HISTO (F): MUSCLE TISSUE

pahintulot

C

Which basic tissue type is specialized for contractility?

a. Epithelia

b. Connective tissue

c. Muscle tissue

d. Nervous tissue

A

What is the embryological origin of essentially all muscle cells?

a. Mesoderm

b. Ectoderm

c. Endoderm

d. Neural crest

B

Which proteins are primarily synthesized during the differentiation of muscle cells?

a. Collagen and Elastin

b. Actin and Myosin

c. Keratin and Vimentin

d. Tubulin and Dynein

C

Which muscle type is characterized by long, multinucleated cells and cross-striations?

a. Smooth muscle

b. Cardiac muscle

c. Skeletal muscle

d. Myofibroblasts

B

What structure is unique to cardiac muscle and binds branched cells together?

a. Tight junctions

b. Intercalated discs

c. Sarcolemma

d. Neuromuscular junction

A

Which muscle type consists of fusiform cells that lack striations?

a. Smooth muscle

b. Skeletal muscle

c. Ventricular muscle

d. Atrial muscle

C

In muscle cell terminology, what is the specific name for the cytoplasm?

a. Sarcoplasmic reticulum

b. Sarcolemma

c. Sarcoplasm

d. Sarcomere

B

What is the muscle-specific name for the smooth endoplasmic reticulum?

a. Sarcolemma

b. Sarcoplasmic reticulum

c. External lamina

d. T-tubule

D

What term describes an increase in muscle tissue size through increased cell volume?

a. Hyperplasia

b. Atrophy

c. Ischemia

d. Hypertrophy

C

Which muscle type retains the capacity for hyperplasia through mitosis?

a. Skeletal muscle

b. Cardiac muscle

c. Smooth muscle

d. Striated muscle

A

During embryonic development, which cells fuse to form myotubes?

a. Mesenchymal myoblasts

b. Satellite cells

c. Fibroblasts

d. Pericytes

B

Where are the nuclei located in a skeletal muscle fiber?

a. Centrally located

b. Peripherally, just under the sarcolemma

c. Within the intercalated discs

d. Inside the sarcoplasmic reticulum

B

What is the name of the reserve progenitor cells adjacent to skeletal muscle fibers?

a. Myofibrils

b. Muscle satellite cells

c. Myocytes

d. Neuroglia

C

Which connective tissue layer surrounds the entire muscle organ?

a. Endomysium

b. Perimysium

c. Epimysium

d. Deep fascia

B

A bundle of muscle fibers is known as a:

a. Sarcomere

b. Fascicle

c. Myofilament

d. Myofibril

D

Which layer immediately surrounds an individual muscle fiber?

a. Perimysium

b. Epimysium

c. Deep fascia

d. Endomysium

B

What structures join skeletal muscle to bone or skin?

a. Intercalated discs

b. Tendons

c. Gap junctions

d. Caveolae

A

What are the long cylindrical filament bundles that fill the sarcoplasm of skeletal muscle?

a. Myofibrils

b. Myofilaments

c. Sarcoplasmic reticulum

d. T-tubules

C

The dark bands of skeletal muscle are known as:

a. I bands

b. Z discs

c. A bands

d. H zones

B

What is the functional subunit of the contractile apparatus, extending from Z disc to Z disc?

a. Myofibril

b. Sarcomere

c. Fascicle

d. Motor unit

C

Which protein makes up the thick filaments of the sarcomere?

a. Actin

b. Tropomyosin

c. Myosin

d. Troponin

A

Myosin heads have binding sites for which two substances?

a. Actin and ATP

b. Calcium and Sodium

c. Tropomyosin and Troponin

d. Collagen and Elastin

C

Which subunit of the troponin complex binds to calcium ions?

a. TnT

b. TnI

c. TnC

d. TnA

B

What is the largest protein in the body, providing scaffolding for thick filaments?

a. Nebulin

b. Titin

c. Desmin

d. Myomesin

C

What is the largest protein in the body, providing scaffolding for thick filaments?

