Ch. 9: Muscles and Muscle Tissue

I. Functions of the Muscular System

A. List and describe the seven major functions of muscles:

  1. ______________________________________________________________ ______________________________________________________________ ______________________________________________________________

  2. ______________________________________________________________ ______________________________________________________________ ______________________________________________________________

  3. ______________________________________________________________ ______________________________________________________________ ______________________________________________________________

  4. ______________________________________________________________ ______________________________________________________________ ______________________________________________________________

  5. ______________________________________________________________ ______________________________________________________________ ______________________________________________________________

  6. ______________________________________________________________ ______________________________________________________________ ______________________________________________________________

  7. ______________________________________________________________ ______________________________________________________________ ______________________________________________________________

II. General Functional Characteristics of Muscle

A. Properties of Muscle

  1. Contrability is __________________________________________________

    • Muscle shortens ______________________________

    • Muscle strengthens ______________________________

  2. Excitability is __________________________________________________

    • Normally, stimulation comes from ____________________

    • Stimulation can also come from ____________________

  3. Extensibility means ______________________________________________

  4. Elasticity is __________________________________________________

B. Types of Muscle Tissue

  1. Skeletal Muscle

    • Where do you find skeletal muscle? ______________________________

    • What shape are skeletal muscle cells? ____________________________

    • How much of the body is composed of skeletal muscle? ______________

    • Functionally, skeletal muscle is responsible for many actions, including: 

      1. ______________________________ 

      2. ______________________________ 

      3. ______________________________ 

      4. ______________________________ 

  2. Smooth Muscle

    • Where do you find smooth muscle? ______________________________ ___________________________________________________________

    • What shape are smooth muscle cells? ____________________________

    • Smooth muscle has a wide variety of functions, including:

      1. ______________________________ 

      2. ______________________________ 

      3. ______________________________ 

      4. ______________________________ 

  3. Cardiac Muscle

    • Where do you find cardiac muscle? ______________________________

    • What shape are cardiac muscle cells? ____________________________

    • Functionally, cardiac muscle is responsible for ______________________

    • What does autorhythmic mean? _________________________________

    • What does involuntary control mean? _____________________________

III. Skeletal Muscle Structure 

A. General

  1. Skeletal muscles are composed of:

    • ______________________________ 

    • Associated with:

      1. ______________________________ 

      2. ______________________________ 

      3. ______________________________ 

  2. What is a skeletal muscle fiber? ______________________________

  3. Each fiber is a single ____________________ containing _______________ located ________________________________________ 

  4. What is a myoblast? ________________________________________

  5. What converts a myoblast to a muscle fiber? __________________________

  6. How does a muscle enlarge after birth? ______________________________

  7. What does the term striated refer to? ________________________________

  8. How long are skeletal muscle fibers? ______________________________

  9. How thick are skeletal muscle fibers? ______________________________

B. Connective Tissue 

  1. What is the external lamina? ______________________________________

    • The external lamina is produced by ______________________________

  2. The sarcolemma is the ________________________________________

  3. Endomysium

    • It is composed of ___________________________________________

    • Where is it located? ________________________________________

  4. Perimysium 

    • It is composed of ________________________________________

    • What does it enclose? ________________________________________

    • What does the term fasciculus refer to? ______________________________________________________________________________________

