Gary Kwong
I. OVERVIEW OF MUSCLE TISSUE
1. Match the muscle types listed with the descriptions
a. Cardiac b. Skeletal c. Smooth
1. Involuntary – A, C
2. Banded appearance - A, B
3. Longitudinally and circularly arranged layers - B, C
4. dense connective tissue packaging.
5. Gap junctions – A, C
6. Coordinated activity allows it to act as a pump - A
7 Moves bones and the facial skin. - B
8 Referred to as the muscular system - B
9. Voluntary - B
10. Best at regenerating when injured. - B
2. State four functions of skeletal muscle tissue that are important for maintenance, of homeostasis.
Movement, posture, joints, and heat.
3. Match the characteristics of muscles listed with the descriptions below.
d.Contractility c.Excitability b.Elasticity a.Extensibility
a. Ability of muscle to stretch without damaging the tissue
b. Tendency of stretched or contracted muscle to return to its original shape
c. Ability of muscle cells and nerve cells to respond to stimuli by producing action
potentials (impulses); irritability
d. Ability of muscle tissue to shorten and thicken.
II. SKELETAL MUSCLE ANATOMY
1. Contrast two kinds of fascia by indicating which of the following are characteristics
of Superficial or beep Fascia.
a. Located immediately under the skin. -Superficial
b. Composed of dense connective tissue that extends inward to surround and
compartmentalize muscles. Deep Fascia
c. A route for nerves and blood vessles to enter muscles; contain.3 much fat, so
provides insulation and protection Deep Fascia
d. Also called subcutaneous layer. Superficial
2. Match column A with column B.
1. Connective tissue surrounding fascicle - epimysium
2. Just deep to the deep fascia - myofibril
3. Contractile unit of muscle - sarcomere
4. A muscle cell - sarcoplasm
5. Thin connective tissue investing each muscle cell - fiber
6 Plasma membrane of the muscle cell - sarcolemma
7. A long filamentous organelle found within muscle cells that has a bonded appearance.
Perimysium, fascicle
8 Actin, myosin, or titin - containing structured - myofilament
9. Cordlike extension of connective tissue beyond the muscle, serving to attach it to the bone - tendon
10. A discrete bundle of muscle cells - endomysium
3. Complete and rewrite the following statements concerning the sarcomere and its
components:
a. In muscle tissue, fibers are cells, whereas in connective tissue, fibers are intercellular material.
b. Each muscle fiber is surrounded by a membrane called the sarcolemma and contains
cytoplasm called plasma.
c Nuclei and mitochondria within muscle cells are located close to the
d. SR is comparable to endoplasmic reticulum in nonmuscle cells Ca2+ stored in SR is released to sarcoplosm as the trigger for muscle contraction.
c. Transverse (T) tubules are continuous with the sarcolemma, and lie parallel to SR.
f. AT tubule, along with the terminal cisterns of the SR on cither side, is called a triad.
g Each myofibril consists of bundles of thick and thin rods stacked in compartments called fasicles.
h The ends of sarcomeres are marked by Z-discs.
i. In relaxed skeletal muscle, each sarcomere is about 2.6 millimicrons long Of this, the 1.6 millimicrons is a dark band called the A band. The light colored bonds at the ends of the sarcomere, called I bands, total about 1.0 tnillimicrsrs. These alternating light and dark bands give the muscle its striped appearance.
j. Which portion of the sarcomere contains thick filaments? A band
In the center of this zone is the M line, which consists of threads
that appeor to connect adjacent thick filaments. Which part of the sarcomere contains only thin filaments? I band
k. Thick filaments are composed of myosin.
l. Thin filaments are composed mostly of the molecule named actin along with two
other molecules named troponin and tropomyosin of these molecules are proteins.
m. Myosin molecules are shaped like rods with round heads called cross bridges.
4 Describe and identify the following structures found in a muscle sarcomere.
C.Sorcomere riband E. A band D. A band A. Sarcoplasm B. Triad
a. Cytoplasm of muscle cell
b. A transverse tubule, along with terminal cisterns of the SR on either side.
c. Extends from Z-disc to Z-disc.
d. Dark area in striated muscle; contains thick and thin filaments.
e. Light area on either side of Z-disc; location of thin filaments .
