Skeletal Muscle Contraction

Question 1

Animal Movement is due to what?

Answer 1

Muscle Contraction

Question 2

Skeletal Muscle

Answer 2

Bundle of long fibers attached to the bone that runs the length of the muscle.

Question 3

Each fiber is comprised of

Answer 3

A single cell with many nuclei. Each fiber is composed of smaller myofibrils.

Question 4

Myofibrils

Answer 4

Bundles of protein filaments

Question 5

Myofibrils are comprised of

Answer 5

Thin and thick protein filaments.

Question 6

Thin filaments are made up of…

Answer 6

2 strands of actin, and the regulatory proteins tropomyosin and troponin.

Question 7

Actin

Answer 7

Globular Protein

Question 8

Tropomyosin

Answer 8

Regulatory protein that blocks myosin binding sites.

Question 9

Troponin

Answer 9

Is a regulatory protein that regulates the position of tropomyosin.

Question 10

Thick filaments are comprised of

Answer 10

Thick filaments are comprised of myosin molecules.

Question 11

What results in muscle movement?

Answer 11

Interaction between actin and myosin

Question 12

Sliding Filament Model

Answer 12

Length of thin and thick filaments stays the same during muscle contraction. Each filament passes each other during muscle contraction.

Question 13

First three steps of Muscle Movement

Answer 13

1. Action potential reaches the presynaptic terminal.
2. Release of Acetylcholine (excitatory neurotransmitter) into the synaptic cleft through exocytosis.
3. Acetylcholine binds to Na+ channel proteins (excitatory) which causes them to open, resulting in depolarization and the generation of an Action potential in the postsynaptic cell.

Question 14

Steps 4 and 5 of muscle movement

Answer 14

4. Ca2+ is released by sarcoplasmic reticulum.
5. Ca2+ binds to troponin, which alters the structure of the tropomyosin-troponin complex, exposing the myosin binding sites.

Question 15

Step 6 of muscle movment

Answer 15

6. Myosin and actin now able to interact.
   a. The myosin head is initially bound to ATP and thus unable to bind to actin.
   b. Hydrolysis of ATP changes the conformation of the myosin head, allowing it to bind to actin and form a cross-bridge.
   c. ADP and Pi are released, changing the conformation of the myosin head, moving the actin.
   d. binding of ATP breaks myosin-actin cross-bridge, returning the actin back to its resting position.

Question 16

Step 7 of muscle movement

Answer 16

7. Contractions stop when Ca2+ levels return to normal.