Functions and basic properties of muscle tissue

Which property allows muscle cells to respond to chemical signals with electrical changes?

A) Conductivity | B) Excitability | C) Elasticity | D) Contractility

Excitability

Which property sends a rapid wave of electrical excitation along the entire cell?

A) Excitability | B) Extensibility | C) Conductivity | D) Elasticity

Conductivity

Which unique property allows muscle cells to shorten forcefully and pull on bones?

A) Contractility | B) Elasticity | C) Extensibility | D) Conductivity

Contractility

Which property allows skeletal muscle cells to stretch up to 3x their length without tearing?

A) Elasticity | B) Contractility | C) Excitability | D) Extensibility

Extensibility

Which property causes a stretched muscle cell to recoil to its resting length?

A) Extensibility | B) Elasticity | C) Conductivity | D) Contractility

Elasticity

Which muscle function circulates blood and propels food through hollow organs?

A) Stability | B) Glycemic control | C) Movement | D) Heat production

Movement

Which muscle function maintains posture and prevents unwanted joint motions?

A) Stability | B) Communication | C) Heat production | D) Control of passages

Stability

Which muscle function enables speech, facial expressions, and body language?

A) Stability | B) Glycemic control | C) Movement | D) Communication

Communication

Which muscle function uses sphincters to regulate food, bile, blood, and waste?

A) Heat production | B) Stability | C) Communication | D) Control of body openings and passages

Control of body openings and passages

Which muscle function generates up to 85% of body warmth to keep enzymes active?

A) Glycemic control | B) Heat production | C) Stability | D) Movement

Heat production

Which muscle function absorbs and stores glucose to regulate blood sugar levels?

A) Glycemic control | B) Heat production | C) Control of passages | D) Stability

Glycemic control

Which muscle type is voluntary, striated, and usually attached to bones?

A) Cardiac muscle | B) Smooth muscle | C) Skeletal muscle | D) Visceral muscle

Skeletal muscle

What are the alternating light and dark transverse bands on skeletal muscle cells called?

A) Striations | B) Myofibers | C) Fascicles | D) Tendons

Striations

Why is skeletal muscle described as voluntary?

A) It never attaches to bone | B) It lacks striations | C) It is subject to conscious control | D) It contracts automatically

It is subject to conscious control

How are cardiac and smooth muscle classified since they are not under conscious control?

A) Voluntary | B) Skeletal | C) Striated | D) Involuntary

Involuntary

What are individual skeletal muscle cells called due to their extraordinary length?

A) Myofibers | B) Collagen fibers | C) Fascicles | D) Striations

Muscle fibers (myofibers)

Skeletal muscle is composed of muscular tissue along with fibrous connective tissue. Which fibrous connective tissue layer surrounds each individual muscle fiber?

A) Epimysium | B) Perimysium | C) Tendon | D) Endomysium

Endomysium

Which connective tissue layer bundles muscle fibers together into fascicles?

A) Endomysium | B) Perimysium | C) Epimysium | D) Sarcolemma

Perimysium

Which connective tissue sheath encloses the entire skeletal muscle?

A) Endomysium | B) Perimysium | C) Epimysium | D) Myofiber

Epimysium

Which thick, dark intercellular connections join cardiac muscle cells end to end?

A) Striations | B) Perimysium | C) Satellite cells | D) Intercalated discs

Intercalated discs

Which structures within intercalated discs allow electrical signals to pass directly between neighboring cardiomyocytes?

A) T tubules | B) Myofibrils | C) Gap junctions | D) Endomysium

Gap junctions

What term describes the heart's ability to contract rhythmically and independently without nervous stimulation?

A) Voluntary | B) Autorhythmic | C) Anaerobic | D) Fibrotic

Autorhythmic

How do cardiomyocytes structurally differ from skeletal muscle fibers?

A) They lack striations | B) They are shorter, thicker, and branched | C) They have peripheral nuclei | D) They are wrapped in epimysium

They are shorter, thicker, and branched

Where are the nuclei located in a cardiac muscle cell (cardiomyocyte)?

A) One or two near the middle of the cell | B) Pushed against the outer edge | C) Inside the intercalated discs | D) Absent in mature cells

One or two near the middle of the cell

Which connective tissue layers are present around cardiac muscle cells?

A) Epimysium and fascia only | B) Endomysium, perimysium, and epimysium | C) Endomysium only | D) None at all

Endomysium only (there is no perimysium or epimysium)

Where does cardiac muscle get extra Ca2+ during contraction since its sarcoplasmic reticulum is less developed?