5. Do the following exercise concerning the type of filaments in skeletal muscle fibers.
a. Thin filaments are anchored at Z-discs and do extend into M-zones. These filaments are composed mostly of bean-shaped actin molecules that are twisted into a helix. Thin filaments also contain two other proteins. The protein that covers myosin binding sites in relaxed muscle is called tropomyosin.
b Each thick filament is composed of about 200 myosin molecules. Each molecule is shaped like two intertwined golf clubs. The ends of the "handles" point toward the Z-discs. The rounded head of the "club" is called a cross bridge and it attaches to actin as muscles begin contraction
c. The third type of filament, called an elastic filament, is composed of the protein named titin.
III. SKELETAL MUSCLE PHYSIOLOGY
1 Complete ond rewrite the following statements concerning muscle contraction:
a. In order to effect muscle shortening, heads (cross-bridges) of thick filaments act like oar's pulling on actin molecules of thin filaments.
b. As a result, thin filaments move toward the center of the sarcomere. Since the thick and thin filaments slide to decrease the length of the sarcomere, this theory of muscle contraction is called the sliding filament theory.
2. Put the following in order.
a. Calcium ions bind to troponin.
b. Troponin changes shape.
c. Tropomyosin is moved in the groove between the F-actin strands exposing the active sites on actin.
d. ADP and P (inorganic phosphate) are released from the thick filament.
e. Myosin heads bind to active sites on actin molecule.
f. Myosin heads pull on the thin filaments (working stroke) and slide them toward the
center of the sarcomere.
g. ATP binds to the thick filament.
h. Myosin cross bridges detach from actin.
i. Myosin heads return to their high-energy shape (cocked), ready for the next working stroke.
j. ATP is hydrolyzed.
k. Cycling continues until calcium ions are sequestered by the SR.
3. Complete this exercise describing the principal events.
a. As a muscle is stimulated, the action potential spreads from the sarcolemma via T-tubules to the SR
b. In a relaxed muscle the concentration of calcium in the sarcoplasm is low. The effect of the nerve impulse and transmitter is to cause Ca to pass from storage areas in SR out to the sarcoplasm surrounding the filaments.
c. In relaxed muscle, myosin cross bridges ore not attached to the actin in the thin
filaments ADP Pi is bound to myosin cross-bridges, while the tropomyosin completely blocks the binding sites on actin.
d. The released calcium ions attach to troponin causing a structural change which leads to exposure of binding sites on actin.
e. Breakdown of ATP, on the myosin cross-bridge, occurs via action of the enzyme
named ATPase. Energy derived from ATP activates the myoin cross-bridges to bind
to and move actin. The oarlike action of myosin cross-bridges upon actin is called
a power stroke.
f Repeated power strokes slide act in filaments toward or even across the H-zone and M-line, and so shorten the sarcomere. If this process is compared to running on a treadmill, myosin plays the role of the runner staying in one place, whereas the treadmill that slides backward is comparable to the thin sliding filament.
g. Relocation of muscle occurs when a synaptic cleft enzyme named _____ destroys
ACh This terminates the impulse conduction over the muscle. Calcium ions are then
sequestered from sarcoplasm back into ____ by ____ and via a calcium-binding protein named ___.
h. With a low level of Ca2' now in the sarcopiasm surrounding filaments, ____ reforms from ADP on myosin cross-bridges, while tropomyosin-troponin complex once again blocks the binding sites on ___. As a result, thick and thin filaments detach, slip back into normal position, and the muscle is said to ____
i. The movement of Ca back into the SR is ___ process. After death, a supply of ATP is not available, so an active transport process cannot occur.
j. Explain why the condition of rigor mortis results after death.
IV. MOTOR UNIT
1. In most cases a single neuron innervates an average of 150 muscle fibers The combination of a neuron plus the muscle fibers it innervates is called a motor unit. An example of a motor unit that is likely to consist of just two or three muscle fibers precisely innervated by one neuron laryngeal muscle controlling speech.
2 In other words, motor neurons form at least two, and possible thousands of branches
called axon terminals each of which supplies an individual skeletal muscle fiber. When the
motor neuron "fires," all muscle fibers within that motor unit will be stimulated to contract.
3. On the portion of a motor unit at which a branch of one neuron stimulates a single
muscle fiber, the nerve impulse travels down the muscle toward one muscle fiber. The
axon is enlarged at its end into a bulb-shaped neuromuscular junction.
4. The nerve impulse causes synaptic vesicles to fuse with the plasma membrane of the
axon. Next the vesicles release the neurotransmitter named ACh into the synaptic
5. The region of the muscle fiber membrane, close to the axon terminals is
called motor end plate. This site contains specific sarcolemma that recognize and bind to ACh A typical motor end plate contains about 30-40 million ACh receptors.
