AP1 Ch. 10 Muscle Tissue Physiology

a. Two terminal cisternae and a T-tubule

A triad consists of: a. Two terminal cisternae and a T-tubule b. An M line and two zones of overlap c. Two T-tubules and a terminal cisterna d. A zone of overlap and two M lines

-the muscle fiber is not allowed to relax between stimuli. (Each consecutive stimulus arrives before relaxation begins, and this results in fused tetanus.)

According to this graph, __________. -the muscle fiber relaxes completely between stimuli. -the muscle fiber has entered the relaxation period. -the muscle fiber is not allowed to relax between stimuli. -the muscle fiber relaxes between stimuli, but not completely.

d. An action potential arriving at the synaptic terminus.

Acetylcholine is released from the synaptic terminus in response to a. A ligand binding to a receptor on the synaptic terminus. b. Sodium flowing into the synaptic terminus. c. Potassium entering the synaptic terminus. d. An action potential arriving at the synaptic terminus.

d. Ligand-gated sodium channels to close

Acetylcholinesterase in the synaptic cleft degrades acetylcholine, allowing: a. Depolarization of the motor end plate. b. Calcium levels in the sarcoplasm to rise. c. Tropomyosin to expose actin active sites. d. Ligand-gated sodium channels to close

-Myasthenia gravis, a disease in which the ACh receptors are damaged and the muscle becomes progressively weaker. (The use of AChE inhibitors is helpful in treating diseases characterized by a decrease in ACh in the synapse. These inhibitors may also be used to treat Alzheimer's disease, which may be due to a decrease in ACh in synapses in the brain.)

Acetylcholinesterase inhibitors have therapeutic value in the treatment of some medical conditions and diseases. Which of the following do you think would be a clinical application of these drugs? -Cosmetic treatment of wrinkles and frown lines. -Muscular dystrophy, a genetic disease that results in abnormal muscle proteins and causes a loss of muscle mass. -Myasthenia gravis, a disease in which the ACh receptors are damaged and the muscle becomes progressively weaker. -Polio, a disease in which motor neurons are attacked and damaged.

-If it affected the phrenic nerve, the diaphragm muscle would be paralyzed. (A toxin that blocks the release of ACh will paralyze skeletal muscles. If the diaphragm is paralyzed, the individual will not be able to breath. Remember that when the diaphragm contracts, inhalation occurs. Without ACh, this cannot happen and cessation of respiration (asphyxiation) can occur.)

As previously mentioned, this toxin can cause a fatal disease known as botulism. If the toxin becomes systemic, it can block the release of ACh from nerves in other locations. Why do you think botulism can be fatal? -If it affected the phrenic nerve, the diaphragm muscle would be paralyzed. -If it affected nerves to the lower extremity, the individual would be unable to walk. -If it affected cardiac nerves, the heart would stop beating. -If it affected nerves to the brainstem, the brainstem would not be able to carry out its functions.

-The muscle will be unable to contract, known as paralysis. (ACh is necessary for the opening of Na+ channels and the depolarization of the muscle fiber. If the muscle fiber does not depolarize, it will be unable to contract and paralysis will occur. This is good if you want to relax muscles. When wrinkles and frown lines occur in the face, the injection of Botox paralyzes the facial muscles, which relaxes them, and the skin becomes smooth, which reduces the appearance of wrinkles and frown lines.)

Botulinum toxin is a very powerful toxin produced by the bacteria Clostridium botulinum. It is the cause of the sometimes fatal disease, known as botulism. This toxin prevents the release of ACh from the motor neuron. What effect will it have on muscle function? -The muscle will contract at a high frequency, known as tetany. -The muscle will be unable to contract, known as paralysis. -The muscle will contract and be unable to relax, known as spastic paralysis. -The muscle will contract, but will fatigue much faster.

a. Action potential arrives at triad, calcium is released from the terminal cisternae, calcium binds to troponin, tropomyosin exposes the actin active sites.

Choose the correct sequence of events that occur in preparation for contraction: a. Action potential arrives at triad, calcium is released from the terminal cisternae, calcium binds to troponin, tropomyosin exposes the actin active sites. b. Tropomyosin exposes the actin active sites, calcium binds to troponin, action potential arrives at triad, calcium is released from the terminal cisternae. c. Calcium is released from the terminal cisternae, calcium binds to troponin, action potential arrives at triad, tropomyosin exposes the actin active sites. d. Calcium binds to troponin, action potential arrives at triad, calcium is released from the terminal cisternae, tropomyosin exposes the actin active sites

-can generate faster, more powerful contractions. (Type II fibers are larger in diameter than Type I fibers, and therefore contain more contractile proteins capable of generating more tension.)

