Mastering Chapter 10 Activities

The following is a list of the events that occur during a muscle contraction. What is the correct sequence of these events? 1. Myosin cross-bridges bind to the actin. 2. The free myosin head splits ATP. 3. Calcium ion is released from the sarcoplasmic reticulum. 4. The myosin head pivots toward the center of the sarcomere. 5. Calcium ion binds to troponin. 6. The myosin head binds an ATP molecule and detaches from the actin.

3. calcium ion is released from the sarcoplasmic reticulum 5. calcium ion binds to troponin 1. myosin cross-bridges bind to the actin 4. the myosin head pivots toward the center of the sarcomere 6. the myosin head binds an ATP molecule and detaches from the actin 2. the free myosin head splits ATP

Put the following events of excitation-contraction coupling in the order in which they occur. 1. Excitation 2. Sarcomere shortening 3. Generation of muscle tension 4. Neural control 5. Contraction cycle begins 6. Release of calcium ions

4. neural control 1. excitation 6. release of calcium ions 5. contraction cycle begins 2. sarcomere shortening 3. generation of muscle tension

Put the following events of the neuromuscular junction in the order in which they occur. 1. Action potential is propagated in the sarcolemma. 2. Acetylcholine binds to ligand gated sodium channels. 3. Action potential arrives at the neuromuscular junction. 4. Vesicles full of acetylcholine are stored at the axon terminal. 5. Acetylcholine is released into the synaptic cleft.

4. vesicles full of acetylcholine 3. action potential arrives at the neuromuscular junction 5. acetylcholine is released into the synaptic cleft 2. acetylcholine binds to ligand gated sodium channels 1. action potential is propagated in the sarcolemma

Put the following events of the contraction cycle in the order in which they occur. 1. Cross-bridge detachment 2. Cross-bridge formation 3. Active site exposure 4. Myosin reactivation 5. Calcium ions bind troponin 6. Myosin head pivoting

5. calcium ions bind troponin 3. active site exposure 2. cross-bridge detachment 6. myosin head pivoting 1. cross-bridge detachment 4. myosin reactivation

Put the following structures in order from superficial to deep. 1. muscle fiber 2. perimysium 3. myofibril 4. fascicle 5. endomysium 6. epimysium

6. epimysium 2. perimysium 4. fascicle 5. endomysium 1. muscle fiber 3. myofibril

Which of the following is NOT an effect that exercise will have on muscle tissue? A. higher concentration of glycolytic enzymes B. increase in the number of myofibrils C. increase in the amount of tension produced when the muscle contracts D. an increase in the amount of fibrous connective tissue

D. an increase in the amount of fibrous connective tissue

QUESTION 4: Drag the measurements of different regions of the sarcomere to their respective locations (bins) to describe what happens during the sliding filament mechanism of sarcomere shortening. BIN 1: decreasing in length or distance BIN 2: no change in length or distance BIN 3: increasing in length or distance Length of A band Length if I band Length of H zone Length of thin filament length of thick filament distance between Z discs

Decreases in length or distance 1.) Length of I band 2.) Length of H zone 3.) Distance between Z discs No change in length or distance 1.) Length of A band 2.) Length of thick filament 3.) Length of thin filament

QUESTION 4: Drag the appropriate events of excitation-contraction coupling to their respective locations (bins). Tropomyosin shifts position Motor neuron signals muscle fiber contraction Calcium ions are released Sodium channels open along sarcolemma Myosin forms cross bridges with actin Action potential is conducted along T tubule Calcium ions bind to troponin

First bin: Motor neuron signals muscle fiber contraction Sodium channels open along sarcolemma Second bin: Calcium ions are released Action potential is conducted along T tubule Third bin: Myosin forms cross bridges with actin Tropomyosin shifts position Calcium ions bind to troponin

QUESTION 3: Drag each tile to the appropriate bin to indicate whether it shows the neuromuscular junction at rest or active (in the process of transmitting a signal).

Neuromuscular junction at rest: 1.) chemically gated channels closed 2.) no Na+ diffusion 3.) calcium channels closed 4.) more negative charges inside sarcolemma 5.) ACh in synaptic vesicles Neuromuscular junction active: 1.) Na+ diffusion 2.) calcium channels open 3.) chemically gated channels open 4.) less negative charges inside sarcolemma 5.) ACh in synaptic cleft

Problems 1-5 view in the assignment

Please study for this exam. I will buy you (myself) lots of starbs and fast food if I study lotssssss bc i know macstudiesalot

QUESTION 4: Match the term in the left column to the blanks near their definition on the right. acetylcholine receptor synaptic vesicle synaptic cleft Sodium channel acetylcholinesterase calcium channel acetylcholine a. a type of voltage-gated ion channel located on the sarcolemma of the muscle fiber. b. a type of voltage-gated ion channel located on the axon terminal. c. a type of chemically-gated ion channel located on the junctional folds of the muscle fiber. d. membranous sac located in the axon terminal that contains neurotransmitter. e. enzyme located in the synaptic cleft that breaks down acetylcholine. f. neurotransmitter that stimulates skeletal muscle contraction. g. the space between the axon terminal and junctional folds.

Sodium channel : a type of voltage-gated ion channel located on the sarcolemma of the muscle fiber. Calcium channel : a type of voltage-gated ion channel located on the axon terminal. Acetylcholine receptor : a type of chemically-gated ion channel located on the junctional folds of the muscle fiber. Synaptic vesicle : membranous sac located in the axon terminal that contains neurotransmitter. Acetylcholinesterase : enzyme located in the synaptic cleft that breaks down acetylcholine. Acetylcholine : neurotransmitter that stimulates skeletal muscle contraction. Synaptic cleft : the space between the axon terminal and junctional folds.

