Muscles and Muscle tissue

Why would inflammation of the knee joint be a "good thing" when there's been an acute quadriceps injury? A) because fluid accumulation reduces joint movement B) because it prevents rupture of the patellar ligament C)because the rate of muscle contraction is slower D) because joint flexibility is greatly improved

because fluid accumulation reduces joint movement

Exhaustion of glycogen storage within a muscle fiber would have the biggest effect on ________. A) slow oxidative fibers B) fast oxidative fibers C) both slow and fast oxidative fibers D) fast glycolytic fibers

fast glycolytic fibers

____ : ion entering muscle fiber through open chemically gated ion channels

Na+

____ diffuses into the muscle fiber through open chemically gated ion channels.

Na+

_______ : container of many neurotransmitter molecules

synaptic vesicle

T tubule

: a structure that forms a path from the membrane to the cell interior

Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________. A) arise in the epimysium of a skeletal muscle and extend to individual skeletal muscle fibers B) extend from the brain to the sarcolemma of a skeletal muscle fiber C) extend from the spinal cord to the sarcolemma of a skeletal muscle fiber D) extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber

extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber ( The cell bodies of motor neurons to muscles in the head and neck are located in the brain. The cell bodies of motor neurons to the rest of our muscles are located in the spinal cord.)

Rigor mortis occurs because ________. A) the cells are dead B) sodium ions leak into the muscle causing continued contractions C) no ATP is available to release attached actin and myosin molecules D) proteins are beginning to break down, thus preventing a flow of calcium ions

no ATP is available to release attached actin and myosin molecules

Myoglobin ________. A) produces the end plate potential B) is a protein involved in the direct phosphorylation of ADP C) breaks down glycogen D) stores oxygen in muscle cells

stores oxygen in muscle cells

_________: location of acetylcholinesterase

synaptic cleft

______ : neurotransmitter at neuromuscular junction

ACh (Acetylcholine)

_______ : protein embedded in the sarcolemma

ACh receptor

______: portion of sarcolemma containing Ach receptors

Junctional folds

Fasicle

bundle of muscle fibers (cells) surrounded by a perimysium

Which of the following surrounds an individual muscle cell? A) Fascicle B) endomysium C) epimysium D) perimysium

endomysium (myofibril= "individual" muscle cell)

Which of the following properties is most directly associated with changes to a muscle cell's membrane potential (the voltage across the plasma membrane)? A) elasticity B) excitability C) extensibility D) contractibility

excitability ( Excitability, also termed responsiveness, is the ability of a cell to receive and respond to a stimulus by changing its membrane potential. For example, a neurotransmitter released by a nerve cell may cause the depolarization of the muscle cell's sarcolemma)

In the neuromuscular junction of the fusing synaptic vesicles, what cellular event is being used? A) endocytosis B) exocytosis C) atp D) facilitated diffusion

exocytosis (Neurotransmitters stored in synaptic vesicles are released into the synaptic cleft by exocytosis)

In the neuromuscular junction of the fusing synaptic vesicles, what event directly triggers the release of neurotransmitter? A) diffusion of K+ into the axon terminal B) diffusion of Na+ into the axon terminal C) diffusion of Na+ out of the axon terminal D) diffusion of Ca2+ into the axon terminal

diffusion of Ca2+ into the axon terminal (A nerve impulse arrives at the axon terminal triggering the opening of Ca2+ channels, which allows for the diffusion of Ca2+ into the terminal. This in turn leads directly to the release of neurotransmitters by exocytosis)

When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods? A) relaxation period B) latent period C) fatigue period D) refractory period

refractory period

The __________ shorten(s) during muscle contraction A) z lines B) thick filament C) actin D) sarcomere

sarcomere (As actin slides over myosin, the z lines are pulled closer together, shortening the sarcomere)

Which type of muscle requires somatic (voluntary) nervous stimulation for activation? A) cardiac B) smooth C) visceral D) skeletal

skeletal ( In order to contract, skeletal muscle fibers must be voluntarily stimulated by motor neurons of the somatic nervous system).

