Which of these statements about skeletal muscles is false?
A) Their fibers branch.
B) They store nutrient reserves.
C) They pull on tendons.
D) They support soft tissues.
answer
A) Their fibers branch.
question
Which type of muscle tissue has the greatest effect on the body's heat production?
A) skeletal
B) cardiac
C) smooth
D) All of these muscle types have about the same effect on the body's heat production.
answer
A) skeletal
question
Skeletal muscle does each of these except __________.
A) produce movement
B) maintain posture
C) ventilate the lungs
D) pump blood
answer
D) pump blood
question
Muscle Contraction Cycle
answer
The contraction cycle begins with the arrival of calcium ions to the zones of overlap via excitation-contraction coupling. Then, calcium ions bind to the troponin-tropomyosin complex, causing troponin to change position. Troponin's movement rolls tropomyosin away from actin's active sites, thus allowing them to form cross-bridges with energized myosin heads. After cross-bridge formation, the energy that was stored in the resting state is released as the myosin head pivots towards the M line (coincident with the release of bound ADP and P). This is known as the power stroke. Finally, to disengage cross-bridges following the power stroke, ATP binds to the myosin head, and the bond between myosin and actin is broken. Myosin is reactivated for further cycling when ATP is converted into ADP and P, and the myosin head returns to its original conformation.
question
The capillaries that wrap around each muscle fiber are located within the __________.
A) perimysium
B) epimysium
C) sarcolemma
D) endomysium
answer
D) endomysium
question
Muscles are attached to bones by tendons or __________.
A) ligaments
B) aponeuroses
C) perimysium
D) superficial fascia
answer
B) aponeuroses
question
A thin layer of connective tissue that surrounds a muscle fascicle is called the __________.
A) endomysium
B) perimysium
C) tendon
D) epimysium
answer
B) perimysium
question
What is the function of the sarcoplasmic reticulum?
answer
Calcium storage/regulation
question
The _______ of the cell is the organelle that contains the chromosomes - the human inheritable material.
answer
nucleus; houses genetic material
question
The _________ _______ are a conduit for the passage of the action potential from the sarcolemma to the sarcoplasmic reticulum.
answer
transverse tubules; part of coupling the action potential to contraction
question
Aerobic ATP production in all cells is performed by the ____________.
answer
mitochondria; power-house of cell
question
The _ ____ is a lighter region of the sarcomere where only thick filaments are found.
answer
H band
question
The _ ____ marks the boundary between neighboring sarcomeres.
answer
Z line
question
The _ ____ is the central portion of the sarcomere
answer
M line
question
The _ ____extends from the A band of one sarcomere to the A band of the neighboring sarcomere and is the region where only thin filaments are found.
answer
I band
question
Which thick filament binds to actin once its active binding sites are exposed?
A) troponin
B) actin
C) tropomyosin
D) myosin
answer
D) myosin
question
The action potential in skeletal muscle fibers is generated by the __________.
A) sarcoplasmic reticulum
B) sarcophagus
C) sarcoplasm
D) sarcolemma
answer
D) sarcolemma
question
Titin is a(n) __________.
A) thin filament protein
B) elastic protein
C) calcium-binding protein
D) tropomyosin-binding protein
answer
B) elastic protein
question
Sarcomere is best defined as ___________.
A) actomyosin proteins
B) a storage form of calcium
C) a repeating unit of striated muscle
D) thick and thin filaments
answer
C) a repeating unit of striated muscle
question
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 diffuses away from the cleft.
B) Acetylcholine is transported back into the axon terminal by a reuptake mechanism.
C) Acetylcholine is transported into the postsynaptic neuron by receptor-mediated endocytosis.
D) Acetylcholine is degraded by acetylcholinesterase.
answer
D) 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.
question
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) Acetylcholine is released and moves across the synaptic cleft bound to a transport protein.
B) When the action potential reaches the end of the axon terminal, voltage-gated sodium channels open and sodium ions diffuse into the terminal.
C) Acetylcholine is released by axon terminals of the motor neuron.
D) Acetylcholine binds to its receptor in the junctional folds of the sarcolemma. Its receptor is linked to a G protein.
answer
C) Acetylcholine is released by axon terminals of the motor neuron.
Acetylcholine is released into the synaptic cleft via exocytosis.