The conversion of an action potential (AP) generated by a motor neuron to contraction of skeletal muscle fiber is called excitation-contraction coupling. This activity will test your understanding of the sequence of events that occur during excitation-contraction coupling. Place the events that occur during excitation-contraction coupling in the correct order from left to right. AP propagates along sarcolemma Sarcoplasmic reticulum releases Ca2+ AP travels down T tubules to triads Ca2+ levels in sarcoplasm increase Voltage-sensitive proteins open Ca2+ channels

Step 1: AP propagates along sarcolemma Step 2: AP travels down T tubules to triads Step 3: Voltage-sensitive proteins open Ca2+ channels Step 4: Sarcoplasmic reticulum releases Ca2+ Step 5: Ca2+ levels in sarcoplasm increase

QUESTION 5: Arrange the sequence of events at the NMJ from first to last. Rank the sequence of events at the NMJ that initiate an action potential in the muscle fiber, from first to last. Action potential is initiated on the sarcolemma Acetylcholine binds to its receptors on the junctional folds. Action potential arrives at the axon terminal. Acetylcholine is released into the synaptic cleft. Calcium ions enter the axon terminal. Synaptic vesicles fuse to membrane of axon terminal. Junctional folds become depolarized.

Step 1: Action potential arrives at the axon terminal. Step 2: Calcium ions enter the axon terminal. Step 3: Synaptic vesicles fuse to membrane of axon terminal. Step 4: Acetylcholine is released into the synaptic cleft. Step 5: Acetylcholine binds to its receptors on the junctional folds. Step 6: Junctional folds become depolarized. Step 7: Action potential is initiated on the sarcolemma

QUESTION 4: Below are boxes showing the events that occur at the NMJ. Drag and drop the boxes into the correct sequence of events. Drag the boxes into the correct sequence where the first box is the first event of the sequence. Ach diffuses across the synaptic cleft Na+ rushed into the sarcolemma to generate an action potential An action potential reaches the synaptic terminal AChE degrades ACh, ending synaptic communication ACh enters the synaptic cleft via exocytosis Ach binds to ACh receptors

Step 1: An action potential reaches the synaptic terminal Step 2: ACh enters the synaptic cleft via exocytosis Step 3: Ach diffuses across the synaptic cleft Step 4: Ach binds to ACh receptors Step 5: Na+ rushed into the sarcolemma to generate an action potential Step 6: AChE degrades ACh, ending synaptic communication

QUESTION 1: The site where a motor neuron excites a skeletal muscle fiber is called the neuromuscular junction. This activity will test your understanding of the sequence of events that occur at the neuromuscular junction. Using the images for help, place in the correct order of occurrence from left to right the events that occur at the neuromuscular junction after the action potential reaches the axon terminal. Membrane potential is less negative. Ca2+ enters the axon terminal. Na+ enters and K+ exits. ACh binds to ACh receptors. Ligand-gated cation channels open. Synaptic vesicles release ACh.

Step 1: Ca2+ enters the axon terminal. Step 2: Synaptic vesicles release ACh. Step 3: ACh binds to ACh receptors. Step 4: Ligand-gated cation channels open. Step 5: Na+ enters and K+ exits. Step 6: Membrane potential is less negative.

Arrange the steps of the contraction cycle in the correct order from left to right. The myosin heads bind to actin active sites Calcium ions arrive within the zone of overlap The free myosin head "recocks". ADP and P are released calcium ions bind to troponin. active sites on actin are exposed ATP binds to the myosin head, breaking the link The myosin head pivots (power stroke). ADP and P are released

Step 1: Calcium ions arrive within the zone of overlap Step 2: calcium ions bind to troponin. active sites on actin are exposed Step 3: The myosin heads bind to actin active sites Step 4: The myosin head pivots (power stroke). ADP and P are released Step 5: ATP binds to the myosin head, breaking the link Step 6: The free myosin head "recocks". ADP and P are released

QUESTION 5: Rank the sequence of cross bridge cycling, starting with the myosin-binding sites being exposed and ending with relaxation due to cross bridge cycling ending. Do not overlap any events. Calcium ions pumped into the sarcoplasmic reticulum Myosin head forms cross bridge with actin Myosin binding sites covered Power stroke moves thin filament Cross bridges detach from actin Myosin head is re-energized Calcium ion concentration decreases below the threshold for binding to troponin ATP attaches to myosin head

Step 1: Myosin head forms cross bridge with actin Step 2: Power stroke moves thin filament Step 3: ATP attaches to myosin head Step 4: Cross bridges detach from actin Step 5: Myosin head is re-energized Step 6: Calcium ions pumped into the sarcoplasmic reticulum Step 7: Calcium ion concentration decreases below the threshold for binding to troponin Step 8: Myosin binding sites covered

The sarcomere shortens when the myosin heads of the thick filaments, in a cocked position, form cross bridges with the actin molecules in thin filaments. This activity will test your understanding of the steps that occur in one complete cross bridge cycle. Place the steps that occur during a single cross bridge cycle in the correct order from left to right. ATP binds to the myosin head and detaches it from actin. The activated myosin head binds to actin,forming a cross bridge. ATP is hydrolyzed to ADP and Pi and the energy released re-cocks the myosin head. ADP is released and myosin slides the thin filament toward the center of the sarcomere.

Step 1: The activated myosin head binds to actin,forming a cross bridge. Step 2: ADP is released and myosin slides the thin filament toward the center of the sarcomere. Step 3: ATP binds to the myosin head and detaches it from actin. Step 4: ATP is hydrolyzed to ADP and Pi and the energy released re-cocks the myosin head.

QUESTION 5: Rank the sequence of events in excitation-contraction coupling from first to last. Do not overlap any events. Tropomyosin moves off of actin binding sites. Depolarization of the junctional folds triggers an action potential. Calcium ions flood the sarcoplasm. Myosin heads form crossbridges with actin. Calcium ions bind to troponin. Troponin changes shape. Action potential travels along the sarcolemma. Action potential along the T tubules opens calcium channels.

Step 1:Depolarization of the junctional folds triggers an action potential. Step 2: Action potential travels along the sarcolemma. Step 3: Action potential along the T tubules opens calcium channels. Step 4: Calcium ions flood the sarcoplasm. Step 5: Calcium ions bind to troponin. Step 6: Troponin changes shape. Step 7: Tropomyosin moves off of actin binding sites. Step 8: Myosin heads form crossbridges with actin.