Which of the following are correctly paired? A) cardiac muscle; nonstriated B) smooth muscle; striated C) skeletal muscle; voluntary control D) cardiac muscle; voluntary control

skeletal muscle; voluntary control (Skeletal muscle is under voluntary control)

Addition of more mitochondria to a muscle fiber will have the greatest effect on ________. A) fast glycolytic fibers B) fast oxidative fibers C) slow oxidative fibers D) both slow and fast oxidative fibers

slow oxidative fibers

Endomysium

Connective tissue sheath surrounding an individual muscle fiber

The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge? A) Calcium bound to troponin B) Troponin bound to tropomyosin C) ATP bound to a myosin head D) A myosin head bound to actin

A myosin head bound to actin (As soon as the activated myosin head forms a cross bridge with actin, the power stroke begins)

______: membrane surrounding muscle fiber

Sarcolemma

Of the following items listed below, which is the best description for why skeletal muscle stores glycogen? A) Glycogen provides a smooth surface for filaments to slide on. B) Skeletal muscle is a heavy consumer of energy. C) Glycogen is part of muscles rigid supporting framework. D) The glycogen is an insulating layer that helps regulate body temperature.

Skeletal muscle is a heavy consumer of energy.

Calcium entry into the axon terminal triggers which of the following events? A) Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine. B) Acetylcholine binds to its receptor. C) Acetylcholine is released into the cleft by active transporters in the plasma membrane of the axon terminal. D) Cation channels open and sodium ions enter the axon terminal while potassium ions exit the axon terminal.

Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine. (When synaptic vesicles fuse to the plasma membrane, acetylcholine is released via exocytosis.)

Although all the anatomical parts of muscle work together to give it it's characteristics, which of the following proteins listed below would be most associated with the characteristics of contractility? A) elastin (titin) filaments B) voltage gated sodium channels C) thick (myosin) filaments D) potassium (K+) leak channels

thick (myosin) filaments

The sliding filament model of contraction states that __________. A) during contraction, the thin myofilaments slide past the thick myofilaments so that the actin and myosin myofilaments overlap to a greater degree B) during contraction, the thin myofilaments slide past the thick myofilaments so that calcium ions can be released from the sarcoplasmic reticulum C) during contraction, the thin myofilaments slide past T tubules so that the Z discs are overlapping D) during contraction, the thin myofilaments slide past the thick myofilaments so that the actin and myosin myofilaments no longer overlap

(The sliding filament model of contraction states that during contraction, the thin myofilaments slide past the thick myofilaments so that actin and myosin myofilaments overlap to a greater degree. In a relaxed muscle fiber, the thick and thin myofilaments overlap only at the ends of the A band)

Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine? A) Acetylcholine is degraded by acetylcholinesterase. B) Acetylcholine is transported back into the axon terminal by a reuptake mechanism. C) Acetylcholine diffuses away from the cleft. D) Acetylcholine is transported into the postsynaptic neuron by receptor-mediated endocytosis.

Acetylcholine is degraded by acetylcholinesterase. (Acetylcholinesterase is an enzyme that degrades acetylcholine. This degradation results in a rapid cessation of the acetylcholine signal and a swift removal from the cleft)

Which of the following is most directly required to initiate the coupling of myosin to actin? A)glucose B) ATP C) Ca++ D) ACh

Ca++ (Ca++ binds to troponin, which removes tropomyosin, from the myosin binding site on actin.

____: ion triggering exocytosis

Ca2+ (calcium)

The molecular interaction described as a cross bridge involves the binding of which two proteins? A) myosin and actin B) elastin and myosin C) actin and troponin

Cross bridges between thin and thick myofilaments are formed by the specific interaction between actin and myosin head groups

Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process? A) Excitation refers to the shape change that occurs in voltage-sensitive proteins in the sarcolemma. B) Excitation, in this case, refers to the propagation of action potentials along the sarcolemma. C) Excitation refers to the propagation of action potentials along the axon of a motor neuron. D) Excitation refers to the release of calcium ions from the sarcoplasmic reticulum.

Excitation, in this case, refers to the propagation of action potentials along the sarcolemma.

Which selection best describes the initial event in contraction? A) Myosin heads bind to the newly exposed myosin-binding sites on actin to form cross bridges. B) Calcium binds actin to myosin to begin the cross bridge cycle. C) The myofilaments slide closer together. D) Tropomyosin binds to myosin heads and actin bridges with tropomyosin.