Acetylcholine does bind to receptors located in the junctional folds of the sarcolemma. These receptors contain ligand-gated cation channels. They are not linked to G proteins.
question
Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________.
A) extend from the brain to the sarcolemma of a skeletal muscle fiber
B) extend from the spinal cord to the sarcolemma of a skeletal muscle fiber
C) extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber
D) arise in the epimysium of a skeletal muscle and extend to individual skeletal muscle fibers
answer
C) 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.
question
Calcium entry into the axon terminal triggers which of the following events?
A) Acetylcholine binds to its receptor.
B) Acetylcholine is released into the cleft by active transporters in the plasma membrane of the axon terminal.
C) Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.
D) Cation channels open and sodium ions enter the axon terminal while potassium ions exit the axon terminal.
answer
C) 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.
question
Acetylcholine binds to its receptor in the sarcolemma and triggers __________.
A) the opening of ligand-gated cation channels
B) the opening of calcium-release channels
C) the opening of ligand-gated anion channels
D) the opening of voltage-gated calcium channels
answer
A) the opening of ligand-gated cation channels
These channels permit sodium ions to diffuse inward and potassium ions to diffuse outward.
question
Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why?
A) The inside surface of the sarcolemma is negatively charged compared to the outside surface. Potassium ions diffuse inward 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 outside surface of the sarcolemma is negatively charged compared to the inside surface. Sodium ions diffuse outward along favorable chemical and electrical gradients.
D) The outside surface of the sarcolemma is negatively charged compared to the inside surface. Potassium ions diffuse outward along favorable chemical and electrical gradients.
answer
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.
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.
question
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 refers to the propagation of action potentials along the axon of a motor neuron.
C) Excitation refers to the release of calcium ions from the sarcoplasmic reticulum.
D) Excitation, in this case, refers to the propagation of action potentials along the sarcolemma.
answer
D) Excitation, in this case, refers to the propagation of action potentials along the sarcolemma.
These action potentials set off a series of events that lead to a contraction.
question
Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction?
A) Sodium release from the sarcoplasmic reticulum initiates the contraction.
B) Action potentials propagate into the interior of the skeletal muscle fiber.
C) Calcium release from the sarcoplasmic reticulum initiates the contraction.
D) Voltage-sensitive proteins change shape.
answer
C) 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.
question
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) Voltage-gated sodium channels.
C) A series of proteins that control calcium release.
D) Potassium leak channels.
answer
C) 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.
question
What is name given to the regularly spaced infoldings of the sarcolemma?
A) transverse or T tubules
B) sarcoplasmic reticulum
C) motor endplates
D) terminal cisternae
answer
A) transverse or T tubules
T tubules penetrate a skeletal muscle fiber and provide a pathway for excitation into the interior.
question
Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?
A) Calcium ions.
B) Action potentials.
C) Sodium ions.
D) Acetylcholine.
answer
A) 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.
question
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) Motor neurons always innervate thousands of skeletal muscle fibers.
C) Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron.
D) A motor neuron typically innervates only one skeletal muscle fiber.
answer
C) 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
question
The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge?
A) Troponin bound to tropomyosin
B) ATP bound to a myosin head
C) Calcium bound to troponin
D) A myosin head bound to actin
answer
D) A myosin head bound to actin
As soon as the activated myosin head forms a cross bridge with actin, the power stroke begins.
question
What structure is the functional unit of contraction in a skeletal muscle fiber?
A) The junctional folds of the sarcolemma
B) The cross bridge
C) The triad
D) The sarcomere
answer
D) 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.
question
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 sarcoplasmic reticulum.
B) Calcium ions are stored in the transverse tubules.
C) Calcium ions are stored in the nuclei.
D) Calcium ions are stored in the mitochondria.
answer
A) 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.
question
After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment?
A) Acetylcholine binds to receptors in the junctional folds of the sarcolemma.
B) ADP and inorganic phosphate are bound to the myosin head.
C) Calcium ions bind to troponin.
D) ATP binds to the myosin head.
answer
D) 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.
question
How does the myosin head obtain the energy required for activation?
A) The energy comes from the hydrolysis of ATP.
B) The energy comes from oxidative phophorylation.
C) The energy comes from the direct phosphorylation of ADP by creatine phosphate.
D) The energy comes from the hydrolysis of GTP.
answer
A) 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.
question
What specific event triggers the uncovering of the myosin binding site on actin?