QUESTION 3: Match the term in the left column to the blanks near their function on the right. Junctional folds terminal cistern tropomyosin T tubule troponin block(s) binding sites on actin. receive(s) stimulus from the motor neuron. conduct(s) action potentials throughout the interior of the muscle fiber. change(s) shape upon binding with calcium ions. release(s) calcium ions into the sarcoplasm.

Tropomyosin: block(s) binding sites on actin. Junctional folds: receive(s) stimulus from the motor neuron. T tubule: conduct(s) action potentials throughout the interior of the muscle fiber. Troponin: change(s) shape upon binding with calcium ions. Terminal cistern: release(s) calcium ions into the sarcoplasm.

QUESTION 3: Identify the regions of the sarcomere. Note that labels may be used more than once.

View image on question 13

The region of the sarcomere containing the thick filaments is the a. A band b. M line c. H band d. Z line e. I band

a. A band

QUESTION 2: Which of the following is/are mechanism(s) to end neural transmission at the neuromuscular junction? Select all the correct answers. a. ACh diffuses away from the synaptic cleft b. ACh is taken up by the axon terminal via endocytosis c. ACh is broken down into acetic acid and choline by the enzyme acetylcholinesterase (AChE) d. ACh binds to ACh receptors

a. ACh diffuses away from the synaptic cleft c. ACh is broken down into acetic acid and choline by the enzyme acetylcholinesterase (AChE)

The characteristic muscle stiffness associated with rigor mortis is due to the inability of myosin filaments to detach from the active site on actin filaments. What molecule is essential for this detachment? a. ATP b. calcium c. acetylcholine d. acetylcholinesterase

a. ATP

Which of the following statements about excitation-contraction coupling is incorrect? a. Calcium ions travel through the transverse tubule b. Troponin binds calcium ion and signals tropomyosin to move c. Tropomyosin moves to expose myosin binding sites on actin d. Relaxation requires uptake of calcium ion by the sarcoplasmic reticulum e. Calcium ion is released from the sarcoplasmic reticulum

a. Calcium ions travel through the transverse tubule

QUESTION 1: How is delayed-onset muscle soreness (DOMS) different from muscle fatigue? a. Delayed-onset muscle soreness occurs a day or more after the physical exertion b. Muscle performance is impaired c. There may be damage to the sarcolemma e. Delayed-onset muscle soreness involves pain

a. Delayed-onset muscle soreness occurs a day or more after the physical exertion

QUESTION 2: What structure most directly stimulates a skeletal muscle fiber to contract? a. Motor neuron b. Voltage-gated calcium channels c. Synaptic cleft d. Acetylcholinesterase

a. Motor neuron

Which of the following statements is true concerning motor units? a. Movement of the eyeball requires fewer muscle fibers with less tension being produced b. A motor unit consists of all the muscle fibers it controls as well as the area of the spinal cord where it originates c. Lesser tension is required in lifting a dumbbell than in lifting a cup of coffee d. An increased number of motor neurons is needed in precise movements such as lifting a cup of coffee than in lifting a dumbbell e. A small number of muscle fibers with increased tension is needed in large, gross movements

a. Movement of the eyeball requires fewer muscle fibers with less tension being produced

Identify the incorrect statement about a single motor unit. a. The more neurons involved, the more powerful the contraction b. Fine motor skills depend on the development of small motor units c. The smaller the number of muscle fibers, the more precise the movement d. Some motor units include as many as 2000 muscle fibers e. Muscle fibers of one motor unit intermingle with the fibers of another motor unit

a. The more neurons involved, the more powerful the contraction

QUESTION 2: Why do the disease tetanus and the normal sustained muscle contraction called tetanus share the same name? a. They both eliminate the relaxation phase in the affected muscle fibers b. They are both brought on by bacterial infections c. They both enable muscle fibers to reach near maximum tension d. All of the listed responses are correct.

a. They both eliminate the relaxation phase in the affected muscle fibers

Triggering of the muscle action potential occurs after a. acetylcholine binds to chemically-gated channels in the motor end plate b. the action potential jumps across the neuromuscular junction c. acetylcholinesterase is released from synaptic vesicles into the synaptic cleft d. calcium ion binds to channels on the motor end plate e. Any of these can produce an action potential in the muscle cell

a. acetylcholine binds to chemically-gated channels in the motor end plate

QUESTION 5: What causes the vesicles inside a neuron to fuse with the plasma membrane? a. an action potential in the neuron b. acetylcholine being broken down by acetylcholinesterase c. an action potential in the muscle fiber d. acetylcholine binding to acetylcholine receptors

a. an action potential in the neuron

A(n) ________ can be described as a broad tendinous sheet. a. aponeurosis b. interstitium c. fasciae e. retinaculum d. tympanum

a. aponeurosis

Active sites on the actin become available for binding after a. calcium binds to troponin b. calcium binds to tropomyosin c. actin binds to troponin d. myosin binds to troponin e. troponin binds to tropomyosin

a. calcium binds to troponin

Muscles that move the eyeball have ________ fibers. a. fast b. circular c. slow d. intermediate e. All of the answers are correct.

a. fast

Large-diameter, densely packed myofibrils, large glycogen reserves, and few mitochondria are characteristics of a. fast fibers b. fatty muscles c. red muscles d. intermediate fibers e. slow fibers.

a. fast fibers

QUESTION 2: Which of the following processes produces molecules of ATP and has two pyruvic acid molecules as end products? a. glycolysis b. Krebs cycle and oxidative phosphorylation c. hydrolysis of creatine phosphate

a. glycolysis

The type of contraction where the tension is less than the load is called a. isotonic eccentric contraction b. isometric eccentric contraction c. isometric contraction d. isotonic concentric contraction e. isometric concentric contraction.