a. Nebulin

b. Titin

c. Desmin

d. Myomesin

C

Which enzyme catalyzes the transfer of phosphate from phosphocreatine to ADP?

a. Actomyosin ATPase

b. Acetylcholinesterase

c. Creatine kinase

d. Myosin light-chain kinase

C

What are the tubular invaginations of the sarcolemma that penetrate the sarcoplasm?

a. Terminal cisternae

b. Sarcoplasmic reticulum

c. T-tubules

d. Caveolae

B

In skeletal muscle, a "triad" consists of a T-tubule and:

a. Two Z discs

b. Two terminal cisternae

c. One myofibril

d. Two motor end plates

C

What ion is released from the sarcoplasmic reticulum to initiate contraction?

a. Sodium (Na⁺)

b. Potassium (K⁺)

c. Calcium (Ca²⁺)

d. Magnesium (Mg²⁺)

D

According to the sliding filament mechanism, what happens to filament length during contraction?

a. Both thick and thin filaments shorten

b. Only thin filaments shorten

c. Only thick filaments shorten

d. Neither thick nor thin filaments change length

A

In a resting muscle, what blocks the myosin-binding sites on actin?

a. Troponin-tropomyosin complex

b. Calcium ions

c. Acetylcholine

d. a-actinin

B

What provides energy for the myosin head pivot (power stroke)?

a. Calcium binding

b. ATP hydrolysis

c. Acetylcholine release

d. Sodium influx

D

What condition occurs after death when ATP is absent and crossbridges become stable?

a. Myasthenia gravis

b. Hypertrophy

c. Ischemia

d. Rigor mortis

C

The synapse between a motor nerve and a muscle fiber is called the:

a. Intercalated disc

b. Gap junction

c. Neuromuscular junction

d. Triad

B

Which neurotransmitter is released at the motor end plate?

a. Norepinephrine

b. Acetylcholine

c. Dopamine

d. Serotonin

C

What enzyme removes acetylcholine from the synaptic cleft?

a. Creatine kinase

b. Myosin light-chain kinase

c. Acetylcholinesterase

d. ATPase

C

A single motor neuron and all the muscle fibers it innervates is a:

a. Sarcomere

b. Fascicle

c. Motor unit

d. Myofibril

B

Which autoimmune disorder involves antibodies against acetylcholine receptors?

a. Duchenne muscular dystrophy

b. Myasthenia gravis

c. Leiomyoma

d. Ischemia

B

Which proprioceptors act as stretch detectors among muscle fascicles?

a. Golgi tendon organs

b. Muscle spindles

c. Intercalated discs

d. Caveolae

B

What do Golgi tendon organs detect?

a. Changes in muscle length

b. Changes in tension within tendons

c. Oxygen levels

d. Acetylcholine concentration

C

Mutations in the gene for which protein cause Duchenne muscular dystrophy?

a. Myosin

b. Actin

c. Dystrophin

d. Titin

C

Which muscle fiber type is adapted for slow, continuous contractions and is red in color?

a. Fast glycolytic

b. Fast oxidative-glycolytic

c. Slow oxidative

d. Myofibroblasts

B

Fast glycolytic fibers appear white because they have:

a. High myoglobin levels

b. Few mitochondria and capillaries

c. Many mitochondria

d. A rich capillary network

B

What determines the metabolic type of a skeletal muscle fiber?

a. The type of bone it attaches to

b. Its motor nerve supply

c. The individual's gender

d. The amount of calcium available

A

How many nuclei does a typical cardiac muscle cell have?

a. One, centrally located

b. Multiple, peripherally located

c. None

d. Hundreds

C

Which type of junction in intercalated discs provides ionic continuity and acts as an "electrical synapse"?

a. Desmosomes

b. Fascia adherens

c. Gap junctions

d. Tight junctions

B

What is the major fuel source stored in cardiac muscle?

a. Glycogen

b. Fatty acids (as triglycerides)

c. Phosphocreatine

d. Myoglobin

B

What is the term for the T-tubule and terminal cisternae complex in cardiac muscle?