Compared to Type I fibers, Type II fibers __________. -can maintain longer periods of contraction, and therefore have more endurance. -are more "red" in appearance. -have more mitochondria. -can generate faster, more powerful contractions.

-Recruitment (As greater external force is applied to the muscle, a normal response is to activate more motor units to match or exceed that external force with greater muscle tension. The action of the tetanus toxin is similar to this normal response.)

Continuous stimulation of motor neurons by the tetanus toxin generates maximum muscle tension given time. This is similar to the normal response known as _____________, where greater muscle tension is generated by activating more motor units to accommodate a heavy external force. -Recruitment -Isometric contraction -Isotonic concentric contraction -Isotonic eccentric contraction

-isometric contraction

During an __________________, the muscle is contracting but is neither lengthening nor shortening. -isotonic contraction -isometric contraction -eccentric contraction -concentric contraction

a. The resting membrane potential is restored.

During muscle fiber relaxation, calcium channels in the SR close because: a. The resting membrane potential is restored. b. Calcium levels in the SR are depleted. c. Calcium is released from the SR. d. Calcium is pumped into the extracellular fluid.

b. Calcium is pumped back into the SR.

During muscle fiber relaxation: a. Calcium levels in the sarcoplasm rise. b. Calcium is pumped back into the SR. c. Calcium is released from the SR. d. Calcium is pumped into the extracellular fluid

b. Recocking of the myosin heads.

Hydrolysis of ATP is responsible for: a. Release of the myosin heads from the actin active sites. b. Recocking of the myosin heads. c. The power stroke. d. The movement of tropomyosin, exposing the actin active sites.

-anaerobic catabolism. (Anaerobic catabolism involves glycolysis and the production of lactic acid.)

If oxygen is not available, the muscle fiber will produce ATP by __________. -oxidative catabolism -synthesis of creatine phosphate -using fatty acids for energy -anaerobic catabolism

c. Triads

In order to trigger a muscle contraction, an action potential must reach the a. Sarcomeres b. Mitochondria c. Triads d. Nuclei

The H-zone in the central region of the A band.

In which band are there thick filaments only, with no thin filament overlap?

-The concentration of acetylcholine would increase in the synaptic cleft. (Stimulation of affected motor neurons would cause them to repeatedly release acetylcholine into the synaptic cleft of the neuromuscular junction.)

Knowing what tetanus toxin does to motor neuron activity, predict what would happen to the concentration of acetylcholine in the synaptic cleft. -The concentration of acetylcholine would remain unchanged in the synaptic cleft. -The concentration of acetylcholine would increase in the synaptic cleft. -The concentration of acetylcholine would decrease in the synaptic cleft. -There is not enough information to predict would happen to acetylcholine.

1. The membrane is at the resting membrane potential (RMP), and voltage-gated Na+ and K+ channels are closed. 2. Depolarization stage: in response to a stimulus, voltage-gated Na+ channels open and Na+ enter the cell, making the membrane potential less negative. 3. Repolarization Stage: Na+ channels close while voltage-gated K+ channels open and K+ leave the cell, making the membrane potential more negative again.

Put the stages of generating an action potential in the correct order: -Repolarization Stage: Na+ channels close while voltage-gated K+ channels open and K+ leave the cell, making the membrane potential more negative again. -The membrane is at the resting membrane potential (RMP), and voltage-gated Na+ and K+ channels are closed. -Depolarization stage: in response to a stimulus, voltage-gated Na+ channels open and Na+ enter the cell, making the membrane potential less negative.

b. Restores the resting membrane potential.

Sarcolemma repolarization during relaxation: a. Means that the interior of the cell becomes less negative. b. Restores the resting membrane potential. c. Only occurs at the motor end plate of the fiber. d. Is caused by closure of calcium channels.

-Muscles will contract and be unable to relax, known as spastic paralysis. This can cause spasms of the diaphragm and bronchi, which lead to asphyxiation. (Any toxin that interferes with acetylcholinesterase's function will result in an increase in ACh in the synapse. This increases skeletal muscle contractions and digestive functions (nausea, vomiting, diarrhea). The signs and symptoms of poisoning by these agents are chest tightening, nausea, vomiting, diarrhea, excessive salivation, pupil constriction, and muscle spasms and convulsions.)

Some nerve agents have been used as bioweapons. Unfortunately, Sarin gas has been used as a bioweapon several times in other countries. Sarin is an acetylcholinesterase (AChE) inhibitor and even exposure to low levels can be fatal. Based on your knowledge of muscle physiology, why do you think Sarin has these effects? -The muscle will contract and relax normally, but inhibiting with acetylcholinesterase will decrease cardiac function. -Muscles will contract but fatigue much faster. This will decrease skeletal muscle activity in the body. -Muscles will be unable to contract, known as paralysis. If the diaphragm is paralyzed, breathing will not occur and death will occur by asphyxiation. -Muscles will contract and be unable to relax, known as spastic paralysis. This can cause spasms of the diaphragm and bronchi, which lead to asphyxiation.

