Chapter 10 Muscular Tissue

Identify the four steps of the contraction cycle in order of occurrence. What is needed for these steps to continuously repeat?

(10.3 Model Answer) 1. ATP hydrolysis, 2. Attachment of myosin to actin forming crossbridges, 3. The power stroke, then 4. Detachment of myosin from actin. The cycle will continue as long as ATP and calcium ions are available.

How does a nerve impulse elicit a muscle action potential?

(10.3 Model Answer) A nerve impulse reaches the synaptic end bulb and causes the release of acetylcholine, which diffuses across the synaptic cleft and binds to and activates acetylcholine receptors on the motor end plate. Binding of acetylcholine opens an ion channel in the acetylcholine receptors allowing Na+ to flow into the cell, which generates an action potential in the muscle cell.

What are the three ways that ATP can be produced in muscle fibers?

(10.4 Model Answer) ATP can be produced: 1. from creatine phosphate, 2. by anaerobic cellular respiration, 3. and by aerobic cellular respiration.

Which of the following is a characteristic of both cardiac and smooth muscle, but not skeletal muscle? A. involuntary B. well developed sarcoplasmic reticulum C. autorhymicity D. myosin and actin E. calmodulin F. striated

A. involuntary

Which of the following is NOT required for muscles to contract and relax? A. calcium ions B. potassium ions C. ATP D. ACh

B. potassium ions

Place the muscle tissue type in order from least to most ability to regenerate. A. cardiac, skeletal, smooth B. skeletal, cardiac, smooth C. cardiac, smooth, skeletal D. skeletal, smooth, cardiac E. smooth, skeletal, cardiac

B. skeletal, cardiac, smooth

Which term describes a somatic motor neuron and all the skeletal muscle fibers it stimulates? A. reflex arc B. synapse C. neuromuscular junction D. motor unit E. motor end plate

D. motor unit

Compare and contrast the structural characteristics of the three different types of muscular tissue.

(10.1 Model Answer) Both cardiac and skeletal muscle tissues are striated and smooth muscle is not, hence its name. Skeletal muscle cells have more than one nucleus, are large and run parallel to each other. Cardiac muscle cells usually have only one, sometimes two, centrally located nuclei and are branched. They also are connected to each other via gap junctions. Smooth muscle cells are small but form thick layers of hollow organs. Like cardiac muscle cells, some smooth muscle cells communicate via gap junctions. Skeletal muscle is voluntarily controlled while both cardiac and smooth muscle tissue are involuntary and autorhythmic.

In embryonic muscle development, what happens to the somites?

(10.1 Model Answer) Somite cells differentiate into myotome, dermatome, and sclerotome.

After the fusion of myoblasts, the muscle fiber loses its ability to __?__. A. relax B. undergo mitosis C. grow D. contract E. lengthen

B. undergo mitosis

Describe the factors that lead to muscle fatigue.

(10.4 Model Answer) Although the precise mechanisms that cause muscle fatigue are still not clear, several factors are thought to contribute. One is inadequate release of calcium ions from the SR, resulting in a decline of Ca2+ concentration in the sarcoplasm. Depletion of creatine phosphate also is associated with fatigue, but surprisingly, the ATP levels in fatigued muscle often are not much lower than those in resting muscle. Other factors that contribute to muscle fatigue include insufficient oxygen, depletion of glycogen and other nutrients, buildup of lactic acid and ADP, and failure of action potentials in the motor neuron to release enough acetylcholine.

Diltiazem is a calcium channel blocker that reduces free intracellular calcium. Assuming diltiazem affected skeletal muscle, use the myogram shown in your answer to explain what stage of the myogram would be affected immediately. Include in your explanation a brief summary of what is occurring with calcium in each of the three periods shown (and name these periods).