Myosin heads bind to the newly exposed myosin-binding sites on actin to form cross bridges. (Contraction begins when myosin binds to actin and forms cross bridges)

What structure is the functional unit of contraction in a skeletal muscle fiber? A) The sarcomere B) The cross bridge C) The junctional folds of the sarcolemma D) The triad

The sarcomere (A sarcomere is a regular arrangement of thin and thick myofilaments that extends from one Z disc to the next. A myofibril consists of a series of sarcomeres)

The smallest contractile unit within skeletal muscle would correspond to the distance between which two points in the figure? (from z disc to z disc) A) 2-6 B) 1-7 C) 3-5 D) 1-3

1-7 (The distance between points 1 and 7 spans a sarcomere, the smallest contractile unit of a muscle fiber)

The region between which two points corresponds to the entire A (dark) band? A) 1 and 2 B) 2 and 3 C) 3 and 5 D) 2 and 6

2 and 6 (The A band, also know as the dark band, is occupied by the entire length of thick myofilaments)

Voltage-sensitive tubule protein

: a protein that changes shape as a direct result of an action potential

Myosin

: a protein with heads that attach in cross bridging

Troponin

: the protein that binds calcium

Which of the following choices best summarizes excitation-contraction coupling? A) A series of events in which an electrical stimulus is conveyed to a muscle fiber to enact contraction B) A series of events in which calcium gradients are used to convey a signal to the muscle fiber to enact contraction C) A series of events in which an action potential triggers the release of chemical messengers D) A series of events in which actin binds myosin to enact contraction

A series of events in which an electrical stimulus is conveyed to a muscle fiber to enact contraction

A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected? A) Myosin cross-bridge binding sites. B) Potassium leak channels. C) A series of proteins that control calcium release. D) Voltage-gated sodium channels.

A series of proteins that control calcium release. (When action potentials propagate along T-tubules, a voltage-sensitive protein changes shape and triggers a different protein to open it's channels, resulting in the release of calcium from the terminal cisternae.

Which of the following best describes how ACh changes the ion permeability of the sarcolemma? A) ACh activates acetylcholinesterase. B) ACh entry into the axon terminal causes neurotransmitter release. C) ACh binds to receptors in the junctional folds. D) ACh entry into the muscle fiber causes Ca2+ to be released by the sarcoplasmic reticulum.

ACh binds to receptors in the junctional folds. (The junctional folds of the muscle fiber's sarcolemma contain ACh receptors. These receptors are chemically gated ion channels. When ACh binds to these receptors, they open, allowing ions to diffuse across the sarcolemma. This represents an increase in the sarcolemma's ion permeability)

Which step precedes all of the other listed steps? A)Na+ rushes into the cell. B) The sarcoplasmic reticulum is activated. C) An action potential starts on the sarcolemma. D) ACh is released by the motor neuron.

ACh is released by the motor neuron. (The first step toward generating a skeletal muscle contraction is nervous stimulation of the muscle fiber in order to generate an action potential. The site of muscle stimulation, where the nerve ending communicates with the muscle fiber, is called the neuromuscular junction)

After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment? A) ATP binds to the myosin head. B) Acetylcholine binds to receptors in the junctional folds of the sarcolemma. C) Calcium ions bind to troponin. D) ADP and inorganic phosphate are bound to the myosin head.

ATP binds to the myosin head. ( The binding of ATP to the myosin head weakens the bond between myosin and actin, forcing the myosin head to detach. ATP also provides the energy for the next power stroke.)

The neuromuscular junction is a well-studied example of a chemical synapse. Which of the following statements describes a critical event that occurs at the neuromuscular junction? A) When the action potential reaches the end of the axon terminal, voltage-gated sodium channels open and sodium ions diffuse into the terminal. B) Acetylcholine is released by axon terminals of the motor neuron. C) Acetylcholine binds to its receptor in the junctional folds of the sarcolemma. Its receptor is linked to a G protein. D) Acetylcholine is released and moves across the synaptic cleft bound to a transport protein

Acetylcholine is released by axon terminals of the motor neuron. (Acetylcholine is released into the synaptic cleft via exocytosis.)

