Structure of Muscle Tissue and Muscle Contraction Chapter 2 Structure of Muscle Tissue and Muscle Contraction

Key Concepts

“A” band acetylcholine (ACH) actin action potential adenosine triphosphate (ATP) cardiac muscle cross-bridge recycling cross-bridges endomysium epimysium fasciculus fast twitch glycotic (FG) fast twitch oxidative glycotic (FOG) H zone

I band mitochondria motor unit myofibrils myofilaments myosin myosin ATPase neuromuscular junction perimysium sarcolemma sarcomere sarcoplasm sarcoplasmic reticulum skeletal muscle

sliding filament model slow twitch oxidative (SO) smooth muscle synapse tropomyosin troponin Z-line

Review Questions

Name the three types of human muscle tissue. Where are they found? Smooth, nonstriated muscle is found in the walls of the hollow viscera and blood vessels. Skeletal, striated muscle is attached to the skeleton and provides the force for movement of the bony leverage system. Cardiac, striated muscle is found only in the heart.

What nervous system innervates smooth muscle? The autonomic nervous system

What nervous system innervates skeletal muscle? The voluntary or somatic nervous system

Cardiac muscle contracts rhythmically and automatically, without ________. outside stimulation

Describe the structure of smooth muscle. Long, spindle-shaped fibers. External shape may change to conform to the surrounding elements. Each fiber usually has only one nucleus.

Name four characteristics of the structure of skeletal muscle. Long, cylindrical muscle fibers. Each fiber is a large cell with up to several hundred nuclei. Each cell is structurally independent of its neighboring fiber or cell. The muscle has cross-striations of alternating light and dark bands.

Name three characteristics of the structure of cardiac muscle. A network (syncytium) of striated muscle fibers. Made up of discrete fibers that can contract individually. The network of fibers responds to innervation with a wavelike contraction that passes through the entire muscle.

In the following diagram of skeletal muscle, what do A, B, C, and D refer to? Fascia D Epimysium Fasciculus C B Perimysium

In the following diagram of an individual skeletal muscle fiber, what do A, B, C, and D refer to? Endomysium Sarcolemma A Sarcoplasm Myofibrils B C D

The motor unit consists of A motor neuron All the fibers the neuron innervates Do small muscles have few or many fibers? Few Do large muscles have few or many fibers? Many Muscles fibers within a motor unit are the same or different types? Same

What are the three primary fiber types in human skeletal muscle? Slow twitch oxidative (SO) Fast twitch oxidative glycolytic (FOG) Fast twitch glycolytic (FG)

What are the characteristics of SO fibers? Speed of contraction Strength of contraction Fatigability Aerobic capacity Anaerobic capacity Size Capillary density Slow Low Fatigue resistant High Low Small High

What are the characteristics of FG fibers? Speed of contraction Strength of contraction Fatigability Aerobic capacity Anaerobic capacity Size Capillary density Fast High Most fatigable Low High Large Low

What are the characteristics of FOG fibers? Speed of contraction Strength of contraction Fatigability Aerobic capacity Anaerobic capacity Size Capillary density Fast High Fatigable Medium Medium Large High

There are significant differences between men and women with regard to fiber type distribution patterns. True or False? False

Our fiber type pattern is genetically determined. True or False?

How can training affect muscle fiber? Within fast twitch fibers, endurance and resistance training result in a shift from FG to FOG fibers.

A person with a high percentage of SO fibers would be a good candidate for what sort of sports? This person would be a good candidate for distance running or other endurance events, because SO fibers are highly fatigue resistant.

A person with a high percentage of fast twitch (FT) fibers would be a good candidate for what sort of sports? This person would be most successful in power and sprint events.

In the following diagram of a sarcomere, what do the letters A through F correspond to? B. C. D. Z-Line A band H zone I band D D B

What is the series of events that leads to muscle contraction in the sliding filament model? At Rest Tropomyosin inhibits actin-myosin binding. Calcium is stored in the sarcoplasmic reticulum. Contraction Neural stimulation causes the sarcoplasmic reticulum to release calcium. Calcium binds to troponin, which removes the inhibitory effect of tropomyosin and actin-myosin bind. Myosin cross-bridges swivel, pulling the actin and z-lines. Fresh ATP binds to the myosin cross-bridges, leading to cross-bridge recycling. Neural stimulation ceases and relaxation occurs

Fill in the blanks for the sliding filament model 1. travels along to 2. releases into and binds to 3. creates that travels along the 4. moves into the through 5. intersects with releasing into the 6. binds with which is bound to 7. causes change in shape to uncovering 8. binds with 9. breaks down to and providing used in Electrical impulse motor neuron end bulb. End bulb ACH synapse ACH motor end plate. ACH binding action potential sarcolemma. Action potential muscle fiber t-tubules. Action potential sarcoplasmic reticulum calcium sarcoplasm. Calcium troponin tropomyosin. Calcium-troponin binding tropomyosin molecule binding sites on the actin molecule. Myosin cross-bridge actin molecule. ATP ADP inorganic phosphate energy muscle contraction.

Explain Theory 1 regarding the way in which energy from the breakdown of ATP is used in muscle contraction. Actin-myosin bind Activates myosin ATPase Breakdown of ATP molecule liberates energy Energy causes myosin cross-bridge to swivel to center of sarcomere Myosin is bound to actin, which is bound to Z-lines Z-lines pulled closer together Sarcomere shortened Fresh ATP molecule binds to myosin cross-bridge Actin-myosin binding released Myosin cross-bridge stands back up Actin-myosin rebinds at new site And process repeats

Explain Theory 2 regarding the way in which energy from the breakdown of ATP is used in muscle contraction. Myosin cross-bridge stores energy from breakdown of ATP by myosin ATPase Actin-myosin binding releases stored energy Energy causes myosin cross-bridge to swivel ADP and Pi are released from the myosin cross-bridge Fresh ATP molecule binds to myosin cross-bridge Actin-myosin binding released ATP is broken down and energy causes myosin cross-bridge to stand back up (re-energized) Fresh ATP molecule is broken down Energy reenergizes myosin cross-bridge Repeat of process

How is Theory 1 similar to Theory 2 in explaining how energy from the breakdown of ATP is used in muscle contraction? Both theories state that fresh ATP binds to the myosin cross-bridge to release it from actin during cross-bridge recycling.

How do the theories differ in describing how energy from the breakdown of ATP is used in muscle contraction? Theory 2 states that after the myosin-actin binding is released, the fresh ATP molecule is broken down and the energy released is used to reenergize the myosin cross-bridge. According to Theory 1, energy is not needed to cause the myosin cross-bridge to stand back up.

Useful Websites

Muscles www.ultranet.com/~jkimball/BiologyPages/M/Muscles.html Muscle Physiology—Myofilament Structure http://muscle.ucsd.edu/musintro/fibril.shtml Muscle Histology www.unomaha.edu/~swick/2740musclehistology.html Histology of Muscle http://views.vcu.edu/ana/OB/Muscle~1/index.htm

Selected Images

Figure 2.1 Skeletal muscle fibers showing cross-striations.

Figure 2.2 Muscle fibers and connective tissue sheaths.

Figure 2. 3 A sarcomere extends from Z-line to Z-line Figure 2.3 A sarcomere extends from Z-line to Z-line. Also shown are the A, H, and I bands that give skeletal muscle its striated appearance.

Figure 2.4 Contractile proteins actin, myosin, troponin, and tropomyosin.

Figure 2.5 Aspects of the sliding filament model of muscle contraction.