A) From the nuclei | B) T tubules from extracellular fluid | C) From gap junctions | D) From satellite cells

T tubules from extracellular fluid

How is damaged cardiac muscle typically repaired after a heart attack?

A) Rapid mitosis | B) Satellite cell regeneration | C) Fibrosis | D) Endomysium splitting

Fibrosis (scar tissue)

How long does cardiac muscle maintain tension during a contraction to expel blood?

A) 5 to 10 ms | B) 50 to 75 ms | C) 200 to 250 ms | D) 1 to 2 seconds

200 to 250 ms

Why is cardiac muscle highly resistant to fatigue?

A) It uses anaerobic fermentation | B) It contracts only when stimulated by somatic nerves | C) It has no T tubules | D) It uses aerobic respiration with mitochondria

It uses aerobic respiration with mitochondria

Why is smooth muscle given its name?

A) It has no nuclei | B) It has no striations | C) It is wrapped in epimysium | D) It contracts rapidly

It has no striations

What shape is a smooth muscle myocyte, and where is its single nucleus located?

A) Fusiform (tapered ends) with one middle nucleus | B) Branched cylinder with central nucleus | C) Long cylinder with peripheral nuclei | D) Cube-shaped with multiple nuclei

Fusiform (tapered ends) with one middle nucleus

Which connective tissue layer encloses smooth muscle myocytes?

A) Epimysium and fascia | B) Perimysium only | C) Endomysium only | D) Endomysium, perimysium, and epimysium

Endomysium only (there are no fascicles, perimysium, or epimysium)

Which protein plaques anchor thin filaments in smooth muscle instead of Z discs?

A) Intercalated discs | B) Dense bodies | C) Varicosities | D) Caveolae

Dense bodies

What are the neurotransmitter-filled swellings along autonomic nerve fibers in smooth muscle called?

A) Motor end plates | B) T tubules | C) Sarcolemmas | D) Varicosities

Varicosities

Unlike skeletal and cardiac muscle, how does injured smooth muscle regenerate?

A) Fibrosis only | B) Mitosis and hyperplasia | C) Satellite cell fusion | D) It cannot repair itself

Mitosis and hyperplasia (cell division)

Which type of smooth muscle has myocytes that respond independently (e.g., iris, hair follicles, large arteries)?

A) Unitary (visceral) smooth muscle | B) Striated muscle | C) Cardiac muscle | D) Multiunit smooth muscle

Multiunit smooth muscle

Which more common type of smooth muscle uses gap junctions so cells contract together as a single unit in hollow organs?

A) Multiunit smooth muscle | B) Unitary smooth muscle | C) Skeletal muscle | D) Longitudinal muscle

Unitary (single-unit / visceral) smooth muscle

How does smooth muscle contraction speed and energy use compare to skeletal and cardiac muscle?

A) Slower contraction, sustained tension | B) Faster contraction, rapid fatigue | C) Same speed, high ATP use | D) Fast twitches, no sustained tension

Slower contraction, sustained tension

Where does smooth muscle get most of its CA2+ for contraction?
A) Dense bodies | B) Gap junctions | C) Extracellular fluid via caveolae | D) The nucleus

Extracellular fluid via caveolae

Which mode of stimulation uses acetylcholine and norepinephrine to excite or inhibit smooth muscle?

A) Autonomic nerve fibers and neurotransmitters | B) Temperature | C) Stretch | D) Autorhythmicity

Autonomic nerve fibers and neurotransmitters

Which mode of stimulation triggers labor contractions via oxytocin or relaxes arteries via histamine?

A) Chemicals | B) Stretch | C) Autorhythmicity | D) Temperature

Chemicals (hormones, gases, and pH changes)

Which mode of stimulation causes hair erection in the cold and relaxes skin arteries in the warmth?

A) Stretch | B) Chemicals | C) Temperature | D) Autonomic nerves

Temperature

Which mode of stimulation causes the stomach and urinary bladder to contract as they fill?

A) Autorhythmicity | B) Chemicals | C) Temperature | D) Stretch

Stretch

Which mode of stimulation involves pacemaker cells spontaneously depolarizing in the stomach and intestines?

A) Autonomic nerves | B) Stretch | C) Temperature | D) Autorhythmicity

Autorhythmicity

Which thin sleeve of loose connective tissue surrounds each individual muscle fiber?