A) Sodium ions bind to troponin and change its shape.
B) Calcium ions bind to tropomyosin and change its shape.
C) Calcium ions bind to troponin and change its shape.
D) Calcium release channels open in the sarcoplasmic reticulum, and calcium levels rise in the sarcoplasm.
answer
C) 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.
question
When does cross bridge cycling end?
A) Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin.
B) Cross bridge cycling ends when calcium ions are passively transported back into the sarcoplasmic reticulum.
C) Cross bridge cycling ends when calcium release channels in the sarcoplasmic reticulum open.
D) Cross bridge cycling ends when ATP binds to the myosin head.
answer
A) 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.
question
In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?
A) serotonin
B) norepinephrine
C) dopamine
D) acetylcholine (ACh)
answer
D) acetylcholine (ACh)
question
When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?
A) chemically gated calcium channels
B) voltage-gated sodium channels
C) voltage-gated potassium channels
D) voltage-gated calcium channels
answer
D) voltage-gated calcium channels
the action potential opens voltage-gated calcium channels and calcium rushes into the axon terminal, leading to the release of the neurotransmitter.
question
What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
A) a channel
B) exocytosis
C) a protein carrier
answer
B) exocytosis
question
The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?
A) Binding causes chemically gated potassium channels to open in the motor end plate.
B) Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate.
C) Binding causes voltage-gated sodium channels to open in the motor endplate.
D) Binding causes potassium voltage-gated channels to open in the motor endplate.
answer
B) Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate.
question
How is acetylcholine (ACh) removed from the synaptic cleft?
A) acetylcholinesterase (AChE; an enzyme)
B) diffusion away from the synaptic cleft
C) a reuptake pump on the axon terminal
answer
A) acetylcholinesterase (AChE; an enzyme)
question
The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?
A) sarcolemma
B) T tubule
C) terminal cisternae of the sarcoplasmic reticulum
D) cytosol
answer
C) terminal cisternae of the sarcoplasmic reticulum
question
The neuromuscular junction is a connection between a neuron and a __________.
A) muscle fiber
B) synaptic terminal
C) myofibril
D) vesicle
answer
A) muscle fiber
question
The end of a neuron, where acetylcholine-filled vesicles are located, is called the __________.
A) synaptic cleft
B) motor end plate
C) synaptic terminal
D) acetylcholine receptor
answer
C) synaptic terminal
question
What is the synaptic cleft?
A) the space between the synaptic terminal and the motor end plate
B) the border between the motor end plate and the sarcolemma
C) the step where acetylcholinesterase (AChE) breaks down, or cleaves, acetylcholine
D) the region of the neuron containing synaptic vesicles
answer
A) the space between the synaptic terminal and the motor end plate
question
Inside a neuron, acetylcholine is contained within __________.
A) vesicles
B) acetylcholine receptors
C) the synaptic cleft
D) the motor end plate
answer
A) vesicles
question
What causes the vesicles inside a neuron to fuse with the plasma membrane?
A) acetylcholine binding to acetylcholine receptors
B) acetylcholine being broken down by acetylcholinesterase
C) an action potential in the neuron
D) an action potential in the muscle fiber
answer
C) an action potential in the neuron
question
Acetylcholine receptors are primarily located __________.
A) inside the muscle fiber
B) on the synaptic terminal
C) inside vesicles
D) on the motor end plate
answer
D) on the motor end plate
question
An action potential in the muscle fiber causes __________.
A) the release of acetylcholine into the synaptic cleft
B) acetylcholine to bind to receptors on the motor end plate
C) acetylcholinesterase to break down acetylcholine
D) the muscle fiber to contract
answer
D) the muscle fiber to contract
question
The role of acetylcholinesterase in the neuromuscular junction is to __________.
A) release acetylcholine from the synaptic terminal
B) generate a muscle action potential
C) increase the sodium permeability of the motor end plate
D) remove acetylcholine from the synaptic cleft
answer
D) remove acetylcholine from the synaptic cleft
question
Myofibrils are __________.
A) bundles of muscle cells inside a whole muscle
B) made of a series of sarcomeres
C) connections between actin and myosin
D) proteins that cover active sites on actin
answer
B) made of a series of sarcomeres
question
Z lines define the edges of which of the following?