(10.5 Model Answer) Note that a brief delay occurs between application of the stimulus (time zero on the graph) and the beginning of contraction. The delay, which lasts about 2 msec, is termed the latent period. During the latent period, the muscle action potential sweeps over the sarcolemma and calcium ions are released from the sarcoplasmic reticulum. The second phase, the contraction period, lasts 10-100 msec. During this time, Ca2+ binds to troponin, myosin‐binding sites on actin are exposed, and cross‐bridges form. Peak tension develops in the muscle fiber. During the third phase, the relaxation period, also lasting 10-100 msec, Ca2+ is actively transported back into the sarcoplasmic reticulum, myosin‐binding sites are covered by tropomyosin, myosin heads detach from actin, and tension in the muscle fiber decreases. The actual duration of these periods depends on the type of skeletal muscle fiber.

What is the major difference between the two types of smooth muscle tissue?

(10.9 Model Answer) In single-unit smooth muscle tissue, action potentials are initiated in response to neurotransmitters, hormones, or an autorhythmic signal. The action potential spreads throughout the tissue by moving through gap junctions that connect all the muscle cells together within the tissue. It is found in the skin and in tubular arrangements that form part of the walls of small arteries and veins and of hollow organs such as the stomach, intestines, uterus, and urinary bladder. In multi-unit smooth muscle tissue, muscle cells have few gap junctions with neighboring cells and thus must be excited by their own motor neuron terminal. It is found in the walls of large arteries, in airways to the lungs, in the arrector pili muscles that attach to hair follicles, in the muscles of the iris that adjust pupil diameter, and in the ciliary body that adjusts focus of the lens in the eye.

Discuss the steps involved in contraction of smooth muscle and explain why smooth muscle has a slower contraction cycle.

(10.9 Model Answer) Upon neural stimulation of the muscle, Ca2+ stored in the caveolae start to flow into the cell. Calmodulin, the regulatory protein in smooth muscles, will bind with the Ca++ which will activate the enzyme myosin light chain kinase (MLCK). This enzyme will use ATP to add a phosphate to the myosin head so that it can bind to actin so that the contraction can occur. The sliding of the actin and myosin is similar to the skeletal muscle. The slowness of the process is due to slow influx of Ca++ from caveolae into the cells (smooth muscles have a poor SR system, therefore, there is very little intercellular Ca++ storage). Also, the enzyme MLCK works very slowly which in turn causes the muscle to contract slowly.

Where would you expect to find calcium ions stored, based on this diagram? A. A B. B C. C D. D E. E F. F G. G

A. A

Which regions of the sarcomere contain thick filaments? A. A and I bands, H zone B. M line C. M line and Z disc D. A and I bands E. H zone and Z disc

A. A and I bands, H zone

On the diagram, a tendon is formed by the merging of which structures? A. C, D and E B. G and H C. B D. E, G and H E. B and C

A. C, D and E

After prolonged strenuous exercise has stopped, heavy breathing will often continue for several minutes in order to provide the oxygen needed to __?__. A. all of these are reasons for prolonged heavy breathing following exercise B. resynthesize creatine phosphate C. replace oxygen displaced from muscle myoglobin D. convert excess lactic acid produced during exercise back into glycogen

A. all of these are reasons for prolonged heavy breathing following exercise

Which means of ATP production would enable you to run in place for one minute? A. anaerobic cellular respiration (glycolysis) B. glycogen granules C. the Kreb's (citric acid) cycle D. stored creatine phosphate E. aerobic cellular respiration (electron transport)

A. anaerobic cellular respiration (glycolysis)

If ATP, or another energy source is available, contraction of myofibrils within a muscle fiber begins when __?__. A. calcium is released from the sarcoplasmic reticulum B. an action potential travels into the t-tubules C. sodium enters the muscle fiber D. calcium is moved into the sarcoplasmic reticulum E. acetylcholine binds to ligand gates

A. calcium is released from the sarcoplasmic reticulum

Which type of muscle tissue contracts when excited by their own autorhythmic muscle fibers? A. cardiac muscle B. multi-unit smooth muscle C. slow twitch oxidative skeletal muscle D. fast twitch glycolytic skeletal muscle E. fast twitch oxidative skeletal muscle