a. isotonic eccentric contraction

What is the function of the structure indicated by the arrow? (question 37) a. making of energy (ATP); "power house" of the cell b. distribute action potentials throughout the interior of the skeletal muscle cell c. houses the genetic material (DNA) of the cell d. storage of calcium

a. making of energy (ATP); "power house" of the cell

When acetylcholine binds to receptors at the motor end plate, the sarcolemma becomes a. more permeable to sodium ions b. less permeable to potassium and sodium ions c. less permeable to sodium ions d. less permeable to potassium ions e. more permeable to calcium ions

a. more permeable to sodium ions

The advantage of having many nuclei in a skeletal muscle fiber is the ability to a. produce large amounts of muscle proteins b. contract much more forcefully c. produce nutrients for muscle contraction d. store extra DNA for metabolism e. produce more ATP with little oxygen

a. produce large amounts of muscle proteins

Since each myofibril is attached at either end of the muscle fiber, when sarcomeres shorten, the muscle fiber a. shortens b. strengthens c. weakens d. pulls from the middle e. lengthens

a. shortens

Which of the following best describes the term sarcoplasmic reticulum? a. storage and release site for calcium ions b. protein that accounts for elasticity of resting muscle c. repeating unit of striated myofibrils d. largely made of myosin molecules e. thin filaments are anchored here

a. storage and release site for calcium ions

What is the function of the structure indicated by the arrow? (question 34) a. storage of calcium b. houses the genetic material (DNA) of the cell c. distribute action potentials throughout the interior of the skeletal muscle cell d. making of energy (ATP); "power house" of the cell

a. storage of calcium

The narrow space between the synaptic terminal and the muscle fiber is the a. synaptic cleft b. motor end plate c. synaptic knob d. M line e. motor unit

a. synaptic cleft

In the sarcomere which elastic protein attaches the thick filament to the Z line? a. titin b. actin c. G actin d. nebulin e. myosin

a. titin

Each thin filament consists of a. two actin protein strands coiled helically around each other b. a rod-shaped structure with "heads" projecting from each end c. a double strand of myosin molecules d. chains of myosin molecules e. six molecules coiled into a helical structure

a. two actin protein strands coiled helically around each other

QUESTION 5: Which type of muscle fiber has a large quantity of glycogen and mainly uses glycolysis to synthesize ATP? a. white fast twitch fibers b. red slow twitch fibers

a. white fast twitch fibers

In a sarcomere, cross-bridge attachment occurs specifically in the a. zone of overlap b. H band c. A band d. M line e. I band

a. zone of overlap

The region of sarcomere where thin and thick filaments are located is called the a. zone of overlap b. Z line c. I band d. M line e. A band

a. zone of overlap

When a skeletal muscle fiber contracts, the a. zones of overlap get larger b. width of the A band increases c. H bands and I bands get larger d. Z lines move further apart e. All of the answers are correct

a. zones of overlap get larger

QUESTION 2: Which of the following events directly occurs due to an action potential generated on the motor neuron? Choose the best answer. a. ACh binds to ACh receptors b. ACh is released at the synapse.Na rushes into the sarcolemma c. AChE breaks down ACh in the synaptic cleft d. An action potential is generated on the muscle fiber.

b. ACh is released at the synapse.Na rushes into the sarcolemma

QUESTION 3: The post-synaptic reaction on the sarcolemma is short in duration. Which of the following explanations describes why the reaction of the sarcolemma is short in duration? Select all that are correct. a. Muscle tissue has a smaller membrane potential than nervous tissue b. AChE acts to breakdown the ACh in the synaptic cleft c. ACh diffuses across the synaptic cleft toward the sarcolemma d. ACh diffuses out of the synaptic cleft e. The ACh receptors respond only for a short period of time.

b. AChE acts to breakdown the ACh in the synaptic cleft d. ACh diffuses out of the synaptic cleft

QUESTION 1: What causes the release of calcium ions into the sarcoplasm from the terminal cisterns? (question 15) a. The change in the shape of troponin b. An action potential traveling along the t tubule c. The binding of myosin heads to actin d. Acetylcholine entering the sarcoplasm of the muscle fiber

b. An action potential traveling along the t tubule

How would the loss of acetylcholinesterase from the motor end plate affect skeletal muscle? a. It would make the muscles less excitable b. It would cause muscles to stay contracted c. It would produce muscle weakness d. It would cause muscles to stay relaxed e. It would have little effect on skeletal muscles

b. It would cause muscles to stay contracted

EGTA is a substance that binds calcium ions. Imagine an experimental setup with a motor neuron and a muscle fiber. Stimulation of the motor neuron causes contraction of the muscle fiber through activity at the neuromuscular junction and excitation-contraction coupling. Now, inject the muscle fiber with EGTA. Which of the following effects would EGTA have on excitation-contraction coupling after the neuron releases acetylcholine at the neuromuscular junction? a. It would prevent the junctional folds from triggering an action potential b. It would prevent myosin from forming cross bridges with actin c. It would prevent conduction of an action potential along the sarcolemma d. It would prevent the release of calcium ions from the terminal cisterns

b. It would prevent myosin from forming cross bridges with actin

QUESTION 1: Inadequate calcium in the neuromuscular junction would directly affect which of the following processes? (question 17) a. Breakdown of acetylcholine by acetylcholinesterase b. Release of acetylcholine from the synaptic vesicles c. Conduction of action potentials by the motor neuron d. Depolarization of the junctional folds

b. Release of acetylcholine from the synaptic vesicles

QUESTION 1: Which of the following statements is true? Choose the best answer. a. The acetylcholine (ACh) receptors are located on the myofibril b. The neurotransmitter is stored in the presynaptic motor neuron c. The sarcolemma is the presynaptic membrane d. Acetylcholinesterase (AChE) is stored in vesicles within the presynaptic motor neuron

b. The neurotransmitter is stored in the presynaptic motor neuron

The skeletal muscle complex known as the triad consists of a. A bands, H bands, and I bands b. a transverse tubule and two terminal cisternae c. actin, myosin, and titin filaments d. actin, myosin, and sarcomeres e. filaments, myofibrils, and sarcomeres

b. a transverse tubule and two terminal cisternae

In response to action potentials arriving along the transverse tubules, the sarcoplasmic reticulum releases a. sodium ions b. calcium ions c. potassium ions d. hydrogen ions e. acetylcholine

b. calcium ions

QUESTION 1: What is the type of chemical reaction used to rebuild ADP into ATP? a. hydrolysis b. dehydration synthesis c. rehydration synthesis

b. dehydration synthesis

What is the function of the structure indicated by the arrow? (question 36) a. making of energy (ATP); "power house" of the cell b. distribute action potentials throughout the interior of the skeletal muscle cell c. houses the genetic material (DNA) of the cell d. storage of calcium

b. distribute action potentials throughout the interior of the skeletal muscle cell