Which of the following best describes the role of acetylcholinesterase molecules at the neuromuscular junction? A) Acetylcholinesterase prevents Na+ and K+ from passing through chemically gated ion channels. B) Acetylcholinesterase molecules close once ACh is released, which decreases the sarcolemma's permeability to Na+ and K+. C) Acetylcholinesterase binds ACh, preventing it from binding to chemically gated ion channels. D) Acetylcholinesterase breaks down ACh, which allows chemically gated ion channels to close.

Acetylcholinesterase breaks down ACh, which allows chemically gated ion channels to close. (The chemical signal at the neuromuscular junction is quite brief. As soon as ACh is released from the axon terminal, acetylcholinesterase molecules in the synaptic cleft begin to break it down. This ensures that ACh receptors are open only for the brief amount of time required to initiate an action potential in the muscle fiber)

_______ binds to ACh receptors, causing them to open chemically gated ion channels.

Ach (Acetylcholine) (The binding of ACh to ACh receptors increases the permeability of the sarcolemma to both Na+ and K+)

Which of the choices below correctly describes how an action potential generated at the neuromuscular junction (NMJ) is converted to excitation in the muscle fiber? A) An action potential in the motor neuron causes ACh to be released into the synaptic cleft. Binding of ACh at the membrane receptor initiates a direct action potential. B) An action potential in the motor neuron directly triggers an action potential at the sarcolemma. C) An action potential in the motor neuron causes ACh to be released into the synaptic cleft. Binding of ACh to sarcolemma receptors initiates graded potentials. D) ACh binds at a receptor in the motor neuron, which initiates graded potentials.

An action potential in the motor neuron causes ACh to be released into the synaptic cleft. Binding of ACh to sarcolemma receptors initiates graded potentials (An action potential traveling down a motor neuron arrives at the axon terminal and causes exocytosis of the neurotransmitter ACh into the synaptic cleft. ACh diffuses into the synaptic cleft, binds to the receptor proteins on the junctional folds of the muscle sarcolemma (motor end plate), and initiates graded potentials. These graded potentials sum to an action potential, thus initiating excitement of the muscle fiber)

Which statement accurately describes the event indicated by ACh receptors on the junctional folds/ motor end plates? A) Diffusion of Ca2+ into the muscle fiber triggers the diffusion of acetylcholine out of the muscle fiber. B) Binding of acetylcholine to a receptor triggers the opening of an ion channel. C) Diffusion of acetylcholine into the muscle fiber triggers the opening of an ion channel. D) The binding of acetylcholine directly causes the formation of a wave of depolarization.

Binding of acetylcholine to a receptor triggers the opening of an ion channel (Binding of acetylcholine to its receptor opens chemically (ligand) gated ion channels that allow Na+ and K+ to diffuse across the sarcolemma)

The cross bridge cycle starts when _________. A) ATP binds to troponin and is hydrolyzed to ADP and Pi B) Ca2+ from the sarcoplasmic reticulum binds to tropomyosin C) acetylcholine diffuses away from the synaptic cleft D) Ca2+ is actively transported into the sarcoplasmic reticulum E) Ca2+ from the sarcoplasmic reticulum binds to troponin

Ca2+ from the sarcoplasmic reticulum binds to troponin (The release of Ca2+ is triggered by the propagation of an action potential along a skeletal muscle fiber. Ca2+ is released from the sarcoplasmic reticulum and into the sarcoplasm of the muscle fiber. When Ca2+ concentration is high in the sarcoplasm, Ca2+ binds to troponin causing change in its shape. This shape change alters the position of tropomyosin and moves it away from myosin binding sites on actin, thus allowing the myosin head to bind actin and form a cross bridge.)

Which selection correctly describes the role of calcium in coupling? A)Calcium binds to actin, which triggers troponin to fall off and expose myosin-binding sites. B)Calcium binds to actin, which triggers it to bind to myosin. C) Calcium binds to tropomyosin, which moves tropomyosin and exposes the myosin-binding sites on actin. D) Calcium binds to troponin, which moves tropomyosin and exposes the myosin binding sites on actin

Calcium binds to troponin, which moves tropomyosin and exposes the myosin-binding sites on actin. (The thin filament in a sarcomere is composed of actin, troponin, and tropomyosin. Troponin and tropomyosin are attached to one another, both overlaying actin. When a muscle is relaxed, tropomyosin blocks actin's myosin-binding sites. Calcium binds to troponin, initiating a shape change that removes the blocking action of tropomyosin. This exposes the myosin-binding sites on actin to the myosin heads for cross bridging)

Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers? A) sodium ions B) calcium ions C) Acetylcholine D) Action potentials

Calcium ions (Action potentials propagating down the T-tubule cause a voltage-sensitive protein to change shape. This shape change opens calcium release channels in the sarcoplasmic reticulum, allowing calcium ions to flood the sarcoplasm. This flood of calcium ions is directly responsible for the coupling of excitation to contraction in skeletal muscle fibers.)

Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber? A) Calcium ions are stored in the nuclei. B) Calcium ions are stored in the transverse tubules. C) Calcium ions are stored in the sarcoplasmic reticulum. D) Calcium ions are stored in the mitochondria.

Calcium ions are stored in the sarcoplasmic reticulum. (Sarcoplasmic reticulum is the specific name given to the smooth endoplasmic reticulum in muscle fibers. The sarcoplasmic reticulum is very elaborate in skeletal muscle fibers, allowing for significant storage of calcium ions)

What specific event triggers the uncovering of the myosin binding site on actin? A) Calcium release channels open in the sarcoplasmic reticulum, and calcium levels rise in the sarcoplasm. B) Sodium ions bind to troponin and change its shape. C) Calcium ions bind to troponin and change its shape. D) Calcium ions bind to tropomyosin and change its shape.

Calcium ions bind to troponin and change its shape. (The shape change caused by the binding of calcium to troponin shifts tropomyosin away from the myosin binding sites on actin)

Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction? A) Calcium release from the sarcoplasmic reticulum initiates the contraction. B) Voltage-sensitive proteins change shape. C) Action potentials propagate into the interior of the skeletal muscle fiber. D)Sodium release from the sarcoplasmic reticulum initiates the contraction.

Calcium release from the sarcoplasmic reticulum initiates the contraction. (Sarcoplasmic reticulum is the specific name given to the smooth endoplasmic reticulum in muscle cells. It is especially abundant and convoluted in skeletal muscle cells. It functions in the storage, release, and reuptake of calcium ions.)

Perimysium

Connective tissue surrounding muscle fiber bundles

When does cross bridge cycling end? A) Cross bridge cycling ends when calcium ions are passively transported back into the sarcoplasmic reticulum. B) Cross bridge cycling ends when ATP binds to the myosin head. C) Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin. D) Cross bridge cycling ends when calcium release channels in the sarcoplasmic reticulum open.

Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin (The sarcoplasmic reticulum contains Ca2+-ATPases that actively transport Ca2+ into the SR. Without Ca2+, troponin returns to its resting shape, and tropomyosin glides over and covers the myosin binding sites on actin)

Curare is a poisonous plant extract. Curare molecules have a chemical structure like the neurotransmitter ACh. Curare can bind to the ACh receptor site on the chemically gated ion channels in the motor end plate. Even though curare will bind to the receptor site it will not open the ion channel and no ions will pass through. What do you think the symptoms of curare poisoning would look like? A) Smooth muscles will become stimulated causing quick movement of nutrients through the digestive system. B) Muscles will respond too quickly and cause a severe tremor. C) Curare will only affect muscles with ACh receptors, paralyzing them. D) Curare will only affect cardiac muscle, causing fibrillations of the heart.

Curare will only affect muscles with ACh receptors, paralyzing them.

The action potential propagates along the sarcolemma. As the action potential spreads down the T tubules of the triads, voltage-sensitive tubule proteins change shape. How doe the shape change of these proteins lead to contraction? A) It permits calcium to exit the cistern and enter the T tubule. B) It facilitates ACh's binding to the sarcolemma. C) It allows calcium to exit the sarcoplasmic reticulum and enter the cytosol. D) It allows calcium to exit the cytoplasm and enter the cisterns.

It allows calcium to exit the sarcoplasmic reticulum and enter the cytosol. (As the action potential propagates, it changes the shape of T tubule proteins. These proteins are linked to calcium channels in the terminal cisterns of the sarcoplasmic reticulum. When these proteins' calcium channels open, a massive amount of calcium flows into the cytosol)

The end plate potential is primarily, and most directly, caused by the movements of _____.

Na+ (The movement of Na+ into the muscle fiber is primarily responsible for the change in membrane potential known as the end plate potential.)