A) Epimysium | B) Endomysium | C) Perimysium | D) Fascia

Endomysium

What is the main role of the endomysium in reaching each muscle cell?

A) Creates room for capillaries and nerve fibers | B) Separates neighboring muscles | C) Surrounds the entire muscle | D) Bundles fascicles together

Creates room for capillaries and nerve fibers

Which connective tissue sheath wraps 20 to 60 muscle fibers together into fascicles?

A) Perimysium | B) Endomysium | C) Epimysium | D) Compartment

Perimysium

What are fascicles?

A) Individual muscle cells | B) Sheets separating muscle groups | C) Muscle fibers visible as parallel strands | D) Outer sheaths around whole muscles

Muscle fibers visible as parallel strands

Which fibrous sheath surrounds the entire muscle?

A) Endomysium | B) Perimysium | C) Fascia | D) Epimysium

Epimysium

Which connective tissue sheet separates neighboring muscles or groups of muscles into compartments?

A) Endomysium | B) Fascia | C) Perimysium | D) Tendon

Fascia

Which muscle shape is thick in the middle and tapered at both ends (e.g., biceps brachii)?

A) Fusiform | B) Parallel | C) Pennate | D) Circular

Fusiform

Which muscle type has uniform width, shortens more than other types, and produces less force (e.g., rectus abdominis, sartorius)?

A) Pennate | B) Triangular | C) Parallel | D) Fusiform

Parallel

Which fan-shaped muscle type is broad at one end and converges to a narrower end (e.g., pectoralis major)?

A) Circular | B) Pennate | C) Triangular (convergent) | D) Fusiform

Triangular (convergent)

Which feather-shaped muscle type has fascicles inserting obliquely onto a tendon and generates the most force?

A) Fusiform | B) Parallel | C) Circular | D) Pennate

Pennate

What are the three subtypes of pennate muscles?

A) Unipennate, bipennate, multipennate | B) Fusiform, parallel, circular | C) Convergent, quadrilateral, sphincter | D) Superficial, deep, intermediate

Unipennate, bipennate, multipennate

Which muscle is a classic example of a multipennate muscle?

A) Biceps brachii | B) Deltoid | C) Rectus femoris | D) Orbicularis oculi

Deltoid

Why do pennate muscles generate more force than other muscle shapes?

A) They shorten over longer distances | B) They fit more muscle fibers into a given length | C) They lack tendons | D) They have fewer fascicles

They fit more muscle fibers into a given length

Which muscle type arranges fascicles in rings to constrict body openings and passages (e.g., orbicularis oculi)?

A) Triangular | B) Fusiform | C) Parallel | D) Circular (sphincters)

Circular (sphincters)

What is the plasma membrane of a muscle fiber called?

A) Sarcoplasm | B) Sarcolemma | C) Endomysium | D) Myofibril

Sarcolemma

What is the cytoplasm of a muscle fiber called?

A) Sarcoplasm | B) Sarcolemma | C) Glycogen | D) Sarcoplasmic reticulum

Sarcoplasm

Which long protein cords fill most of the sarcoplasm and run the entire length of the muscle cell?

A) Myoblasts | B) T tubules | C) Myofibrils | D) Terminal cisterns

Myofibrils

Which stored carbohydrate and red oxygen-binding pigment are abundant in the sarcoplasm to fuel muscle activity?

A) Calsequestrin and dynein | B) Glycogen and myoglobin | C) Actin and myosin | D) Mitochondria and satellite cells

Glycogen and myoglobin

Which smooth endoplasmic reticulum network wraps around each myofibril and stores CA2+ at rest?

A) Transverse (T) tubules | B) Sarcoplasmic reticulum (SR) | C) Sarcolemma | D) Satellite cells

Sarcoplasmic reticulum (SR)

What are the dilated end sacs of the sarcoplasmic reticulum called?

A) Terminal cisterns | B) T tubules | C) Myofibrils | D) Myoblasts

Terminal cisterns

Which tubular infoldings of the sarcolemma penetrate through the muscle cell between two terminal cisterns to signal Ca2+ release?
A) Myofibrils | B) Satellite cells | C) Transverse (T) tubules | D) Endomysium

Transverse (T) tubules

Which embryonic stem cells fuse together during development to form a single multinucleated muscle fiber?

A) Satellite cells | B) Myoblasts | C) Myofibrils | D) Cardiomyocytes

Myoblasts

Which unspecialized adult stem cells sit between the muscle fiber and endomysium to help with muscle growth and larger injury repair?