    • How many fasciculi does a muscle contain? ________________________

  5. Epimysium

    • It is composed of _____________________________________________

    • Where is it located? ________________________________________

  6. Fascia 

    • What is a fascia? ________________________________________

    • What is the fascia around an individual muscle called? _______________

  7. The connective tissue components of muscles are continuous with:

    • ______________________________ 

    • ______________________________ & 

    • ______________________________ 

  8. Functionally, the connective tissue of muscle:

    • Holds ________________________________________ 

    • Attaches ________________________________________ 

C. Nerve and Blood Vessels

  1. Functionally, motor neurons ______________________________

  2. Extending through the muscle connective tissue with the nerve is

    • an____________________ & one or two ____________________

  3. What is a synapse or neuromuscular junction? ____________________

  4. Each motor neuron innervates ______________________________

  5. Every muscle fiber receives ______________________________

D. Muscle Fibers 

  1. The cytoplasm of a skeletal muscle fiber is called ____________________

  2. What is a myofibril? _____________________________________________

    • How long is a myofibril compared to the muscle fiber? ________________

  3. Myofibrils are composed of protein filaments called ____________________

  4. Actin myofilaments (thin myofilaments):

    • Are approximately __________ in diameter & __________ in length

  5. Myosin myofilaments (thick myofilaments):

    • Are approximately __________ in diameter & __________ in length

  6. What is a sarcomere? ____________________________________________ 

  7. Actin Myofilaments 

    • What is the shape of globular actin (G-actin)? ____________________

    • Connecting approximately 200 G-actin molecules together forms one polymer strand called ______________________________ 

    • Two strands of F actin are coiled to ______________________________ ___________________________________________________________

    • Each G-actin monomer has _____________________________________

    • Tropomyosin is an ____________________________________________

    • How many G-actin active sites does tropomyosin cover? ______________

    • Troponin is composed of __________ subunits:

      1. One subunit binds to ____________________ 

      2. One subunit binds to ____________________ 

      3. One subunit binds to ____________________ 

    • The complex of tropomyosin and troponin regulates _________________ ___________________________________________________________

  8. Myosin Myofilaments

    • What is the basic shape of a myosin molecule? ____________________

    • Each myosin molecule is composed of:

      1. Two ____________________ wound together to _________________ lying parallel ________________________________________ 

      2. Two __________ that extend ____________________ 

    • Where are the four light chain myosin molecules located? _____________

    • How many myosin molecules are in a myosin myofilament? ______________

    • What are the three functions of the myosin heads?

      • Heads can _______________________________________________

      • Have a hinge region that ____________________________________

      • Heads have ____________________ that ______________________

  9. Sarcomeres

    • A sarcomere extends from __________ to an ____________________

    • What is a Z disk? __________________________________________

    • What causes the striated appearance of a myofibril? _________________

    • The I band consists only of ______________________________

    • The A band extends the ______________________________

      1. The __________ & __________ myofilaments ___________________

      2. Each myosin myofilament is surrounded by _____________________

    • The H zone contains only ______________________________

    • Where is the M line? ________________________________________

    • What is the M line? ________________________________________

    • Since the A bands and I bands of parallel myofibrils are aligned, it creates ________________________________________ a microscope 

IV. Sliding Filament Model

  1. Actin and myosin myofilaments ____________________ length

  2. Actin and myosin myofilaments ____________________ 

    • This results in the sarcomere ____________________

  3. When sarcomeres shorten, the ____________________ shorten

  4. When myofibrils shorten, the ____________________ shorten

  5. Therefore, sarcomeres are responsible for ______________________________ 

V. Physiology of Skeletal Muscle Fibers 

A. Membrane Potentials

  1. What does polarized mean? _______________________________________ _____________________________________________________________

  2. What is the resting membrane potential? _____________________________ _____________________________________________________________

  3. The membrane becomes polarized when ____________________________ _____________________________________________________________

  4. What is the resting membrane potential of a muscle cell? ________________

  5. Why is this reported as a negative number? __________________________

B. Ion Channels 

  1. The permeability of the plasma membrane changes as a result of ______________________________ 

  2. The diffusion of ions through the channels ____________________________ and produces an ______________________________ 

  3. Ligand-gated ion channels 

    • What is a ligand? ________________________________________

    • What is a receptor? ________________________________________

    • How are ligand-gated ion channels opened? __________________________________________________________________________________

    • What is a neurotransmitter? ______________________________

  4. How are voltage-gated ion channels opened or closed? _________________ ____________________________________________________________

  5. Can any ion move through any ion channel? Why? ____________________ ____________________________________________________________

  6. When ions move through ion channels, do they move up or down the concentration gradient? ____________________

C. Action Potentials 

  1. The two phases of an action potential are _____________ & _____________

  2. Depolarization occurs ________________________________________

  3. Depolarization is triggered if the membrane is changed to _______________

  4. What is repolarization? ________________________________________

  5. Depolarization and repolarization result from __________________________

  6. Before stimulation, the gated ion channels are ____________________

  7. When the cell is stimulated:

    • Gated Na+ channels __________ & Na+ ____________________

    • The positively charged Na+ makes the inside ____________________

    • If the threshold is reached, many __________ open rapidly & __________ into the cell until ______________________________ briefly 

