Summary Of Skeletal Muscle Contraction

Front 1

Step 1

Back 1

An action potential travels along an axon membrane to neuromuscular junction.

Front 2

Step 2
something opens

Back 2

Ca channels open and Ca enters the presynaptic terminal.

Front 3

Step 3
something is release

Back 3

Acetylcholine is released from the synaptic vesicles in the presyaptic terminal of neuron.

Front 4

Step 4
something diffuses

Back 4

Acetylcholine diffusion across the synaptic cleft and binds to receptor causing Na channels to open.

Front 5

Step 5

Back 5

Sodium ions diffuse into the muscle cell. The action potentials travel along the sarcolemma and T tubule membranes.

Front 6

Step 6

Back 6

Action potential in the T tubules causes the sarcoplasmic reticulum to release Ca.

Front 7

Step 7

Back 7

Calcium ions bind to tropin molecules, associated with actin myofilaments. The binding causes tropomysin molecules to move into grooves along the actin myofilament, exposing the myosin attachment sites.

Front 8

Step 8

Back 8

Muscle contraction requires energy. ATP molecules, bound to the myosin heads, are broken down to ADP and P, releasing energy, which is briefly stored in the myosin head.

Front 9

Step 9

Back 9

Some of the stored energy is used to supply the energy for movement of the myosin myofilaments bind to exposed attachment sites on the actin myofilaments, forming cross-bridges. The P are released from the myosin heads.

Front 10

Step 10

Back 10

The heads of the myosin myofilaments bend, causing the actin myofilaments to slide over the surface of the myosin myofilaments.

Front 11

Step 11

Back 11

ADP molecules are released from the myosin head.

Front 12

Step 12

Back 12

ATP molecules bind to the myosin heads and are broken down to ADP and P. Energy is stored in the myosin heads bend back to their resting position.

Front 13

Step 13

Back 13

As long as Ca remain attached to troponin, and as long as ATP remains available, steps 8 to 11 are repeated.