Muscle fibers differ from "typical cells" in that muscle fibers a. are very small b. have many nuclei c. lack mitochondria d. lack a plasma membrane e. have large gaps in the cell membrane

b. have many nuclei

A muscle producing almost peak tension during rapid cycles of contraction and relaxation is said to be in a. recruitment b. incomplete tetanus c. wave summation d. treppe e. complete tetanus

b. incomplete tetanus

Muscle fatigue occurs because of a buildup of __________ and a(n) __________ in pH. a. creatine phosphate; increase b. lactic acid; decrease c. creatine phosphate; decrease d. lactic acid; increase

b. lactic acid; decrease

QUESTION 1: Bacteria that cause tetanus release a neurotoxin. Which of the following components of the neuromuscular junction (NMJ) does this neurotoxin affect directly? a. sarcolemma b. motor neurons c. epimysium d. myofilaments

b. motor neurons

Each skeletal muscle fiber is controlled by a motor neuron at a single a. sarcomere b. neuromuscular junction c. synaptic cleft d. transverse tubule e. synaptic knob

b. neuromuscular junction

Communication between axons and muscle fibers occurs at specialized synapses called a. nervous units b. neuromuscular junctions c. synaptic terminals d. motor end plates e. motor units.

b. neuromuscular junctions

QUESTION 6: Acetylcholine receptors are primarily located __________. a. inside the muscle fiber b. on the motor end plate c. inside vesicles d. on the synaptic terminal

b. on the motor end plate

QUESTION 8: The role of acetylcholinesterase in the neuromuscular junction is to __________. a. increase the sodium permeability of the motor end plate b. remove acetylcholine from the synaptic cleft c. generate a muscle action potential d. release acetylcholine from the synaptic terminal

b. remove acetylcholine from the synaptic cleft

After death, muscle fibers run out of ATP and calcium begins to leak from the sarcoplasmic reticulum into the sarcoplasm. This results in a condition known as a. tetany b. rigor mortis c. depolarization d. treppe e. oxygen debt

b. rigor mortis

The plasma membrane of a skeletal muscle fiber is called the a. sarcoplasm b. sarcolemma c. sarcoplasmic reticulum d. sarcomere e. sarcosome

b. sarcolemma

The repeating unit of a skeletal muscle fiber is the a. myofibril b. sarcomere c. myofilament d. sarcolemma e. sarcoplasmic reticulum

b. sarcomere

At each end of the muscle, the collagen fibers of the epimysium, perimysium, and endomysium, come together to form a a. ligament b. tendon c. tenosynovium d. sheath e. satellite cell

b. tendon

Which of the following statements correctly describes the structure (band or line) of the sarcomere indicated by the arrow? (question 41) a. the point of connection for adjacent thick filaments b. the region of the sarcomere that contains only thin filaments c. the region of the resting sarcomere that only contains thick filaments d. the boundary between adjacent sarcomeres

b. the region of the sarcomere that contains only thin filaments

All of the following proteins are part of the thin filaments except a. tropomyosin b. titin c. actin d. troponin e. None of the answers is correct; there are no exceptions

b. titin

At rest, the tropomyosin molecule is held in place by a. actin molecules b. troponin molecules c. myosin molecules d. calcium ions e. ATP molecules

b. troponin molecules

QUESTION 1: Tamara's muscle weakness and fatigue becomes progressively worse over the course of the day. This is a hallmark sign of myasthenia gravis, an autoimmune disorder that affects the ability of a motor neuron to communicate with a muscle fiber. What synaptic events must happen first for excitation to occur? a. The action potential travels down the T tubules in the sarcolemma and triggers the release of calcium ions from the sarcoplasmic reticulum b. Calcium binds to tropomyosin, shifting it from the active site on actin, allowing cross-bridge formation to occur as myosin binds to the active site c. Acetylcholine is released from the axon terminal and diffuses across the synapse to bind to a receptor in the surface of the motor end plate d. Sodium ions from the extracellular fluid diffuse into the cytosol of the muscle fiber, triggering the generation of an action potential in the sarcolemma

c. Acetylcholine is released from the axon terminal and diffuses across the synapse to bind to a receptor in the surface of the motor end plate

QUESTION 3: The injection that dramatically improved Tamara's symptoms was Tensilon, an acetylcholinesterase inhibitor. What is acetylcholinesterase, and why was this injection effective in relieving Tamara's symptoms? a. Acetylcholinesterase is an enzyme that degrades the ACh receptors. When acetylcholinesterase is inhibited, there are more receptors available for acetylcholine to bind, and muscle function improves b. Acetylcholinesterase is an acetylcholine antagonist that binds to motor end plate receptors and decreases the permeability of the sarcolemma to sodium. Inhibiting acetylcholinesterase increases the influx of sodium, leading to the generation of action potentials and an improvement in muscle function c. Acetylcholinesterase is the enzyme that clears acetylcholine from the synapse. Inhibiting this enzyme will enable acetylcholine to be available for a longer period to bind to receptors d. Acetylcholinesterase is a regulatory enzyme that inhibits the ACh receptors on the motor end plate. Inhibiting acetylcholinesterase improves muscle function because the ACh receptors are temporarily more active

c. Acetylcholinesterase is the enzyme that clears acetylcholine from the synapse. Inhibiting this enzyme will enable acetylcholine to be available for a longer period to bind to receptors

Which of the following is a way that muscle fibers get energy needed for contraction? a. Aerobic exercise is beneficial to a muscle because it increases the muscle's ability to acquire greater amounts of glucose from the blood for ATP production b. During moderate exercise, such as jogging on the treadmill, pyruvate and hydrogen ions accumulate causing muscle fatigue c. During peak activity levels, glycolysis is the only pathway by which ATP can be produced to supply energy to the muscle d. When a muscle is contracting during peak activity, it quickly uses up stored creatine phosphate which was produced during moderate exercise. e. Because energy demands are low in a resting muscle, a resting muscle is able to meet its ATP requirement through glycolysis

c. During peak activity levels, glycolysis is the only pathway by which ATP can be produced to supply energy to the muscle