  8. Shortly after, the inside of the plasma membrane becomes positive:

    • Closing of __________ & opening of ____________________

      1. The movement of __________ into the cell stops 

      2. The movement of __________ out of the cell increases 

    • Therefore, the inside of the plasma membrane becomes __________ and the outside of the plasma membrane becomes ________________

  9. The resting membrane potential is reestablished when __________________

  10. The all-or-none principle

    • What does the “all” refer to? ____________________________________

    • What does the “none” refer to? __________________________________

  11. What does propagate mean in terms of an action potential? ______________ ______________________________________________________________

  12. What is action potential frequency? _________________________________

D. Neuromuscular Junction 

  1. Neuromuscular junction (synapse) consists of ____________________ & ______________________________ 

  2. What is a presynaptic terminal? ______________________________

  3. What is a synaptic cleft? ________________________________________

  4. What is the postsynaptic membrane (motor end-plate)? _________________________________________________________ 

  5. Where are the synaptic vesicles located? __________________________

  6. Acetylcholine functions as a ____________________ 

  7. What does a neurotransmitter do? __________________________________ ______________________________________________________________

  8. When an action potential reaches the presynaptic terminal, it:

    • Causes ____________________ to open 

    • As a result, ____________________ into the cell 

    • Inside the cell, the Ca2+ causes ____________________ by ____________

    • The acetylcholine diffuses across __________ & binds to _____________

    • This causes ____________________ to open & ____________________ 

  9. What is acetylcholinesterase, and what does it do?___________________________________________________________________

  10. Acetylcholine is broken down into _______________ & _______________

    • What happens to the choline molecules? __________________________

    • What happens to the acetic acid molecules? _______________________

E. Excitation-Contraction Coupling 

  1. What is a transverse tubule (T tubule)? ______________________________ ______________________________________________________________

  2. What is the sarcoplasmic reticulum? ______________________________

    • The enlarged portion of the sarcoplasmic reticulum is called ___________

  3. What are the 3 components of a triad? ______________________________

  4. What is stored inside the sarcoplasmic reticulum? __________________

  5. Excitation-contraction coupling begins at ____________________________ with the production of ____________________________ in the sarcolemma

    • The action potential is propagated ______________________________

    • The T tubules undergo ____________________ 

    • Depolarization at the triads causes ______________________________

    • This allows __________ to rapidly ______________________________

    • __________ bind to ____________________ of the actin myofilaments

    • This combination causes the ___________________________________

    • That exposes __________ on the G-actin, which then binds to __________ of ____________________ to form ____________________ 

F. Cross-Bridge Movement 

  1. After the myosin heads bind to the actin active site: 

    • Myosin molecules move ______________________________

    • Forcing ____________________ to slide ____________________

  2. After movement, the myosin head releases and ____________________

  3. The myosin head can then ________________________________________ followed by __________, release of __________, and __________________

  4. The cycle is: cross-bridge _________, _________, _________, & _________

  5. Each cycle of cross-bridge formation requires energy from ______________

    • Release of the myosin head requires __________ to bind ____________

    • ATPase in the myosin head ____________________________________

      1. Energy is stored in ______________________________

      2. Both __________ & __________ remain ____________________

    • The cross-bridge is released as a result of _________________________, and the myosin head returns ______________________________

    • Then the myosin molecule binds _________________________________

      1. As a result of this binding __________________ from the myosin head

    • Much of the stored energy is used for _____________ & _____________

      1. And the ____________________ is released from the myosin head

    • Before the cross-bridge can be released __________________________

  6. What is a power stroke? ________________________________________

  7. What is a recovery stroke? ________________________________________

G. Muscle Relaxation 

  1. Occurs as a result of the ____________________ back into _____________

  2. This results in the troponin-tropomyosin complex ____________________ which __________________________________________________

