Chapter 9&10_Muscle, Tissue & System

Question 1

List four important functions of muscle tissue.

Answer 1

• Movement of bones or fluids (e.g., blood)
• Maintaining posture and body position
• Stabilizing joints
• Heat generation (especially skeletal muscle)

Question 2

Name the Two Skeletal Muscle Attachments

Answer 2

• Insertion – movable bone
• Origin – immovable (less movable) bone

Question 3

Describe the gross structure of a skeletal muscle

Answer 3

• Fascicle - bundle of muscle fibers
• Muscle fiber - elongated cell
• Epimysium - Dense irregular connective tissue- surrounds entire muscle
• Perimysium - fibrous connective tissue, surrounds individual fiber (fascicles)
• Endomysium - Areolar connective tissue; surrounds each muscle fiber

Question 4

Describe the microscopic structure and functional roles of the myofibrils

Answer 4

Myofibrils:

Structure -

• densely packed, rod-like elements

Function -

• Exhibit striations; perfectly aligned repeating series of dark A bands and light I bands

Question 5

Describe the microscopic structure and functional roles of the sarcoplasmic reticulum

Answer 5

Sarcoplasmic reticulum (blue)

Structure -

• network of sER surrounding each myofibril

Function -

• regulates intracellular Ca2+ levels

Question 6

Describe the microscopic structure and functional roles of the T tubules of skeletal muscle fibers.

Answer 6

T tubules (light grey band)

Structure -

• continuous with sarcrolemma
• lumen continuous with extracellular space
• penetrate cellular interior at A-I band junction

Function -

• conduct impulses deep into muscle fiber; every sarcomere

Question 7

Describe the Myofribril’s Filaments

Answer 7

• Thick filaments - run entire length of an A band
• Thin filaments - run length of I band and partway into A band

Question 8

Name the functions & location of M Line is Myofibrils

Answer 8

M Line

• line of protein myomesin bisects H zone
• is stability protein that keeps the Sarcomere protected during intense contractions

Question 9

Describe the structure and & functions of the Z disc (line) of the Myofibrils

Answer 9

Z disc (line)

• coin-shaped sheet of proteins on midline of light I band that anchors thin filaments
• connects myofibrils to one another
• makes up the Sarcomere

Question 10

Describe the function and structure of Sarcomere

Answer 10

Sarcomere

• Smallest contractile unit of muscle fiber
• Align along myofibril like boxcars of train
• Contains A band with ½ I band at each end
• Composed of thick and thin myofilaments made of contractile proteins

Question 11

Explain how muscle fibers are stimulated to contract by describing events that occur at the neuromuscular junction.

(Figure 9.8)

Answer 11

1. Skeletal muscles stimulated by somatic motor neurons
2. Each axon forms several branches as it enters muscle
3. Each axon ending forms neuromuscular junction with single muscle fibers

Question 12

Describe how an action potential is generated.