A&P I Muscle Tissue
The terminal cisternae that form a triad along with a T tubule are part of what organelle?
The terminal cisternae are part of the sarcoplasmic reticulum.
Identify the three types of muscle tissue and cite their major functions.
The three types of muscle tissue are skeletal muscle, cardiac muscle, and smooth muscle. Skeletal muscle tissue moves the body by pulling on our bones, cardiac muscle tissue pumps blood through the cardiovascular system, and smooth muscle tissue pushes fluids and solids along the digestive tract and other internal organs, and regulates the diameters of small arteries.
True or False. Each cell in skeletal muscle tissue is a single muscle fiber.
True
True or False. T tubules are narrow tubes whose surfaces are continuous with the sarcolemma and extend deep into the sarcoplasm.
True
True or False. Although the membranes of the triad are tightly bound together, their fluid contents are non separate and distinct.
False Although they are tightly bound together, their fluid contents are separate and distinct.
Describe muscle fatigue.
Muscle fatigue is a muscle's reduced ability to contract due to low pH (hydrogen ion buildup), low ATP levels, or other problems.
How do muscle fibers continuously synthesize ATP?
Muscle fibers synthesize ATP continuously by utilizing creatine phosphate (CP) and metabolizing glycogen and fatty acids. Most cells generate ATP only through aerobic metabolism in the mitochondria and through glycolysis in the cytosol.
Define oxygen debt.
Oxygen debt is the amount of oxygen required to restore normal, preexertion conditions in muscle tissue.
Describe the neuromuscular junction.
The neuromuscular junction, is the synapse between a motor neuron and a skeletal muscle cell (fiber). This connection enables communication between the nervous system and a skeletal muscle fiber.
The striations of skeletal muscle are due to what?
The precise arrangements of thin (actin) and thick (myosin) filaments in myofibrils.
Predict what would happen to a muscle if the motor end plate lacked acetylcholinesterase (AChE).
Without acetylcholinesterase (AChE), the motor end plate would be stimulated continuously by acetylcholine, locking the muscle in a state of contraction.
What is the treatment for myasthenia gravis?
acetylcholinesterase (AChE) inhibitor; ex. Tensilon
Thin filaments are known as ____________.
actin
Skeletal muscle fibers remove calcium ions from the cytosol by ________________ (actively, passively) transporting them into the _____________________ of the SR.
actively; terminal cisternae
What is the name of a broad tendinous sheet that may serve as the origin or insertion of a skeletal muscle?
aponeurosis
At the end of the muscle, the collagen fibers of the epimysium, perimysium, and endomysium come together to form a) ligaments b) tendons c) gap junction d) elastic connective tissue e) none of the above
b) tendons
Terminal cisternae contain the protein __________________, which reversibly binds Ca2+.
calsequestrin
The epimysium is connected to the ______________ fascia, a dense connective tissue layer.
deep
Each muscle fibers has which of the following? a) many superficial nuclei b) mitochondria c) myofibril d) other organelles e) all of the above
e) all of the above
What common properties do muscle tissues share? a) excitability b) contractility c) extensibility d) elasticity e) all of the above
e) all of the above
Which of the following does perimysium contain? a) collagen b) elastic fibers c) blood vessels d) nerves e) all of the above
e) all of the above
Muscle fibers are surrounded by a/an _________________.
endomysium
The ______________ is a dense layer of collage fibers that surrounds the entire muscle.
epimysium
The muscle tissue in skeletal muscle is surrounded by three layers of connective tissue, what are the three?
epimysium, perimysium, endomysium
________________ is stretching movement of a muscle, while _________________ is the ability of a muscle to recoil (spring back) to its resting length.
extensibility; elasticity
Skeletal muscle consists of _______________ enclosed by the _______________.
fascicles; epimysium
Muscle fascicles are compromised of bundles of _____________________.
muscle fibers
Which autoimmune disease is characterized by the immune system mistakenly creating antibodies that target and damage the acetylcholine (ACh) receptor sites on the surface of the motor end plates of skeletal muscle fibeers?
myasthenia gravis
During development, groups of embryonic cells called _______________ fuse together to form multinucleate skeletal muscle.
myoblasts
Muscle fascicles are surrounded by __________________.