QUESTION 2: Myasthenia gravis is an autoimmune disorder that results in the production of antibodies that either block or cause the destruction of the ACh receptor. Why do you think that Tamara's symptoms become worse as the day progresses? a. In myasthenia gravis the ACh receptors have a hyperaffinity to acetylcholine. After muscle activity, fatigue and weakness occur as fewer unbound receptors are available to bind acetylcholine b. In the morning, the reserves of ATP are larger, allowing for sufficient acetylcholine release to overcome the unresponsive receptors. However, as the day progresses and stores of ATP become depleted, muscle function becomes progressively worse c. In the morning, the neuronal reserves of acetylcholine are larger, allowing for sufficient neurotransmitter release and resulting in effective muscle signaling. As the day progresses and the stores of acetylcholine become depleted, muscle function becomes progressively worse. d. As the muscle becomes fatigued over the course of the day's activities, the receptors bind less acetylcholine, which results in smaller and smaller action potentials being generated. Smaller action potentials mean weaker contractions, as seen by the increasing muscle weakness.

c. In the morning, the neuronal reserves of acetylcholine are larger, allowing for sufficient neurotransmitter release and resulting in effective muscle signaling. As the day progresses and the stores of acetylcholine become depleted, muscle function becomes progressively worse.

QUESTION 3: Which of the following processes produces 36 ATP? a. hydrolysis of creatine phosphate b. glycolysis c. Krebs cycle and oxidative phosphorylation

c. Krebs cycle and oxidative phosphorylation

Myasthenia gravis is a disease resulting from an autoimmune attack on the ACh receptors of the motor end plate. Binding of antibodies to the ACh receptors results in generalized muscle weakness that progresses as more ACh receptors are destroyed. Which of the following medications would help alleviate the muscle weakness? a. a drug that blocks the release of acetylcholine (botulinum toxin) b. a drug that binds to the acetylcholine receptor and prevents it from opening (curare) c. a drug that binds to and inactivates acetylcholinesterase (neostigmine) d. a drug that prevents acetylcholine from being loaded into synaptic vesicles (vesamicol)

c. a drug that binds to and inactivates acetylcholinesterase (neostigmine)

The cytoplasm of the neuromuscular terminal contains vesicles filled with molecules of the neurotransmitter a. adrenaline b. antidiuretic hormone c. acetylcholine d. norepinephrine e. epinephrine

c. acetylcholine

Muscle tissue, one of the four basic tissue groups, consists chiefly of cells that are highly specialized for a. conduction b. cushioning c. contraction d. secretion e. peristalsis

c. contraction

At what point during excitation contraction coupling does exocytosis play a role? a. when ATP splits into ADP and P on the free myosin head b. during calcium ion reuptake into the sarcoplasmic reticulum c. during acetylcholine release from the synaptic terminal d. when sodium channels open up on the motor end plate e. when the action potential surges through the T-tubules

c. during acetylcholine release from the synaptic terminal

The sequence of processes that links the action potential to contraction is called a. cross bridge formation. b. neuromuscular junction c. excitation-contraction coupling d. action potential propagation e. sliding filament theory

c. excitation-contraction coupling

A fascicle is a a. layer of connective tissue that separates muscle from skin b. collection of myofibrils in a muscle fiber c. group of muscle fibers that are encased in the perimysium d. group of muscle fibers and motor neurons e. group of muscle fibers that are all part of the same motor unit

c. group of muscle fibers that are encased in the perimysium

What is the function of the structure indicated by the arrow? (question 35) a. making of energy (ATP); "power house" of the cell b. part of coupling the action potential to contraction c. houses the genetic material (DNA) of the cell d. storage of calcium

c. houses the genetic material (DNA) of the cell

Which of the following is not an effect of aging on the muscular system? a. smaller muscle fibers b. decreased recovery from muscle injuries c. hypertrophy d. exercise tolerance decreases e. muscles become less elastic

c. hypertrophy

Heat energy gained from muscle contraction is released by the ________ system. a. respiratory b. cardiovascular c. integumentary d. urinary e. endocrine

c. integumentary

The type of contraction where the tension exceeds the load is called a. isometric concentric contraction b. isometric contraction c. isotonic concentric contraction d. isometric eccentric contraction e. isotonic eccentric contraction.

c. isotonic concentric contraction

In an isotonic contraction, a. postural muscles stabilize the vertebrae b. the peak tension is less than the load c. muscle tension exceeds the load and the muscle lifts the load d. many twitches always fuse into one e. tension rises and falls but the muscle length is constant.

c. muscle tension exceeds the load and the muscle lifts the load

In which of the following would the motor units have the fewest muscle fibers? a. postural muscles of the back b. muscles of the neck c. muscles that control the eyes d. thigh muscles e. calf muscles

c. muscles that control the eyes

A patient takes a medication that blocks ACh receptors of skeletal muscle fibers. What is this drug's effect on skeletal muscle contraction? a. increases tone in the muscle b. produces a strong, continuous state of contraction c. reduces the muscle's ability for contraction d. causes a strong contraction similar to a "charlie horse" cramp e. increases the muscle's excitability

c. reduces the muscle's ability for contraction

The type of muscle fiber that is most resistant to fatigue is the ________ fiber. a. intermediate b. fast c. slow d. high-density e. anaerobic

c. slow

Which of the following types of muscle fibers are best adapted for prolonged contraction such as standing all day? a.intermediate fibers b. uninucleated fibers c. slow fibers d. striated fibers e. fast fibers

c. slow fibers

Which of the following hormones directly stimulates growth of muscle tissue, leading to increased muscle mass? a. epinephrine b. thyroid hormone c. testosterone d. parathyroid hormone e. calcitonin

c. testosterone

Which of the following statements correctly describes the structure (band or line) of the sarcomere indicated by the arrow? (question 39) a. the region of the resting sarcomere that only contains thick filaments b. the point of connection for adjacent thick filaments c. the boundary between adjacent sarcomeres d. the region of the sarcomere that contains only thin filaments

