then broken down by the enzyme acetylcholinesterase.

Front 25

What happens as the action potential moves down the T Tubules?

Back 25

An action potential is generated that propagates along the sarcolemma in all directions and down the T tubules.

Front 26

What happens when calcium ion is present in the cytosol of the muscle cell?

Back 26

There is a release of calcium ions from the terminal cisternae into the cytosol.

Front 27

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.

Back 27

1. f. Action potential arrives at the axon terminal.

2. j. Calcium ions enter the axon terminal.

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

4. a. Acetylcholine is released into the synaptic cleft.

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

6. d. Motor end plate becomes depolarized.

7. e. Action potential is initiated on the sarcolemma.

8. b. Action potential propagates along the sarcolemma and down the T tubules.

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

10. i. The muscle cell contracts.