6 The effect of ACh is to cause Na' channels in the sarcolemma to open so that Na enters the muscle fiber As a result, an action potential is initiated, leading to contraction of the muscle fiber. The diagnostic technique of recording such electrical activity in muscle cells is called myogram.
7. The combination of the axon terminals and the motor end plate is known as a motor axon.
At only one site along a muscle fiber (at about its middle) does o nerve approach a
muscle cell to innervate it. In other words, there are usually many neuromuscular junction(s) for each muscle fiber.
V. MUSCLE CONTRACTION
1. State the all or none principle. This principle applies to an entire muscle such as the biceps.
2 Match the terms with the definitions below.
a. Rapid, Jerky response to a single stimulus - Twitch
b. Recording of a muscle contraction - Myogram
c. Period between application of a stimulus and the start of contraction; Ca is being
released from the SR during this time. Latent Period
d. Period when a muscle is not responsive to a stimulus - Refractory Period
e. Active transport of Ca back into the SR is occurring - Relaxation period
f. A short period in skeletal muscle and a long one in cardiac muscle. - Contraction Period
3. Select the type of contraction that fits each descriptive phrase
a Sustained partial contraction of some portion of skeletal muscle; some fiber
contracted, others are not – Muscle tone
b. Sustained contraction due to stimulation at a rate of 20 100 stimuli per second - Tetanus
c. More forceful contraction of skeletal muscle in response to same strength stimuli
after muscle has contracted several times - Treppe
d. Phenomenon That is the principle behind athletic warm-ups - Treppe
e. Most voluntary contraction of muscles, such as biceps contraction – Muscle tone
f One to a progressive buildup of Ca^ in the sarcoplasm – Treppe
4. Contrast isometric and isotonic contractions by doing this exercise.
a. A contraction in which a muscle shortens while tension of the muscle remains constant is known as an isotonic contraction.
b. In an isometric contraction the muscle length stays about the same and tension of the muscle increases.
c. Isometric exercise, such as carrying heavy objects, weight lifting, or waterskiing may be dangerous for cardiac patients since blood pressure may increase dramatically during the exercise period.
VI. MUSCLE METABOLISM
1. Breakdown of ATP provides the energy muscles use for contraction. Recall that ATP is attached to myosin cross bridges and so is available to energize the power stroke. Complete the chemical reaction showing ATP breakdown: ATPà ADP + Pi.
2. But ATP is used for other cell activities such as ___. To assure adequate energy
for muscle work, muscle cells contain an additional molecule for transporting high
energy phosphate; this is called ____.
3. How is PC regenerated during time when muscles ore at rest?
When the muscle fibers are producing more ATP than they need.
4. ATP and PC, together called the phosphorylation system, provide only enough energy to power muscle activity for about 15 seconds. After that, muscles turn first to anaerobic pathways, and later to aerobic.
5. During strenuous exercise an adequate supply of oxygen may not be available to
muscles. They must convert pyruvic acid to lactic acid by an aerobic process. Excessive amount of lactic acid in muscle tissue contribute to some muscle fatigue and soreness.
6. One substance in muscle that stores oxygen until oxygen is needed by mitochondria is
____This protein is structurally somewhat like the myoglobin molecule in blood
that also binds to and stores oxygen. Both of these molecules have a ___ color that
accounts for the color of blood and also of red muscle.
7. During exercise lasting more than 10 minutes, more than 90% of ATP is provided by the aerobic breakdown of pyruvic acid. Athletic conditioning increases the maximal rate at which mitochondria can use oxygen for aerobic catabolism. This rate is known as maximal aerobic endurance.
VII. Types of Muscle Fibers
Characteristic / Slow Oxidative fibers / Fast glycolytic fibers / Fast oxidative fibersRapid twitch rate / Slow / Fast / Fast
Fast myosin ATPases / Slow / Fast / Fast
Use mostly aerobic metabolism / Aerobic / Aerobic / Aerobic glycolysis
Large myoglobin stores / High / High / Low
Large glycogen stores / Low / Intermediate / High
Fatigue slowly / Slow / Slow / Fast
Fibers are white / red / Red to pink / White
Fibers are Small / Small / Intermediate / Large
Fibers contains many capillaries and mitochondria / Many / Many / many