perimysium
The _________________ divides the skeletal muscle into bundles of muscle fibers called a fascicle.
perimysium
What is the plasma membrane of a muscle fiber called?
sarcolemma
The arrangement of myosin and actin filaments forms the repeating functional unit called a __________________.
sarcomere
What are the smallest functional units of the muscle fiber?
sarcomeres
What is the cytoplasm of a muscle fiber called?
sarcoplasm
What is the specialized site to where the storage and release of calcium ions occurs in muscles?
sarcoplasmic reticulum
The tubules of the sarcoplasmic reticulum enlarge, fuse, and form expanded chambers called _______________________________.
terminal cisternae
Where would you expect to find the greatest concentration of Ca2+ in a resting skeletal muscle fiber?
the terminal cisternae of the sarcoplasmic reticulum
What does a sarcomere contain?
thick filaments, thin filaments, proteins that stabilize the positions of the thick and thin filaments, and proteins that regulate the interactions between thick and thin filaments
There are two types of myofilaments, what are they?
thin filaments (primarily composed of actin) and thick filaments (composed primarily of myosin)
In addition, myofibrils contain __________, elastic myofilaments associated with the thick filaments.
titin
Skeletal muscles must contract at the same time. The signal to contract is propagated through what?
transverse tubules (T tubules)
The combination of a pair of terminal cisterae plus a T-tubulel is known as a ___________.
triad
The endomysium is a elastic connective tissue layer that contains three of the following:
1. Capillary networks that supply blood to the muscle fibers 2. Myosatellite cells, which are stem cells that help repair damaged muscle tissue 3. Nerve fibers that control the muscle
What are the functions of skeletal muscles?
1. Producing Movement 2. Maintaining Posture and Body Position 3. Supporting Soft Tissues 4. Guarding Body Entrances and Exits 5. Maintaining Body Temperature 6. Storing Nutrients
Identify the common properties shared by muscle tissues.
1. excitability (the ability to receive and respond to a stimulus) 2. contractility (the ability of a muscle cell to shorten when it is stimulated) 3. extensibility (stretching movement of a muscle) 4. elasticity (the ability of a muscle to recoil to its resting length).
How would a drug that inhibits AChE make a myasthenia gravis patient stronger?
A drug that inhibits acetylcholinesterase (AChE) is inhibiting the enzyme that breaks down the neurotransmitter acetylcholine (ACh). As a result, ACh is present longer in the neuromuscular junction (NMJ). Because a patient with myasthenia gravis does not have enough functioning ACh receptors, a greater amount of ACh is better for strength of muscular response. In short, by inhibiting the breakdown of ACh, the drug strengthens the patient's muscular response.
Why does a muscle that has been overstretched produce minimal tension?
A muscle's ability to contract depends on the formation of cross-bridges between the myosin and actin myofilaments in the muscle. In a muscle that is overstretched, the myofilaments would overlap very little, so very few cross-bridges between myosin and actin could form and, thus, the contraction would be weak. If the myofilaments did not overlap at all, then no cross-bridges would form and the muscle could not contract.
Why would a sprinter experience muscle fatigue before a marathon runner would?
A sprinter requires large amounts of energy for a short burst of activity. To supply this energy, the sprinter's muscles rely on anaerobic metabolism. Anaerobic metabolism is less efficient in producing energy than aerobic metabolism, and the process also produces acidic wastes; this combination contributes to muscle fatigue. Conversely, marathon runners derive most of their energy from aerobic metabolism, which is more efficient and produces fewer wastes than anaerobic metabolism does.
How would a drug that blocks acetylcholine release affect muscle contraction?
Acetylcholine (ACh) release from the axon terminal is necessary for skeletal muscle contraction, because it serves as the first step in the process that leads to the formation of cross-bridges in the sarcomeres. A muscle's ability to contract depends on the formation of cross-bridges between the myosin heads and actin myofilaments. A drug that blocks ACh release would interfere with this cross-bridge formation and prevent muscle contraction.
Which activity would be more likely to create an oxygen debt: swimming laps or lifting weights?
Activities that require short periods of strenuous activity produce a greater oxygen debt, because such activities rely heavily on energy production by anaerobic metabolism. Because lifting weights is more strenuous over the short term than swimming laps, which is an aerobic activity, weight lifting would likely produce a greater oxygen debt than would swimming laps.
