Sliding Filament Theory Steps

Question 1

SFT: Step 1

Answer 1

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

Question 2

SFT: Step 2

Answer 2

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

Question 3

SFT: Step 3

Answer 3

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

Question 4

SFT: Step 4

Answer 4

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

Question 5

SFT: Step 5

Answer 5

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

Question 6

SFT: Step 6

Answer 6

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

Question 7

SFT: Step 7

Answer 7

Sarcoplasmic Reticulum releases Calcium (Ca+).

Question 8

SFT: Step 8

Answer 8

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

Question 9

SFT: Step 9

Answer 9

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

Question 10

SFT: Step 10

Answer 10

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

Question 11

SFT: Step 11

Answer 11

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

Question 12

SFT: Step 12

Answer 12

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

Question 13

SFT: Step 13

Answer 13

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

Question 14

SFT: Step 14

Answer 14

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