A) myosin
B) cross-bridges
C) sarcomeres
D) myofibrils
answer
C) sarcomeres
question
Myosin molecules form what part of the sarcomere?
A) actin
B) thick filament
C) thin filament
D) tropomyosin
answer
B) thick filament
question
Which of the following is involved in the power stroke?
A) myosin
B) Z lines
C) myofibrils
D) tropomyosin
answer
A) myosin
question
Which of the following proteins contains the active site involved in cross-bridge formation?
A) actin
B) troponin
C) myosin
D) tropomyosin
answer
A) actin
question
When the sarcomere is at rest, what is covering the active sites on actin?
A) tropomyosin
B) troponin
C) cross-bridges
D) myosin
answer
A) tropomyosin
question
When calcium is released inside a muscle cell, what does it bind to?
A) actin
B) tropomyosin
C) troponin
D) myosin
answer
C) troponin
question
Myosin molecules form cross-bridges when they attach to __________.
A) actin
B) tropomyosin
C) troponin
D) calcium
answer
A) actin
question
What happens immediately after the myosin head binds to the active site on actin?
A) The myosin head detaches from the active site on actin.
B) Tropomyosin moves away from the active site on actin.
C) The myosin head pivots, moving the actin strand.
D) ATP binds to the myosin head.
answer
A) The myosin head detaches from the active site on actin.
When the myosin head binds to actin, the head pivots towards the center of the sarcomere. This action moves the actin strand, pulling the Z-lines inward. This is the basis of sarcomere shortening during muscle contraction.
ATP binding happens later in the cross bridge cycle.
question
ATP binding leads to which of the following actions?
A) cross-bridge formation
B) exposure of active sites on actin
C) detaching and resetting cross-bridges
D) pivoting of the myosin head
answer
C) detaching and resetting cross-bridges
question
Triads in skeletal muscle fibers function in __________.
A) calcium ion uptake
B) neuromuscular transmission
C) calcium ion release
D) sarcomere shortening
answer
C) calcium ion release
question
During neuromuscular transmission, the axon terminals release __________.
A) calcium ions
B) acetylcholine
C) acetylcholinesterase
D) sodium ions
answer
B) acetylcholine
question
The muscle action potential penetrates into a fiber along the __________.
A) Z discs
B) sarcoplasmic reticulum
C) neuromuscular junction
D) transverse tubules
answer
D) transverse tubules
question
In response to an action potential along the transverse tubules, the __________ release(s) calcium ions into the sarcoplasm.
A) calcitonin
B) thin filaments
C) sarcoplasmic reticulum
D) troponin molecules
answer
C) sarcoplasmic reticulum
question
Cycling of myosin cross-bridges results in ___________.
A) ATP hydrolysis
B) muscle shortening
C) force production
D) Repeated cycling of cross-bridges causes all of these effects
answer
D) Causes all of these:
ATP hydrolysis
muscle shortening
force production
question
What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?
A) arrival of an action potential
B) troponin
C) calcium ion pump
D) ATP
answer
A) arrival of an action potential
question
What energizes the power stroke?
A) calcium
B) hydrolysis of ATP
C) binding of ATP
answer
B) hydrolysis of ATP
question
A single muscle action potential will normally be followed by __________.
A) treppe
B) incomplete tetanus
C) a single pulse of calcium ion release
D) two pulses of calcium ion release
answer
C) a single pulse of calcium ion release
question
To increase muscle tension, the nervous system can __________.
A) increase the number of active motor units
B) recruit larger motor units
C) increase the stimulation frequency
D) All of these can increase muscle tension.
answer
D) all of the above
-increase the number of active motor units -
-recruit larger motor units
-increase the stimulation frequency
question
When a muscle contraction develops tension but doesn't shorten the muscle, the contraction is called __________.
A) isometric
B) unfused tetanus
C) isotonic
D) incomplete twitch
answer
A) isometric
question
What is the type of chemical reaction used to rebuild ADP into ATP?
A) rehydration synthesis
B) hydrolysis
C) dehydration synthesis
answer
C) dehydration synthesis
question
Which of the following processes produces molecules of ATP and has two pyruvic acid molecules as end products?