Place the steps that occur during a single cross bridge cycle in the correct order from left to right.

The activated myosin head binds to actin, forming a cross bridge. ADP is released and myosin slides the thin filament toward the center of the sarcomere. ATP binds to the myosin head and detaches it from actin. ATP is hydrolyzed to ADP and Pi and the energy released re-cocks the myosin head. The thin filaments are pulled toward the center of the sarcomere by the myosin heads of the thick filament. This shortens the sarcomeres in the muscle fiber and causes the whole skeletal muscle to contract. The cross bridge cycle ends when Ca2+ are actively transported back into the sarcoplasmic reticulum. The cycle repeats as long as the binding sites on actin remain exposed, and both Ca2+ and ATP are available.

How does the myosin head obtain the energy required for activation? A) The energy comes from oxidative phophorylation. B) The energy comes from the hydrolysis of ATP. C) The energy comes from the direct phosphorylation of ADP by creatine phosphate. D) The energy comes from the hydrolysis of GTP.

The energy comes from the hydrolysis of ATP. (Myosin is a large, complex protein with a binding site for actin. It also contains an ATPase. The energy released during the hydrolysis of ATP activates the myosin head.)

Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why? A) The outside surface of the sarcolemma is negatively charged compared to the inside surface. Potassium ions diffuse outward along favorable chemical and electrical gradients. B) The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients. C) The inside surface of the sarcolemma is negatively charged compared to the outside surface. Potassium ions diffuse inward along favorable chemical and electrical gradients. D) The outside surface of the sarcolemma is negatively charged compared to the inside surface. Sodium ions diffuse outward along favorable chemical and electrical gradients.

The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients. (The resting membrane potential of all cells is negative (inside compared to outside). Therefore, given the direction of the chemical and electrical gradients, more sodium ions diffuse inward than potassium ions diffuse outward.)

Based on what you know of the relationship between the thick and the thin filaments, what would happen if a disorder existed that caused a person to produce no tropomyosin? A)The muscle tissues would never be able to relax. B) Actin will spontaneously fall apart. C) The muscle would be weaker than normal. D) The muscle would never contract.

The muscle tissues would never be able to relax (The tropomyosin covers the myosin binding site on actin. Without tropomyosin, the myosin would constantly have access to those binding sites)

What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated? A) A skeletal muscle fiber is innervated by multiple motor neurons. B) Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron. C) A motor neuron typically innervates only one skeletal muscle fiber. D) Motor neurons always innervate thousands of skeletal muscle fibers.

Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron. (There are many more skeletal muscle fibers than there are motor neurons. The ratio of neurons to fibers varies from approximately one to ten to approximately one to thousands).

Signals flowing through the neuromuscular junction pass through several structures in a single direction. Arrange the structures below in the order in which signals travel through them. (from beginning to end (4)

axon->axon terminal->synaptic cleft->sarcolemma (an electrical signal in the motor neuron's axon leads to an electrical signal in the muscle fiber's sarcolemma. However, the electrical signal is briefly converted to a chemical signal as the information crosses the synaptic cleft.)

Proper application of RICE--rest, ice, compression, and elevation--can effectively control inflammation due to an ankle sprain. Why would compression provided by a correctly wrapped elastic Ace bandage be helpful in preventing further inflammation? A) because it reduces pain associated with joint injury B) because it promotes fluid leakage into injured tissue C) because it immobilizes/stabilizes an injured ankle D) because it promotes increased blood flow to the injury

because it immobilizes/stabilizes an injured ankle

description of the part of the excitation-contraction coupling to the correct order of occurrence from left to right

description of the part of the excitation-contraction coupling to the correct order of occurrence from left to right 1. Action potential is generated at the sarcolemma 2. Action potential goes down the T tubule 3. Voltage-gated tubule protein changes shape 4. Calcium ion channels open 5. Calcium exist the cistern into sarcoplasm 6. Calcium binds to troponin 7. Actin sites are exposed 8. Cross bridges form between actin and myosin (Coupling begins with an action potential after the arrival of ACh and graded potentials, and it ends before cross bridge cycling)

muscle fiber (myofibrils composed of actin and myosin filaments called sarcomeres)