a. Triad

b. Dyad

c. Sarcomere

d. Fascicle

C

Which peptide hormone is released by atrial muscle granules to affect water balance?

a. Oxytocin

b. Acetylcholine

c. Atrial natriuretic factor (ANF)

d. Norepinephrine

A

Why does cardiac muscle have very little potential for regeneration?

a. It lacks satellite cells

b. It cannot undergo hypertrophy

c. It has too many gap junctions

d. It uses fatty acids for fuel

C

Which muscle type is found in the walls of the digestive and respiratory tracts?

a. Skeletal muscle

b. Cardiac muscle

c. Smooth muscle

d. Striated muscle

C

Smooth muscle cells are described as being:

a. Long and cylindrical

b. Branched

c. Fusiform (tapering)

d. Multinucleated

B

In smooth muscle, what structures are functionally similar to Z discs?

a. Caveolae

b. Dense bodies

c. Intercalated discs

d. T-tubules

A

Which protein replaces troponin in smooth muscle contraction?

a. Calmodulin

b. Myomesin

c. Dystrophin

d. Titin

C

What are the periodic swellings on autonomic nerves in smooth muscle called?

a. Motor end plates

b. Synaptic clefts

c. Varicosities

d. Junctional folds

C

Which hormone stimulates smooth muscle contraction in the uterus?

a. Atrial natriuretic factor

b. Norepinephrine

c. Oxytocin

d. Acetylcholine

B

What are benign tumors arising from smooth muscle called?

a. Sarcomas

b. Leiomyomas

c. Myopathies

d. Infarcts

A

Which cells are the source of regeneration in skeletal muscle?

a. Satellite cells

b. Fibroblasts

c. Myoblasts

d. Pericytes

C

Damage to cardiac muscle is typically replaced by:

a. New muscle fibers

b. Proliferating satellite cells

c. Connective tissue (scarring)

d. Hyperplasia of existing cells

C

Which muscle type has the most active regenerative response?

a. Cardiac muscle

b. Skeletal muscle

c. Smooth muscle

d. Striated muscle

B

What cells participate in the repair of vascular smooth muscle?

a. Schwann cells

b. Pericytes

c. Myofibrils

d. Intrafusal fibers

C

The universal cell property optimized by muscle tissue is:

a. Secretion

b. Conductivity

c. Contractility

d. Absorption

A

The force for muscle contraction is generated by actin and:

a. Myofibrillar proteins

b. Connective proteins

c. Elastic proteins

d. Sarcoplasmic proteins

C

Which of the following is under voluntary control?

a. Smooth muscle

b. Cardiac muscle

c. Skeletal muscle

d. All of the above

B

Which muscle type is described as rhythmic and vigorous?

a. Skeletal muscle

b. Cardiac muscle

c. Smooth muscle

d. Myoepithelial cells

C

The "husk" of a muscle cell is the:

a. Sarcoplasm

b. Sarcoplasmic reticulum

c. Sarcolemma

d. Sarcomere

B

Hyperplasia in smooth muscle occurs through:

a. Cell volume increase

b. Mitosis

c. Fusion of myoblasts

d. Satellite cell activation

B

Skeletal muscle fiber diameters typically range from:

a. 1-2 µm

b. 10-100 µm

c. 15-30 µm

d. 85-120 µm

C

Connective tissue septa in the epimysium carry:

a. Only nerves

b. Only blood vessels

c. Nerves, blood vessels, and lymphatics

d. Myofibrils

C

The perimysium surrounds which functional unit?

a. Individual fiber

b. Whole muscle

c. Fascicle

d. Myofilament

C

Collagen fibers from tendons associate with which part of the muscle at junctions?

a. Nucleus

b. Sarcoplasm

c. Sarcolemma infoldings

d. Sarcoplasmic reticulum

B

Why are I bands called "isotropic"?

a. They are dark in color

b. They do not alter polarized light

c. They are birefringent

d. They contain thick filaments

C

What is the approximate length of a sarcomere in resting muscle?