-resting membrane potential.

The Na+/K+ pump helps a muscle cell maintain a state of: -propagation. -depolarization. -action potential. -resting membrane potential.

-hinge

The ____________ is the flexible point on each myosin molecule, where the neck meets the tail. -neck -tail -head -hinge

-hinge

The arrow points to the __________ region of myosin. -neck -tail -head -hinge

a. Release of the myosin heads from the actin active sites.

The binding of A T P to myosin is responsible for: a. Release of the myosin heads from the actin active sites. b. Recocking of the myosin heads. c. The power stroke. d. The movement of tropomyosin, exposing the actin active sites.

b. Voltage-gated channels

The channels that open in the sarcolemma surrounding the motor endplate and generate an action potential are a. Ligand-gated channels b. Voltage-gated channels c. Na+/K+ pumps d. Mechanically gated channels

-An increased demand for oxygen by the muscle fiber. (Oxygen requirements would increase as the intensity of contractions increased and the muscle fiber supplied a maximal amount of ATP for continued cycles of contraction.)

The continuous maximum tension generated by the tetanus toxin produces fatigue in muscle cells. Which of the following would be observed in Joe's muscle cells? -An increased demand for oxygen by the muscle fiber. -Decreased levels of ADP and calcium ions in the cytosol of the muscle fiber. -Increased levels of creatine phosphate and glycogen in the muscle fibers. -A decreased demand for oxygen by the muscle fiber

c. A local depolarization

The end plate potential is a. An action potential b. A local repolarization c. A local depolarization d. A local hyperpolarization

b. sodium

The end plate potential is generated by the influx of ____________ into the motor end plate. a. calcium b. sodium c. potassium d. chloride

-creatine phosphate.

The main immediate source of ATP (lasting about 10 seconds) as muscle contractions begin comes from: -fat. -creatine phosphate. -glucose. -glycogen.

c. The power stroke.

The myosin heads return to their low-energy (relaxed) state during a. Release of the myosin heads from the actin active sites. b. Recocking of the myosin heads. c. The power stroke. d. The movement of tropomyosin, exposing the actin active sites

d. Pulls the thin filaments toward the M lines.

The power stroke.. a. Pulls the thick filaments toward the Z lines. b. Positions the myosin heads in their high-energy position. c. Shortens the length of the thin filaments. d. Pulls the thin filaments toward the M lines.

c. The power stroke.

The release of ADP and Pi from myosin occurs during: a. Release of the myosin heads from the actin active sites. b. Recocking of the myosin heads. c. The power stroke. d. The movement of tropomyosin, exposing the actin active sites.

a. Ligand-gated channels

The sodium channels of the motor end plate are a. Ligand-gated channels b. Voltage-gated channels c. Na+/K+ pumps d. Mechanically gated channels

-sarcoplasmic reticulum.

The storage and release of calcium ions is the key function of the: -mitochondrion. -sarcoplasm. -sarcolemma. -sarcoplasmic reticulum.

d. Spread

The term "propagate" when referring to an action potential means a. Stimulate b. Inhibit c. Magnify d. Spread

c. The gap between the neuron and the muscle fiber.

The term "synaptic cleft" refers to: a. A fold on the motor end plate. b. A vesicle in the synaptic terminus. c. The gap between the neuron and the muscle fiber. d. The space between adjacent muscle fibers.

-isotonic eccentric contraction

The type of contraction that causes a skeletal muscle to lengthen is called __________. -miometric contraction -isotonic concentric contraction -isometric contraction -isotonic eccentric contraction

Na+/K+ ATPase pump (As shown in the figure, the Na+/K+ ATPase pump uses ATP to pump Na ions out of the cell and K ions into the cell, thus maintaining the concentration gradients of sodium and potassium ions across the sarcolemma.)

This membrane protein is the __________. - voltage-gated Na+ channel - ligand-gates ion channel - voltage-gated K+ channel - Na+/K+ ATPase pump

a. Covers actin active sites

Tropomyosin a. Covers actin active sites b. Binds calcium ions c. Is a small, globular protein d. Has three subunits

b. Myosin

Troponin has three subunits. Which of the following does NOT bind to one of these subunits? a. Actin b. Myosin c. Calcium d. Tropomyosin

1. Latent period: - action potential spreads through the sarcolemma. 2. Contraction period: -tension rapidly increases during crossbridge cycling. 3. Relaxation period: -tension decreases as Ca2+ are pumped back into SR.

What are the 3 stages involved in a twitch contraction?