A) hydrolysis of creatine phosphate
B) glycolysis
C) Krebs cycle and oxidative phosphorylation
answer
B) glycolysis
glucose is broken down in the process called glycolysis. This process takes place in the cytoplasm and does not require oxygen - hence it is called anaerobic respiration. If oxygen is available, the pyruvic acid moves into the mitochondria and glycolysis contributes to aerobic respiration.
question
Which of the following processes produces 36 ATP?
A) hydrolysis of creatine phosphate
B) glycolysis
C) Krebs cycle and oxidative phosphorylation
answer
C) Krebs cycle and oxidative phosphorylation
This process, which takes place in the mitochondria, is considered aerobic respiration because oxygen is required
question
The "rest and recovery" period, where the muscle restores depleted reserves, includes all of the following processes EXCEPT __________.
A) Glycogen is synthesized from glucose molecules.
B) Oxygen rebinds to myoglobin.
C) Pyruvic acid is converted back to lactic acid.
D) ATP is used to rephosphorylate creatine into creatine phosphate.
answer
C) Pyruvic acid is converted back to lactic acid.
When oxygen is available, lactic acid is converted back to pyruvic acid (not vice versa) that then enters the Krebs cycle. Lactic acid is the end product of the anaerobic pathway.
question
Which type of muscle fiber has a large quantity of glycogen and mainly uses glycolysis to synthesize ATP?
A) red slow twitch fibers
B) white fast twitch fibers
answer
B) white fast twitch fibers
white fast twitch fibers have high glycogen content for a readily available source of glucose for glycolysis. They appear white because of the reduced amount of myoglobin and fewer capillaries surrounding them. Because these fibers have reduced myoglobin and very few capillaries surrounding them, they have very little oxygen available for the Krebs cycle and oxidative phosphorylation. They also have fewer mitochondria (where the Krebs cycle and oxidative phosphorylation would take place).
question
The biochemical reaction that consumes the majority of a muscle's ATP is the __________.
A) sodium-potassium pump
B) muscle action potential
C) neuromuscular transmission
D) actin myosin cross-bridge cycle
answer
D) actin myosin cross-bridge cycle
question
Muscle fatigue occurs due to a buildup of __________ and __________ in pH.
A) creatine phosphate; increase
B) lactic acid; increase
C) creatine phosphate; decrease
D) lactic acid; decrease
answer
D) lactic acid; decrease
question
Anaerobic glycolysis provides energy for muscle contraction when the supply of __________ is limited.
A) glucose
B) oxygen
C) ATP
D) pyruvic acid
answer
B) oxygen
question
The __________ type of muscle fiber has relatively few mitochondria.
A) cardiac
B) slow
C) fast
D) intermediate
answer
C) fast
question
Which of these is not a property of slow muscle fibers?
A) They are rich in myoglobin.
B) They contract slowly.
C) They are large in diameter.
D) They resist fatigue.
answer
C) They are large in diameter.
question
Which of these is true of cardiac muscle fibers?
A) Cardiac fibers have a long twitch duration compared to skeletal fibers.
B) Cardiac fibers branch.
C) Cardiac fibers have a single nucleus.
D) All of these are true of cardiac fibers.
answer
D) All of these are true of cardiac fibers.
- Cardiac fibers have a long twitch duration compared to skeletal fibers.
- Cardiac fibers branch.
- Cardiac fibers have a single nucleus.
question
The intercalated disk is a not site of __________.
A) action potential propagation
B) myofibril attachment
C) force transmission
D) neuromuscular transmission
answer
D) neuromuscular transmission
question
All of the following are found in both skeletal and cardiac muscle fibers except __________.
A) striations
B) mitochondria
C) intercalated disks
D) sarcomeres
answer
C) intercalated disks
question
Smooth muscle contracts when calcium binds to __________ and activates __________.
A) troponin; tropomyosin
B) troponin; myosin light chain kinase
C) calmodulin; myosin light chain kinase
D) calmodulin; troponin
answer
C) calmodulin; myosin light chain kinase
question
Which of these is not a function of smooth muscle?
A) pushing blood into the arteries
B) elevating skin hairs
C) adjusting airway diameter
D) churning the stomach contents
answer
A) pushing blood into the arteries
question
All of the muscle fibers controlled by a single motor neuron constitute a ________.
A) motor unit
B) cross-bridge
C) myoneural junction
D) sarcomere
answer
A) motor unit
question
When pyruvic acid is produced by anaerobic metabolism faster than it can be utilized, the surplus is converted to __________.