A) Myoblasts | B) Terminal cisterns | C) Satellite cells | D) T tubules

Satellite cells

Which protein inside the sarcoplasmic reticulum safely binds and stores Ca2+ so it does not trigger cell death in the cytosol?

A) Myoglobin | B) Glycogen | C) Calsequestrin | D) Dynein

Calsequestrin

Which three types of protein myofilaments bundle together to form a myofibril?

A) Collagen, elastin, keratin | B) Thick, thin, and elastic filaments | C) Actin, tubulin, dynein | D) Sarcolemma, sarcoplasm, SR

Thick, thin, and elastic filaments

Which motor protein makes up the thick filaments (15 nm) and is shaped like a golf club?

A) Actin | B) Titin | C) Myosin | D) Troponin

Myosin

Which two intertwined protein strands form the main backbone of thin filaments (7 nm)?

A) Fibrous (F) actin | B) Myosin tails | C) Titin springs | D) Tropomyosin

Fibrous (F) actin

What are the individual bead-like subunits of F actin called, each containing an active site for myosin binding?

A) Troponin | B) Globular (G) actin | C) Titin | D) Myoblasts

Globular (G) actin

Which regulatory protein on a thin filament blocks the active sites of G actin when a muscle fiber is relaxed?

A) Troponin | B) Myosin | C) Tropomyosin | D) Titin

Tropomyosin

Which calcium-binding protein is attached to tropomyosin on a thin filament?

A) Troponin | B) Myosin | C) Calsequestrin | D) Titin

Troponin

Which huge springy protein makes up elastic filaments (1 nm) and anchors thick filaments to the Z disc and M line?

A) Tropomyosin | B) Fibrous actin | C) Titin | D) Troponin

Titin

What is the main function of titin (elastic filaments) in a sarcomere?

A) Binds calcium to start contraction | B) Blocks active sites at rest | C) Stabilizes thick filaments, prevents overstretching, and provides elastic recoil | D) Forms cross-bridges with actin

Stabilizes thick filaments, prevents overstretching, and provides elastic recoil

Which myofilaments are classified as the contractile proteins that generate pulling force?

A) Troponin and tropomyosin | B) Myosin and actin | C) Titin and calsequestrin | D) Dystrophin and nebulin

Myosin and actin

Which myofilament proteins act as regulatory proteins that turn contraction on and off?

A) Actin and myosin | B) Titin and actin | C) Troponin and tropomyosin | D) Myosin and titin

Troponin and tropomyosin

How do calcium ions (Ca²⁺) activate contraction using the regulatory proteins?

A) Calcium binds to myosin to pull actin | B) Calcium binds to troponin, moving tropomyosin off actin's active sites | C) Calcium binds to dystrophin to stiffen the sarcolemma | D) Calcium breaks down tropomyosin

Calcium binds to troponin, moving tropomyosin off actin's active sites

Which clinically important accessory protein links thin actin filaments to the inner face of the sarcolemma?

A) Tropomyosin | B) Troponin | C) Dystrophin | D) Myosin

Dystrophin

What is the main functional role of dystrophin during muscle contraction?

A) Blocks active sites at rest | B) Transfers pulling force from moving thin filaments to the endomysium and tendon | C) Stores calcium inside the SR | D) Generates ATP for myosin heads

Transfers pulling force from moving thin filaments to the endomysium and tendon

Genetic defects in dystrophin cause which disabling muscle disease?

A) Myasthenia gravis | B) Muscular dystrophy | C) Fibromyalgia | D) Tetanus

Muscular dystrophy

Which connective tissue layer lies just beneath the skin and contains loose connective tissue and fat?

A) Epimysium | B) Deep fascia | C) Superficial fascia | D) Perimysium

Superficial fascia

Which tough connective tissue sheet separates neighboring muscles and binds them into functional groups?

A) Deep fascia | B) Endomysium | C) Superficial fascia | D) Sarcolemma

Deep fascia

What are the functional muscle groups enclosed and separated by deep fascia called (e.g., in the arm or thigh)?

A) Fascicles | B) Compartments | C) Myofibrils | D) Retinacula

Compartments

What are retinacula?

A) Loose fat layers under the skin | B) Tight bands of deep fascia at the wrists and ankles that hold tendons in place | C) Thin sleeves around individual muscle cells | D) Flat sheets attaching abdominal muscles

Tight bands of deep fascia at the wrists and ankles that hold tendons in place