The Sliding Filament Theory

Question 1

Step 1

Answer 1

[ACh]
The motor neuron releases ACh (Acetylcholine), a neurotransmitter, into the synaptic cleft where it diffuses to the muscle cell membrane.

Question 2

Step 2

Answer 2

[Sodium gate]

The neurotransmitter lands on Sodium (Na+) gates in the muscle cell membrane and allows Na+ to diffuse into the cell.

Question 3

Step 3

Answer 3

[Depolarization]
If enough Na+ enters the muscle cell, depolarization of the membrane will
take place.

Question 4

Step 4

Answer 4

[Potassium]

When the muscle cell membrane depolarizes, potassium (K+) is released out of the cell to propagate the signal.

Question 5

Step 5

Answer 5

[Repolarization]

The muscle cell membrane repolarizes with the help of the Sodium-Potassium pump.

Question 6

Step 6

Answer 6

[Signal]
The signal generated from the depolarization of the muscle cell membrane travels down the T-tubules into the Sarcoplasmic Reticulum.

Question 7

Step 7

Answer 7

[Calcium]

Sarcoplasmic Reticulum releases Calcium (Ca+).

Question 8

Step 8

Answer 8

[Tropomyosin]

Calcium allows for the tropomyosin to be removed from the Actin active sites.

Question 9

Step 9

Answer 9

[Cross-bridges]

Once Actin is available, Myosin will form cross-bridges (attachments).

Question 10

Step 10

Answer 10

[Power stroke]

The removal of ADP (Adenosine Diphosphate) and P (Phosphate) from the myosin head causes the Power stroke.

Question 11

Step 11

Answer 11

[ATP}

ATP (Adenosine Triphosphate) is required for the myosin head to be able to release the actin.

Question 12

Step 12

Answer 12

[Broken down]

ATP is broken down into ADP and P, which release energy.

Question 13

Step 13

Answer 13

[High-energy position]

Energy from the breakdown of ATP is used to move the myosin head back into the high-energy position.

Question 14

Step 14

Answer 14

[Continue]

As long as Ca+ is present in the cell, the muscle will continue to contract.