A. cardiac muscle

The relaxation phase of a muscle contraction is often prolonged in a fatigued muscle, raising the likelihood of fused summation of action potentials causing painful disturbances to a skeletal muscle. What disturbance is being described? A. cramps B. tremor C. fibrillation D. fasciculation E. paralysis

A. cramps

The outermost layer of connective tissue surrounding a skeletal muscle is the ___?___. A. epimysium B. perimysium C. tendon D. peritoneum E. endomysium

A. epimysium

Which age group would be most likely to experience an increase in slow oxidative (SO) muscle fibers? A. older adult (30+ years old) B. pre-teen (9-12 years old) C. females post-puberty D. teenager (13-19 years old) E. young adult (20-39 years old)

A. older adult (30+ years old)

Which of the following is a characteristic solely of skeletal muscle? A. well developed sarcoplasmic reticulum B. striated C. myosin and actin D. autorhymicity E. involuntary F. calmodulin

A. well developed sarcoplasmic reticulum

Which of the following energizes the myosin head in preparation for crossbridge formation? A. calcium ion release from the sarcoplasmic reticulum B. ATP hydrolysis C. ADP synthesis D. voltage gated calcium channels opening E. acetylcholine binding the nicotinic receptor

B. ATP hydrolysis

Which structure represents where you would find tropomyosin and troponin? A. A B. B C. C D. D E. E

B. B

On the diagram, which layer is composed of loose areolar connective tissue and surrounds a muscle cell? A. A B. E C. C D. D E. B

B. E

When a skeletal muscle cell contracts, the thin filaments of the sarcomere are pulled towards the __?__. A. A band B. M line C. H zone D. I band E. Z disc

B. M line

A brief contraction of all muscle fibers in a motor unit in response to a single action potential moving down the somatic motor neuron is known as __?__. A. wave summation B. a twitch contraction C. unfused tetanus D. fused tetanus E. the refractory period

B. a twitch contraction

Which protein is used to reinforce the sarcolemma and help transmit the tension generated by the sacromeres to the tendons? A. tropomyosin B. dystrophin C. actin D. myosin E. troponin

B. dystrophin

Muscle damage can be indicated by __?__. A. finding a low concentration of creatine kinase in the sarcoplasm B. finding myoglobin in the blood C. a high amount of glycogen in the sarcoplasm D. having few mitochondria in the muscle fibers E. finding slow myosin ATPase in the muscles

B. finding myoglobin in the blood

Strength training would result in __?__. A. conversion of fast oxidative-glycolytic (FOG) to fast glycolytic (FG) fibers B. hypertrophy of fast glycolytic (FG) fibers C. hypertrophy of slow oxidative (SO) fibers D. hyperplasia of fast glycolytic (FG) fibers E. conversion of fast glycolytic (FG) to slow oxidative (SO) fibers

B. hypertrophy of fast glycolytic (FG) fibers

Myasthenia Gravis is an autoimmune disorder that targets the ACh receptors at the NMJ and ultimately reduces the number of available receptors. Predict what happens if you treat the patient with a drug that inhibits the activity of acetylcholinesterase such as pyridostigmine (Mestinon)? The drug will __?__. A. cause muscle spasm B. increase contraction C. cause weak contraction D. delay contraction E. prevent contraction

B. increase contraction

Which microscopic structure is found only in the cardiac muscle tissue? A. tropomyosin B. intercalated discs C. sarcomeres D. myosin thick fibers E. striations

B. intercalated discs

Which disorder is a result of little to no structural support proteins in the sarcolemma? A. muscular hypertrophy B. muscular dystrophy C. fibromyalgia D. muscular atrophy E. myasthenia gravis

B. muscular dystrophy

Which characteristics describe both skeletal and cardiac muscle? A. cell shape B. striations C. autonomic control D. autorhymicity E. somatic control

B. striations

Mitochondial activity in skeletal muscle cells is matched fairly well to your fitness level. Which variable is universal and will limit their ability to produce ATP? A. there is an accumulation of pyruvic acid B. there is limited O2 availability C. CO2 is produced as a waste product D. there is a lack of cytosolic calcium E. there is limited CO2 availability