1) ATP hydrolysis "cocks" the myosin head. 2) The myosin head binds to actin. 3) the Power Stroke occurs when the phosphate detaches from the myosin head & myosin pulls toward the center of the sarcomere (M-line) ; ATP leaves the myosin head at the end of the power stroke. 4) ATP breaks the attachment of myosin to actin.

What are the correct order of events during the Contraction Phase?

-glucose

What is a necessary reactant for glycolytic, or anaerobic, catabolism to proceed? -myoglobin -glucose -oxygen -creatine phosphate

-stabilize joints.

What is the basic function of all muscle tissue? -stabilize joints -produce voluntary contractions -generate muscle tension -regulate body temperature

1) An action potential arrives at the axon terminal and triggers Ca2+ channels in the axon terminal to open. 2) Ca2+ entry triggers exocytosis of synaptic vesicles. 3) Synaptic vesicles release acetylcholine into the synaptic cleft. 4) Acetylcholine binds to ligand-gated ion channels in the motor end plate. 5) Ion channels open and Na+ enter the muscle fiber. 6) Entry of Na+ depolarizes the sarcolemma locally, producing an end-plate potential.

What is the correct order of the events that occur at the neuromuscular junction in the excitation phase? (skeletal muscle contraction) -Synaptic vesicles release acetylcholine into the synaptic cleft. -Entry of Na+ depolarizes the sarcolemma locally, producing an end-plate potential. -Ion channels open and Na+ enter the muscle fiber. -An action potential arrives at the axon terminal and triggers Ca2+ channels in the axon terminal to open. -Ca2+ entry triggers exocytosis of synaptic vesicles. -Acetylcholine binds to ligand-gated ion channels in the motor end plate.

Cardiac Muscle

What type of muscle has these characteristics?: -contains intercalated discs. -is found in the heart.

Skeletal Muscle

What type of muscle has these characteristics?: -long & cylindrical in shape. -cells are multinucleated. -contains well-developed sarcoplasmic reticulum.

Smooth Muscle

What type of muscle has these characteristics?: -spindle-shaped (long and flaat with pointed ends). -found in digestive organs and blood vessels.

-the A band stays the same. (The A band contains the thick filaments, and the length of the thick filament does not change during contraction.)

When the sarcomere contracts and shortens, __________. -the zones of overlap become smaller -the A band stays the same -the Z-disks move further apart -the I-band becomes larger

d. Pumping calcium ions back into the SR.

Which aspect of muscle relaxation requires ATP? a. Motor end plate repolarization. b. Blockage of actin active sites by tropomyosin. c. Sarcomeres returning to their original length. d. Pumping calcium ions back into the SR.

-creatine phosphate. (Creatine phosphate is an immediate source of energy that would be quickly consumed by continuous muscle contractions.)

Which energy source would you expect to be depleted first during continuous contractions caused by the tetanus toxin? -ATP generated by oxidative or aerobic catabolism. -Myoglobin. -ATP generated by glycolytic or anaerobic catabolism. -Creatine phosphate.

-excess post-exercise oxygen consumption. (Excess post-exercise oxygen consumption is the persisting increased rate of breathing during recovery. It does not contribute to fatigue.)

Which of the following is NOT one of the factors that contribute to muscle fatigue? -environmental conditions such as extreme heat. -decreased availability of oxygen. -excess post-exercise oxygen consumption. -depletion of metabolites.

-Skeletal muscle fibers are striated.

Which of the following is descriptive of skeletal muscle fibers? -Skeletal muscle fibers are smaller than most cells. -Skeletal muscle fibers are striated. -Skeletal muscle fibers lack a sarcolemma and myofibrils. -Skeletal muscle fibers are uninucleate.

-Actin. (Actin is the contractile protein found within the thin filament. This protein would be directly involved in producing muscle spasms.)

Which of the following proteins associated with the myofilaments would be most involved in the muscle spasms? -Titan. -Actin. -Troponin. -Tropomyosin.

-isotonic concentric contraction (Isotonic concentric contractions are also called miometric contractions, where mio means "shorter.")

Which type of contraction causes a skeletal muscle to shorten? -isometric contraction -isotonic concentric contraction -isotonic eccentric contraction -isomorphic contraction

d. Ca++

__________ is released from the SR in response to arrival of an action potential. a. Na+ b. K+ c. Pi d. Ca++

Smooth

__________ muscle, which consists of spindle-shaped cells with a single, oval nucleus and no striations.

-thin filament

___________ consist of two intertwined actin strands, covered by long, ropelike strands of tropomyosin, which is held in place by the smaller globular protein troponin. -sarcomere -muscle fiber -thin filament -thick filament

-Endurance training

_____________________ causes in increase in the number of mitochondria and oxidative enzymes, as well as increases blood supply. This facilitates ATP production that can sustain prolonged muscle activity. -disuse -atrophy -endurance training -resistance training