How would severing the tendon attached to a muscle affect the muscle's ability to move a body part?
Because tendons attach muscles to bones, severing the tendon would disconnect the muscle from the bone, and so the muscle could not move a body part.
Describe general age-related effects on skeletal muscle tissue.
General agerelated effects on skeletal muscles include decreased skeletal muscle fiber diameters, diminished muscle elasticity, decreased tolerance for exercise, and a decreased ability to recover from muscular injuries
What would happen to a resting skeletal muscle if the sarcolemma suddenly became very permeable to calcium ions?
If the sarcolemma of a resting skeletal muscle suddenly became permeable to Ca2+, the cytosolic concentration of Ca2+ would increase, and the muscle would contract. In addition, because the amount of calcium ions in the cytosol must decrease for relaxation to occur, the increased permeability of the sarcolemma to Ca2+ might prevent the muscle from relaxing completely.
Would myasthenia gravis affect Rhetta's heart muscle? Explain.
Myasthenia gravis affects voluntary, skeletal muscle at the neuromuscular junction (NMJ). Cardiac muscle tissue contracts without neural stimulation, a property known as automaticity. There is no neural stimulation, no NMJ, no ACh neurotransmitter or receptor required for cardiac muscle contraction. For these reasons, myasthenia gravis would not affect cardiac muscle.
Describe how myofibrils are able to cause the entire cell to shorten and pull on the tendon?
Myofibrils are anchored to the inner surface of the sarcolemma at each end of the skeletal muscle fiber, therefore, when they contract or shorten, the whole cell will shorten and pulls on the tendon.
Which type of muscle fibers would you expect to predominate in the leg muscles of someone who excels at endurance activities, such as cycling or long-distance running?
People who excel at endurance activities have a higher than normal percentage of slow fibers. Slow fibers are physiologically better adapted to this type of activity than are fast fibers, which are less vascular and fatigue faster.
Describe the components of a sarcomere.
Sarcomeres, the smallest contractile units of a striated muscle cell, are segments of myofibrils. Each sarcomere has a dark A band and light I bands. The A band contains the M line, the H band, and the zone of overlap. Each I band contains thin filaments, but not thick filaments. Z lines bisect the I bands and mark the boundaries between adjacent sarcomeres.
Why do skeletal muscle fibers appear striated when viewed through a light microscope?
Skeletal muscle fibers appear striated when viewed through a light microscope because the Z lines and thick filaments of the myofibrils within the muscle fibers are aligned.
Identify the primary functions of skeletal muscle.
Skeletal muscles produce skeletal movement, maintain posture and body position, support soft tissues, guard body entrances and exits, maintain body temperature, and store nutrients.
Describe the three connective tissue layers associated with skeletal muscle tissue.
The epimysium is a dense layer of collagen fibers that surrounds the entire muscle; the perimysium divides the skeletal muscle into a series of compartments, each containing a bundle of muscle fibers called a fascicle; and the endomysium surrounds individual skeletal muscle cells (muscle fibers). The collagen fibers of the epimysium, perimysium, and endomysium come together to form either bundles known as tendons, or broad sheets called aponeuroses. Tendons and aponeuroses generally attach skeletal muscles to bones.
Identify the three types of skeletal muscle fibers.
The three types of skeletal muscle fibers are (1) fast fibers (also called white muscle fibers, fast-twitch glycolytic fibers, Type II-B fibers, and fast fatigue fibers); (2) slow fibers (also called red muscle fibers, slowtwitch oxidative fibers, Type I fibers, and slow oxidative fibers); and (3) intermediate fibers (also called fast-twitch oxidative fibers, Type II-A fibers, and fast resistant fibers).
Can a skeletal muscle contract without shortening? Explain.
Yes, a skeletal muscle can contract without shortening. The muscle can shorten (isotonic concentric contraction), elongate (isotonic eccentric contraction), or remain the same length (isometric contraction), depending on the relationship between the load (resistance) and the tension produced by actin-myosin interactions.
Myofibrils consist of bundles of protein filaments called ____________________.
myofilaments
Some myoblasts do not fuse with developing muscle fibers and stay as ____________________ cells.
myosatellite
Thick filaments are known as ______________.
myosin