B. there is limited O2 availability

In skeletal muscles, the combined amounts of creatine phosphate and ATP provide enough energy for the muscle to contract maximally for approximately __?__. A. one hour B. 15 minutes C. 15 seconds D. one minute E. indefinitely

C. 15 seconds

Which structure contains motor proteins that convert the energy in ATP into mechanical movements? A. A B. B C. C D. D E. E

C. C

Leg muscles are predominantly composed of which type of muscle fiber? A. Fast oxidative (FO) fibers B. Slow oxidative-glycolytic (SOG) fibers C. Fast oxidative-glycolytic (FOG) fibers D. Fast glycolytic (FG) fibers E. Slow oxidative (SO) fibers

C. Fast oxidative-glycolytic (FOG) fibers

In the diagram, what is the name for the area identified by "D"? A. I band B. H zone C. M line D. Z disc E. A band

C. M line

Which of the following events is NOT required for crossbridge formation? A. myosin binding sites on actin must be exposed B. troponin must bind to calcium C. breakdown of acetylcholine by acetylcholinesterase D. calcium ions must be present in the sarcoplasm E. ATPase breaks down ATP

C. breakdown of acetylcholine by acetylcholinesterase

When an athlete performs a chin up (raising their chin to a bar while their body hangs), the process of pulling the body up so the chin can touch the bar is a(n) ___?__ contraction. A. geometric B. really hard C. concentric D. isometric E. eccentric

C. concentric

Myofibrils contain which proteins? A. contractile proteins B. clotting and tensile proteins, along with enzymes C. contractile, regulatory and structural proteins D. receptor proteins E. enzymes

C. contractile, regulatory and structural proteins

Writer's cramp can occur in Anatomy and Physiology lecture class. What factor would most likely contribute to the muscles not being able to relax? A. insufficient oxygen being delivered by hemoglobin and bound by myoglobin B. insufficient blood flow to the hand C. insufficient ATP which prevents the myosin heads from detaching D. too rapid degradation of ACh by AChE E. excess calcium being pumped into the sarcoplasmic reticulum

C. insufficient ATP which prevents the myosin heads from detaching

Which of the following is a characteristic of all muscle? A. autorhymicity B. calmodulin C. myosin and actin D. well developed sarcoplasmic reticulum E. involuntary F. striated

C. myosin and actin

In a neuromuscular junction, the effect of acetylcholine (ACh) binding to receptors on the motor end plate lasts only briefly due to __?__. A. rapid desensitization of the nicotinic receptor for ACh B. rapid uptake of the ACh into the myofiber C. rapid destruction of ACh in the synaptic cleft by acetylcholinesterase (AChE) D. endocytosis of the ACh into the myofiber E. rapid destruction of ACh in the synaptic cleft by monoamine oxidase (MAO)

C. rapid destruction of ACh in the synaptic cleft by acetylcholinesterase (AChE)

The drug dantrolene inhibits release of calcium into the sarcoplasm. It is an antispasmodic used to treat malignant hyperthermia (where uncontrolled shivering dangerously elevates body temperature). Dantrolene affects the __?__. A. sarcolemma B. sarcomeres C. terminal cisterns D. mitochondria E. motor neuron end plate

C. terminal cisterns

Which region of a sarcomere contains thin filaments? A. A band B. Z disc C. H zone D. Both the I band and A band E. I band

D. Both the I band and A band

On the electron micrograph, the synapse is best indicated by __?__. A. A B. B C. C D. D E. E

D. D

Which of the following correctly lists the sequence of structures that action potentials must move through to excite skeletal muscle contraction? A. sarcolemma, axon of neuron, T tubules B. muscle fiber, axon of neuron, myofibrils C. T tubules, sarcolemma, myofilament D. axon of neuron, sarcolemma, T tubules E. myofibril, myofilaments, mitochondria

D. axon of neuron, sarcolemma, T tubules

When an athlete performs a pull up (raising their chin to a bar while their body hangs), the process of lowering the body down is a(n) __?__ contraction. A. isometric B. concentric C. really hard D. eccentric E. geometric