individual muscle fiber

Cross bridge formation between myosin heads and actin molecules is caused by the elevation of calcium ion concentration in the cytosol. During rigor mortis, this elevation of calcium ion concentration in the cytosol is permanent because ________. A) mitochondria stop producing ATP molecules required by the sarcoplasmic reticulum's calcium ion pumps B) troponin molecules bind irreversibly to calcium ions to prevent them from being removed from the cytosol C) tropomyosin molecules bind irreversibly to calcium ions to prevent them from being removed from the cytosol D) acetylcholine continues to stimulate the release of calcium ions from the sarcoplasmic reticulum

mitochondria stop producing ATP molecules required by the sarcoplasmic reticulum's calcium ion pumps (Solute pumping is an active transport process. Active transport moves molecules against their concentration gradient, which requires energy in the form of ATP)

What part of the sarcolemma contains acetylcholine receptors? A) any part of the sarcolemma B) end of the muscle fiber C) part adjacent to another muscle cell D) motor end plate

motor end plate

Which of the following is the correct sequence of events for muscle contractions? A) muscle cell action potential, neurotransmitter release, ATP-driven power stroke, calcium ion release from SR, sliding of myofilaments B) neurotransmitter release, motor neuron action potential, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke C) motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments D) neurotransmitter release, muscle cell action potential, motor neuron action potential, release of calcium ions from SR, sliding of myofilaments, ATP-driven power stroke

motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments

Which term best identifies a muscle cell? A) myofibril B) muscle fiber C) sarcomere D) muscle fascicle

muscle fiber (Skeletal muscle cells fuse during development to form the mature, multinucleated muscle fibers)

Hypothetically, if a muscle were stretched to the point where thick and thin filaments no longer overlapped, ________. A) ATP consumption would increase because the sarcomere is "trying" to contract B) cross bridge attachment would be optimum because of all the free binding sites on actin C) no muscle tension could be generated D) maximum force production would result because the muscle has a maximum range of travel

no muscle tension could be generated

What is the most distinguishing characteristic of muscle tissue? A) It is composed of multiple cells working together. B) the ability to respond to nervous stimulation C) the ability to transform chemical energy into mechanical energy to move the body D) its cells' inability to reproduce by mitosis

the ability to transform chemical energy into mechanical energy to move the body

What does excess postexercise oxygen consumption represent? A) the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used B) the amount of oxygen equal to the oxygen already used C) amount of oxygen needed for aerobic activity to accomplish the same amount of work D) the amount of oxygen taken into the body immediately after the exertion

the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used

A toxin released by certain bacteria can block the release of neurotransmitters into a neuromuscular synapse. What would result from such a block? A) The muscle would remain fixed at the length it was when the toxin contacted it. B) the loss of ability to contract the muscle C) The muscle would become permanently contracted.

the loss of ability to contract the muscle (Without acetylcholine, the muscle would not be able to contract or even maintain tone).

Acetylcholine binds to its receptor in the sarcolemma and triggers __________. A) the opening of ligand-gated anion channels B) the opening of voltage-gated calcium channels C) the opening of calcium-release channels D) the opening of ligand-gated cation channels

the opening of ligand-gated cation channels. (These channels permit sodium ions to diffuse inward and potassium ions to diffuse outward.)

Which of the following regions best identifies where myosin would have maximum cross-bridge access to actin? A) the region between 3 and 5 B) the region between 1 and 2 C) the region between 2 and 3 D) the region identified at 4

the region between 2 and 3 (Actin and myosin are components of thin and thick filaments, respectively. The region between points 2 and 3 includes the area of overlap between thin and thick filaments)

Cistern

the swollen chamber of an organelle that lies on either side of a T tubule

An enzyme known as acetylcholinesterase is present in the synaptic cleft. What is its role? A) to facilitate the entrance of acetylcholine into the muscle cell B) to facilitated transport of acetylcholine across the cleft C) to break down acetylcholine D) to pump Ca2+ back out of the axon terminal

to break down acetylcholine (Acetylcholinesterase breaks acetylcholine apart, terminating the synaptic transmission. Choline can be taken back into the axon terminal and reuse) .

What is name given to the regularly spaced infoldings of the sarcolemma? A) Sarcoplasmic reticulum B) motor endplates C) terminal cisternae D) transverse or T tubules

transverse or t-tubules (T tubules penetrate a skeletal muscle fiber and provide a pathway for excitation into the interior.)