Skeletal Muscle

Question 1

What is the Epimysium?

Answer 1

Dense Ct thats continuous with the tendon and surrounds the muscle; Deep investing fascia

1. Major nerves and vessels enter here
2. Axons of proprioceptors

Question 2

What is a fascicle?

Answer 2

A bundle of muscle fibers within a whole muscle.

Question 3

What is the perimysium?

Answer 3

Connective tissue surrounding bundles or fasicles.

1. Contains smaller blood vessels and nerve branches
2. Contains muscle spindles

Question 4

What is the Endomysium?

Answer 4

Connective tissue surrounding muscle fibers and their satellite cells.
1. Capillaries are found here.

Question 5

What is a myofibril? Sarcomere?

Answer 5

A bundle of protein inside muscle fibers; Sarcomeres are the functional contractile units stacked inside of each myofibril.

Question 6

What are myofilaments?

Answer 6

Thin and thick moving contractile proteins ( Actin and Myosin)

Question 7

Describe a muscle fiber.

Answer 7

Multinucleated, Striated with contractile properties

Question 8

What is a satellite cell?

Answer 8

Within the basal lamina of muscle fibers; They divide and fuse with fibers to make bigger fibers. Involved with repair of muscle tissue.

Question 9

What are the 3 types of muscle fiber?

Answer 9

1. Type 1: Slow contractile rates and can sustain long contraction durations.
2. Type 2x: Fast contractile rates. Can generate high force levels but can’t sustain repeated contractions; Highly glycolytic
3. Type 2a: Fast contractile rates and high rates of energy use; Oxidative and glycolytic. Generally intermediate between Type 1 and Type 2x.

Question 10

Discuss Hypertrophy

Answer 10

An increase in muscle fiber diameter; Muscle sized is increased by size and number of myofibrils; Response to weight lifting

Question 11

Discuss Atrophy

Answer 11

A decrease in muscle fiber size.

1. Disuse: Decrease in protein synthesis. Just a decrease in size NOT number.
2. Neurogenic: Loss of motor neurons and fibers. Decrease in fiber number and size.

Question 12

Describe muscle repair

Answer 12

If the basal lamina is intact, satellite cells with fuse with existing muscle. If basal lamina is damaged, repair may be limited and fibrous tissue may form instead.

Question 13

What are the benefits of aerobic training?

Answer 13

Increases mitochondria number and capillary density increases

Question 14

What are the benefits of strength training?

Answer 14

Increases glycolytic enzymes.

Question 15

Which germ layer is responsible for skeletal muscle?

Answer 15

Mesoderm

Question 16

Describe the Sarcolemma

Answer 16

Exictable plasma membrane of a muscle cell which can support an action potential. It invaginates to form T-tubules. These allow APs to penetrate the depth of the muscle fiber.

Question 17

Describe Sarcoplasmic Reticulum

Answer 17

A complex of Smooth ER surrounding myofibrils. Calcium is sequestered in the SR and released with an AP in the T-tubule.

Question 18

What is a Sarcomere?

Answer 18

Functional unit of the myofibril. Each sarcomere shortens during contraction.

Question 19

Describe filament movement during contraction.

Answer 19

Actin slides past myosin, shortening the sarcomere, myofibril and muscle fiber.

Question 20

What are the thin filaments?

Answer 20

Actin, Tropomyosin and Troponin

Question 21

Describe the location of tropomyosin.

Answer 21

In the grooves of an actin filament.

Question 22

What are the 3 subunits of Troponin?

Answer 22

1. Tn-T: Tropomyosin binding subunit
2. Tn-C: Calcium binding unit
3. Tn-I: Inhibitory subunit that prevents actin from binding myosin.

Question 23

Describe Myosin

Answer 23

Thick filament; Has one binding region for actin and one for ATP.