c. the boundary between adjacent sarcomeres

QUESTION 7: 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. the muscle fiber to contract d. acetylcholinesterase to break down acetylcholine

c. the muscle fiber to contract

Which of the following statements correctly describes the structure (band or line) of the sarcomere indicated by the arrow? (question 40) a. the region of the sarcomere that contains only thin filaments b. the region of the resting sarcomere that only contains thick filaments c. the point of connection for adjacent tails of the thick filaments d. the boundary between adjacent sarcomeres

c. the point of connection for adjacent tails of the thick filaments

At rest, active sites on the actin are blocked by a. ATP molecules b. calcium ions c. tropomyosin molecules d. myosin molecules e. troponin molecules

c. tropomyosin molecules

The rapid rise and fall in force produced by a muscle fiber after a single action potential is a(n) a. unfused tetanus b. muscle action potential c. twitch d. tetanus e. motor end plate potential

c. twitch

What can the nervous system do to increase muscle tension? a. increase stimulation frequency b. increase the number of active motor units c. recruit larger motor units d. All of the listed responses can increase muscle tension

d. All of the listed responses can increase muscle tension

QUESTION 1: The cross bridge cycle starts when _________. Select the best answer. a. Ca2+ is actively transported into the sarcoplasmic reticulum b. Ca2+ from the sarcoplasmic reticulum binds to tropomyosin c. acetylcholine diffuses away from the synaptic cleft d. Ca2+ from the sarcoplasmic reticulum binds to troponin e. ATP binds to troponin and is hydrolyzed to ADP and Pi

d. Ca2+ from the sarcoplasmic reticulum binds to troponin

QUESTION 1: Which of the following is responsible for muscle relaxation? a. ATP binds to the myosin head to cause cross bridge detachment. b. Calcium ions are released from the terminal cisterns during depolarization of the T tubule c. Sodium ions enter into the sarcoplasm through voltage-gated channels d. Calcium ions are removed from the sarcoplasm by active transport

d. Calcium ions are removed from the sarcoplasm by active transport.

QUESTION 2: Which of the following is NOT a role of ATP in muscle contraction? a. Transporting calcium ions into the sarcoplasmic reticulum b. Energizing the power stroke of the cross bridge c. Detaching the cross bridge from actin d. Exposing myosin binding sites on actin

d. Exposing myosin binding sites on actin

QUESTION 4: The "rest and recovery" period, where the muscle restores depleted reserves, includes all of the following processes EXCEPT __________. a. Oxygen rebinds to myoglobin b. Glycogen is synthesized from glucose molecules c. ATP is used to rephosphorylate creatine into creatine phosphate d. Pyruvic acid is converted back to lactic acid

d. Pyruvic acid is converted back to lactic acid

Which of the following is important to increasing efficiency in tension production? a. increasing calcium reclamation b. lengthening the zone of overlap c. increasing the latent period d. a shortened relaxation phase

d. a shortened relaxation phase

Which of the following situations could contribute to prolonged muscle contraction? a. limited availability of calcium ions b. infrequent neural stimulus c. cross-bridge formation being reduced d. acetylcholinesterase not being produced

d. acetylcholinesterase not being produced

The most important factor in decreasing the intracellular concentration of calcium ion after contraction is a. active transport of calcium into the synaptic cleft b. diffusion of calcium into the sarcoplasmic reticulum c. active transport of calcium across the sarcolemma d. active transport of calcium into the sarcoplasmic reticulum e.diffusion of calcium out of the cell

d. active transport of calcium into the sarcoplasmic reticulum

Creatine phosphate a. is only formed during strenuous exercise b. can replace ATP in binding to myosin molecules during contraction c. cannot transfer its phosphate group to ADP d. acts as an energy reserve in muscle tissue e. is produced by the process of anaerobic respiration.

d. acts as an energy reserve in muscle tissue

The role of acetylcholinesterase is to a. bind to ligand gated sodium channels b. activate acetylcholine c. release acetylcholine into the synaptic cleft d. break down acetylcholine into acetate and choline components e transport acetylcholine across the synaptic cleft

d. break down acetylcholine into acetate and choline components

The point in a muscle twitch when the troponin is bound to calcium is called the a. isotonic period b. stimulus phase c. relaxation phase d. contraction phase e. latent period

d. contraction phase

What area of the thick filament binds to actin once actin's binding sites are exposed? (question 65) a. hinge b. tropomyosin c. troponinmyosin d. cross-bridge (head)

d. cross-bridge (head)

Physical evidence that supports the sliding filament theory of muscle contraction includes a. the I band + H band distance is constant during contraction b. increased width of the I band during contraction c. decreased width of the A band during contraction d. decreased width of the H band during contraction e. constant distance between Z lines during contraction

d. decreased width of the H band during contraction

QUESTION 2: Conduction of an action potential along the sarcolemma depends upon ___________. a. shifting tropomyosin to uncover myosin binding sites b. binding of acetylcholine to chemically gated channels c. release of calcium ions from the terminal cisterns d. diffusion of sodium ions through voltage-gated channels

d. diffusion of sodium ions through voltage-gated channels

Nerves and blood vessels that service a muscle fiber are located in the connective tissues of its a. myofibrils b. sarcomere c. perimysium d. endomysium e. sarcolemma

d. endomysium

QUESTION 2: Activities involving eccentric contractions more commonly lead to delayed-onset muscle soreness than concentric or isometric contractions. Which of the following activities is thus a candidate for delayed-onset muscle soreness? a. pushing against the wall in the gym b. flexion of the biceps brachii c. carrying a bowling ball d. extension of the biceps brachii

d. extension of the biceps brachii

Fast fibers a. have low resistance to fatigue b. have many mitochondria c. rely on aerobic metabolism d. have low resistance to fatigue and quick twitches e. have twitches with a very brief contraction phase.

d. have low resistance to fatigue and quick twitches

A weight-lifter strains to lift a heavy weight and there is no movement of the person's arms holding on to the weight. This type of contraction is called a(n) ________ contraction. a. isotonic b. tetanus c. concentric d. isometric e. treppe

d. isometric

A single motor neuron together with all the muscle fibers it innervates is called a(n) a. end plate b. end foot c. dermatome d. motor unit e. myotome

d. motor unit

Interactions between actin and myosin filaments of the sarcomere are responsible for a. the striped appearance of skeletal muscle b. the conduction of neural stimulation to the muscle fiber c. muscle relaxation d. muscle contraction e. muscle fatigue.