A) carboxylic acid
B) lactic acid
C) creatine phosphokinase
D) adenosine diphosphate
answer
B) lactic acid
question
Peak tension production occurs when all motor units in the muscle contract in a state of ________.
A) twitch
B) treppe
C) complete tetanus
D) wave summation
answer
C) complete tetanus
question
The cell's transmembrane resting potential was created by __________.
A) osmosis
B) facilitated diffusion
C) vesicular transport
D) active transport
answer
D) active transport
question
Which of the following is true of transmembrane potential?
A) Changes can trigger muscle contraction.
B) Positive and negative charges are held apart.
C) It is measured in millivolts.
D) All of the listed responses are correct.
answer
D) All of the above
- Changes can trigger muscle contraction.
- Positive and negative charges are held apart.
- It is measured in millivolts.
question
The transmembrane potential of a cell is the result of equal distribution of ions and charges on both sides of the cell membrane.
A) A transmembrane potential contains potential energy that can be changed or used to do work in a cell.
B) Transmembrane potentials in neurons average about 0.070 volts more negative inside the cell membrane than outside it.
C) The average transmembrane potential of a neuron is about −70 mV.
D) Changes in the transmembrane potential can be used to transfer information or trigger muscle contraction.
answer
A) A transmembrane potential contains potential energy that can be changed or used to do work in a cell.
question
Inside a muscle, bundles of single muscle fibers form __________.
A) thick filaments
B) sarcomeres
C) fascicles
D) T tubules
answer
C) fascicles
question
Which organelle completely surrounds each myofibril inside a muscle fiber?
A) nucleus
B) calcium
C) sarcoplasmic reticulum
D) fascicle
answer
C) sarcoplasmic reticulum
question
Which of the following most correctly describes excitation in the context of excitation-contraction coupling in skeletal muscle?
A) the release of calcium by the sarcoplasmic reticulum
B) the generation of an action potential in the sarcolemma
C) the binding of calcium to troponin
D) the formation of cross-bridges
answer
B) the generation of an action potential in the sarcolemma
question
Which of the following phrases best describes how excitation is coupled to contraction in skeletal muscle fibers?
A) through electrical impulses travelling along the sarcolemma
B) through T tubules
C) through cross-bridge formation
D) through calcium release from the sarcoplasmic reticulum
answer
D) through calcium release from the sarcoplasmic reticulum
question
Malignant hyperthermia (MH) is a rare genetic disease in which the sarcoplasmic reticulum leaks calcium when the patient is put under general anesthesia. Which of the following best describes how anesthesia would affect the skeletal muscles of a patient with MH?
A) The muscles would contract because of increased nerve stimulation.
B) The muscles would relax because of calcium being pumped back into the sarcoplasmic reticulum.
C) The muscles would contract because of calcium binding to troponin.
D) The muscles would contract because of increased action potential generation in the sarcolemma.
answer
C) The muscles would contract because of calcium binding to troponin.
question
Which of the following is an important characteristic of the transmembrane potential?
A) The ions held on either side of the plasmalemma have potential energy.
B) It provides mechanical strength and blocks the passage of water.
C) It adds strength and helps to stabilize the shape of the cell.
D) It serves to balance the negative charges of the cell's proteins.
answer
A) The ions held on either side of the plasmalemma have potential energy
question
Nerves and blood vessels are contained within the connective tissues of the ________.
A) epimysium only
B) epimysium and endomysium
C) endomysium only
D) epimysium, perimysium, and endomysium
answer
D) epimysium, perimysium, and endomysium
question
During the recovery period, the body's oxygen demand is ________.
A) unchanged
B) an irrelevant factor during recovery
C) elevated above normal resting levels
D) decreased below normal resting levels
answer
C) elevated above normal resting levels
question
The TCA cycle __________.
A) occurs inside mitochondria
B) is aerobic
C) is important in ATP production
D) All of the listed responses are true.
answer
D) All of the listed responses are true.
-occurs inside mitochondria
-is aerobic
-is important in ATP production
question
On average, girls have smaller muscles and therefore less muscle mass than boys. Which hormones cause this difference between girls and boys?
A) epinephrine and thyroid hormone
B) thyroid hormone and growth hormone
C) growth hormone and testosterone
D) epinephrine and testosterone
answer
C) growth hormone and testosterone
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