  3. Therefore, ____________________ reform and ____________________

  4. During the relaxation of muscle, ATP is needed for the active transport of:

    • ______________________________ 

    • ______________________________ 

    • ______________________________ 

VI. Physiology of Skeletal Muscle 

A. Muscle Twitch 

  1. What is the lag phase (latent phase)? ______________________________

  2. What is the contraction phase? ____________________________________

  3. What is the relaxation phase? _____________________________________ 

  4. Muscle contraction is measured as a force called ____________________

B. Stimulus Strength and Muscle Contraction

  1. What is the all-or-none law of skeletal muscle contraction? _______________ ______________________________________________________________

  2. What is a subthreshold stimulus? ___________________________________

  3. What is a threshold stimulus? ______________________________________

  4. Define the term “motor unit” _______________________________________

  5. How do motor units respond? ______________________________________

  6. Whole muscles respond to stimuli in ______________________________ 

    • This means _________________________________________________

  7. What does multiple motor unit summation refer to? _____________________ _____________________________________________________________

  8. What is a submaximal stimulus? ___________________________________

  9. A maximal stimulus ______________________________________________

  10. What effect does a supramaximal stimulus have on the strength of muscle contraction? __________________________________________________

  11. What does the phrase “motor units recruited” mean? ___________________ ____________________________________________________________

  12. How many motor fibers in a motor unit are involved in precise movements? _____

  13. How many motor fibers in a motor unit are involved in powerful movements? ____

C. Stimulus Frequency and Muscle Contraction 

  1. As the frequency of action potentials increases ________________________

  2. What happens during incomplete tetanus? ___________________________

  3. What happens during complete tetanus? _____________________________

  4. How would a muscle be stimulated to produce treppe? ________________________________________________________________________________

  5. Treppe is probably the result of ____________________________________ 

VII. Types of Muscle Contractions

A. In isometric contractions, the ____________________ doesn’t change, but the ______________________________changes during the contraction process

B. In isotonic contractions, the ______________________________ is constant, but the ______________________________ changes

  1. What type of isotonic contractions are concentric contractions? __________ ____________________________________________________________

What type of isotonic contractions are eccentric contractions? ______________________________________________________________________

C. Muscle tone refers to _______________________________________________

  1. These contractions are responsible for: 

    • ________________________________________ 

    • ________________________________________ 

    • ________________________________________

  2. Muscles are able to produce smooth movements since motor units are contracting and relaxing ______________________________ 

D. Length Versus Tension

  1. What is active tension? ________________________________________

  2. What is passive tension? ________________________________________

  3. What is total tension? ________________________________________ 

VIII. Fatigue 

A. What is fatigue? __________________________________________________

  1. Psychological fatigue occurs when the individual ________________________

  2. Muscular fatigue results from ______________________________________

  3. Synaptic fatigue occurs in the ________________ due to a lack of __________

B. Physiological Contracture and Rigor Mortis 

  1. What is physiological contracture? __________________________________

    • Caused by a lack of ________________________________________

    • As a result, __________ accumulates in the sarcoplasm 

    • Previously formed cross-bridges ______________________________

C. Rigor Mortis 

  1. This is the development of ________________________________________

  2. Low levels of ATP prevent ________________________________________

  3. Over time, __________ leaks out of the ______________________________

  4. As the __________ increases in the sarcoplasm, ___________________________ 

  5. Cross-bridges are unable to __________ & __________ to cause contraction

  6. Therefore, the muscles remain _____________________________________ 

IX. Energy Sources 

A. Creatine Phosphate 

  1. When is creatine phosphate synthesized? ____________________________

  2. Functionally, creatine phosphate ____________________________________

The chemical formula for the conversion of creatine phosphate to ATP is: ______________________________________________________________

B. Anaerobic Respiration 

  1. When does anaerobic respiration occur? _____________________________

  2. It involves the breakdown of glucose to _______________ & _____________

  3. For each molecule of glucose, there is a net production of ________________ and ______________________________

  4. What happens to most of the lactic acid? _____________________________

  5. What is the advantage of anaerobic respiration? _______________________ ______________________________________________________________ 