a. 1.0 µm

b. 1.5 µm

c. 2.5 µm

d. 15 nm

C

The lateral registration of sarcomeres causes:

a. Hypertrophy

b. Muscle weakness

c. Transverse striations

d. Ischemia

B

What is the molecular weight of the myosin complex?

a. 150 kDa

b. 500 kDa

c. 3700 kDa

d. 8 nm

A

How long are thin actin filaments?

a. 1.0 µm

b. 1.5 µm

c. 40 nm

d. 150 nm

B

Which protein binds thin filaments to a-actinin at the Z disc?

a. Titin

b. Nebulin

c. Myomesin

d. Troponin

B

What holds thick filaments in place at the M line?

a. a-actinin

b. Myomesin

c. Tropomyosin

d. Troponin

C

The sarcoplasmic reticulum surrounds each:

a. Muscle organ

b. Fascicle

c. Myofibril

d. Nucleus

B

What triggers the opening of voltage-gated Ca²⁺ channels in the SR?

a. ATP hydrolysis

b. Membrane depolarization

c. Acetylcholine binding

d. Calcium binding

C

Where do T-tubules encircle myofibrils in skeletal muscle?

a. At the Z disc

b. At the M line

c. At A- and I-band boundaries

d. In the H zone

B

What occurs when calcium binds troponin?

a. ATP is hydrolyzed

b. Tropomyosin moves to expose binding sites

c. The sarcolemma depolarizes

d. Acetylcholine is released

A

How long does one attach-pivot-detach cycle last?

a. 50 milliseconds

b. 500 milliseconds

c. 1 second

d. 10 milliseconds

B

Schwann cells cover the contact points at the:

a. Intercalated discs

b. Neuromuscular junctions

c. Myotendinous junctions

d. Gap junctions

B

Junctional folds in the sarcolemma increase:

a. Mitochondrial count

b. Surface area for receptors

c. Muscle fiber length

d. Calcium storage

B

Striated muscle fibers contract:

a. In grades (partially)

b. All-or-none

c. Only when stretched

d. Rhythmically by default

B

Proprioceptors provide information to the:

a. Sarcoplasm

b. Central nervous system (CNS)

c. Kidney

d. Uterus

B

Intrafusal fibers are found within:

a. Golgi tendon organs

b. Muscle spindles

c. The H zone

d. Motor end plates

B

Myoglobin is a protein that allows for:

a. ATP synthesis

b. O₂ storage

c. Ca²⁺ sequestration

d. Muscle regeneration

B

Which fibers accumulate lactic acid and fatigue rapidly?

a. Slow oxidative

b. Fast glycolytic

c. Fast oxidative-glycolytic

d. Cardiac fibers

B

Interdigitating processes in cardiac muscle form:

a. Long cylindrical tubes

b. Complex junctions

c. Myotubes

d. External sheaths

B

Desmosomes in intercalated discs provide:

a. Ionic continuity

b. Strong intercellular adhesion

c. Ca²⁺release

d. ATP synthesis

C

Mitochondria occupy what percentage of cardiac cell volume?

a. 10%

b. 20%

c. 40%

d. 60%

B

In atrial muscle, T-tubules are:

a. Larger than in ventricles

b. Small or absent

c. Found at the M line

d. Connected to triads

B

The parasympathetic nerve supply to the heart:

a. Accelerates the frequency

b. Decreases the frequency

c. Has no effect

d. Initiates contraction

B

Smooth muscle cells lack T-tubules but have:

a. Triads

b. Caveolae

c. Intercalated discs

d. Multiple nuclei

C

Myofilament bundles in smooth muscle crisscross the sarcoplasm:

a. Parallel to the long axis

b. Perpendicularly

c. Obliquely

d. Only near the nucleus

B

Dense bodies in smooth muscle contain which protein?

a. Myosin

b.a-actinin

c. Troponin

d. Titin

B

Which of the following can smooth muscle cells synthesize?

a. Hemoglobin

b. Collagen and Elastin

c. Acetylcholine

d. Myoglobin

B

Scarring in skeletal muscle regeneration is caused by:

a. Excessive satellite cells

b. Connective tissue growth

c. Lack of oxygen

d. Myasthenia gravis