D. eccentric

Lidocaine is a local anesthetic that inhibits the ion movement required to conduct impulses on excitable cells. How might lidocaine affect the muscle cell? Lidocaine will inhibit __?__. A. calcium channels on the muscle terminal cisterns, preventing calcium release into the muscle cell B. calcium channels on the motor neuron end bulb, preventing release of ACh C. calcium pumps on the sarcoplasmic reticulum, slowing calcium reuptake following contraction D. sodium channels on the motor neuron axon and sarcolemma of the muscle, slowing signal transmission

D. sodium channels on the motor neuron axon and sarcolemma of the muscle, slowing signal transmission

Skeletal muscle contraction is triggered to begin when calcium is released from __?__. A. T-tubules B. myofibrils C. mitochondria D. the terminal cisterns of sarcoplasmic reticulum E. the Golgi apparatus

D. the terminal cisterns of sarcoplasmic reticulum

The __?__ of skeletal muscle are composed of troponin, tropomyosin and actin. A. Z discs B. myofibrils C. thick filaments D. thin filaments E. M line

D. thin filaments

Thapsigargin is non-competitive inhibitor of the sarco/endoplasmic reticulum Ca²⁺ ATPase. Structurally, thapsigargin is classified as a sesquiterpene lactone, and is extracted from a plant, Thapsia garganica. Upon exposure to thapsigargin, what period of the myogram would be affected first? A. Contraction B. Threshold C. Tetanus D. Latent E. Relaxation

E. Relaxation

Why would cardiac muscles have longer refractory periods than skeletal muscles. Choose the best answer? A. Skeletal muscles have a prolonged calcium influx B. Cardiac muscle is not dependent on aerobic respiration to produce ATP C. The muscle types contain different contractile proteins D. Skeletal muscle is autorhythmic to avoid cramping E. To preserve the normal rhythm of the heart and prevent fatigue

E. To preserve the normal rhythm of the heart and prevent fatigue

The opening and closing of ligand gates on the sarcolemma is mediated by __?__. A. acetylcholine attachment B. calcium influx into the motor neuron C. sodium influx into the muscle fiber D. acetylcholinesterase activity E. all the above choices are correct

E. all the above choices are correct

Which of the following is a characteristic solely of cardiac muscle? A. striated B. involuntary C. myosin and actin D. well developed sarcoplasmic reticulum E. autorhymicity F. calmodulin

E. autorhymicity

Smooth muscle tone is maintained by the prolonged presence of ___?___ in the cytosol of the muscle cell. A. sodium ions B. ATP C. oxygen D. acetylcholine E. calcium ions

E. calcium ions

Which property of muscle gives it the ability to stretch without damage? A. autorhymicity B. contractility C. electrical excitability D. elasticity E. extensibility

E. extensibility

When an athlete is preparing to perform a pull up, they hang from the bar. At this point, they are performing what type of muscle contraction? A. non-working B. eccentric C. concentric D. geometric E. isometric

E. isometric

Which protein is the motor protein in all three types of muscle tissue? A. titin B. tropomyosin C. troponin D. actin E. myosin

E. myosin

Which protein helps return a stretched sarcomere to its resting length? A. actin B. myosin C. troponin D. tropomyosin E. titan

E. titan

Which of the following is a characteristic solely of smooth muscle? A. well developed sarcoplasmic reticulum B. myosin and actin C. striated D. autorhymicity E. involuntary F. calmodulin

F. calmodulin

At the neuromuscular junction, __________ ions must enter the synaptic end bulb to allow the release of __________ (acronym), which crosses the synapse and binds to nicotinic receptors so __________ ions can enter the muscle fiber.

calcium, ACh, sodium

World class shot-putters would be expected to have a higher percentage of _____ fibers in their arm muscles.

fast glycolytic

Motor unit recruitment occurs when there is a(n) ________ in the number of active motor units within a skeletal muscle.

increase

The contractile organelles of a skeletal muscle fiber are ______, which are composed of repeating units called________

myofibrils, sarcomeres