  6. ATP formation from creatine phosphate & anaerobic respiration is limited by:

    • Depletion of ____________________ 

    • Depletion of ____________________ 

    • Buildup of ______________________________ 

C. Aerobic Respiration 

  1. What is required by aerobic respiration? _____________________________

  2. It breaks down glucose to produce __________, __________, & __________

  3. Is anaerobic or aerobic respiration more efficient? ____________________

  4. How many ATPs can aerobic respiration produce per glucose? __________

  5. What organic molecule provides the most important energy source for muscles during sustained exercise? ____________________ 

  6. What are the two sets of reactions that occur in the mitochondria called?

    • ______________________________ 

    • ______________________________ 

  7. The major end products of aerobic respiration are:

    • ______________________________ 

    • ______________________________

    • ______________________________ 

  8. What is the chemical equation for the aerobic respiration of one glucose molecule? ______________________________________________________________

  9. What type of activities depend on aerobic respiration? __________________

D. Oxygen Debt 

  1. Define oxygen debt: ____________________________________________ _____________________________________________________________

  2. It represents the difference between _________ needed & __________ used

  3. The increased aerobic metabolism after exercise:

    • Reestablishes __________ & ____________________ in muscle cells

    • Converts excess __________ to __________ and then to __________ 

X. Slow and Fast Fibers

A. Slow-Twitch, or High-Oxidative, Muscle Fibers 

  1. Slow-twitch muscle fibers:

    • Contract ____________________ 

    • Are smaller ____________________ 

    • Have a ______________________________ 

    • Have more ______________________________ & 

    • Are more ______________________________ 

  2. They respond relatively slowly to ______________________________

  3. Break down ATP at ______________________________________________

  4. What is myoglobin? _____________________________________________

What ability does myoglobin enhance? ______________________________

B. Fast-Twitch, or Low-Oxidative, Muscle Fibers 

  1. Fast-twitch muscle fibers respond __________ to nervous stimulation.

  2. Fast-twitch muscle fibers contain myosin that _________________________

  3. This allows cross-bridge cycling to occur _____________________________

  4. Fast-twitch muscle fibers have:

    • Less well-developed ______________________________ 

    • Have very little ______________________________

    • Fewer and smaller ______________________________ 

    • Have large deposits ______________________________ 

    • Well adapted to perform ______________________________ 

  5. The fast-twitch muscle fibers tend to:

    • Contract ___________________ 

    • And fatigue ____________________ 

C. Distribution of Fast-Twitch and Slow-Twitch Muscle Fibers 

  1. Most human muscles have ________________________________________

  2. Large postural fibers contain ______________________________

  3. Muscles of the upper limbs contain ______________________________

  4. A good sprinter would have _______________________________________

  5. A marathon runner would have ____________________________________

A person with a balanced mixture of slow-twitch and fast-twitch muscle fibers would be able to ________________________________________________

D. Effects of Exercise 

  1. In response to exercising a muscle __________________________________

  2. A muscle that is not used ____________________ or __________________

  3. These changes result from ________________________________________

  4. What increases in a muscle cell when it enlarges? _________________________________________________________________________________

  5. What other elements of a muscle increase? __________________________ ______________________________________________________________

  6. When is a decrease in the number of muscle cells possible? _____________ ____________________________________________________________ 

XI. Heat Production 

A. Energy from skeletal muscle metabolism in the form of heat is responsible for normal ______________________________ 

B. The body responds to higher than normal body temperature by:

  1. ____________________ of blood vessels in the ____________________ &

  2. ______________________________

C. The body responds to lower than normal body temperature by _______________ 

XII. Smooth Muscle 

A. General Characteristics of Smooth Muscle 

  1. Smooth muscle cells are __________ than skeletal muscle cells.

  2. Smooth muscle cells contain __________ actin and myosin myofilaments.

  3. There are more __________ than __________ myofilaments. 

  4. Instead of sarcomeres, the myofilaments are ________________________

    • This is the reason that smooth muscle cells are not __________________

  5. What are dense bodies? __________________________________________

    • What are they equivalent to? ___________________________________

  6. What forms an intracellular cytoskeleton? ____________________________

  7. How do smooth muscle cells shorten? _______________________________

  8. Sarcoplasmic reticulum is ________________________________________

  9. What are caveolae? _____________________________________________

    • What is their possible function? _________________________________

B. Physiology of Smooth Muscle 

  1. The Ca2+ needed for smooth muscle contraction _____________________ ____________________ and from ______________________________