d. muscle contraction

QUESTION 1: The neuromuscular junction is a connection between a neuron and a __________. a. vesicle b. synaptic terminal c. myofibril d. muscle fiber

d. muscle fiber

During the recovery period following exercise, all of the following are true except a. heat is generated b. lactic acid is removed from muscle cells c. oxygen is consumed at above the resting rate d. muscle fibers are unable to contract e. the muscle actively produces ATP

d. muscle fibers are unable to contract

The increase in muscle tension that is produced by increasing the number of active motor units is called a. treppe b. complete tetanus c. wave summation d. recruitment e. incomplete tetanus.

d. recruitment

Question 2 The end of a neuron, where acetylcholine-filled vesicles are located, is called the __________. a. acetylcholine receptor b. motor end plate c. synaptic cleft d. synaptic terminal

d. synaptic terminal

Which of the following statements correctly describes the structure (band or line) of the sarcomere indicated by the arrow? (question 38) a. the boundary between adjacent sarcomeres b. the region of the sarcomere that contains only thin filaments c. the point of connection for adjacent thick filaments d. the region of the resting sarcomere that only contains thick filaments

d. the region of the resting sarcomere that only contains thick filaments

QUESTION 3: What is the synaptic cleft? a. the region of the neuron containing synaptic vesicles b. the border between the motor end plate and the sarcolemma c. the step where acetylcholinesterase (AChE) breaks down, or cleaves, acetylcholine d. the space between the synaptic terminal and the motor end plate

d. the space between the synaptic terminal and the motor end plate

Which of the following best describes the term Z line? a. storage site for calcium ions b. largely made of myosin molecules c. repeating unit of striated myofibrils d. thin filaments are anchored here e. protein that accounts for elasticity of resting muscle

d. thin filaments are anchored here

When calcium ion binds to troponin, a. actin heads will bind to myosin b. myosin shortens c. muscle relaxation occurs d. tropomyosin rolls away from the active site e. active sites on the myosin are exposed

d. tropomyosin rolls away from the active site

QUESTION 4: Inside a neuron, acetylcholine is contained within __________. a. the motor end plate b. the synaptic cleft c. acetylcholine receptors d. vesicles

d. vesicles

If a second stimulus arrives before the relaxation phase has ended, a second, more powerful contraction occurs. This addition of one twitch to another is called a. complete tetanus b. incomplete tetanus c. treppe d. wave summation e. recruitment

d. wave summation

Cross bridge detachment is caused by ________ binding to the myosin head. a. acetylcholine b. calcium c. acetylcholinesterase d. magnesium e. ATP

e. ATP

During anaerobic glycolysis, a. carbohydrate is metabolized b. ATP is produced c. oxygen is not consumed d. pyruvic acid is produced e. All of the answers are correct

e. All of the answers are correct

A resting muscle generates most of its ATP by a. hydrolysis of creatine phosphate b. glycogenolysis c. anaerobic respiration d. the tricarboxylic acid cycle e. aerobic metabolism of fatty acids

e. aerobic metabolism of fatty acids

Which of the following is a recognized function of skeletal muscle? a. guard body entrances and exits b. produce movement c. maintain body temperature d. maintain posture e. all of these are correct

e. all of these are correct

When a muscle is stimulated repeatedly at a high rate, the amount of tension gradually increases to a steady maximum tension. This state of maximum tension is called a. recruitment b. incomplete tetanus c. wave summation d. a twitch e. complete tetanus

e. complete tetanus

The dense layer of connective tissue that surrounds an entire skeletal muscle is the a. endomysium b. perimysium c. tendon d. fascicle e. epimysium

e. epimysium

Which of the following allows muscles to return to their original shape during relaxation? a. elastic forces b. opposing muscle contractions c. gravity d. myosin binding e. gravity, opposing muscle contractions, and elastic forces

e. gravity, opposing muscle contractions, and elastic forces

The type of contraction in which the muscle fibers do not shorten is called a. isotonic b. tetany c. concentric d. treppe e. isometric

e. isometric

During the time when the action potential moves through the sarcolemma a muscle twitch is in a. contraction phase b. stimulus phase c. relaxation phase d. isotonic period e. latent period

e. latent period

You try to pick up an object and discover that it is much heavier than you expected. Which process must occur in the muscle to increase tension so you can pick up the object? a. treppe b. isotonic contraction c. complete tetanus d. wave summation e. recruitment

e. recruitment

The structural theory that explains how a muscle fiber contracts is called the ________ theory. a. action-myosin interaction b. neuromuscular c. muscle contraction d. excitation-contraction coupling e. sliding filament

e. sliding filament

The bundle of collagen fibers at the end of a skeletal muscle that attaches the muscle to bone is called a(n) a. fascicle b. epimysium c. ligament d. myofibril e. tendon

e. tendon

Which of the following become connected by myosin cross-bridges during muscle contraction? a. thick filaments and titin filaments b. thick filaments and t-tubules c. thin filaments and t-tubule d. z disks and actin filaments e. thin filaments and thick filaments

e. thin filaments and thick filaments

Action potentials at the sarcolemma are conducted into the inside of a skeletal muscle fiber by a. sarcoplasmic reticulum b. triads c. motor end plates d. neuromuscular junctions e. transverse tubules

e. transverse tubules.

Drag the labels onto the diagram to identify the four different types of effects of repeated stimulation on a skeletal muscle. (question 19)

treppe wave summation incomplete tetanus complete tetanus

Rigor mortis refers to the changes in muscle tissue that occur after death. The muscles become very stiff or rigid and are frozen in a contracted state. Rigor mortis usually sets in within four hours, first in the face and generally smaller muscles. The body reaches maximum stiffness in twelve to forty-eight hours. However, this time may vary due to environmental conditions, with cooler conditions inhibiting rigor mortis. Which of the following images would depict the state of the cross bridge cycle during rigor mortis?

view image in question 14