Ch. 8 Muscular System

Question 1

usually, has a single motor end plate. Their associated connective tissues are flexible but can tear if overstretched.

Answer 1

Muscle fiber

Question 2

a protein that, with actin, forms the filaments that contract muscle fibers

Answer 2

Myosin

Question 3

a protein that forms filaments of the protein myosin, contracting muscle fibers

Answer 3

Actin

Question 4

the structural and functional units of a myofibril

Answer 4

Sarcomeres

Question 5

includes all the events involving muscle contraction, and it gets its name from the way sarcomeres shorten. Thick and thin filaments do not change length. Rather, they slide past one another, with the thin filaments sliding toward the center of the sarcomere from both ends.

Answer 5

Sliding Filament Model

Question 6

Describe the sliding filament model

Answer 6

A nervous impulse arrives at the neuromuscular junction, which causes a release of a chemical called Acetylcholine. The presence of Acetylcholine causes the depolarisation of the motor end plate which travels throughout the muscle by the transverse tubules, causing Calcium (Ca+) to be released from the sarcoplasmic reticulum.
2 In the presence of high concentrations of Ca+, the Ca+ binds to Troponin, changing its shape and so moving Tropomyosin from the active site of the Actin. The Myosin filaments can now attach to the Actin, forming a cross-bridge.
3.The breakdown of ATP releases energy which enables the Myosin to pull the Actin filaments inwards and so shortening the muscle. This occurs along the entire length of every myofibril in the muscle cell.
4.The Myosin detaches from the Actin and the cross-bridge is broken when an ATP molecule binds to the Myosin head. When the ATP is then broken down the Myosin head can again attach to an Actin binding site further along the Actin filament and repeat the ‘power stroke’. This repeated pulling of the Actin over the myosin is often known as the ratchet mechanism.
5. This process of muscular contraction can last for as long as there is adequate ATP and Ca+ stores. Once the impulse stops the Ca+ is pumped back to the Sarcoplasmic Reticulum and the Actin returns to its resting position causing the muscle to lengthen and relax.

Question 7

two examples of this are myosin and actin.

Answer 7

Protein Filament

Question 8

fatigable

Answer 8

Fast Twitch

Question 9

fatigue-resistant

Answer 9

Slow Twitch

Question 10

Rhythmic waves of muscular contraction in the walls of certain tubular organs.

Answer 10

Peristalsis

Question 11

the end of a muscle that attaches to a relatively immovable part

Answer 11

Origin

Question 12

the end of a muscle attachment to a movable part

Answer 12

Insertion