  2. Smooth muscle cells contract more slowly than skeletal muscle because: a. Greater distance ______________________________ 

b. Rate at which ________________________________________ c. Slower rate of ________________________________________

  1. What regulates contraction in smooth muscle cells? ____________________

  2. The sequence of events in smooth muscle contraction is:

    • __________ enters the sarcoplasm and binds to ____________________

    • These 2 molecules bound together activate ____________________

    • ____________________ transfers a phosphate group from __________ to __________________________________________________ 

    • When phosphate groups are bound to ____________________, then ____________________ formation occurs 

  3. Relaxation of smooth muscle depends on the enzyme __________________

    • Functionally, this enzyme removes ______________________________

  4. What is the “latch state”? _________________________________________

  5. As long as Ca2+ is present -_____________________________________

  6. Ca2+ levels in the sarcoplasm are lowered as _________________________

Relaxation occurs in response to ___________________________________

C. Types of Smooth Muscle 

  1. Visceral smooth muscle occurs in __________ & is found in _____________, _____________, & ____________________ tracts 

  2. Visceral smooth muscle has numerous __________________ which allow ___________________________________________________________

  3. As a result, sheets of smooth muscle function ____________________

    • The wave of contraction _____________________________________

  4. Multiunit smooth muscle occurs as:

    • Sheets like in ____________________ 

    • Small bundles like in ____________________ & ____________________

    • Single cells like in ______________________________ 

  5. Multiunit smooth muscle has fewer ______________________________

  6. Which type of smooth muscle can be autorhythmic? ____________________

What type of smooth muscle operates as independent units? _____________

D. Electrical Properties of Smooth Muscle 

  1. What are pacemaker cells? ______________________________________

  2. How does the nervous system regulate smooth muscle contractions? ______ ______________________________________________________________

  3. How do hormones cause smooth muscle to contract? ___________________ ______________________________________________________________

E. Functional Properties of Smooth Muscle 

List and describe four functional properties of smooth muscle:

  • ___________________________________________________________

  • ___________________________________________________________

  • ___________________________________________________________

  • ___________________________________________________________

F. Regulation of Smooth Muscle 

  1. Smooth muscle is innervated by the ___________________ nervous system

  2. What are the two most important neurotransmitters for smooth muscle?

    • ______________________________ 

    • ______________________________

  3. What hormones regulate smooth muscle contraction?

    • ______________________________ 

    • ______________________________ 

  4. Smooth muscle function is also influenced by:

    • ______________________________ 

    • ______________________________ 

  5. The response of smooth muscle to a chemical depends on the type of ____________________ the chemical is binding to 

  6. Receptors that stimulate smooth muscle contraction open __________ or __________ channels

  7. Receptors that inhibit contraction __________ these channels or __________ 

XIII. Cardiac Muscle 

A. Where is cardiac muscle found? ______________________________

B. What are intercalated disks? ________________________________________

C. Cardiac muscle is depolarized due to influx of __________ & __________ 

XIV. Effects of Aging on Skeletal Muscle 

A. Aging of skeletal muscle results in: 

  1. Reduced ______________________________ 

  2. Increased time ______________________________

  3. Reduced ____________________ 

  4. Increased ______________________________ 

B. What happens to the number of muscle fibers? __________________________

  1. This begins as early as ____________________

By age 80, ____________________ mainly due to ____________________

C. What can slow the loss of muscle mass? ______________________________

D. Does a person lose more slow-twitch or fast-twitch muscle fibers? ____________ E. At a synapse, the surface area ____________________ 

  1. Action potentials in neurons stimulate _______________________________

  2. Action potentials may not ________________________________________

F. What happens to the number of motor neurons? _________________________

  1. What effect will this have on muscle control? _________________________

G. What happens to the number of capillaries? _____________________________

1. What effect will this have on exercise? ______________________________