Chapter 8: Skeletal Muscle

Question 1

Functions of skeletal muscle

Answer 1

• force generation for locomotion and breathing
• force generation for postural support
• heat production during cold stress

Question 2

Human body contains over ____ skeletal muscles

Answer 2

600

• 40-50% of total body weight

Question 3

Fascia

Answer 3

Separates individual muscles and holds them in position

Question 4

Epimysium

Answer 4

surrounds entire muscle

Question 5

Perimysium

Answer 5

Surrounds bundles of muscle fibers (fascicles)

Question 6

Endomysium

Answer 6

surrounds individual muscle fibers

Question 7

External lamina (basement membrane)

Answer 7

just below endomysium

Question 8

sarcolemma

Answer 8

muscle cell membrane

Question 9

Muscle cells (fibers)

Answer 9

• unique shape
• contain same organelles with other cells (mitochondria)
• multinucleated
• striated appearance
  – stripes produced by alternating dark and light bands
• each muscle fiber extends the entire length of the muscle

Question 10

Above the sarcolemma and below the external lamina are a group of muscle precursor cells called

Answer 10

satellite cells

Question 11

Satellite cells

Answer 11

• undifferentiated cells involved in muscle growth and repair
• can be activated to increase number of nuclei which allows for greater protein synthesis
• important for adaptations to strength training

Question 12

If muscle cells are destroyed due to injury or disease they _____ be replaced by cell division

Answer 12

cannot

Question 13

Myonuclear domain

Answer 13

the volume of cytoplasm surrounding each nucleus

• each nucleus can support the gene expression (protein synthesis) of a limited myonuclear domain

Question 14

During growth, to maintain a constant ratio of cell volume per nucleus

Answer 14

nuclei from satellite cells are incorporated

Question 15

hypertrophy

Answer 15

increased number of nuclei by activating satellite cells

Question 16

atrophy

Answer 16

decreased number of nuclei

Opposite of muscle growth

Question 17

Myofibrils

Answer 17

threadlike structures contain contractile proteins

subdivided into sarcomeres… divided by thin sheet of structural proteins called a Z-line or Z-disk

Question 18

2 major filaments

Answer 18

Myosin- thick

Actin- thin

Question 19

A-band

Answer 19

myosin filaments in the dark region of the sarcomere

Question 20

I-band

Answer 20

actin filaments in the light regions

Question 21

H-zone

Answer 21

center of sarcomere with no overlap of actin

Question 22

Structures that play an important role for muscular contractions

Answer 22

sarcoplasmic reticulum

transverse tubules

Question 23

Sarcoplasmic reticulum (SR)

Answer 23

a network of channels that surrounds each myofibril

• storage site for calcium

Question 24

Transverse tubules

Answer 24

another set of channels extends from sarcolemma into the muscle fiber and passes completely through the fiber

• transverse tubules pass between two enlarged SR portions called the terminal cisternae

Question 25

Neuromuscular Junction

Answer 25

site where motor neuron and muscle fiber meet

Question 26

Motor end plate

Answer 26

pocket formed around motor neuron by sarcolemma

Question 27

neuromuscular cleft

Answer 27

short gap between neuron and muscle fiber